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Overkill bms + 280amp battery issues

zkywelder

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Aug 13, 2021
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Hello, I recently acquired 4 - 3.2v 280amp (EVE), with overkill BMS. I also got NOCO Genius 10amp 12v battery charger.

The overkill setup is default. The only changes I put in is the capacity (280amp), and cycle capacity(224amp). I don't understand cycle capacity. I don't want the battery continue to discharge when it depletes 75-79 percent of the battery. So It should be either at 70-80amp or 224amp?

I checked each battery and it was .001 voltage difference. I set it in series, then use 12v charger. After trying to get it charged couple times, it won't get to 90 percent. It shuts down. Because the voltage in each batter differ greatly. One could go to 3.45v while others are sitting idle at 3.2v.

I believe that NCO 10amp 12v battery charger has it's own voltage to charge the battery, and it's fighting against the BMS voltage limitations. Also, it isn't charging correctly from what I can understand. It dumps into cell 2 or cell 3 instead of primary cell? It doesn't make any sense. It also tells me that it is full, but it is not. I think it is sitting around 40-50 percent? These are the results. Is there something wrong with my setup? or is it the charger that's causing issues that I should return the charger, and get a better charger?

Also, I decided to do subtle discharge to see how it is functioning. And it's not doing it right either. One of the battery cell voltage would be greatly lower, while one other cell is greatly higher.

Thoughts?
 

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I guess the general rule is that anybody who gets new batteries, and they're all in the same voltage, one should still top balance it?

Thanks for the links. I'll order benchmark power supply.
 
I got my benchmark Power Supply. All of the cells started at 3.28v

I been running for two days now through serial connection to speed up. Now there is a huge difference in voltage based on my BMS. I try make sure they are not over .15 volt. It happened. It was .235 volts difference. I stop and waited for an hour. Then two of the cells voltage seems to drop back to 3.35 range. But two cells were are still in 3.45 range. I unhooked it all. I decided to bring up cell 1 and cell 4 to 3.45 cell range. Waited for few hours. Unplugged it. Check the cell 1 and it is at 3.45 volts. I have not done cell 4 at this moment of writing. I went back to check cell 2 and 3, and it went back down to 3.36 volts from 3.45v. What the hell?

And my BMS now saying that my volt healthy meter went from 92 to 60.

I am lost for words.
 
I got my benchmark Power Supply. All of the cells started at 3.28v

I been running for two days now through serial connection to speed up. Now there is a huge difference in voltage based on my BMS. I try make sure they are not over .15 volt. It happened. It was .235 volts difference. I stop and waited for an hour. Then two of the cells voltage seems to drop back to 3.35 range. But two cells were are still in 3.45 range. I unhooked it all. I decided to bring up cell 1 and cell 4 to 3.45 cell range. Waited for few hours. Unplugged it. Check the cell 1 and it is at 3.45 volts. I have not done cell 4 at this moment of writing. I went back to check cell 2 and 3, and it went back down to 3.36 volts from 3.45v. What the hell?

And my BMS now saying that my volt healthy meter went from 92 to 60.

I am lost for words.
Cells settle.
As long as you fill them all to the top in a deterministic way.
And they all settle to roughly the same voltage.. all should be good.
If one or more keep dropping beyond full resting voltage(~3.4ish volts) that is not good.
 
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Soo Should I just stop and put them in parallel at this point? I don't want to wait two weeks just to top balance it. >.>
 
I mean, if they are like .2 volts difference, then it's making my life way more difficult. Initially, it was the same, and went out of control. I guess, I'll have to suffer and plow it through. Manually go through each cell to make it at 3.5v, then set up in parallel them to 3.6v. Is this a good idea?
 
I mean, if they are like .2 volts difference, then it's making my life way more difficult. Initially, it was the same, and went out of control. I guess, I'll have to suffer and plow it through. Manually go through each cell to make it at 3.5v, then set up in parallel them to 3.6v. Is this a good idea?
Just top each cell of individually to 3.65 volts.
Do each at the same charge current and to the same tail current.

Or put them in parallel they are almost fully charged now so it should not take long.
 
Alright, It finally got to 3.6 volts. I did it via parallel. Not individual.

I don't want to push it to 3.65, there's no reason to do so. I did some studies and some recommended 3.55 or 3.6v to keep it on safe side and not put too much pressure on the cells themselves.

Cell 1 is the positive connection to the charger and cell 4 is the negative connection to the charger.

Cell 1: 3.5v
Cell 2: 3.5v
Cell 3: 3.6v
Cell 4: 3.6v

Seems like I got 2 mismatching cells. What would be the best option then? I still need to get cell 1, and cell 2 to 3.6v?
 
Forgot to mention that the current amp/watt rate still hasn't hit zero. It's at .07amp. I been periodically checking every half hour with my volt meter. Cell 3 and 4 still hasn't went over 3.6* volts. So maybe it's still a good sign that it's still balancing.
 
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Yup. It's completed and it's .1 volt difference.

I'm going do a capacity test to see which hits the bottom first. Then figure out how to deal this mismatching cells.

Oops, I didn't mean to post this. It was suppose to go to another post (edited post). Sorry for the spam.
 
Just FYI, cell 1 is always the negative end.

You need to show 1 more decimal place!

If cell 1 is 3.59 and cell 3 is 3.60, then its pretty darn good.

Good to know that. I had have been confused how BMS indicate which cell is the first one. It's staring to make sense now.

It's actually .1 volt apart. So cell 1-2 are at 3.50, and cell 3-4 are at 3.60. That's why I ended up typing 3.5, and 3.6. ;)

I did a capacity test down to 50 percent. I know it's not enough info since it's not all the way down to 3.20 percent. Sorry. I noticed that all of the cells when not being discharged ends up at the exactly the same voltage. But when it is being discharged, there is a .35-.50 voltage difference range. Not sure if that's a good indicator of healthy battery system or not.

Here are the screenshots. It is in proper order. First picture is when I unhooked it and put in series. I went straight to testing after 10 minutes of getting the system hooked up.

I did forget to screenshot between picture 5 and 6 when it is being in state of discharge. Sorry. I thought I did. Derped! From what I remember, it was at 55amps, 660ish watts, give or take. Make sure you look at the timestamp upper right corner for each picture. The last image is when it was in standby mode for almost 30 minutes.

For this testing I used 1200w induction stove. I wanna push it to the max and see how much I can cook per day. Seems like I can cook 20-25 minutes in a day from fully charged to half charged with above medium to high settings. I should test a low watt/amp per hour cooking to see if this yield better results. Otherwise, induction stove is throwing out of the window. I seen several vans using 100amp battery system and used induction stove top. I thought I could get away with that. >.>
 

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