The last time I got into parallel cells-- needed added resistors would work
if they had the right positive temp coefficent.
series diodes plus a small value resistor can be a viable alternate
solution
if the few tenths of a volt drop across the diodes is acceptable.
"RogerN" <regor@[EMAIL PROTECTED]
> wrote in message
news:BrydnV20KeU9ynLVnZ2dnUVZ_uidnZ2d@[EMAIL PROTECTED]
> Point well taken and I would prefer to error on the side of safety
but...
> My charger doesn't have a separate setting for 15C LiPo's vs 25C LiPo's.
> Since they all charge to the same 4.20V/cell, and all are recommended to
> not discharge below 3V/cell, and they all charge from the same
algorithm,
> shouldn't they work in parallel if you're not pu****ng the limit? I mean
> if the maximum recommended charge current is 1C, you don't want to
exceed
> that but as long as you stay within the recommended bounderies I would
> think it would be OK. It's not like paralleling LiPo's with LiIon or
some
> other chemistry that has a different charge algorithm.
>
> To match them, what I was thinking on doing is after use is balance
> charge/discharge them all to the same voltage, then parallel them with a
> small resistance and a fuse between each connection. Then they could
all
> be held at storage voltage or all be charged together. If one cell went
> bad, it would blow fuses at perhaps 2C and not be able to electrically
> damage the other packs. The fire might damage the other packs though!
:-)
>
> But I do think the better solution would be to connect all packs to a
> multi-****t charger and charge them independantly. That way you wouldn't
> have to worry about getting them to the same voltage before connecting
> them.
>
> RogerN
>
> "The Natural Philosopher" <a@[EMAIL PROTECTED]
> wrote in message
> news:1223628702.17808.0@[EMAIL PROTECTED]
>>
>> Yup. The thing here is that as long as the packs are of the same
>> chemistry/construction style and from the same manufacturer, *even if
the
>> cells are of differing capacity* you can connect two packs in parallel
>> *once you are sure they are at an equal state of charge*.
>>
>> If you are not sure, don't risk it.
>>
>> Now once they ARE in parallel, you can charge and discharge as a single
>> pack.
>>
>> But the moment you use them independently you MUST go through the above
>> procedure all over again to make sure the state of charge is the same.
>>
>> The reason for this is that *as long as the cells are identical
chemistry
>> and construction style*, there is a completely unique relation****p
>> between voltage and charge state. So they will distribute charge and
>> current correctly, and stay in balance. This is of course how large
>> capacity packs are made up: From identical cells in parallel..
>>
>> What is distinctly dangerous, in order of increasing insanity, is
mixing
>> cells of different quality - say 15C packs versus 25C cells - from the
>> same manufacturer, mixing cells from different manufacturers, or
>> connecting cells in parallel when at a different state of charge.
>>
>> You MAY be lucky. Do you feel lucky today?
>
>
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