Electronics > Power/Renewable Energy/EV's

Lithium ion charging balancer questions for 18650s

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Trancistor:
Hi - I am new to this forum, and thank you for reading my post.

I am getting one of those cheap eBay Lion balancer boards (about \$9) from China, about 4 cm x 6 cm.

It is a 5S 12A balancer.  It also protects the cells.  Questions:

1)  Can I use this to balance 3S or 4S?

2)  When balancing 5S, the maximum voltage needed is I suppose 5 * 4.2 = 21 V.  Will this charge the cells to 4.2 V each? What happens if the power supply delivers 25 V constant voltage.  Will the board attenuate that?

3)  What happens if the power supply can only deliver 19 V?  19/5 = 3.8 V.  Will all five cells balance exactly at 3.8 V or will they be random with a total of 19 V?  I understand that the cells will not be fully charged.

4)  When you say 4S3P, is that 4 series of 3P or 3 parallels of 4S?

http://www.ebay.com/itm/5-S-12A-18-5V-Lithium-ion-PCM-BMS-Battery-Protection-Board-LiMn2O4-Balance-New-/122199648617?hash=item1c73aaa969:g:JJoAAOSwal5YEbUr

Thanks!   :-+

fourtytwo42:
Welcome to the forum :) Could you please post a link to exactly what balancer board you are talking about (could be useful) ?

Hang on you already asked these exact questions before here https://www.eevblog.com/forum/beginners/lithium-ion-balancer-questions/msg1250668/?topicseen#msg1250668 and got lots of answers, so why are you reposting the same questions again somewhere else ?

Trancistor:
Done ...

Trancistor:

--- Quote from: fourtytwo42 on July 05, 2017, 12:38:36 pm ---Hang on you already asked these exact questions before here https://www.eevblog.com/forum/beginners/lithium-ion-balancer-questions/msg1250668/?topicseen#msg1250668 and got lots of answers, so why are you reposting the same questions again somewhere else ?

--- End quote ---

Because the audience can be different.

BTW, I did not get very useful answers.  Only two of my 5 questions were answered in a half-hearted manner.

Also, the question is of interest to both groups.

SMdude:

--- Quote from: Trancistor on July 04, 2017, 07:13:48 pm ---Hi - I am new to this forum, and thank you for reading my post.

I am getting one of those cheap eBay Lion balancer boards (about \$9) from China, about 4 cm x 6 cm.

It is a 5S 12A balancer.  It also protects the cells.  Questions:

1)  Can I use this to balance 3S or 4S?

2)  When balancing 5S, the maximum voltage needed is I suppose 5 * 4.2 = 21 V.  Will this charge the cells to 4.2 V each? What happens if the power supply delivers 25 V constant voltage.  Will the board attenuate that?

3)  What happens if the power supply can only deliver 19 V?  19/5 = 3.8 V.  Will all five cells balance exactly at 3.8 V or will they be random with a total of 19 V?  I understand that the cells will not be fully charged.

4)  When you say 4S3P, is that 4 series of 3P or 3 parallels of 4S?

http://www.ebay.com/itm/5-S-12A-18-5V-Lithium-ion-PCM-BMS-Battery-Protection-Board-LiMn2O4-Balance-New-/122199648617?hash=item1c73aaa969:g:JJoAAOSwal5YEbUr

Thanks!   :-+

--- End quote ---

1. Don't think so, you would need a bms specific for the amount of cells you have in series.

2. yes 21v is absolute maximum that should be applied. The board will not attenuate overvoltage, that is the job of your li-ion charger.

3 yes, if less maximum voltage is delivered, all the cells should still be at equal voltages.

4. You are correct, 4 series of 3 Parallel.

I think it is best to use a dedicated li-ion charger, be it a module or complete charger unit. In theory, if you had a 21v 1A supply, it should charge at constant 1A current until it reaches 21v, but I would not encourage it or rely on it and think that you would be taking a big risk in doing so.

Now, where is the 5th question??  >:D

Cheers and be safe with lithium!