Upgrading 15s Battery to 16s

[Supervstech]

Sounds right to me, but... how is the 16th cell connected to the pack? How long is the circuit, and what is the size conductor?
Could simply be a voltage drop from connection size

 

[sunshine_eggo]

On initial charge before installing the BMS I took everything up to 3.6V each (the original 15s pack and the 1 new Eve cell) and then let it settle. Recharged with the BMS installed up to 56.5V, so 3.53/cell and let the BMS finish balancing down to 0 mA.

0 mV?

Should I have done something differently?

Sounds fine. If you can charge to your target full voltage, and you pull full capacity, it's good enough.

 

[Paintedsky]

I am planning on upgrading a 15s battery as well....Does anyone see a problem with adding a 280ah battery to the 15 exisiting 200ah cells?

 

[sunshine_eggo]

I am planning on upgrading a 15s battery as well....Does anyone see a problem with adding a 280ah battery to the 15 exisiting 200ah cells?

Physical constraints not considered - Not if you top balance it and understand that you still have a 200Ah battery... probably less because your 15S 200Ah may not have 200Ah anymore.

 

[Supervstech]

I am planning on upgrading a 15s battery as well....Does anyone see a problem with adding a 280ah battery to the 15 exisiting 200ah cells?

I would get an active balancer for the battery as well, having a single large cell may confuse the bms and cause the others to drift balance.

 

[boarder2k7]

I would get an active balancer for the battery as well, having a single large cell may confuse the bms and cause the others to drift balance.

Yeah mine is behaving a bit oddly at upper states of charge, the new 105 Ah Eve cell voltage jumps up before the other cells, leaving a lot of work for the balancer to do. It does balance out, but I'll be interested to see performance when I get a higher current capable charger.