Just  received and accessory to multiple charge 2 nos 11.1V batteries at the same time :
Product description

Twin pack charge lead (2 x 3S)6S
Designed for iMAX and GT-Power chargers (B6,B8,A8,A6).
This harness allows you to charge and balance 2 3S packs at full rate with the 6S port.
This is a great and simple way to charge two packs at once.

Price : Rs 200 each

How abt G.T. Power A5 ? I think it can fit tat since it can fit A6..

Nice accessory , 200 + shipping ?

good day 

Can the a 5 charge a 6S?
This is like charging 6 S
If yes then OK.
Sai

Quote from: rcforall on August 22, 2009, 11:34:16 AM
Can the a 5 charge a 6S?
This is like charging 6 S
If yes then OK.
Sai

The A5 cannot charge a 6s.. But i guess with this extension it just might..  Not sure..

I use this all the time to charge two 3s packs for the 450 helis at the same time.

This definitely requires a 6s charger with a 6s balance port.

Dear Sai,
apart from the above mentioned adapter  don't  we need a battery connection adapter to connect the two battery packs in series and then connect it to the charger output port?

Rao.

Depends on the type of balance connector on the battery. The adaptor shown above can hold the balance connectors of the two 3s batteries, if the balance connector is of the Align type.  If it is the ThunderPower type, you will need a converter that changes it to the Align type (usually comes with the battery). 

The charging is done through the balance connectors alone. The main discharge ports of the batteries are not used in the charging process.

Use of series charging adapter .
Note discharge leads of batteries are not connected to the charger .

Rgds
sai

Guys,

Please ensure that you charge the same capacity batteries. i.e both the 3S batteries should be of the same capacity.

Cheers!!!

I tried charging  a 2650 mah and 1800 mah at 2 amps charge rate and no problems with it.

sai

Don't see why packs of two different capacities cannot be charged together.  All the charger is doing is to charge and check if the individual cells are up to 4.2 volts each, and that is irrespective of the capacity of each cell.

Just because you didn't see any problems doesn't mean they don't exist. Not that it doesn't work, but there are a couple of things to be aware of while charging this way.

1. The balancer port in the charger can drain only low currents. So if one pack charges earlier than the other the charger will reduce the current to within the limit balancers can handle. This means longer charging time.

2. The balancer plugs are not designed for high current. Usually not a problem upto 1A or so. Above that the connector and the thin balancer wire could start heating up. The first(+ve terminal) and last(-ve) leads are the ones carrying the full charge current.

3. If you using high charge currents the resistance of the connector+thin wire will result in higher voltage drops across the first and last leads. This will cause the first and last cells to be charged a little less and thus imbalanced. However the difference will be small and almost unnoticeable in practice.

This is an issue which can largely be described as "is it OK to charge through a balance connector alone" (versus "can packs of different ratings be charged together using thing method").

In short, packs of say 850Mah and 1100mAh can be charged together (where the 1100mah *may* be pushing the limit, depending on the quality of balance connector wires).  The best efficiency (in terms of charging time) is when packs that are almost same size are charged together.  And it is safer if smaller packs are charged in this method.

Thank you Rajesh for highlighting the non-obvious issues. Typically charging through the balance connectors alone is not an issue up to around 2A, which is what I have seen most people do and I have been doing it myself all along.  For most chargers with 5A/50watts draw limit, you would not charge above 1.9A anyways for a 2 x 3s = 6s setup (even that is borderline, and is typically done at a lower rate).