While Peukert's Law does not change the intrinsic Amp Hour capacity of the battery, it does affect the ability to use that capacity, simply due to series resistance during higher discharge rates.
Hi Knurlknar, I am a mechanical engineer at home today with some back issues laid up in bed and have been watching a LOT of your videos. Due to several recent power outages and the fact that I live in Seattle which is a level 4 earthquake zone I have been thinking about supplementing my Honda EU2000i generator with a large battery bank and an inverter. Anyway I've really been enjoying your videos and the way you present information. Thank you!
This is cool. I did all these experiments back in 1999. You're the only one I've actually heard.- beyond myself - articulate this. Peuker's has gone bonkers. Setting the Peukert coefficient in battery SOC meters also makes a huge mess of things!!
Any product that uses a Peukert coefficient in their marketing/manual is either a scam product or the designers of it didn't know what they were doing and it doesn't work properly. your pick. :) Peukert's coefficients are indeed useful but aside from yourself I've rarely seen them used properly. I would argue, in fact, that they have very little utility in most real-world situations.
@@knurlgnar24 Agree 100% and I think it might be mostly the latter. Almost every 'reputable' / popular AH meter on market implements Peukert coeff and almost-as-misconstrued charge efficiency parameters in order to calculate an almost-always-drifting and bending SOC indication. It's been virtually unchanged for over 20 years now and, imho, it's one of the main reasons the deep cycle lead acid battery industry suffers from such rampant chronic undercharging - and leaving itself wide open to lithium predators :) Rarely do people 'get it'.
It seems to me if you take 5 identical batteries that are all 12V and 100Ah each and you put some load on 1 of them that is say L amps (L is some constant such as 10), you will get some runtime for that battery at that load (let's say 10 hours of useful runtime). If you take the other 4 identical batteries and parallel them together properly (so there is the same resistance path to each battery from the load's point of view), and you make the load 4L, then it seems the runtime should be identical (10 hours). So in that case, 100Ah + 100Ah + 100Ah + 100Ah = 400 Ah since the load is proportional to the battery bank size. Even if it wasn''t, the true Ah capacity of each identical battery is additive regardless of the load. For example, we can approximate a battery's true maximum Ah capacity by using the 100 hour drain rate number. Let's suppose it is 120 Ah. So if I take 4 of those batteries and parallel them, I would then have 480Ah of actual capacity. Whether or not I can get all of that out depends on if my load is fixed or variable. if I "lock" my load at some high amperage, I wont be able to squeeze the last few Ah of power out of my bank, however if I either use a small load or a load that starts "heavy" but then tapers to lighter, I should be able to get the full 480Ah (in this example). If you get a chance, you should do a video on what happens when you take healthy batteries of different Ah ratings and parallel them together then load them. Will each one drain the same amount of Ah or will the load favor the more powerful battery (the one with more Ah). Also, what might happen when you charge this mismatched bank?
Something you said is misleading. I will clarify here... If you take 4 identical 12V 100Ah batteries and put them in parallel, the runtime of those 4 should be IDENTICAL to that of a single battery with load L, if you put a 4L load on the bank of 4. That would mean each battery is seeing about L load. For example, a 12V 100Ah battery with a 10A load might last 4 hours before the low voltage shutoff on an inverter prevents it from discharging further at that rate. Similarly, the 4 battery bank with a 40A load should last the same amount of time. This is assuming the load and batteries are wired in such a way that there is good load sharing in the 4 battery bank, however it need not be perfect. For example, if the actual drain on each battery is 9.25A, 9.75A, 10.25A, and 10.75A, that may be close enough so all drain similarly. Also when the load is removed, they will likely equalize in voltage and capacity once again. So just to be clear 100Ah + 100Ah + 100Ah + 100Ah does indeed = 400Ah, if the load is also 4x (that of the single 100Ah load) in the 400Ah case. Also, another thing that you said that is misleading is that the temperature of the battery as no effect on capacity. That is wrong in at least 2 ways: 1) The Cold Cranking Amps (CCA) of a battery is different than the Hot Cranking Amps (HCA) of that same battery. The HCA is much higher than the CCA. 2) A hot battery will self discharge much quicker than a cold battery. So imagine you have a very light load on a hot battery vs. on a cold battery. The hot battery will NOT run that light load as long as with the cold battery. You mentioned there is a lot of wrong information on the internet. Well that is correct. Unfortunately some of it is in your videos.
Your first paragraph is restating what I stated already in the video. You either did not watch it or you did not comprehend the video. And the capacity vs temperature claim is a straw man. Internal resistance changes with temperature as I mentioned in the video so, yes, CCA changes. Usable capacity also changes with temperature due to the change in internal resistance which I also stated in the video.
I watched it and listened to it again and you said wrong stuff. You said that 4 100Ah batteries paralleled together is not 400Ah. Of course it is! The Ah capacities are directly additive. You didn't say the usable power at some fixed load. Also, temperature DOES change the usable capacity of a battery. At very high temps, the self discharge rate is MUCH higher then at cold temps, therefore more power is lost at high temps. You can test this easily and it will likely be correct. Also, if you discharge a battery VERY fast (relative to its Ah capacity), that is LESS efficient (due to heating) than it is to slowly drain that same battery (at only maybe 10% of its Ah rating). So many things you say (as you say them) are wrong, but perhaps you go on later to explain them more in detail (which I think is a bad way to make statements). That would be like someone saying "electricity takes the path of least resistance", but then later go on to say that it takes all paths of resistance. Even though the first statement is true to some degree, it is very misleading as someone may wrongly interpret as "electricity ONLY takes the path of least resistance". Obviously that is a false interpretation. You seem like a smart and knowledgeable guy, you just don't state your ideas correctly. I can give you exact times where your errors are in this video but I think you are smart enough to find them yourself. Even in the first few minutes there are some "speakos". 1:20 elapsed "that's not really the way it works"... YES IT IS! The actual Ah capacity is directly additive for 4 paralleled batteries. The usable capacity at some fixed load may change but you didn't say it that way! Even your title is wrong. Peukert's Law is NOT wrong. You should have titled this video "Peukert's Law is frequently misinterpreted".
I have got a lithium iron magnesium phosphate batteries that are amp hour 40-watt-hours 512 can I hook them up to an inverter could I power a snowblower at 120 60hz 12amp motor?
Something that wasn't mentioned in this video seems relevant to me. Intentionally or not you just described the reason for not discharging a lead acid battery too far. This is something I feel that you should explain more in depth because there are people who don't understand. I'd do it myself but I still need a new camera because I just haven't gotten around to getting another one.
+Lagm an I am no expert on the subject, but just like if you drop some thing from an aircraft, it will accelerate until it reaches its terminal velocity and then it will go no faster, I think that each terminal material and acid has a limit. In other words lets say you used stainless steel and nitric acid to make a battery then its _chemical speed limit_ will be, lets just guess and say 0.8 V per cell.
Because batteries have a higher internal resistance and electron mobility at cold temperatures than at warm ones. If you don't expect to encounter cold environments then you can use the CA rating, otherwise use the CCA rating. They aren't really both necessary since lead acid batteries are all chemically similar, but it makes comparisons and purchase decisions easier for those people who don't want to learn how to approximate the conversion factors.
As far as calling a single cell a battery. I am not talking about official definition or anything but everyone and the market have already called single cells in fact batteries for a long time. Take the AA battery, take a typical lithium battery in a phone etc. These are all really single cells but are called batteries. Of course official definition I am not so sure about.
Yes, I agree. Two electrons as stated in the video. I didn't specify this by putting a -2 on the charge when writing it out and I was wondering when someone would comment on it. ;)
First you say the law is incorrect, then in the next sentence you suggest it’s being applied incorrectly. You are making very wild statements with no empirical or theoretical data to justify your position. 🤔
My statements are rational, my evidence is empirical as demonstrated in the video, and I give solid theoretical explanations to support my statements. I very clearly stated that the law is 'wrong' as commonly applied, but correct when applied as originally intended. Did you even watch the video?
Sorry but nothing you said here really is anything amazing? Seems you misinterpreted everything and assumed everyone else did. It's a well known fact that if you discharge a battery at a lower rate you can discharge is more and the voltage won't drop as much while constantly being drawn from. 1+1 doesn't = 2.7 but really =2 just like all the information says. The reason that on your other little video that it took a little while longer to drop to the cut off voltage you decided on is that when drawing a battery at a lower current (when you have two in parallel the current is half for each) then the voltage will plummet more slowly. A great example of this would be if you hook something up to your battery that uses even more power such as 3000w. The voltage will plummet ever faster. This does not mean you have reduced your capacity but it's just a property of the battery. Wait for a while and the voltage of the battery will go back up and you can do it again and again etc.
It's a magicians trick. If you notice the two battery parallel had the extra 40 amps each. That allows the heater to run the extra .7 time. The heater cuts off at 60 ah on a single battery. Leaving 40 ah left after recovery. But with two batteries you now have 80 ah. 40 ah each. That 80 ah let the heater run the extra time but the batteries recovery voltage wasn't as high. He left that part out.
A little late! This theory was found to be incorrect in 2006. Try checking Wikipedia, the presentation you are making is, again, a lot of fluff and horse feathers and most certainly deviates from the 2006 scientific study.
While Peukert's Law does not change the intrinsic Amp Hour capacity of the battery, it does affect the ability to use that capacity, simply due to series resistance during higher discharge rates.
Hi Knurlknar,
I am a mechanical engineer at home today with some back issues laid up in bed and have been watching a LOT of your videos. Due to several recent power outages and the fact that I live in Seattle which is a level 4 earthquake zone I have been thinking about supplementing my Honda EU2000i generator with a large battery bank and an inverter.
Anyway I've really been enjoying your videos and the way you present information. Thank you!
I'm enjoying this series of videos on batteries you are putting together. Its clear and concise keep it up.
You're gifted teacher. Rare to find.
How do I get knurlgnar24's intro theme music out of my head?
with a knife.... joking
This is cool. I did all these experiments back in 1999. You're the only one I've actually heard.- beyond myself - articulate this. Peuker's has gone bonkers. Setting the Peukert coefficient in battery SOC meters also makes a huge mess of things!!
Any product that uses a Peukert coefficient in their marketing/manual is either a scam product or the designers of it didn't know what they were doing and it doesn't work properly. your pick. :) Peukert's coefficients are indeed useful but aside from yourself I've rarely seen them used properly. I would argue, in fact, that they have very little utility in most real-world situations.
@@knurlgnar24 Agree 100% and I think it might be mostly the latter. Almost every 'reputable' / popular AH meter on market implements Peukert coeff and almost-as-misconstrued charge efficiency parameters in order to calculate an almost-always-drifting and bending SOC indication. It's been virtually unchanged for over 20 years now and, imho, it's one of the main reasons the deep cycle lead acid battery industry suffers from such rampant chronic undercharging - and leaving itself wide open to lithium predators :) Rarely do people 'get it'.
It seems to me if you take 5 identical batteries that are all 12V and 100Ah each and you put some load on 1 of them that is say L amps (L is some constant such as 10), you will get some runtime for that battery at that load (let's say 10 hours of useful runtime). If you take the other 4 identical batteries and parallel them together properly (so there is the same resistance path to each battery from the load's point of view), and you make the load 4L, then it seems the runtime should be identical (10 hours). So in that case, 100Ah + 100Ah + 100Ah + 100Ah = 400 Ah since the load is proportional to the battery bank size. Even if it wasn''t, the true Ah capacity of each identical battery is additive regardless of the load. For example, we can approximate a battery's true maximum Ah capacity by using the 100 hour drain rate number. Let's suppose it is 120 Ah. So if I take 4 of those batteries and parallel them, I would then have 480Ah of actual capacity. Whether or not I can get all of that out depends on if my load is fixed or variable. if I "lock" my load at some high amperage, I wont be able to squeeze the last few Ah of power out of my bank, however if I either use a small load or a load that starts "heavy" but then tapers to lighter, I should be able to get the full 480Ah (in this example).
If you get a chance, you should do a video on what happens when you take healthy batteries of different Ah ratings and parallel them together then load them. Will each one drain the same amount of Ah or will the load favor the more powerful battery (the one with more Ah). Also, what might happen when you charge this mismatched bank?
Something you said is misleading. I will clarify here... If you take 4 identical 12V 100Ah batteries and put them in parallel, the runtime of those 4 should be IDENTICAL to that of a single battery with load L, if you put a 4L load on the bank of 4. That would mean each battery is seeing about L load. For example, a 12V 100Ah battery with a 10A load might last 4 hours before the low voltage shutoff on an inverter prevents it from discharging further at that rate. Similarly, the 4 battery bank with a 40A load should last the same amount of time. This is assuming the load and batteries are wired in such a way that there is good load sharing in the 4 battery bank, however it need not be perfect. For example, if the actual drain on each battery is 9.25A, 9.75A, 10.25A, and 10.75A, that may be close enough so all drain similarly. Also when the load is removed, they will likely equalize in voltage and capacity once again.
So just to be clear 100Ah + 100Ah + 100Ah + 100Ah does indeed = 400Ah, if the load is also 4x (that of the single 100Ah load) in the 400Ah case.
Also, another thing that you said that is misleading is that the temperature of the battery as no effect on capacity. That is wrong in at least 2 ways:
1) The Cold Cranking Amps (CCA) of a battery is different than the Hot Cranking Amps (HCA) of that same battery. The HCA is much higher than the CCA.
2) A hot battery will self discharge much quicker than a cold battery. So imagine you have a very light load on a hot battery vs. on a cold battery. The hot battery will NOT run that light load as long as with the cold battery.
You mentioned there is a lot of wrong information on the internet. Well that is correct. Unfortunately some of it is in your videos.
Your first paragraph is restating what I stated already in the video. You either did not watch it or you did not comprehend the video. And the capacity vs temperature claim is a straw man. Internal resistance changes with temperature as I mentioned in the video so, yes, CCA changes. Usable capacity also changes with temperature due to the change in internal resistance which I also stated in the video.
I watched it and listened to it again and you said wrong stuff. You said that 4 100Ah batteries paralleled together is not 400Ah. Of course it is! The Ah capacities are directly additive. You didn't say the usable power at some fixed load. Also, temperature DOES change the usable capacity of a battery. At very high temps, the self discharge rate is MUCH higher then at cold temps, therefore more power is lost at high temps. You can test this easily and it will likely be correct. Also, if you discharge a battery VERY fast (relative to its Ah capacity), that is LESS efficient (due to heating) than it is to slowly drain that same battery (at only maybe 10% of its Ah rating). So many things you say (as you say them) are wrong, but perhaps you go on later to explain them more in detail (which I think is a bad way to make statements). That would be like someone saying "electricity takes the path of least resistance", but then later go on to say that it takes all paths of resistance. Even though the first statement is true to some degree, it is very misleading as someone may wrongly interpret as "electricity ONLY takes the path of least resistance". Obviously that is a false interpretation. You seem like a smart and knowledgeable guy, you just don't state your ideas correctly. I can give you exact times where your errors are in this video but I think you are smart enough to find them yourself. Even in the first few minutes there are some "speakos". 1:20 elapsed "that's not really the way it works"... YES IT IS! The actual Ah capacity is directly additive for 4 paralleled batteries. The usable capacity at some fixed load may change but you didn't say it that way! Even your title is wrong. Peukert's Law is NOT wrong. You should have titled this video "Peukert's Law is frequently misinterpreted".
can please tell me what is the difference between AGM and GEL battery and wich one is better for solar system?
I have got a lithium iron magnesium phosphate batteries that are amp hour 40-watt-hours 512 can I hook them up to an inverter could I power a snowblower at 120 60hz 12amp motor?
Something that wasn't mentioned in this video seems relevant to me. Intentionally or not you just described the reason for not discharging a lead acid battery too far. This is something I feel that you should explain more in depth because there are people who don't understand. I'd do it myself but I still need a new camera because I just haven't gotten around to getting another one.
Very interesting! Nothing is better to wake up in the morning than a good battery video. :D
Why is the voltage for a Pb cell around 2V?
+Lagm an I am no expert on the subject, but just like if you drop some thing from an aircraft, it will accelerate until it reaches its terminal velocity and then it will go no faster, I think that each terminal material and acid has a limit. In other words lets say you used stainless steel and nitric acid to make a battery then its _chemical speed limit_ will be, lets just guess and say 0.8 V per cell.
Do you plan on making more videos in the future? Hope so.
Fantastic Information - keep up the great work
Why do manufacturers rate their batteries with a cold cranking amps and regular cranking amps?
Because batteries have a higher internal resistance and electron mobility at cold temperatures than at warm ones. If you don't expect to encounter cold environments then you can use the CA rating, otherwise use the CCA rating. They aren't really both necessary since lead acid batteries are all chemically similar, but it makes comparisons and purchase decisions easier for those people who don't want to learn how to approximate the conversion factors.
Where did "wu ming" go from your 1000Ah Battery Bank Part8 - Upgrade Update!! video?
I think he needs to open a window and let some of the wrong out.
Add me to the fan club. I have learned much of the WHYS not just this is it trust me, by watching your videos.
As far as calling a single cell a battery. I am not talking about official definition or anything but everyone and the market have already called single cells in fact batteries for a long time. Take the AA battery, take a typical lithium battery in a phone etc. These are all really single cells but are called batteries. Of course official definition I am not so sure about.
the SO4 is -2, I think
Yes, I agree. Two electrons as stated in the video. I didn't specify this by putting a -2 on the charge when writing it out and I was wondering when someone would comment on it. ;)
Fantastic Information
Where does the other oxygen atom go?
*dramatic flare sound*
Batteries are disproved by a RUclips commenter
The Earth is flat. You will fall off the edge. Does it really matter? Enough to spend this much energy on?
thanks
First you say the law is incorrect, then in the next sentence you suggest it’s being applied incorrectly. You are making very wild statements with no empirical or theoretical data to justify your position. 🤔
My statements are rational, my evidence is empirical as demonstrated in the video, and I give solid theoretical explanations to support my statements. I very clearly stated that the law is 'wrong' as commonly applied, but correct when applied as originally intended. Did you even watch the video?
If he is German, it is pronounced Poykert.
You sound like Obama, very nice video :)
Sorry but nothing you said here really is anything amazing? Seems you misinterpreted everything and assumed everyone else did.
It's a well known fact that if you discharge a battery at a lower rate you can discharge is more and the voltage won't drop as much while constantly being drawn from. 1+1 doesn't = 2.7 but really =2 just like all the information says.
The reason that on your other little video that it took a little while longer to drop to the cut off voltage you decided on is that when drawing a battery at a lower current (when you have two in parallel the current is half for each) then the voltage will plummet more slowly.
A great example of this would be if you hook something up to your battery that uses even more power such as 3000w. The voltage will plummet ever faster. This does not mean you have reduced your capacity but it's just a property of the battery. Wait for a while and the voltage of the battery will go back up and you can do it again and again etc.
It's a magicians trick.
If you notice the two battery parallel had the extra 40 amps each. That allows the heater to run the extra .7 time.
The heater cuts off at 60 ah on a single battery. Leaving 40 ah left after recovery. But with two batteries you now have 80 ah. 40 ah each. That 80 ah let the heater run the extra time but the batteries recovery voltage wasn't as high. He left that part out.
It’s because the heat comes from the current (I) not the voltage.
A little late! This theory was found to be incorrect in 2006. Try checking Wikipedia, the presentation you are making is, again, a lot of fluff and horse feathers and most certainly deviates from the 2006 scientific study.
Zzzzzzzzzzzzz boooooooring