Important LiPo series/parallel charging Question!

[big4x4]

Here is a question for you experts out there! I have four 7 cell lipo packs (25.9v Nominal) at 5Ah each. I have hooked them in series/parallel 2s2p to my bicycle at 51.2v 10Ah. I want to be able to charge it with one charging wire (pos. and neg.) and one balancing 7 pin connector. I want it as simple as possible.

I know I can get a 4-to-1 seven pin balance connector in parallel and use a digital charger to charge up the batteries at 25.9v nominal. The MILLION DOLLAR question is, is there any way to do this while the battery is still plugged into the bike at 51.2v (series)? Can I tap the pos and neg. out of each battery (before the series connector) to make a charge connector (with anderson connectors) separate from each battery's discharge connector (deans plugs), and then put all the batteries in parallel from the charging connectors? So what I will end up doing is plugging in my digital charger and 7 pin connector into the battery to charge all batteries at once at 25.9v, while the batteries are still hooked to the bike at 51.8v... Is this possible??? Please help. Thanks ahead of time to all of you genius's out there!

 

[wesnewell]

The simpliest solution would be to get a 14s charger like the Hyperion 1420i, Y the power connectors and make a custom 14s balance plug between the pack and charger. With the right connector you could combine the power and balance leads all into one plug as a few others have done. I think there's pics in the hyperion thread here.

 

[neptronix]

What wesnewell said. 7s packs are friggin' perfect for the 14s hyperion.

Sounds like you are trying to connect one way serial, and another parallel... it doesn't work that way, that's how you make a short circuit and make LiveForPhysics' lipo fire testing videos look like child's play

Another option is to use a 48v 350w meanwell from sureelectronics. The one i recieved a few weeks ago can be adjusted all the way up to 59v! If you charge that 14S pack to 4.15v/cell ( 58.1v ), and do a current limiting mod on the meanwell ( restrict it to about 6 amps ), you got yourself a nice bulk charger for the pack at it's native 14S.

As for balancing, a cheap little 8s balancing charger from hobbyking will work for you. Ask around for recommendations. Otherwise if you have the cash, the iCharger series is the absolute best.

Or you probably have a balancing charger already, so rock on.
You'll notice that if you have a good pack without some funky cells in it, the bulk charge from the meanwell will do it for ya 95% of the time.

The hyperion is the best option ultimately, just thought i'd throw another option out there though if you already had a balancing charger.

 

[dogman dan]

You cannot paralell batteries while still series connected. Well, you can, if you like big sparks and want to get to throw away ruined packs.

 

[big4x4]

OK, thank you very much for your input. OK, and if I move away from 14S...What about charging with a lipo charger with no balance leads... Is there a BMS or individual balancers like a blinky that you can leave plugged into each individual battery's balancing tabs the whole time? Maybe with a cutoff to turn off below 3.9v or so, since I only need it operating above 4V when it is charging? Is there even such thing as a BMS you can hook up to the individual balancing tabs only that doesn't limit current?