Overkill BMS - quick question regarding balancing

smoothJoey

House finch
Last note on this. With the charge voltage increased to 14.3 two of the cells were steadily climbing, sitting at 3.625. I’ve dropped the charge voltage back to 14.2.
BTW you are discharging so no balancing should be taking place.
If you re-configured the bms to balance on discharge it would be nice to let us know so that we can help you better.
 

Gazoo

Dumb Dumb
Appreciate the direction here for sure. Admittedly I’m a little nervous charging a single cell, really have no idea what I would be doing and see too much that can go wrong. I may run off of the single battery for now until I can tear it down and re-balance.
Charging a cell in a pack is the same as charging a cell out of the pack. There is no where for current to flow other into the cell you are charging. Nothing can go wrong as long as you connect with the correct polarity and monitor closely because the cell will top up fairly quickly. I have done it myself with zero issues. But they are your cells. Do as you wish :)
 

Gould

Solar Enthusiast
Charging a cell in a pack is the same as charging a cell out of the pack. There is no where for current to flow other into the cell you are charging. Nothing can go wrong as long as you connect with the correct polarity and monitor closely because the cell will top up fairly quickly. I have done it myself with zero issues. But they are your cells. Do as you wish :)
So I completely disconnect all cells out of series and top up the single cell?
 

Gazoo

Dumb Dumb
So I completely disconnect all cells out of series and top up the single cell?
No. You leave everything connected in series including the BMS, and connect your charger to the weak cell. Turn off balancing on the BMS and make sure there is nothing connected to the battery...meaning no load or charger.

Since you are charging each cell individually and they are at close to a full state of charge, charge with 2 amps or so. You can watch the cell voltage increase using the BMS app and/or a DMM. Don't go over 3.65 volts.
 

Gould

Solar Enthusiast
Interesting, never would have thought you can push voltage into a single cell with them all connected together. I may give that a shot.
 

Gould

Solar Enthusiast
theees a lot of great info on this thread but I getting lost in the detail. Taking this approach of enabling balancing full time, do I need to disconnect from load and charging source or simply turn it on business as usual?
 

time2roll

Solar Addict
No need to disconnect or do anything except update the setting and save it to the BMS real time instantly. Reset anytime without precautions.
 

Gould

Solar Enthusiast
Thank you, will do so in the morning.

Appreciate all the help once again. I questioned my sanity getting into battery building, can’t imagine doing it without this great community.
 

Gould

Solar Enthusiast
Quick update. For the battery with the suspect cell I’ve turned off balance only while charging and have set the balancing to kick in at 8mv. Here’s where we’re at, I find it interesting that the cell I’m worried about is the high one. This is a far cry from the 170mv delta yesterday.
 

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Gould

Solar Enthusiast
Quick update. After a couple of days with balancing enabled full time, there hasn’t been much progress. Balancing is set to 3.35v and 8mv. I do find the balancing to be inconsistent. The SCC is in absorption right now yet there is no balancing happening.
 

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Gould

Solar Enthusiast
Argh, definitely looks like a rebalance is needed, really hoping it isn’t a bad cell. I spoke with the reseller and his supplier is saying this is normal and that it will level out after charge. Doesn’t add up for me as the other battery is within 3mv consistently.
 

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