On 9/27/2013 5:39 AM, RussellMc wrote:
>> I will convert to NiMH; just a NiMH charger circuit, no balancing
>> needed. The small amount of weight savings doesn't justify Li-anything.
> After my experiences with NimH over the last few years I'd be very
> wary of using them in lieu of eg LiIon.
> If each cell can obtain its charging energy from an independent
> (effectively "floating") source (as opposed to a series string with
> common current) then each module becomes an independent charger and
> any sort of cell becomes essentially no harder or easier than making
> single cell chargers.
>
> If you have a series string with charge current flowing down the
> string then NimH is going to have to deal with unwanted current just
> as LiIon is. My 'short circuit the feed when unwanted' system would
> work as well (or badly) there.
>
> NimH used in a series tring of substantial length do need balancing -
> especially modern ones which, unlike those of lower capacity, cannot
> tolerate ANY long term trickle charge. With cells that support trickle
> charge  a string may be balanced "reasonably well" by charging all
> cells to near full capacity then trickle charging the string for an
> extended period. Modern NimH with high capacity per volumes (eg say >-
> 2000 mAh in AA) do not tolerate trickel charging.
>
>
>          R
His stack is only 24V high. Like NiCAD, NiMH levels each cell, unless=20
the stack is so huge that one or more cells is destroyed by overheating.

I always monitor the temperature of each 12V increment, though, to catch=20
a defective cell; I should have said that.

--BobA



--=20

The only place success comes before work is in the dictionary.

VINCE LOMBARDI

--=20
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