For a mains adaptor, anything between 12v and 18v DC output capable of giving at least 5Amps
I use a Toshiba laptop supply and it works great.
I tried a Lenovo laptop supply but this puts out 20v and the B6 charger rejects it.
Take care when changing the little plug that goes into the B6, the positive needs to go on the centre contact
A 12v car battery works good for a 4S, the B6 ups the voltage from 12v to suit the 4 cell pack