Setting up a 989 to charge two 4S lipos

[BrianG]

Well, if they are always going to be used in parallel, why not simply parallel everything (including the balance taps)? Then, you can use a single balancer and set the charger to 4s (just double the charge current of one pack since you effectively now have a 2p pack).

However, doing the initial hookup may be a little convoluted to ensure each cell in each pack is exactly the same voltage. This would require the use of a low value resistor to equalize each cell. I can go into detail if that's what you want to do. Be aware that this procedure would be used only if you plan to permanently hook the packs together....

[JThiessen]

I don't think that's the way we should go with it. This is for my B'in Law, and it needs to be as simple as possible, and the closer to plug and play, the better off he'll be.

[lincpimp]

I would hook them up as you describe in your second option. Using 2 balancers and having all of the cells balanced will get the longest life out of the packs, regardless of how they are wired.

You cannot wire the 2 packs in series and use one balancer, as those balancers are only good for 6s, not 8s. Your 2 4s packs in series would be 8s.

[JThiessen]

Ahh....that is true. I forgot that they were 6S limited.