I parallel charge almost all the time.
I am charging with a Meanwell 1000 watt supply and Icharger 306B. I can charge six 5,000 packs at 1c all at one time or two packs at 3c, etc.
The thing with parallel charging is you can not mix cell counts, but you can mix size capacity of batteries. In other words, let’s say you have a five cell 4,000 ma and a five cell 5,000 pack. Just add them together, which is 9,000 ma or 9 amps.
I use both Paraboard and Progressive’s. Both are excellent. The big pain is unless you standardize your batteries, you could wind up with a ton of boards. I stick to Deans and Thunder Power for the balance taps. I have Dean’s on all my main leads and just use balance lead convertors from my packs that don’t take Thunder Power balance leads.
In fact, one thing I have found is, it can be a real pain to plug in six balance taps into the one board when I am charging 5’s. It really get’s tight. It actually works better to have a lead extension from the battery balance connector to the board. I just leave the balance extenders (convertors) on the board and plug the batteries into them.
One of the down sides is you can not tell how much you are putting into each battery. As far as your charger is concerned, it’s just charging one big battery.
Yes, they will be balanced if you charge with a balance lead.
I would assume if one battery is out of whack, your charger is going to sense that and shut down. I have charged dozens and dozens of cycles and never had that happen.
The way Cellpro charges (2 sides), I understand it can be an issue. I read that Cellpro was coming out with their own parallel system.