Those battery I only charge one at the time...from a dual PL8 Hookup on a bump controller or a single PL8 also on another bump controller.

I assume I could charge the parallel, but never felt the need, I also recharge at the end of the day, they are not Lipo....so I keep them charge, give them a little boost either before leaving home, or at the field while assembling the jet...

I have one tag for 2.6 one 3.1 and one for 5.2.....I don’t keep track since they are not balance from the charger....