So it begins...... Battery spot welder

[sternwake]

I finished up my 3s4p Samsung 50E tonight.

It is 11.1v nominal, and 20 amp hours., so 222 watt hours.

My 12v nominal 22AH AGM is 264 watt hours when it was new.  I think I got it in 2019.

Here they are side by side.
   

That AGM was just barely able to start my engine by itself, when it was new.

My Samsung 50E 3s4p is limited by the 6$ 40 amp bms.  It can probably handle a 60amp surge for a second or 2. I only used 14awg , unlike the dual 8 awg on the AGM.
I wired a 4 pin JST connector to it, so I can see individual  parallel group voltages, and 'hobby chargers are designex to balance lipo batteries using this connector.

This BMS is supposed to passively top balance. In addition to the over  current, short circuit overvoltage/undervoltage protections.

Quality cells with good connections should stay in balance on their own until they start aging and differing in resistance and capacity.

BMS use little resistors to bleed very small currents off the cells which reach 4.18v first when charging,  but this is not foolproof.  If a p grojo exceeds 4.25v the bms disconnects the charging source.  the charger light might go green, and the human thinjs all is well, but one P group or several could have been well below their full charge voltage when  the bms cut power

So when a 10s battery which shoukd come off the charger at very close to 42v, but is well below that, it can be a sign the balance is poor, and the balancing resistor is not abke to bleex off enough voltage from the higher  voltage  cells fast enough.

My 10s BMS' are supposed to start balancing at 4.18v, so when I want to balance, I set my charger to 41.8v, and I limit amps to very low levels, and  let it go for many hours.
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I've not tested this BMS.  
Kind of like with lead acid batteriez, one needs to be smarter than their' smart ' charger, with lithium one should at least be aware of what their BMS is capable of and how it works., or is supposed to work.