Crazy 2S hardcase charging question
 

This is probably a terrible idea, but I'm interested in learning why this will not work (I also did search on this first):

Is it possible to charge both cells at once of a 2s hard case lipo by using 2 independent chargers utilizing the lipo hard case center pin per the following illustration?

http://i.minus.com/ifDcTf9kuRxUK.jpg

In principle it probably would work but I wouldn't recommend it simply because the two chargers will charge the cells potentially different. The whole point of that centre pin is to allow ONE charger to correctly BALANCE charge the lipo. An unbalanced lipo is a recipe for disaster.

Ah I see. So that's the real risk element to consider. I would imagine that many 2S saddle pack owners make use of 2 chargers and have to be careful of that as well.

One major concern is connecting the grounds of the chargers to 2 different voltage points. If the charger outputs are not completely "floating", meaning isolated from ground, that would create a short circuit of sorts. Not good, would not recommend trying it. Even with floating outputs there is the possibility of any control noise from one charger interfering with the other.

If done one charger/cell at a time balance shouldn't be an issue as long as the charger is correctly charging a single cell to 4.2V. I experimented with charging and discharging individual cells like this before I had balancing chargers. I used the technique to balance packs and to experiment with cell balance and such as I was learning about charging and balancing lipos. And then learning about and testing balance chargers.

If I may ask I'm curious why you want to try this?

This will work.. no problem I have tested this to disprove said theories that you can not.. only issue I would not recommend putting more than a single 1 amp charge.. not comfortable putting more thru a 2 mm plug..
I used 2 bc6 minis.. and also a 2 indy 16x lithium (w lcd display)

As per Dave H, it depends on the charger topology if they are isolated or you use separate isolated supplies no problem.

I have lipos that support high charge rates (5C), however just a pair of 6A chargers at the moment.

If both chargers accurately measured cell voltage, I could charge a lipo in less than half the time vs. a traditional balance charge (minutes saved from the balancing phase.)

Being limited to 1A would defeat the potential benefit. A gold plated 2mm should support 10-20A according to online sources.

Did you measure each cell's voltage after your tests?

I would not recommend putting 10A through a 26g wire.

Will your charger achieve 6 amps on a 2S? If so don't think you will see much benefit on a 2S, as each cell will still see 6 amps. If the higher cell count was current limited then you idea might be worth investigating further.

Unless the pack balance is way off don't expect much time saved in balancing. Still will have the relatively slow Constant Voltage portion of the charge where the amps drop off.

Ah there we go, it is pointless then as my Turnigy chargers will handle 6A @ 2S and won't supply any higher at 1S. As I said, probably terrible idea but interested in learning.

Thanks for your input!

raz .. yes i did measure voltages.. they where dead-on...4.200 and 4.201... I used the same computer ps to power both chargers...as 4 putting 20 amp thru a 2mm contact LETS SEE that done for 15 seconds...I see smoke in that 15...

no real benefit unless u have a stubborn cell that just wont reach the desired 4.200 like I charge to..