Hello Andy, thank you for everything you're doing for everyone on your channel. I'd gladly buy you a beer, especially since I also lived in Queensland, Australia, 10 years ago and know exactly what summer, thirst, and 40 degrees outside mean😊. Keep it up, I always follow you! P.S. I just bought the J.K. BMS, can't wait to receive it! Thank you very much!
11:05 When everything is OFF, you are practically measuring the voltage difference of two power supplies that have a common positive pole. The charger has 56.00 V and the battery open-circuit voltage is 55.60 V.
And later on, the discharge is off which means you have a voltage drop over the discharge mosfets's parasitic diode. Enabling discharge eliminates this problem. The BMS does this automatically at higher currents, even if you disable discharge - however in this case the BMS will still prevent the battery from discharging once the charge current drops again.
@@diydsolar Charging was on, discharging was off. At low currents, the discharge mosfets are just parasitic diodes. As soon as the current increases, the BMS enables the discharge mosfets, and now the drop is gone and charging continues as usual. If he had discharge enabled from the beginning, he would not see this.
@@upnorthandpersonal thanks I understand you. You are right. Only one question.... May be you have disabled discharge for any reason.... why does the bms has to enalbed it ? May be risky in same cases ? Does daly do the the same ?
@@diydsolar It doesn't - it only does this when the charge current grows, which means there is current not used for the load and the battery would not be discharged in any case. Once the current drops, the settings take effect and prevent any current from going out of the battery. In other words: the setting means: 'don't discharge the battery', which is doesn't.
15:05 the large voltage difference across the BMS FETs has nothing to do with how much current the BMS is passing. You DISCONNECTED the battery from the power source by turning off charge and discharge, so the battery and source voltage are now independent just like they would when the contactor is open on the Q BMS. No current (open switch) = "large" difference, high current (closed/connected switch) = low voltage difference. Same as measuring voltage across a a ceiling light switch: light is on, 0V across the switch, light is off, full AC mains voltage across the open switch. It may not be as you would like it to be but it isn't defective. With a FET-based BMS, you can set your PPT to 58.2V fixed max voltage and let the BMS disconnect charging whenever necessary.
Andy, Since the charge and discharge are disabled, the BMS is basically an open switch. the 350mV you are measuring is the difference between the charger and the battery.
Actually, the real issue later on in the video when he has charging enabled is that he has discharging disabled. This means he's measuring the drop over the parasitic diode in the discharge mosfets. All he needs to do is enable discharge...
15:36 I can see discharge is OFF on your phone. The missing 0.4 V is the drop across the parasitic body diode of the DISCHARGE MOSFET being turned OFF. PLEASE repeat the test at 16:00 with the Discharge ENABLED.
@@upnorthandpersonal No, it's two completely separate power sources with a shared ground. He's measuring a battery and measuring a power supply that are completely disconnected from each other and getting obviously differing results
@@MrHantu666 No, they are not sharing a ground reference. The battery and BMS ground reference is the B- wire. The power supply ground reference is the P- wire. Between B- and P- are two MOSFETs connected back to back in series, but with opposing polarity. One MOSFET permits current inflow while on and turns into a reverse biased blocking diode while off and still trying to charge. The other MOSFET permits current outflow while on and likewise turns into a diode while off, however since it is connected in reverse polarity of and in series with the charging MOSFET, this diode is in forward conduction while the discharge MOSFET is off and you still force current into the battery. The only time B- and P- are the same ground reference is when both the charge and discharge MOSFETs are both on simultaneously. The BMS automatically turns on the discharge MOSFET during charging (despite being off in the App) when it detects sufficient charge current to avoid overheating the body diode in this discharge MOSFET.
@@MrHantu666 Later in the video he has charge enabled, closing the switch - he still measures the gap. It's when he's slowly increasing the voltage on the charger, sees low currents and a big drop until it suddenly changes. That's the point where the BMS opens the discharge mosfets. The drop before that happens is the diode voltage drop of the closed discharge mosfets.
It's not a special feature, on all mosfet bms there is 2 mosfet Nch in serial configuration, one for charging one for discharging. When you don't activate discharge mode and at very low current charging, mosfet discharging is off (voltage drop is 0.5V) but when charging current is consistent bms activate mosfet discharging to remove this 0.5V body diode drop, even discharge mode is off. There is absolutely no problem at all.
I have a *similar* behavior on my Overkill/JBD BMS, and like I have seen a few others mention, it depends on the charge/discharge switches in the BMS app. I have a shunt connected on the negative side, downstream of the BMS, and when I turn the charging off through the BMS, the voltage reported by the shunt is about half a volt lower than the voltage reported by the BMS. If I turn the charging back on in the BMS then the shunt sees full voltage again (even with no charge voltage applied).
Yeah, usually, charge and discharge are both turned on and they get disabled if the BMS if voltage goes too high or low. My discharge was turned off manually. It's in the next video.
Andy get the new 500A version of the QUCC BMS they have their new version with 2 contactors. One for Charge & one for discharging. The reason I say this is because at some stage you will want to parallel your battery banks. With a MOSFET based BMS you cannot parallel at all. So you have a pending problem with your JK BMS in the future already. Please go ahead & run the experiment yourself. The behaviour of the parallel BMS will scare the living day lights out of you. The QUCC guys are really onto something good with their contactor approach! Great Video thank you again...
Why can't you parallel banks with a MOSFET BMS? I say this because I have 3 banks in parallel running my house and they have been in parallel for over a year without an issue. Not really sure what issus you are having where you can't parallel multiple MOSFET based BMSs.
Andy, you are measuring the difference between two power supplies because the MOSFETs are not conducting, that is why when you rise the power supply voltage the voltage difference rises
Andy... Your charge setting in the BMS is off, the FETs in the BMS is in high resistance mode, the loss you think you have is no loss, it's just a difference between your power supply and the battery state because the FETs are not conducting.
@@TheGalifrey don't want to uhm rain on you parade here but this has nothing to do with ohm's law. Since there is no current to induce a voltage in a resistance, ohm's law doesn't apply. This is just a matter of two voltage sources sharing a common and measuring the other side
@@babaluto It's just the drop over the parasitic internal diode of the discharge mosfet - he has discharge disabled in his settings. Enabling discharge eliminates this problem. The BMS does this automatically at higher currents, even if you disable discharge - however in this case the BMS will still prevent the battery from discharging once the charge current drops again.
@@upnorthandpersonal yes this seems very logical, i have no experience with this BMS or any BMS but I do have a good understanding of electronics. I wonder if Andy would be so kind to repeat the measurements with discharge and charge ON in the BMS to confirm
This video is very interesting and informative. Can you please clarify how the charger is disconnected from the battery pack without the load being disconnected. I have a Chargery BMS16 that has a connection to a relay that disconnects the charging if cell differences are above settings or an individual cell is above maximum. This doesn't affect the load.
The JK-BMS (like many others) use MOSFET transistors to control the charging and discharging separately. One side can be turned of but it still lets the current flow in the other direction.
All Victron gear natively shows in the VRM. To connect the BMS as well, we need to modify a few things. It will come later on this channel once the battery is in place and working.
on the dally BMS both mosfets are tuned on ( charge and discharge ) so their body diode are bypassed by the mosfets hence the low drop voltage of few mV across the BMS P- and B-
@andy Why is this a problem? You have a Victron smartshunt that measures accurately at the battery and sends that to your Victron smartsolar. So your smartsolar allways uses the proper battery voltage and doesn’t use the voltage it measures itself. So No problemo then. That is what makes Victron great stuff to work with.
Because the plan is to use more than one 16s pack, each having its own bms and then they will be paralleled after the bms, at least this is my understanding of the new plan Andy has. The victron will only use the voltage reading from one place, so the victron gear wont help with Andys new setup. If the plan was to combine this bms with a Victron shunt or smart battery sense on a single pack, sure it would not be an issue.
@@lexicase8805 hmmm… 2x16s would balance out so measuring on one bank should still work fine. After all, if one bank has a lower voltage it will get the grant of the charge would it not?
I am confused. If you opened all of the connections in the BMS then are the battery and the charger two isolated systems? Why would you expect their potential to remain the same if they are isolated. The battery will begin its journey towards 53.7, while the supply will be fixed by its AC side. What am I missing?
@Andy - just an early in the morning theory: the BMS itself has a consumption for it's internal controler and BT. As soon charging happens it takes it's power from the "charging line" but not before - maybe this has something todo with the observed behaviour?
Andy Andy Andy... :) At 9:37 you said "If they are turned on, if they are conducting there should be almost no voltage drop at all" Right... but you just showed us that you had them turned off. :D Yes I know I'm probably really late to the party. Still catching up.
It's probably not defective, it's probably just a bad design. 0.4v sounds like the voltage drop of a diode, BTW power mosfets have diodes built-in between the source and drain. This might be what you're seeing.
I think it's good that someone looks at the minutiae of these things and questions every tiny little detail. For me, I am really more interested in the practical application (usage) of the batteries, charge controllers, inverters and solar panels. I don't worry about 1/3 of a volt over a 16S pack, when it is at rest. In practical use, the pack will typically be charging and/or discharging most of the time, so this "deviation" will be negligible, if it exists at all. It seems like it went away when the pack was charging, so is this a deep dive into something of little consequence? I don't know for sure, but it seems that way to me.
Agreed.. if you see the cell voltage is at 3.55-+. that perfectly good for any setup practically. we not sending rocket ship to venus here till we need to make sure the battery full at exact 3.65V at all time. Mean here practically if this is genuinely how the BMS behaviour,, no issue at all.
When you have charging or discharging disabled it turns off one side of back to back MOSFET's. The other allowed current direction has a MOSFET body diode voltage drop from the turned off MOSFET. That gives you the 0.6v drop across BMS. To make things more complicated, if current gets above 3-6 amps on the non-disabled path, the BMS will override the disable setting and turn both back to back MOSFET's back on. This is to avoid too much heating of MOSFET's due to the higher current and extra MOSFET body diode voltage drop. Current will be monitored by BMS current shunt (level and direction of current flow) and restore the disable setting when the allowed pass current drops back down to low levels. You should not use the disable function for anything but supervised testing. One problem BMS does have is with cell overvoltage charge disable, coupled with a sporadic higher discharge currents from inverter is the charge disable override to handle the sporadic moderate discharge current. Because the MOSFET turn on and tun off time is slow in BMS, there will be a short 'squirt' of charging when inverter load drops off and the BMS goes back to disabling the MOSFET that blocks charge current. There is some delay in re-disabling charging that allow a short 'squirt' of charging current to leak through to battery for a fraction of second. If inverter load is bouncing up and down causing BMS override of charging disable to turn off and on it can end up overvoltaging a cell beyond the overvoltage cell cutoff voltage. Nothing you can do to stop it other than control the inverter discharge current from happening or disconnect any charging source. o
Yes, way too many people "balance" by placing cells in parallel. You have both sets of FETs turned off, pretty normal. The 2 amp trigger is pretty standard. If you let the Daly go to sleep, it will exhibit the same behavior.
Ive learned a lot from you. My packs i charge to max 3.55 and cut off at 2.5 . Hardly need a bms . Never get run away cells . I think the internal circuit is using some power maybe? Try disconnect the +ve and see what happens.
it is normal behavior , you have turned off charge and discharge mosfets so the battery is disconnected from the power supply, you set your power supply higher than the battery , hence the voltage difference
Daly bms behaves the same if you turn off discharge switch and charge switch then turn charge switch back on and try to charge. The bms have a capacitor (or something that behaves like one) between BMS and P- conductor.
Hi....How can I synchronize the JK bms so that it gives the correct reading of the SOC? I was making some parameter changes and when I clicked "ok" I changed the SOC to a lower one (100% to 76%), the battery was already at 100% (54.4V). .I need help
The voltage drop measured is the difference of potential between the two power sources and is what you would expect to see when the mosfets are turned off. In at least one of your demonstrations, it appears that you have manually disabled the mosfets. If the mosfets are turning off automatically when idling, then that is the problem. Look in the app to see if there's a setting to disable that behavior.
good morning Andy, I also wanted to try out the JK bms but... The device seems well made but mine....does not seem to be reliable. 2 weeks ago I received the B2A20S20P model so without instructions I installed the app Ver. 4.21.0 on V11.XA hardware Version Now, I notice that I cannot edit Calibration current as you do in the videos and when I activate the Balance from the control panel in the settings screen it is disabled as well as the Discharge. ..In my opinion this Ver. is still full of bugs But the worst thing is when I have a load like a simple heat gun on the Bms I have -40A😳 , confirmed with ammeter. Yesterday a water pump (2HP) started and the ATS (100A) burned out probably due to too many amps. What to do in these cases, does it depend on the software, the settings or BMS to be thrown away? Ask for a HEELP to the whole team. thanks
Irgendwie erinnert mich das ganze an die float Funktion von den Laderegler, wenn der Strom unter 1,5A fällt, wird die Spannung vermindert, könnte also vielleicht ein Feature sein
@@OffGridGarageAustralia ein BMS ist dafür da, Akkus zu managen, wo auch der Schutz und die Erhaltung zu gehört, warum sollte ein BMS sowas also nicht haben?
I have always wanted to do this well done to you Andy. I too can confirm the DALYBMS has very minimal voltage deviation. Voltage readings from the BMS compared to the battery monitoring system are identical. I agree with you and would say it would be a faulty BMS.
No, he's got discharging disabled and is measuring the parasitic diode voltage drop from disabled mosfets. It's absolutely normal behavior - all e needs to do is enable discharge.
@@jasondevine6014 He's just measuring the voltage drop over the parasitic diode of the discharge MOSFETS. He disabled discharge in the app, which means these MOSFETs aren't active until a certain current flows (the BMS has to prevent the battery from providing any current as per this setting, but will enable these discharge MOSFETS once enough charge current is flowing). If he enabled discharge in the app, the 'problem' would be gone...
I would call it defective at this point, but offhand I can't imagine why you are getting a such a high forward voltage drop across the MOSFETs in the charge direction. Do you also see a similar drop going the other way under load? If you have an scope you might check for a frequency in that voltage drop that might indicate the MOSFETs are being switched on and off rapidly, suggesting some issue with the MOSFET trigger voltage supply.
He gets the voltage drop from the discharge MOSFETs, which he has turned off in the app. Charge and discharge MOSFETs are in the same circuit. When discharge is disabled, these MOSFETs act as a diode (parasitic diode in the MOSFET). Once the charge current rises, the BMS enables the discharge MOSFETS as well. That's what he's seeing when he increases the voltage to see that 1.5A current. The discharge function still works as expected: the battery will not be discharged since as soon as the charge current drops again, the discharge MOSFETs are off again as per the settings.
@@jackoneil3933 Also, at 15:33 and 17:15 you can see that the discharge is off. This is when he has the 0.4V drop and no current flowing. Then, he increases the voltage and you can see when current starts flowing, discharge is on - e.g. at 14:05. This is where the BMS enabled the discharge.
The voltage drop is lower when you switch on the Mosfets, try to Switch on the Mosfets and measure the voltage, it should fit. When the BMS switches off, there is No battery the Charge controller could charge. I think the BMS is acting normal
Servus Andi, @~11:00 I think, it's not strange at all, it's totally normal to see a voltage diff when all switches are open, you have both, charge and discharge, switched off at this point. The battery sits at a lower voltage than your power supply - and due to the open switches you see the voltage diff... And the increasing amps after you switched on the charging below the 1.5amps might be some kind of a soft-start, what do you think?
Totally right. Battery and supply are disconnected so they can have every voltage they want, when charge and discharge are disabled. But in the end you had it enabled. So this behavior seems not normal.
@@philippk.5242 It is. He has discharge disabled. What he sees is the voltage drop over the internal Mosfet diode of the discharge Mosfets. At higher currents, the BMS will enable these discharge Mosfets to get rid of this drop (even when discharge is disabled). He should just keep discharge enabled as well. Remember, a BMS is a last line of defense, not a general switch for charger/load. The BMS does exactly what it is supposed to.
@@upnorthandpersonal at this sequence charge and discharge are off. So both voltages are more or less independent, no current flowing. Later in the video he had charge enabled.
Ran into that before on many bms's and though bms was bad,however just do a quick discharge at high current and voila you will be at full voltage just PFM -normal
I guess you wouldn’t like my 6kw growatt inverter-charger it says the voltage is 1.1 volts higher than the battery!! I called about it and they said it’s fine the way it is. I guess on a positive note I can never over charge cause max charge voltage is 58.4😂.but my BMS doesn’t act like yours. Max difference through the BMS in or out is .03 at 50 amps either direction. I didn’t check at 100 amps though. Thanks for your thoughts
When the mosfets turn on, their resistance goes to only a few miliohms, allowing current to flow, and the voltage measures correctly. When the mosfets are off, the resistance across them goes up, which inhibits current flow, and makes a voltage drop.
It was confusing to start with as you showed both charge and discharge switches off and so I was screaming at the video ‘what d you expect ffs?’ However watching further it seems you had actually turned on the charge one. I think the problem was that you had the discharge one turned off. This would not be a normal configuration and I suspect that things may well work if the discharge switch is switched on. In a situation of low voltage disconnect this will not be a problem for charging as charge voltage will be at least 0.6v above low voltage disconnect and so it will turn on and then, once the battery has reached low voltage reconnect, the discharge will be turned on and all will roses in the garden again.
So the .4V is the switch or forward voltage for the mosfet to latch? Does the qucc bms use bjt transistors? If so they are not reliant on a voltage to latch on as they use current and mosfet uses voltage to latch, seems like a design flaw¿?
Andy you are testing two different power sources that are not connected together. For instance. You have a 16s battery that is at 48v and another 16s battery that is at 53v and they are connected but by the positive cable only and delete the thought of BMS. Now do the same test. You will have a delta of 5volts. Your .3v - .6 volt is the delta between
when you measure 0.3 to 0.6v.. that look batteries charged BMS in floating mode and when the BMS wake up, the charging mode is working fine.. or.. in your BMS settings, have you set a minimum working current around 1.5amp?
Andy, the battery is 55.6 and the charger is set at 56 volts with charging off, the positive of the charger is still connected so there is a 0.4v potential difference, with the charger running there will be no voltage drop, disconnect everything and measure resistance across the BMS it will read 0 which is no voltage drop. The voltage drop is non existent other than in your head due to a misunderstanding of potential difference. The only PD you're reading is the difference between the charger and the actual battery pack. If the PD was 0 then no current would flow. Voltage pushes current!
Just enable "Discharging". What you see is the voltage drop of the Discharge Diode. When the BMS detects that it charges with a higher current, it protects the discharging diodes from overheating by switching on "Discharging". Just repeat the test and enable "Discharging" at all times, and you will see that the voltage drop disappears.
Vollkommen normal. Da Netzteil und Akku nicht miteinander verbunden sind, wenn im BMS Charge und discharge Off sind, siehst du einmal die Batterie Spannung 55,63v und die Netzteilspannung 56v. Und da du mit dem Multimeter dazwischen misst, misst du nunmal die Differenz. Technisch absolut richtig 👍🏻 Ersetze BMS durch einfachen Ausschalter und du hast das gleiche Verhalten.
This is an interesting experiment, as is everything that Andy does. It is certain that there are differences in fine detail on the designs. This 0.4V drop is that of a diode across a MOSFET, some internal current draw. PD and EMF come into the equation here as well. The point when the MOSFET(s) conduct is clear. In practise the unit is working, it is interesting though to see the differences between products in such fine detail. I am sure the unit is not faulty though. Whether Andy can use these in his particular installation with 2 banks of batteries and different BMS and charge controllers will be determined by further experiments. Great U-Tube educational channel, you don't get this stuff on the BBC do we?
@@marcosmercado5648 I recall the instructions calling for external BMS power source under some conditions suh as a lower voltage pack. May be going external in this config would resolve this.
Never seen one with voltage calibration? Which one has that? It would not make sense to offset the voltage in the SCC. The voltage drop to the battery is dependent of your cables and amps.
@@OffGridGarageAustralia My midnite classic has voltage calibration for both battery and the pv. My old Plasmatronics had separate battery voltage sense cables.
Not a problem. It is normal When you have discharge turned off one of the back to back MOSFET's is turned off to prevent discharging. Charging is on which keeps one of the back to back MOSFET's on. The body diode of the turned off MOSFET will give you the voltage drop. When both back to back MOSFET's are on you get little voltage drop across BMS. This is the normal operation. Only when there is undervoltage cutout would the situation you manually invoked will occur. This only allows a lower charge rate because of the heat created by the body diode drop. This is only during LV cutoff and will allow full charge current again when cell voltage rises above reset LV cutout in normal operation and both back to back MOSFET's turn back on. There is not a problem only that they gave you the control to go and manually shut off discharge. This is not a normal manual control on most BMS's. They also gave you manual ability to turn both charge and discharge off so there will be voltage drop across BMS of any amount. This state would normally only occur in normal operation if an over temperature and maybe overcurrent cutoff occurs. Overcurrent discharge cutoff may keep charging ability. Overcurrent charge may shut off both directions. They have an extra single MOSFET with a power resistor in series at end of MOSFET string on PCB. This may be the low voltage cutoff charging path or path to avoid startup surge current.
If you have no current flowing then you have no voltage drop - but you do have a voltage difference between voltage sources. You have the power supply + connected to the battery +. You have isolated the battery supply (-) from the power supply (-) by turning off the mosfets in your bms. If you disconnect the wire from the power supply (-) and read the voltage across P- and B- of your BMS I bet it says 0.00, zilch, nada. Keeping the wire diconnected and reading from battery (-) to power supply (-) you will probably still see your voltage difference.
I have a B2A8S20P with self power consumption 65Ma@12,25v 0,8w with all disconnect and functions disabled, JK false advertised as having standby function. Only on off available for bms. I don't want discharge my battery. This is a big problem!
Looks like the extra voltage required to turn on the bms has some strange sort of correlation with this behaviour where volts drops are happening... Or is a sideeffect of the capacitor used in the balance function...? Probably over thinking, is just faulty... 🤔
The Voltage drop can't be caused by the FETs as they have incredibly low series resistance when on. For some reason the BMS is not turning on the FETs. My guess is that the BMS will isolate the batteries until it is sure that the supply is high enough to begin charging, because it can't measure current until significant current is actually flowing. So instead it measures Voltage, then switches on the FETs when the current is sufficient to measure. Another possibility is that to save energy, it is in "sleep mode" until there is significant forward or reverse voltage difference. A simpler explanation is that you have charging switched off.
His discharge MOSFETs are turned off - that's why (later part in the video, charging is on, discharging off). The BMS turns these on (even if you have it turned off in the app) once enough charge current flows. The closed discharge MOSFETs act as a diode (parasitic diode in a MOSFET) and causes the voltage drop. It will still prevent the battery from discharging once the current drops as per the settings. If he had enabled discharging in the app, he wouldn't have seen this. The BMS is operating normally.
Hi, I need help! I bought a small sailing boat with JK BMS installed. The previous owner changed the password. I need to reset it, but after several attemps asking the manufacturer (they do not repond) I looked on thew internet and found you. Can you help me out? That would be very nice if you can, thanks in advance Portcall
Also bei meinem Dali bms ist kein Spannungsfall mes bar und ich verstehe deine Probleme mit dem Dali bms ich muss aber sagen ich bin zufrieden damit und finde auch mosfets bms besser da die kontakte nicht zusammen geschweißt werden können
This might be a silly question but I'm unable to find a contract number for victron I am unable to login to my victron VRM account and I have not been able to access my account for almost a year now were can I find a number to talk with someone from victron that maybe able to assist me in gaining access to my account again also the reason I can't login is I recive an sms when I log in and well that sim card got damaged hope you may be able to help
I have done the rest password multiple times but I can't do it as the mobile number I will receive I code to allow me to reset my password because I enabled second step verification and yeah since I lost the ability to receive text messages codes I even created a new account but I'm not able to link any of my gear because it's already linked to my account I can't access but I'll try to call the number in the Netherlands again I'm sure there is a way
this is normal it's the body diode of the mossfet , when the body diode reverse voltage trip 0.6v a circuit trigger the mosfet to bypass the body diode in order to not dissipate power inside the diode
The difference between the relay BMS and the MOSFET BMS is that you have a sense wire on the BMS side of the relay which is effectively your battery voltage. You do not have this sense wire with the JK BMS. What you have described is ohms law. Infinite resistance (MOSFET or relay off because BMS charge is off) means no current and the potential difference (voltage) is the voltage difference between the battery and the charger voltage. Exactly what you see and what is EXPECTED.
I think what you are measuring without current flowing is the difference between the battery and the supply.... the voltage would still be there even without the BMS inline.... starting the charging on the BMS and measuring the drop across the BMS, shows what the drop on the MOSFETS really is.... and it really is 3-4mV... Think about this: you have a light and a light switch in series, powered by the grid voltage. with the switch ON, you measure 230V across the light bulb and zero volts across the switch.... With the switch OFF, you measure 230V across the switch, and zero across the lightbulb....
But still a strange behaviour of the BMS turning on so late, and building half a volt across.... Curious, I wonder if that is intentional or a mistake on their behalf...
@@andreyrules4ever It's Andy's mistake: he has discharge disabled. He's measuring the voltage drop over the internal (parasitic) diode of the discharge mosfets at low current. At higher current, the BMS activates the discharge mosfets (even if you have this disabled) to get rid of this drop.
You are measuring a voltage difference of .4V across your BMS, but the supply/charge current is 0A. That is odd. It makes me think the BMS is possibly getting current from the batt or from it's supercap/s. One way to answer that question is to measure the current between the batt & the BMS & also between the supply/charger to the BMS to see if current is moving from either potential energy source to the BMS. If you see no current flowing from either direction to the BMS, then the BMS is supplying the current or the output circuitry of the BMS is leaking a bit of energy some how... So your BMS cuts-off in batt bulk charging mode .4 V lower than your supply/charger V. Why is that a big deal? If you want it to reach cut-off at the same V as your supply/charger V, then raise the BMS cut-off to .4 V higher than it is currently set. Won't that work? I'd consider that 'problem' as a safety feature if I was you.
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Hello Andy, thank you for everything you're doing for everyone on your channel. I'd gladly buy you a beer, especially since I also lived in Queensland, Australia, 10 years ago and know exactly what summer, thirst, and 40 degrees outside mean😊.
Keep it up, I always follow you!
P.S. I just bought the J.K. BMS, can't wait to receive it!
Thank you very much!
Thank you very much for your support!
11:05 When everything is OFF, you are practically measuring the voltage difference of two power supplies that have a common positive pole.
The charger has 56.00 V and the battery open-circuit voltage is 55.60 V.
And later on, the discharge is off which means you have a voltage drop over the discharge mosfets's parasitic diode. Enabling discharge eliminates this problem. The BMS does this automatically at higher currents, even if you disable discharge - however in this case the BMS will still prevent the battery from discharging once the charge current drops again.
But it is impossible to be off when he is trying to charge with 100ma, 1a, 2a, ... until 5a
@@diydsolar Charging was on, discharging was off. At low currents, the discharge mosfets are just parasitic diodes. As soon as the current increases, the BMS enables the discharge mosfets, and now the drop is gone and charging continues as usual. If he had discharge enabled from the beginning, he would not see this.
@@upnorthandpersonal thanks I understand you. You are right. Only one question.... May be you have disabled discharge for any reason.... why does the bms has to enalbed it ? May be risky in same cases ?
Does daly do the the same ?
@@diydsolar It doesn't - it only does this when the charge current grows, which means there is current not used for the load and the battery would not be discharged in any case. Once the current drops, the settings take effect and prevent any current from going out of the battery. In other words: the setting means: 'don't discharge the battery', which is doesn't.
15:05 the large voltage difference across the BMS FETs has nothing to do with how much current the BMS is passing. You DISCONNECTED the battery from the power source by turning off charge and discharge, so the battery and source voltage are now independent just like they would when the contactor is open on the Q BMS. No current (open switch) = "large" difference, high current (closed/connected switch) = low voltage difference. Same as measuring voltage across a a ceiling light switch: light is on, 0V across the switch, light is off, full AC mains voltage across the open switch.
It may not be as you would like it to be but it isn't defective. With a FET-based BMS, you can set your PPT to 58.2V fixed max voltage and let the BMS disconnect charging whenever necessary.
Andy, Since the charge and discharge are disabled, the BMS is basically an open switch. the 350mV you are measuring is the difference between the charger and the battery.
This was hard to watch, I was like ITS OPEN ANDY!
Actually, the real issue later on in the video when he has charging enabled is that he has discharging disabled. This means he's measuring the drop over the parasitic diode in the discharge mosfets. All he needs to do is enable discharge...
15:36 I can see discharge is OFF on your phone. The missing 0.4 V is the drop across the parasitic body diode of the DISCHARGE MOSFET being turned OFF.
PLEASE repeat the test at 16:00 with the Discharge ENABLED.
Exactly.
@@upnorthandpersonal No, it's two completely separate power sources with a shared ground. He's measuring a battery and measuring a power supply that are completely disconnected from each other and getting obviously differing results
@@MrHantu666 No, they are not sharing a ground reference. The battery and BMS ground reference is the B- wire. The power supply ground reference is the P- wire. Between B- and P- are two MOSFETs connected back to back in series, but with opposing polarity. One MOSFET permits current inflow while on and turns into a reverse biased blocking diode while off and still trying to charge. The other MOSFET permits current outflow while on and likewise turns into a diode while off, however since it is connected in reverse polarity of and in series with the charging MOSFET, this diode is in forward conduction while the discharge MOSFET is off and you still force current into the battery. The only time B- and P- are the same ground reference is when both the charge and discharge MOSFETs are both on simultaneously. The BMS automatically turns on the discharge MOSFET during charging (despite being off in the App) when it detects sufficient charge current to avoid overheating the body diode in this discharge MOSFET.
@@MrHantu666 Later in the video he has charge enabled, closing the switch - he still measures the gap. It's when he's slowly increasing the voltage on the charger, sees low currents and a big drop until it suddenly changes. That's the point where the BMS opens the discharge mosfets. The drop before that happens is the diode voltage drop of the closed discharge mosfets.
I am glad I wasn't the only one to see this.
It's not a special feature, on all mosfet bms there is 2 mosfet Nch in serial configuration, one for charging one for discharging.
When you don't activate discharge mode and at very low current charging, mosfet discharging is off (voltage drop is 0.5V) but when charging current is consistent bms activate mosfet discharging to remove this 0.5V body diode drop, even discharge mode is off.
There is absolutely no problem at all.
Thank you - at least someone else who got this :)
Very much this.
Andy, Andy you only have to turn on the discharge switch and your problems ar solved 👍🏻
I know now. It's been discussed in the community section of the channel already BEFORE you made this post 😁
I have a *similar* behavior on my Overkill/JBD BMS, and like I have seen a few others mention, it depends on the charge/discharge switches in the BMS app. I have a shunt connected on the negative side, downstream of the BMS, and when I turn the charging off through the BMS, the voltage reported by the shunt is about half a volt lower than the voltage reported by the BMS. If I turn the charging back on in the BMS then the shunt sees full voltage again (even with no charge voltage applied).
Yeah, usually, charge and discharge are both turned on and they get disabled if the BMS if voltage goes too high or low. My discharge was turned off manually. It's in the next video.
Andy get the new 500A version of the QUCC BMS they have their new version with 2 contactors. One for Charge & one for discharging. The reason I say this is because at some stage you will want to parallel your battery banks. With a MOSFET based BMS you cannot parallel at all. So you have a pending problem with your JK BMS in the future already. Please go ahead & run the experiment yourself. The behaviour of the parallel BMS will scare the living day lights out of you. The QUCC guys are really onto something good with their contactor approach! Great Video thank you again...
Why can't you parallel banks with a MOSFET BMS? I say this because I have 3 banks in parallel running my house and they have been in parallel for over a year without an issue. Not really sure what issus you are having where you can't parallel multiple MOSFET based BMSs.
Thanks Andy
Andy, you are measuring the difference between two power supplies because the MOSFETs are not conducting, that is why when you rise the power supply voltage the voltage difference rises
Yes, that is correct. We discussed this in the community section and it is in the new video 😊
Andy... Your charge setting in the BMS is off, the FETs in the BMS is in high resistance mode, the loss you think you have is no loss, it's just a difference between your power supply and the battery state because the FETs are not conducting.
Understanding Ohm's Law is essential when you make videos like these haha
@@TheGalifrey don't want to uhm rain on you parade here but this has nothing to do with ohm's law. Since there is no current to induce a voltage in a resistance, ohm's law doesn't apply. This is just a matter of two voltage sources sharing a common and measuring the other side
@@alexschulein7002 as in an idle voltage divider. Still doesn't seem to explain the quiescent voltage state. Curious.
@@babaluto It's just the drop over the parasitic internal diode of the discharge mosfet - he has discharge disabled in his settings. Enabling discharge eliminates this problem. The BMS does this automatically at higher currents, even if you disable discharge - however in this case the BMS will still prevent the battery from discharging once the charge current drops again.
@@upnorthandpersonal yes this seems very logical, i have no experience with this BMS or any BMS but I do have a good understanding of electronics.
I wonder if Andy would be so kind to repeat the measurements with discharge and charge ON in the BMS to confirm
This video is very interesting and informative. Can you please clarify how the charger is disconnected from the battery pack without the load being disconnected. I have a Chargery BMS16 that has a connection to a relay that disconnects the charging if cell differences are above settings or an individual cell is above maximum. This doesn't affect the load.
The JK-BMS (like many others) use MOSFET transistors to control the charging and discharging separately. One side can be turned of but it still lets the current flow in the other direction.
How did you solve it?
how do you manage BMS - battery - remote monitoring with Victron energy app -? Thx
All Victron gear natively shows in the VRM. To connect the BMS as well, we need to modify a few things. It will come later on this channel once the battery is in place and working.
Andy, perhaps is needs a trickle to charge a capacitor ready for the balancing stage so it depends at what stage some of the other parameters are at.
on the dally BMS both mosfets are tuned on ( charge and discharge ) so their body diode are bypassed by the mosfets hence the low drop voltage of few mV across the BMS P- and B-
As we discussed in the community post two days ago... I know now 😊
@@OffGridGarageAustralia thanks ! Did not see the community post before the video so I m late on the topic 😋
C an you put different ah together like 100 ah with 215 or 275???
In parallel, yes.
@andy Why is this a problem? You have a Victron smartshunt that measures accurately at the battery and sends that to your Victron smartsolar. So your smartsolar allways uses the proper battery voltage and doesn’t use the voltage it measures itself. So No problemo then. That is what makes Victron great stuff to work with.
Because the plan is to use more than one 16s pack, each having its own bms and then they will be paralleled after the bms, at least this is my understanding of the new plan Andy has. The victron will only use the voltage reading from one place, so the victron gear wont help with Andys new setup. If the plan was to combine this bms with a Victron shunt or smart battery sense on a single pack, sure it would not be an issue.
@@lexicase8805 hmmm… 2x16s would balance out so measuring on one bank should still work fine. After all, if one bank has a lower voltage it will get the grant of the charge would it not?
Try to change over voltage protection for battery bank in BMS to +0,4V and check if it will allow to charge on top.
I am confused. If you opened all of the connections in the BMS then are the battery and the charger two isolated systems? Why would you expect their potential to remain the same if they are isolated. The battery will begin its journey towards 53.7, while the supply will be fixed by its AC side. What am I missing?
It's in the next video.
@Andy - just an early in the morning theory: the BMS itself has a consumption for it's internal controler and BT. As soon charging happens it takes it's power from the "charging line" but not before - maybe this has something todo with the observed behaviour?
This comes all from the battery though and not from the charger. And, it is very little >10mA.
Heya, oke that good be a rabbit hole to solve this because it is working🙃
Discharge should be on to open the BMS discharge mosFETs!
Where does the Bluetooth module take his power from? from the charger when charging, from the battery when not charching?
It's been powered from the battery. Otherwise it would stop when no charger is connected.
Andy Andy Andy... :) At 9:37 you said "If they are turned on, if they are conducting there should be almost no voltage drop at all"
Right... but you just showed us that you had them turned off. :D
Yes I know I'm probably really late to the party. Still catching up.
Keep watching 😊
It's probably not defective, it's probably just a bad design. 0.4v sounds like the voltage drop of a diode, BTW power mosfets have diodes built-in between the source and drain. This might be what you're seeing.
Thanks, yeah something like this. I show it in the second video from this morning.
I think it's good that someone looks at the minutiae of these things and questions every tiny little detail. For me, I am really more interested in the practical application (usage) of the batteries, charge controllers, inverters and solar panels. I don't worry about 1/3 of a volt over a 16S pack, when it is at rest. In practical use, the pack will typically be charging and/or discharging most of the time, so this "deviation" will be negligible, if it exists at all. It seems like it went away when the pack was charging, so is this a deep dive into something of little consequence? I don't know for sure, but it seems that way to me.
Agreed.. if you see the cell voltage is at 3.55-+. that perfectly good for any setup practically. we not sending rocket ship to venus here till we need to make sure the battery full at exact 3.65V at all time.
Mean here practically if this is genuinely how the BMS behaviour,, no issue at all.
0.6V could the the border you don't want to cross though.
Sehr interessante Videoreihe (Kanal ist direkt abonniert). Vielen Dank dafür. Weiter so! 🙂
Danke Dir, Waldi!
turn on both charge and discharge function in the bms, and check the voltage again.
Yep, as discussed in the community section of my channel 😊
enable both mosfets ( charge and discharge toggle switchs) you will not have the 0,6v delta on charge with low current
When you have charging or discharging disabled it turns off one side of back to back MOSFET's. The other allowed current direction has a MOSFET body diode voltage drop from the turned off MOSFET. That gives you the 0.6v drop across BMS.
To make things more complicated, if current gets above 3-6 amps on the non-disabled path, the BMS will override the disable setting and turn both back to back MOSFET's back on. This is to avoid too much heating of MOSFET's due to the higher current and extra MOSFET body diode voltage drop. Current will be monitored by BMS current shunt (level and direction of current flow) and restore the disable setting when the allowed pass current drops back down to low levels.
You should not use the disable function for anything but supervised testing.
One problem BMS does have is with cell overvoltage charge disable, coupled with a sporadic higher discharge currents from inverter is the charge disable override to handle the sporadic moderate discharge current. Because the MOSFET turn on and tun off time is slow in BMS, there will be a short 'squirt' of charging when inverter load drops off and the BMS goes back to disabling the MOSFET that blocks charge current. There is some delay in re-disabling charging that allow a short 'squirt' of charging current to leak through to battery for a fraction of second. If inverter load is bouncing up and down causing BMS override of charging disable to turn off and on it can end up overvoltaging a cell beyond the overvoltage cell cutoff voltage. Nothing you can do to stop it other than control the inverter discharge current from happening or disconnect any charging source.
o
Thanks for sharing and explanation!
Hi, one question. Do you think you can connect this JK BMS to the Victron GX device via CANBUS?
Yes, way too many people "balance" by placing cells in parallel. You have both sets of FETs turned off, pretty normal. The 2 amp trigger is pretty standard. If you let the Daly go to sleep, it will exhibit the same behavior.
Thanks John. I'll test the Daly again and play around with the charge/discharge option.
@@OffGridGarageAustralia Trust me, the Daly is not worth the effort. It will work fine, but the quality and reliability are missing ingredients.
@@john_in_phoenix I can see this already since my first year.
Ive learned a lot from you. My packs i charge to max 3.55 and cut off at 2.5 . Hardly need a bms . Never get run away cells . I think the internal circuit is using some power maybe? Try disconnect the +ve and see what happens.
it is normal behavior , you have turned off charge and discharge mosfets so the battery is disconnected from the power supply, you set your power supply higher than the battery , hence the voltage difference
Daly bms behaves the same if you turn off discharge switch and charge switch then turn charge switch back on and try to charge.
The bms have a capacitor (or something that behaves like one) between BMS and P- conductor.
I'll try that with my Daly.
Hi....How can I synchronize the JK bms so that it gives the correct reading of the SOC? I was making some parameter changes and when I clicked "ok" I changed the SOC to a lower one (100% to 76%), the battery was already at 100% (54.4V). .I need help
B+ B- BMS standby power with Bluetooth or not?
It's the battery voltage and the power supply voltage, they are separate but with common ground. Turn the power supply knob and you'll see!
I mean they are turned off so no longer connected together apart from the ground.
Is the the P-N junction forward bias?
Yes, something like this... It's in the next video on my channel.
Just curious, why do you set your clocks to 24 hour time? I am retired US military and do the same thing out of habit.
Because I'm from Europe where this is the norm. Easier for me to read and understand
The voltage drop measured is the difference of potential between the two power sources and is what you would expect to see when the mosfets are turned off. In at least one of your demonstrations, it appears that you have manually disabled the mosfets. If the mosfets are turning off automatically when idling, then that is the problem. Look in the app to see if there's a setting to disable that behavior.
Doesn't the battery sense tell the charge controllers the correct voltage and they can compensate?
good morning Andy, I also wanted to try out the JK bms but... The device seems well made but mine....does not seem to be reliable.
2 weeks ago I received the B2A20S20P model so without instructions I installed the app Ver. 4.21.0 on V11.XA hardware Version
Now, I notice that I cannot edit Calibration current as you do in the videos and when I activate the Balance from the control panel
in the settings screen it is disabled as well as the Discharge. ..In my opinion this Ver. is still full of bugs
But the worst thing is when I have a load like a simple heat gun on the Bms I have -40A😳 , confirmed with ammeter.
Yesterday a water pump (2HP) started and the ATS (100A) burned out probably due to too many amps.
What to do in these cases, does it depend on the software, the settings or BMS to be thrown away?
Ask for a HEELP to the whole team. thanks
Ask JK how much energy the Bluetooth is pulling to stay on?
Irgendwie erinnert mich das ganze an die float Funktion von den Laderegler, wenn der Strom unter 1,5A fällt, wird die Spannung vermindert, könnte also vielleicht ein Feature sein
Aber ein BMS hat doch keine Float Funktion...
@@OffGridGarageAustralia ein BMS ist dafür da, Akkus zu managen, wo auch der Schutz und die Erhaltung zu gehört, warum sollte ein BMS sowas also nicht haben?
You say no current is flowing? But what powers the BMS BlueTooth?
That's been powered by the battery supply for the BMS.
I have always wanted to do this well done to you Andy.
I too can confirm the DALYBMS has very minimal voltage deviation.
Voltage readings from the BMS compared to the battery monitoring system are identical.
I agree with you and would say it would be a faulty BMS.
No, he's got discharging disabled and is measuring the parasitic diode voltage drop from disabled mosfets. It's absolutely normal behavior - all e needs to do is enable discharge.
I wonder is you are measuring the gate bias voltage. Try measuring under load that is what matters
It could also be a design feature. If the current is under a certain amount it may use a different current sense resistor for higher accuracy.
@@jasondevine6014 He's just measuring the voltage drop over the parasitic diode of the discharge MOSFETS. He disabled discharge in the app, which means these MOSFETs aren't active until a certain current flows (the BMS has to prevent the battery from providing any current as per this setting, but will enable these discharge MOSFETS once enough charge current is flowing). If he enabled discharge in the app, the 'problem' would be gone...
I would call it defective at this point, but offhand I can't imagine why you are getting a such a high forward voltage drop across the MOSFETs in the charge direction. Do you also see a similar drop going the other way under load?
If you have an scope you might check for a frequency in that voltage drop that might indicate the MOSFETs are being switched on and off rapidly, suggesting some issue with the MOSFET trigger voltage supply.
He gets the voltage drop from the discharge MOSFETs, which he has turned off in the app. Charge and discharge MOSFETs are in the same circuit. When discharge is disabled, these MOSFETs act as a diode (parasitic diode in the MOSFET). Once the charge current rises, the BMS enables the discharge MOSFETS as well. That's what he's seeing when he increases the voltage to see that 1.5A current. The discharge function still works as expected: the battery will not be discharged since as soon as the charge current drops again, the discharge MOSFETs are off again as per the settings.
@@upnorthandpersonal Seems a plausible explanation. I did not notice such a setting did you?
@@jackoneil3933 yes, at 10:43 in the video. I have the same BMS as well.
@@jackoneil3933 Also, at 15:33 and 17:15 you can see that the discharge is off. This is when he has the 0.4V drop and no current flowing. Then, he increases the voltage and you can see when current starts flowing, discharge is on - e.g. at 14:05. This is where the BMS enabled the discharge.
You have charging off... Your just comparing battery to charger voltage because they are still both tied at one end.
The voltage drop is lower when you switch on the Mosfets, try to Switch on the Mosfets and measure the voltage, it should fit. When the BMS switches off, there is No battery the Charge controller could charge. I think the BMS is acting normal
Servus Andi, @~11:00 I think, it's not strange at all, it's totally normal to see a voltage diff when all switches are open, you have both, charge and discharge, switched off at this point. The battery sits at a lower voltage than your power supply - and due to the open switches you see the voltage diff... And the increasing amps after you switched on the charging below the 1.5amps might be some kind of a soft-start, what do you think?
Totally right. Battery and supply are disconnected so they can have every voltage they want, when charge and discharge are disabled. But in the end you had it enabled. So this behavior seems not normal.
@@philippk.5242 It is. He has discharge disabled. What he sees is the voltage drop over the internal Mosfet diode of the discharge Mosfets. At higher currents, the BMS will enable these discharge Mosfets to get rid of this drop (even when discharge is disabled). He should just keep discharge enabled as well. Remember, a BMS is a last line of defense, not a general switch for charger/load. The BMS does exactly what it is supposed to.
@@upnorthandpersonal 🤔
@@upnorthandpersonal at this sequence charge and discharge are off. So both voltages are more or less independent, no current flowing. Later in the video he had charge enabled.
@@philippk.5242 Yes, that's what I'm saying: later in the video he had charge enabled, not discharge.
Villeich ne Dioden Durchbruch Spannung/Strom?
Does the voltage drop matter in reality? What I mean is that if you run your solar setup with the JK BMS would this be a problem?
Oh, yes it matter! 0.6V is a lot!
Ran into that before on many bms's and though bms was bad,however just do a quick discharge at high current and voila you will be at full voltage just PFM -normal
It's in the next video 😊
I guess you wouldn’t like my 6kw growatt inverter-charger it says the voltage is 1.1 volts higher than the battery!! I called about it and they said it’s fine the way it is. I guess on a positive note I can never over charge cause max charge voltage is 58.4😂.but my BMS doesn’t act like yours. Max difference through the BMS in or out is .03 at 50 amps either direction. I didn’t check at 100 amps though.
Thanks for your thoughts
When the mosfets turn on, their resistance goes to only a few miliohms, allowing current to flow, and the voltage measures correctly. When the mosfets are off, the resistance across them goes up, which inhibits current flow, and makes a voltage drop.
But why are they becoming conductive all of the sudden when increasing the voltage?
It was confusing to start with as you showed both charge and discharge switches off and so I was screaming at the video ‘what d you expect ffs?’ However watching further it seems you had actually turned on the charge one. I think the problem was that you had the discharge one turned off. This would not be a normal configuration and I suspect that things may well work if the discharge switch is switched on. In a situation of low voltage disconnect this will not be a problem for charging as charge voltage will be at least 0.6v above low voltage disconnect and so it will turn on and then, once the battery has reached low voltage reconnect, the discharge will be turned on and all will roses in the garden again.
Hahaha, it's good my videos are causing reactions 😁
Yeah, the disabled discharge was the problem as I show in the next video.
So the .4V is the switch or forward voltage for the mosfet to latch? Does the qucc bms use bjt transistors? If so they are not reliant on a voltage to latch on as they use current and mosfet uses voltage to latch, seems like a design flaw¿?
FEts don't "latch". It depends if the controller is switching then on or not.
@@graemezimmer604 agreed, sorry wrong word, hard switch is prob more accurate 👍
were you able to fix or solve this problem?
Yes, it was in the next video after that.
sounds like a diode problem, a voltage drop of that size is normal when a diode is in series with voltage
Yeah, something like this. But why does it 'break' once we increase the voltage and it conducts then? Next video 😁
Keep up the excellent work Andy love your videos
Thank you.
What you're seeing is your discharge MOSFET (parasitic) diode voltage drop since you have discharging disabled.
Yes, I know now. Thank you. Has been discussed in the community section already. I made a second video showing and explaining it 😊
Thanks Andy I love it when you poke your stick in the hornets nest, it gives me hours of entertainment!
Hahaha, and me more grey hair 😁
Look like the drop across the meter !
Disconnect just the BMS & see what 's on the DVM .
Andy you are testing two different power sources that are not connected together.
For instance. You have a 16s battery that is at 48v and another 16s battery that is at 53v and they are connected but by the positive cable only and delete the thought of BMS. Now do the same test. You will have a delta of 5volts.
Your .3v - .6 volt is the delta between
The power supply and the BMS are surely connected to the same battery.
when you measure 0.3 to 0.6v.. that look batteries charged BMS in floating mode and when the BMS wake up, the charging mode is working fine.. or.. in your BMS settings, have you set a minimum working current around 1.5amp?
Andy, the battery is 55.6 and the charger is set at 56 volts with charging off, the positive of the charger is still connected so there is a 0.4v potential difference, with the charger running there will be no voltage drop, disconnect everything and measure resistance across the BMS it will read 0 which is no voltage drop. The voltage drop is non existent other than in your head due to a misunderstanding of potential difference. The only PD you're reading is the difference between the charger and the actual battery pack. If the PD was 0 then no current would flow. Voltage pushes current!
Just enable "Discharging". What you see is the voltage drop of the Discharge Diode. When the BMS detects that it charges with a higher current, it protects the discharging diodes from overheating by switching on "Discharging".
Just repeat the test and enable "Discharging" at all times, and you will see that the voltage drop disappears.
Vollkommen normal. Da Netzteil und Akku nicht miteinander verbunden sind, wenn im BMS Charge und discharge Off sind, siehst du einmal die Batterie Spannung 55,63v und die Netzteilspannung 56v. Und da du mit dem Multimeter dazwischen misst, misst du nunmal die Differenz. Technisch absolut richtig 👍🏻
Ersetze BMS durch einfachen Ausschalter und du hast das gleiche Verhalten.
Gut erklärt, genau so ist es.
This is an interesting experiment, as is everything that Andy does. It is certain that there are differences in fine detail on the designs. This 0.4V drop is that of a diode across a MOSFET, some internal current draw. PD and EMF come into the equation here as well. The point when the MOSFET(s) conduct is clear. In practise the unit is working, it is interesting though to see the differences between products in such fine detail. I am sure the unit is not faulty though. Whether Andy can use these in his particular installation with 2 banks of batteries and different BMS and charge controllers will be determined by further experiments. Great U-Tube educational channel, you don't get this stuff on the BBC do we?
Thanks Dave, all solved in the next video 😊
Since charge/discharge is both off you are measuring two different sources. Battery - Charger = your diff. Not strange at all.
What is the current on the 16 wire which supplies power to the bms?
Yes, yes, the S16 wire!!!??? This is the one who powers the BMS processor and Bluetooth, I guess?
@@marcosmercado5648 I recall the instructions calling for external BMS power source under some conditions suh as a lower voltage pack. May be going external in this config would resolve this.
Good solar charge controllers that don't use separate voltage sense cables should have voltage calibration.
Never seen one with voltage calibration? Which one has that?
It would not make sense to offset the voltage in the SCC. The voltage drop to the battery is dependent of your cables and amps.
@@OffGridGarageAustralia My midnite classic has voltage calibration for both battery and the pv. My old Plasmatronics had separate battery voltage sense cables.
@@JimmyLLL cool thanks for sharing. Never heard about such a feature in a SCC...
@@OffGridGarageAustralia No problem. The classic is an excellent charge controller. Been running my house entirely since 2012.
Not a problem. It is normal When you have discharge turned off one of the back to back MOSFET's is turned off to prevent discharging. Charging is on which keeps one of the back to back MOSFET's on.
The body diode of the turned off MOSFET will give you the voltage drop.
When both back to back MOSFET's are on you get little voltage drop across BMS. This is the normal operation. Only when there is undervoltage cutout would the situation you manually invoked will occur. This only allows a lower charge rate because of the heat created by the body diode drop. This is only during LV cutoff and will allow full charge current again when cell voltage rises above reset LV cutout in normal operation and both back to back MOSFET's turn back on.
There is not a problem only that they gave you the control to go and manually shut off discharge. This is not a normal manual control on most BMS's. They also gave you manual ability to turn both charge and discharge off so there will be voltage drop across BMS of any amount. This state would normally only occur in normal operation if an over temperature and maybe overcurrent cutoff occurs. Overcurrent discharge cutoff may keep charging ability. Overcurrent charge may shut off both directions.
They have an extra single MOSFET with a power resistor in series at end of MOSFET string on PCB. This may be the low voltage cutoff charging path or path to avoid startup surge current.
Plenty of comments that don't get this...
Thanks. I know this now. A MOSFET is not a relay right?!😊
up to 96S LFP and NMC BMS
If you have no current flowing then you have no voltage drop - but you do have a voltage difference between voltage sources. You have the power supply + connected to the battery +. You have isolated the battery supply (-) from the power supply (-) by turning off the mosfets in your bms. If you disconnect the wire from the power supply (-) and read the voltage across P- and B- of your BMS I bet it says 0.00, zilch, nada. Keeping the wire diconnected and reading from battery (-) to power supply (-) you will probably still see your voltage difference.
Exactly my thought.
Well that's just P•I•E in your face. Makes sense. Curious to see where this goes.
Is it the bodydiode of the mosfet?
Was the discharge off all the time?
@@1978jra yep - that's the issue.
I have a B2A8S20P with self power consumption 65Ma@12,25v 0,8w with all disconnect and functions disabled, JK false advertised as having standby function. Only on off available for bms. I don't want discharge my battery. This is a big problem!
That's 1.5Ah per day...
Did you contact JK about it?
My Daly BMS has the exact same thing
Looks like the extra voltage required to turn on the bms has some strange sort of correlation with this behaviour where volts drops are happening...
Or is a sideeffect of the capacitor used in the balance function...?
Probably over thinking, is just faulty...
🤔
If you check his other post he figured it out two days ago, but still posted this video as is.
Yes, the videos were already made so I share the information anyway for others to learn. Also watch the next video where I explain what happened.
The Voltage drop can't be caused by the FETs as they have incredibly low series resistance when on.
For some reason the BMS is not turning on the FETs.
My guess is that the BMS will isolate the batteries until it is sure that the supply is high enough to begin charging, because it can't measure current until significant current is actually flowing. So instead it measures Voltage, then switches on the FETs when the current is sufficient to measure.
Another possibility is that to save energy, it is in "sleep mode" until there is significant forward or reverse voltage difference.
A simpler explanation is that you have charging switched off.
His discharge MOSFETs are turned off - that's why (later part in the video, charging is on, discharging off). The BMS turns these on (even if you have it turned off in the app) once enough charge current flows. The closed discharge MOSFETs act as a diode (parasitic diode in a MOSFET) and causes the voltage drop. It will still prevent the battery from discharging once the current drops as per the settings. If he had enabled discharging in the app, he wouldn't have seen this. The BMS is operating normally.
You take comments down from people who actually know what there doing
Hi,
I need help! I bought a small sailing boat with JK BMS installed. The previous owner changed the password. I need to reset it, but after several attemps asking the manufacturer (they do not repond) I looked on thew internet and found you. Can you help me out?
That would be very nice if you can, thanks in advance Portcall
I have a jk only Balancer and it shows 0.4 v more than my BMS and if i measure manually same result (so jk) had to adapt to that !
Also bei meinem Dali bms ist kein Spannungsfall mes bar und ich verstehe deine Probleme mit dem Dali bms ich muss aber sagen ich bin zufrieden damit und finde auch mosfets bms besser da die kontakte nicht zusammen geschweißt werden können
Wer misst, misst mist 😉
But it's not 💩!
This might be a silly question but I'm unable to find a contract number for victron I am unable to login to my victron VRM account and I have not been able to access my account for almost a year now were can I find a number to talk with someone from victron that maybe able to assist me in gaining access to my account again also the reason I can't login is I recive an sms when I log in and well that sim card got damaged hope you may be able to help
I would reset the password here: vrm.victronenergy.com/login
Or I googled 'victron contact'
www.victronenergy.com/contact
I have done the rest password multiple times but I can't do it as the mobile number I will receive I code to allow me to reset my password because I enabled second step verification and yeah since I lost the ability to receive text messages codes I even created a new account but I'm not able to link any of my gear because it's already linked to my account I can't access but I'll try to call the number in the Netherlands again I'm sure there is a way
this is normal it's the body diode of the mossfet , when the body diode reverse voltage trip 0.6v a circuit trigger the mosfet to bypass the body diode in order to not dissipate power inside the diode
W JK BMS masz kondensator który pracując pobiera lub oddaje prąd :-))
Is the KY internally or externally powered in your config?
Nothing like internally powered KY, makes the wife happy!
@@pmacgowan HeHe, you got that, did ya?
you guys 🤦♂️😁
Your test on the Daly was not the same just to be fair. You did not have the the charge and discharge off on the Daly.
I didn't pay attention to this setting and will do the Daly test again.
@@OffGridGarageAustralia no reason to. The test will be that same as the jk
The difference between the relay BMS and the MOSFET BMS is that you have a sense wire on the BMS side of the relay which is effectively your battery voltage. You do not have this sense wire with the JK BMS. What you have described is ohms law. Infinite resistance (MOSFET or relay off because BMS charge is off) means no current and the potential difference (voltage) is the voltage difference between the battery and the charger voltage. Exactly what you see and what is EXPECTED.
My 'FET based BMS doesn't do that ....
Yes 👍 🔌 🔋 ⚡ 💡
The BMS is not perfect, but it does have active balancing!
I think what you are measuring without current flowing is the difference between the battery and the supply.... the voltage would still be there even without the BMS inline.... starting the charging on the BMS and measuring the drop across the BMS, shows what the drop on the MOSFETS really is.... and it really is 3-4mV...
Think about this: you have a light and a light switch in series, powered by the grid voltage. with the switch ON, you measure 230V across the light bulb and zero volts across the switch.... With the switch OFF, you measure 230V across the switch, and zero across the lightbulb....
But still a strange behaviour of the BMS turning on so late, and building half a volt across.... Curious, I wonder if that is intentional or a mistake on their behalf...
@@andreyrules4ever It's Andy's mistake: he has discharge disabled. He's measuring the voltage drop over the internal (parasitic) diode of the discharge mosfets at low current. At higher current, the BMS activates the discharge mosfets (even if you have this disabled) to get rid of this drop.
@@upnorthandpersonal Exactly, it makes perfect sense.
You are measuring a voltage difference of .4V across your BMS, but the supply/charge current is 0A. That is odd. It makes me think the BMS is possibly getting current from the batt or from it's supercap/s. One way to answer that question is to measure the current between the batt & the BMS & also between the supply/charger to the BMS to see if current is moving from either potential energy source to the BMS. If you see no current flowing from either direction to the BMS, then the BMS is supplying the current or the output circuitry of the BMS is leaking a bit of energy some how...
So your BMS cuts-off in batt bulk charging mode .4 V lower than your supply/charger V. Why is that a big deal? If you want it to reach cut-off at the same V as your supply/charger V, then raise the BMS cut-off to .4 V higher than it is currently set. Won't that work? I'd consider that 'problem' as a safety feature if I was you.
It's been solved in the next video.