question

gully avatar image
gully asked

Lithium batteries in series not balanced

One of my batteries gets warm 81 Fahrenheit while the multiplus is on bulk charge. It goes up to 15 volts, then says it’s busy and charging is stopped. Then it restarts and does the same thing. The other battery is fine at 13.3 v and temp at 60 something. Brand new batteries and I did an initial charge on each before connecting then together. This same battery also acted differently from the other one. Any advice on what I should do? I want to let the multiplus charge them up but worried about what is going on.

battery charging
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JohnC avatar image JohnC ♦ commented ·

What are the batteries and BMS specifically?


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Alexandra avatar image Alexandra ♦ commented ·

@Gully You could take them back to the supplier. But JohnC is right in asking what they are. Are they managed batteries? Do they active balancing or passive balancing? Some Lithium batteries cannot be series connected. Victron does sell battery balancing equipment for managing these issues in banks.

https://www.victronenergy.com/battery-monitors/battery-balancer

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gully avatar image
gully answered ·

They are 12v Victron Smart Lithium batteries. I turned the output of the multiplus down to 5A to see if that made any difference. The problem battery reaching 87 farenheight and shutting down charging just over 15v. Voltage drops back down and temp drops a little too then starts charging again. the second battery at 13.... volts and 66 degrees. The red light turns on on the BMS while the battery says BUSY

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gully avatar image gully commented ·

Regarding bms. It’s all Victron equipment

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Daniël Boekel (Victron Energy Staff) avatar image Daniël Boekel (Victron Energy Staff) ♦♦ commented ·

Hi @Gully

How did you set up your system? what BMS are you using? do you have a GX device in the system?

(do you have a diagram of the system?)


https://www.victronenergy.com/batteries/lithium-battery-12-8v#downloads

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ianddindustries avatar image
ianddindustries answered ·

Hi

Check the cells on the warm battery whilst charging or discharging under load on the connect app. See that they aren’t jumping all over the place, I have had a similar issue and the problem was a loose internal busbar inside the battery


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gully avatar image
gully answered ·

Update: I decided to put a load on the batteries overnight and draw them down a bit since charging didn't seem to be working well. I then turned on the multiplus and they charged great 5A output. Set the multiplus back to 37A output and no problem. The multiplus went into absorption. The problem battery began to heat up again and charged in the upper 14V area. But it didn't exceed 15 volts and stop charging this time. The temp went up high again so I shut off the multiplus. It seems like it might be getting better and balancing out a bit more. I think I will repeat this process again and I am hopeful it will be resolved. I did check for any loose connections in the system, all is good there. I am using the Ve Bus Bus. I don't have a drawing of my system, I feel fairly confident the wiring is correct. Though this is my first time doing a project like this. I dont have a GX device in the system. The individual cells seem fairly stable to me, they fluctuate only slightly.

After I turned the multiplus off, temp dropped rapidly and cells balanced nicely. I still had a refrigerator going, and its still running this way till later tonight or tomorrow. I will charge it again and report back. Thanks for the help

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Daniël Boekel (Victron Energy Staff) avatar image Daniël Boekel (Victron Energy Staff) ♦♦ commented ·

Hi @Gully

Please contact your dealer / distributor about this to have your setup checked.

Before the battery reached 15 volts, the BMS should have directed the Multi to stop charging. Something is wrong with the system and things can get damaged like this.


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gully avatar image gully Daniël Boekel (Victron Energy Staff) ♦♦ commented ·

Thanks, I will do that.

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john-poul avatar image john-poul gully commented ·
Do you solve the problem and what was the problem?
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