> Harold Hallikainen wrote:
>>> Just be very careful when charging Li-Ion cells. Use a quality
>>> self-contained chip to do it with; DON'T
>>> use a PIC to charge the battery. Proper charging requires a thermistor
>>> to measure battery temperature.
>>>
>>> My personal preference is to NOT use Li-Ion, but to use NiMH cells,
>>> which are quite safe and are being
>>> constantly improved. (The inherent instability of Li-Ion cells and the
>>> problem with Chinese manufacture of
>>> defective cells cause me not to use them.)
>>>
>>> In any case:  Good luck.
>>>
>>> --Bob
>>>
>>
>>
>> Are there any single chip NiMH chargers around? All the single chip
>> chargers I find are Li-Ion. I used one of the LTC Li-Ion chargers in one
>> project, and it worked out well. I'm working on another project now
>> using
>> NiMH. So far I have the PIC controlling the charging.
>>
>> Harold
>>
>>
> Actually, there are a few NiMH charging chips (LT makes a couple). But
> you CAN charge NiMH with a PIC.
> I just pulse the battery with 0.1C to 0.2C and let it rise slowly until
> it reaches the 'dip'.
>


Thanks! The NiMH chargers I've seen take a bunch of parts around them.
They're not nearly as simple as the Li-Ion chargers. The "constant current
charge and wait for voltage dip" is close to what I'm using now. I'm
watching the voltage and if it hasn't gone up from the max received so far
in this charge cycle for some period of time, I say it's done. I had to do
this because the charging battery was still powering a varying load. In my
redesign, I'll have the rest of the circuit running on the external supply
instead of the battery during charge.

Harold

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