How does ANT BMS balance the battery pack and how long does it take?

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Archocell   1 µW

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How does ANT BMS balance the battery pack and how long does it take?

Post by Archocell » May 09 2021 7:54pm

Hello everyone,

I have a 20s 19p Panasonic 3400mah battery pack and I recently replaced the BMS with the ANT BMS. I realized that the battery pack was not balanced for just one of the parallel connections. I was wondering how long it takes for the BMS to balance the battery pack and I'm confused about how it balances it. Do I have to plug in the charger? How long will it take? Does it reduce the voltage to be equal and then charge up? I attached a screenshot of the ANT BMS app showing the status of the battery pack.

Link for the BMS: https://a.aliexpress.com/_mMZQrUN
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Jonno   100 W

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Re: How does ANT BMS balance the battery pack and how long does it take?

Post by Jonno » May 10 2021 2:43am

Normally 4 or 5 days just balancing with that voltage difference with no charge - BUT you may have some bad cells in row 12.
You could charge ROW 12 only using a 4.2v charger and see if the voltage rises.
If it doesn't then it battery apart time to find the dead ones :wink:

Jonno
Modified EEB frame, 888 forks, 280mm DNM pit bike shock, QS273 40h V3 3.5t, Nucular Electronics 24F controller 300a, 92V @ 36ah 26650 cells, 300a BMS with bypass,
Hope V4 + Galfer 223mm discs + Variable regen braking.
and 5 x QS205s

gobi   10 W

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Re: How does ANT BMS balance the battery pack and how long does it take?

Post by gobi » May 10 2021 9:00am

That row is quite low, if you look up the specs of your BMS, it will tell you the MAX balancing current and at what voltage it activates.

Can you charge that row by itself as mentioned above and then do a capacity test on that row?


19x3.1 = 58.9ah @ 3.7 v

0.5 amp balance current max for BMS (??)

Look at the discharge curve for cells and possible your cells are at 30%?

70% of 58.9 ah = 41 ah

you will need 82 hours to balance at 0.5 a rate, hence the suggestion to charge the cell row,
check connection for bms wire, are they soldered? or rings?
I would also take the voltage at the cell to confirm that BMS is seeing the proper voltage.

999zip999   100 GW

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Re: How does ANT BMS balance the battery pack and how long does it take?

Post by 999zip999 » May 10 2021 9:47am

You need to balance the pack before you install the b m s. The BMS and its tiny balance circuit will help to keep a balance battery balance. Yes I would charge up to the low parallel group and don't over charge. Whatch for the cells don't get hot . sometimes a cell that is bad only take so much charge even though you're still trying to get it to 4.2v or so . It just makes heat. So watch it.

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onemorejoltwarden   100 W

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Re: How does ANT BMS balance the battery pack and how long does it take?

Post by onemorejoltwarden » May 10 2021 9:51am

Are you saying: ?
First just charge the battery normally
then recheck, open and inspect as needed , of course calibrating equipment, as needed.
then try isolated charging, with precision limited voltage ,
then cell by cell inspection?

Would it be too nuts to use a 5 volt wall wart with frequent monitoring against overcharging,
and of course all protection (ie outside, etc) to see if you can bring it into range (<4.0v say?)
on the cell group that is low, without disassembly ?
I just need a CV DC Power Supply, I know. Can one be used as a regular charger if so I should have gotten one yesterday?

I am familiar with non BMC RC pack balancing, and was wondering if adding 7s x2 balancing wires to a pack
would be tempting too many gods to create more problems?

Thanks
"One more jolt, Warden, he's still twitching."

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gobi   10 W

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Re: How does ANT BMS balance the battery pack and how long does it take?

Post by gobi » May 10 2021 11:32am

See my home grown

Gobi Balancer 9000 aka the GK9000

I use individual low amp chargers to "level" my cells,

I use this for 25ah cells to 280ah cells.
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E-HP   10 MW

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Re: How does ANT BMS balance the battery pack and how long does it take?

Post by E-HP » May 10 2021 12:02pm

You can charge the bad group via the balance leads but unplugging the bms and tap into the leads for that group. If you use a lipo or other charger, where you can set the voltage and charge current, then set it to 4.2V and ~2A charge current and monitor the voltage until it matches the others.

Archocell   1 µW

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Re: How does ANT BMS balance the battery pack and how long does it take?

Post by Archocell » May 10 2021 7:47pm

Thank you everyone for all your replys!

So I left it for the BMS to balance overnight and it has not changed in terms of the voltage gap between the highest and the lowest. in fact, it increased... the MAX balancing current for the BMS is 18ma and if I were to set it any higher it will overheat. So I decided to try and charge that specific cell group like the picture I have below... The charger I have is for 18650 cells and I just added wires to it and connected it to the negative and positive of the 12th cell group. (is that the right way of charging that cell group?)

It's been charging for 6 hours so far today and the voltage has not changed... I'm guessing that 0.5amp charge rate is going to take a long time to charge the 19parallel connections... Is there any other ways I could speed up the charging process for the battery cell group?

The BMS I had connected was reading the right voltage and I confirmed it by using a multimeter for that specific cell group. For tonight, I will leave the battery to charge using the charger I have before I take apart the battery pack and inspect for bad cells... But I'm curious how many bad cells are required for the voltage to drop that low for the whole 12th sereies.. would it be one or two cells gone bad or most of them? Also, if I were to take apart the battery pack, How can I check which cells are good and which cells aren't
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