On Thu, 09 Oct 2008 09:37:53 -0500, RogerN wrote:
> Since LiPo's are charged at constant voltage, if you were to make a
> harness with perhaps 1/2 Ohm between each pack, would it be possible to
> charge/discharge multiple LiPo's in parallel?
>
> For example, after returning home from the field, connect all discharged
> batteries to a parallel adapter connected to a balancer. The adapter
> would have small value resistors to limit the current between packs
> since they are most likely not discharged to the same voltage. If you
> aren't going back to the field until next week, set the charger to
> charge to storage voltage of approx. 3.8V per cell. Then start the
> charge before the next planned use.
>
> Advantages: All packs are stored at storage voltage and all packs are
> charged to be ready before use. Use a single charger on multiple packs.
>
> Need: Mating connectors for balance plugs and ~ 1/2 Ohm resistors to
> limit current in case you throw in fully charged pack with discharged
> packs. Fuses or other current limiting devices would be needed if you
> might throw in a discharged pack with multiple charged packs.
>
> RogerN
Roger,
Please don't do this. You won't be able to be sure that all the packs are
at the same charge level before you connect them in parallel especially
after use.
The only time that it is relatively safe is to connect the packs
immediately after charging when they are all fully charged and even then
only do it after checking the pack voltage.
A better approach would be a multiple output charger: each output charges
and monitors one LiPo cell but they can stay in series and all the
charging circuitry can be fed from the same power source. That way all
you are doing is creating copies of lower wattage charging circuits
rather than one big charging circuit. Ok it means more work to calibrate
and more expensive & complicated construction but it would make it easier
to keep the cells within tolerances and safe.
--
Chris
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