I would suggest an interval on timer for this type of water heating. Trigger that on timer with your voltage relay. In that way heating starts when battery reaches a set voltage, runs for say five minutes and then shuts off. Should voltage still be high, it will retrigger and run again. I am really against using a voltage relay to turn on and off. That can leave your battery with less power at the end of the day. I do advanced water heating right from array voltage taking only excess power be it 5W or 1000W 0r anything in between. Works in parallel with any charge controller and doesn't use any resources of CC, inverter or battery. No need to oversize your system just to get hot water. Higher heater voltages result in less wire loss. This is a very efficient system that electronically matches the heating element to the panels. Those with electronic skills check me out. This is simple circuitry that costs far less than the battery method. Batteries are left with the highest charg at the end of the day.
I have since ran a separate cable to the voltage controller and it is working very well. I normally turn the whole thing off about 4.00pm to ensure the batteries are full. I am not going to spend out on a different system at the moment, I have no funds to do that. If down the line I have problems and need to think again and have the money to do so I will keep this in mind
I have a 48V system which puts out no more than 80V. I'm in the US where our mains are 120V. My dump is one of those 1960s lamps with 3 adjustable cone-shaped lamp-holders. I put 3 100W incandescent light bulbs in them . They don't care whether they are fed AC or DC, and any voltage up to 120. In heating season, this heat is not wasted. In summer I know it is a dumb thing to be adding this heat to the house, and I should use some sort of outdoor fixture, or actually do something useful as you have done. My main goal was to protect my panels.
My MPPT controller does switch the panels off if the power is not being used, but wasting all the excess power I foresaw a use for the extra power at quite a small cost to add.
Hello I develop and test a lot of new ideas and possibilities with solar energy. I can tell you that you cannot take output power from the solar cell charger it only delivers the volt you have selected (set) if you have selected 14.5 volts for charging you cannot start heating the water with 14.5 volts, you get a current reduction with a higher load (example the battery takes 15ah water the heater takes 15ah total 30ah) the output voltage drops and the heating of the hot water is turned off to start again when the voltage rises again to 14.5 volts, this will always continue. To solve the problem, the power to heat the water must be taken directly from the solar cells (before the battery charger). You need a controller that measures the current from the solar cells and you can set it to the current you need both volts and ah, if the current is too low to provide both charging and heating of the water, this unit shuts off the power to heat the water and the solar cells only supply the charger with sufficient current both work, if only charging takes place, when the battery is fully charged the current will increase from the solar cells. and then the controller switches on so that you heat the water. Otherwise, I can say that two switches o is unnecessary. Feed the main switch with + o - from there to a relay that is controlled by the controller, when the controller says ok relay 1 switches to o leaving power to the thermostat which regulates relay 2 switches to the heater to the water if the temperature of the water is below the desired temp is turned off. You get a fully automatic machine that you can turn on and off with the main switch, double switches not necessary Sincerely larry
those cheapo ebay relay models are almost always terminated with wire made of copper coated aluminium (cca) rather than proper stranded copper. You can check by seeing if strands melt with a cigarette lighter
A nice project Trev. I would be inclined to get rid of the mains voltage switch that you have in line. The contacts in those can be oxidised even when new. Not so critical at 240 volts. Plus the mains fuse in there is another candidate for voltage drop, assuming it’s in line. As a quick calculation, 3metres of 6mm mains cable (which can be pushed to 45 amps very safely) run as feed and return, will give a voltage drop of half a volt. Your 30amp cable is possibly no more than 3mm, which would give a drop of a volt. So the closer your panel is to the bus bar the better for accurate control. Sounds like you’re on the right track anyway.
@@TrevsTravelsByNarrowboat You are more than welcome Trev . I can honestly say that you never cease to amaze me .. I have to take my hat off to you ..for have a go at anything that happens to come your way... Unfortunately I will never be able to operate a narrow boat again . To me my life on the canals has been the best years of my life. .. Even when things were getting me down I always stopped and thought to my self what could be possibly better than being able to get up and move to another location... To be perfectly honest if I had my life over again I would do exactly what I have done in the past.
Hiya Trev, a couple of points. I would always wire a separate input feed to the A30 direct from the busbar then the A30 has to read the same voltage as the MPPT etc. You can also verify that the A30 is displaying the correct voltage by measuring it at the input connections with a multimeter. Note: I've had a faulty A30 delivered. Are the cables feeding the immersion heater rated / large enough diameter to handle 16.6A (20A with headroom)? Thanks for the great video as usual.
I have actually added separate cabling now for the controller. The main cables are I do have 20 amp fuse on the bus bar. I used 30a in case I decide I can change the immersion to a 300w
Relays are switches that work for a desired action. The first one switches on when the voltage controller tells it to. Then that sends power to the second relay which operates if the water is below the designated target. When the temperature is reached it will switch the relay off. Other relays on the boat would have there own designated function.
He's using the onboard relay on the A30 module just to switch the larger relay. This adds a bit of complexity and I'm not sure I would have done it that way, but if you're risk-averse, it does mean you're guaranteed not to put a large load through the potentially rubbish quality relay on the A30 module.
I love to see people having a go, but unfortunately you've made a huge assumption about how 12v power systems work and what power is available at what voltage. Sadly your plan is fundamentally flawed and relying on the battery voltage (especially in the high 13s) simply can't work efficiently or effectively. Essentially, batteries can supply very little power at, say, 14v before the voltage drops to the nominal 12.8v. There are two ways of achieving your aim 'correctly'. The first is what you've done - switch manually. The second way is to use a shunt to measure battery SOC and then programmatically switch the immersion on or off (e.g. turn the immersion on when the battery is full and then off again when it's below 95%). This is absolutely doable, but it wouldn't come cheap. Can I also comment that you really shouldn't be using mains switches to switch high power 12v systems. Say your immersion is 200W. At 12v that's 16A. The fused spur switch will be rated to 13A. In addition, the fused spur is designed to switch AC and not DC. I really would recommend you replace the mains switch with a proper 12v switch. Finally, if it were me, I'd be putting several fuses on the board just to add a little protection. Sorry, I didn't come here to p!$$ all over your project. Honest.
I am not trying to draw 14 volts, only to turn the immersion on when the batteries read 14 volts. The immersion is 12v 200w I have a max of 720w of solar at 12v. I fixed the voltage controller by wiring it independently from the bus bar.
@@TrevsTravelsByNarrowboat Yes, I understand that you want to draw 200W at whatever voltage is available, but only when the voltage is above a specific value. My comments were based on this understanding. Glad you've found a solution that works for you.
@@opera5714 Not sure if you're being serious or not, but if you are, that's not a wise thing to do... A 12v 200W immersion heater has a resistance of 0.7 ohms. (R=12v/(200W/12v)). Run that at a higher voltage and (assuming the panel can provide it) you're going to be dumping ((v/0.7R)*v)W into the tank from the element. This, in itself may be OK (assuming you have a bulletproof temperature cut-off), but as the voltage goes up, the current goes up too and instead of running 17A through the element (200W/12v), you'll be running (v/0.7R)A. Again it may be OK if you're lucky and v is low, but the element life is going to be reduced (and drastically reduced if v is too high). Yes there is some tolerance in a 12v element, after all they could see up to 15v in normal day to day use and a good element will have been built to cope with that. Beyond 15v and it's getting more and more likely to fail sooner and sooner.
@@nabarnes I am dead serious and you missed that I operate from panel voltage because I don't want those high currents. And by the way, I have operated with 40V from two 12V panels in series and pulsed that into a 0.7 ohm heating element efficiently. I wouldn't recommend it, just wanted to see if it would work. I test my boards at 30A. Just try to find someone on YT who knows more about heating water from PV than I do. Maximum power to element can also be set. ruclips.net/video/-7O5WzFcBBE/видео.html
I would suggest an interval on timer for this type of water heating. Trigger that on timer with your voltage relay. In that way heating starts when battery reaches a set voltage, runs for say five minutes and then shuts off. Should voltage still be high, it will retrigger and run again. I am really against using a voltage relay to turn on and off. That can leave your battery with less power at the end of the day.
I do advanced water heating right from array voltage taking only excess power be it 5W or 1000W 0r anything in between. Works in parallel with any charge controller and doesn't use any resources of CC, inverter or battery. No need to oversize your system just to get hot water. Higher heater voltages result in less wire loss. This is a very efficient system that electronically matches the heating element to the panels. Those with electronic skills check me out. This is simple circuitry that costs far less than the battery method. Batteries are left with the highest charg at the end of the day.
I have since ran a separate cable to the voltage controller and it is working very well. I normally turn the whole thing off about 4.00pm to ensure the batteries are full. I am not going to spend out on a different system at the moment, I have no funds to do that. If down the line I have problems and need to think again and have the money to do so I will keep this in mind
Thanks Trev Im sure you will sort it, glad your DIYing saves money sometimes...thanks for sharing regards Doc
I have fixed it since recording. I ran a separate cable from the bus bar for the controller.
Well done.
thank you
The foot bone’s connected to the leg bone.
The leg bone’s connected to the knee bone.
The knee bone’s connected to the thigh bone.
I went a bit like that.
I have a 48V system which puts out no more than 80V. I'm in the US where our mains are 120V. My dump is one of those 1960s lamps with 3 adjustable cone-shaped lamp-holders. I put 3 100W incandescent light bulbs in them . They don't care whether they are fed AC or DC, and any voltage up to 120. In heating season, this heat is not wasted. In summer I know it is a dumb thing to be adding this heat to the house, and I should use some sort of outdoor fixture, or actually do something useful as you have done. My main goal was to protect my panels.
My MPPT controller does switch the panels off if the power is not being used, but wasting all the excess power I foresaw a use for the extra power at quite a small cost to add.
Hello
I develop and test a lot of new ideas and possibilities with solar energy.
I can tell you that you cannot take output power from the solar cell charger it only delivers the volt you have selected (set) if you have selected 14.5 volts for charging you cannot start heating the water with 14.5 volts, you get a current reduction with a higher load (example the battery takes 15ah water the heater takes 15ah total 30ah) the output voltage drops and the heating of the hot water is turned off to start again when the voltage rises again to 14.5 volts, this will always continue.
To solve the problem, the power to heat the water must be taken directly from the solar cells (before the battery charger).
You need a controller that measures the current from the solar cells and you can set it to the current you need both volts and ah, if the current is too low to provide both charging and heating of the water, this unit shuts off the power to heat the water and the solar cells only supply the charger with sufficient current both work, if only charging takes place, when the battery is fully charged the current will increase from the solar cells. and then the controller switches on so that you heat the water.
Otherwise, I can say that two switches o is unnecessary.
Feed the main switch with + o - from there to a relay that is controlled by the controller, when the controller says ok relay 1 switches to o leaving power to the thermostat which regulates relay 2 switches to the heater to the water if the temperature of the water is below the desired temp is turned off.
You get a fully automatic machine that you can turn on and off with the main switch, double switches not necessary
Sincerely
larry
I have now wired the voltage controller separately and it is now working.
Those voltage dependants switches are no good for lifepo4 batteries as the voltage stays the same until the batteries are almost flat
I have lead acid batteries. I have actually fixed it now by running a separate cable to the voltage controller
Pretty smart - If that switch fused sour is switching 12V id chage it for a 12V switch.
I modified the inside to take a 12V 25A fuse.
@@TrevsTravelsByNarrowboat switch contacts aren't designed for switching DC loads
Very well done! I'm rubbish when it comes to electrics. 😒
I did do electrical engineering at college so I guess I should know a little bit
Enjoyed the diy project. Well done. Thinking maybe the differential is too close. Can you get around 12.5 v cutoff to work for you.
I have now wired the voltage controller separately from the bus bar.
voltage drop means you prob need larger conductors
I put in a separate feed, I have 30 amp cable for a draw of 16.6 amps max. 200w 12v
those cheapo ebay relay models are almost always terminated with wire made of copper coated aluminium (cca) rather than proper stranded copper. You can check by seeing if strands melt with a cigarette lighter
They are stranded copper wire. They were not cheap ones from eBay.
yeh - you need to measure your voltage at the source, also seeing a significant volt drop indicates your wires aren’t thick enough for the distance.
I have 30 amp cable and the immersion draws 16.6 amps. since recording I ran a separate cable for the controller from the bus bar.
A nice project Trev. I would be inclined to get rid of the mains voltage switch that you have in line. The contacts in those can be oxidised even when new. Not so critical at 240 volts. Plus the mains fuse in there is another candidate for voltage drop, assuming it’s in line. As a quick calculation, 3metres of 6mm mains cable (which can be pushed to 45 amps very safely) run as feed and return, will give a voltage drop of half a volt. Your 30amp cable is possibly no more than 3mm, which would give a drop of a volt. So the closer your panel is to the bus bar the better for accurate control. Sounds like you’re on the right track anyway.
You amaze me with your skills Trev! 👍
Jack of all trades. I also did electrical engineering at college
good vid on channel keep up the good vid on channel thanks lee
Thanks, will do!
Well done Trev another stunning video from you very interesting and informative as usual.
Anyway Trev keep yourself safe and well mate..
Thank you wayne
@@TrevsTravelsByNarrowboat
You are more than welcome Trev .
I can honestly say that you never cease to amaze me .. I have to take my hat off to you ..for have a go at anything that happens to come your way...
Unfortunately I will never be able to operate a narrow boat again .
To me my life on the canals has been the best years of my life. ..
Even when things were getting me down I always stopped and thought to my self what could be possibly better than being able to get up and move to another location...
To be perfectly honest if I had my life over again I would do exactly what I have done in the past.
Hiya Trev, a couple of points.
I would always wire a separate input feed to the A30 direct from the busbar then the A30 has to read the same voltage as the MPPT etc. You can also verify that the A30 is displaying the correct voltage by measuring it at the input connections with a multimeter. Note: I've had a faulty A30 delivered.
Are the cables feeding the immersion heater rated / large enough diameter to handle 16.6A (20A with headroom)?
Thanks for the great video as usual.
I have actually added separate cabling now for the controller. The main cables are I do have 20 amp fuse on the bus bar. I used 30a in case I decide I can change the immersion to a 300w
@@TrevsTravelsByNarrowboat reading the A30 manual the 3rd setting is for a voltage differential - that should be set to 0.00V
Why the extra relays? What is the onboard relay for if not for power output?
Relays are switches that work for a desired action. The first one switches on when the voltage controller tells it to. Then that sends power to the second relay which operates if the water is below the designated target. When the temperature is reached it will switch the relay off. Other relays on the boat would have there own designated function.
He's using the onboard relay on the A30 module just to switch the larger relay. This adds a bit of complexity and I'm not sure I would have done it that way, but if you're risk-averse, it does mean you're guaranteed not to put a large load through the potentially rubbish quality relay on the A30 module.
I love to see people having a go, but unfortunately you've made a huge assumption about how 12v power systems work and what power is available at what voltage. Sadly your plan is fundamentally flawed and relying on the battery voltage (especially in the high 13s) simply can't work efficiently or effectively. Essentially, batteries can supply very little power at, say, 14v before the voltage drops to the nominal 12.8v.
There are two ways of achieving your aim 'correctly'. The first is what you've done - switch manually. The second way is to use a shunt to measure battery SOC and then programmatically switch the immersion on or off (e.g. turn the immersion on when the battery is full and then off again when it's below 95%). This is absolutely doable, but it wouldn't come cheap.
Can I also comment that you really shouldn't be using mains switches to switch high power 12v systems. Say your immersion is 200W. At 12v that's 16A. The fused spur switch will be rated to 13A. In addition, the fused spur is designed to switch AC and not DC. I really would recommend you replace the mains switch with a proper 12v switch.
Finally, if it were me, I'd be putting several fuses on the board just to add a little protection.
Sorry, I didn't come here to p!$$ all over your project. Honest.
I am not trying to draw 14 volts, only to turn the immersion on when the batteries read 14 volts. The immersion is 12v 200w I have a max of 720w of solar at 12v. I fixed the voltage controller by wiring it independently from the bus bar.
@@TrevsTravelsByNarrowboat Yes, I understand that you want to draw 200W at whatever voltage is available, but only when the voltage is above a specific value. My comments were based on this understanding.
Glad you've found a solution that works for you.
Your method is still draconian compared to what I do. I take excess right from panels. Higher voltages, less wire loss. Nobody outperforms my method.
@@opera5714 Not sure if you're being serious or not, but if you are, that's not a wise thing to do... A 12v 200W immersion heater has a resistance of 0.7 ohms. (R=12v/(200W/12v)). Run that at a higher voltage and (assuming the panel can provide it) you're going to be dumping ((v/0.7R)*v)W into the tank from the element. This, in itself may be OK (assuming you have a bulletproof temperature cut-off), but as the voltage goes up, the current goes up too and instead of running 17A through the element (200W/12v), you'll be running (v/0.7R)A. Again it may be OK if you're lucky and v is low, but the element life is going to be reduced (and drastically reduced if v is too high).
Yes there is some tolerance in a 12v element, after all they could see up to 15v in normal day to day use and a good element will have been built to cope with that. Beyond 15v and it's getting more and more likely to fail sooner and sooner.
@@nabarnes I am dead serious and you missed that I operate from panel voltage because I don't want those high currents. And by the way, I have operated with 40V from two 12V panels in series and pulsed that into a 0.7 ohm heating element efficiently. I wouldn't recommend it, just wanted to see if it would work. I test my boards at 30A. Just try to find someone on YT who knows more about heating water from PV than I do. Maximum power to element can also be set.
ruclips.net/video/-7O5WzFcBBE/видео.html