Whats a good voltage cutoff for......

[BrianG]

The charger will see the total of your pack. If you have two 2s packs in series, it will see 4s. And it will be able to charge the full 5A as long as the charger has around a 100w or higher power limit for a 4s pack. For 6s, you would need a power limit of around 130w to charge at the full 5A. A lower power limit (like 50w) will mean it won't be able to charge at the full current.

I believe there is a balance board you can buy that will take care of the balancer connections, just make absolutely sure you hook it up right according to the main charging leads. Or, you can build your own using my diagrams. I personally prefer building my own since I can be sure it is done safely, but that's up to you.