Hi,
   Has anyone here got a recorded charge profile from a NiMH battery? What I'm 
after is - in effect - a spreadsheet with three columns:
   - Time
   - Voltage
   - Current (optional)

Does anyone have anything like this kicking around their HDD? The battery 
manufacturers seem to be quite happy to give out pretty pictures of their 
charge profiles, but don't seem to publish actual numbers.

I want to play around with charge termination detection algorithms for my 
(half-done) NiMH charger, and I don't have any test data to feed into my 
detection algorithms. I figure while I'm waiting for the parts for the 
discharger circuitry to turn up (a DAC, a voltage reference and a few 
op-amps), I might as well get some of the software algorithms tested and 
tweaked for use on a PIC.

What's bugging me is that the manufacturers are saying one thing (wait for dV 
to hit -5mV per cell) while all the books and websites I've been scanning 
through are saying different things. One suggested "zero voltage delta" (wait 
for dV to get close to zero) and another suggested "inflection point sensing". 
The latter involved calculating the first or second-order derivative of dV/dt 
and looking for the point where the derivative crosses zero. Surely that would 
produce the same result as zero-delta sensing though?

The main thing is that -dV is reputed to slightly overcharge the cells (which 
produces heat, which is bad) and 0dV allegedly stops that. But if you get the 
trip point wrong, you end up undercharging the cells, which is also bad.

As far as preferences go, data for any cell manufacturer is fine, but Sanyo 
(or anyone who rebrands Sanyo cells - Kodak, Energizer or Duracell) or another 
name-brand (Uniross excepted) would be preferred. Same for cell count - given 
the number of cells in a pack, I can get the per-cell voltage back pretty easily.

Thanks.
-- 
Phil.                         | Kitsune: Acorn RiscPC SA202 64M+6G ViewFinder
philpem@dsl.pipex.com         | Cheetah: Athlon64 3200+ A8VDeluxeV2 512M+100G
http://www.philpem.me.uk/     | Tiger: Toshiba SatPro4600 Celeron700 256M+40G
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