Li-ion batteries must be balance charged. Either with a smart charger that monitors each cell voltage, or with a BMS that monitors each cell voltage and can interrupt the charge current.
A balance board with a 2A discharge current is not enough to prevent damage to your battery, and or a dangerous thermal runaway.
There are a lot of reasons why the voltage can spike on any given cell group during charge. The charging system used must be able to stop the charge if a cell group exceeds 4.2 volts.
I have had many times when my charger stopped charging because it detected high voltage on a cell. Any Li-ion balance charger will do this.
Charging your battery the way you describe is extremely dangerous and sooner or later the battery is going to explode or catch fire. And if you haven’t seen what happens when a 2 Kwh battery goes it’s scary. It’ll burn your whole city block down and or destroy your car.
Once the battery has been damaged with cell voltage above 4.2 it’s a ticking time bomb. It might thermally runaway while on charge, or it might later while being stored or used.
Commercial built batteries that charge with a simple charger are protected by a BMS that monitors the individual cell voltage and can interrupt the charge current if a problem is detected. I don’t trust BMSs. So I balance charge.
These batteries demand respect. Please be careful.
