your bms is no voltage regulator.
if you have a 6s battery you need to charge the battery with a 6s charger.
if you have a 10s battery you need to charge the battery with a 10s charger.
you can´t mix that up even with bms.
Be very, very careful. Not understanding li-ion batteries & chargers is a sure fire way to burn your house down.
Make sure you read up and fully understand this technology, the charger requirements, and safety. These are very dangerous if you don’t take the time to understand and respect the tech.
You need a matched voltage CC/CV power supply. They are called chargers in common vernacular but should not be confused with lipo/liion chargers which are not CC/CV