Philip,

 Do you measure the tempature of the battery while
charging it? If so what method are you using?

John

--- Martin Klingensmith <martin-distlists@nnytech.net>
wrote:

> I found this website:
> <http://www.mpoweruk.com/chargers.htm>
> I don't know if you're going to find the spreadsheet
> you're looking for.
> There are many methods of charging batteries. What
> you may need to do is
> some experimentation.
> You mention that the -dv method slightly overcharges
> cells, creating
> heat. It was my impression that NiMH cells heated up
> as a result of
> becoming fully charged.
> My AA cells get pretty warm in the charger. There
> was an EV (the RAV4?)
> that had to run the A/C when charging, to keep the
> huge NiMH cells at a
> reasonable temp.
> --
> Martin K
> 
> 
> Philip Pemberton wrote:
> 
> >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.
> >  
> >
> 
> 
> 
> -- 
> Martin Klingensmith
> http://wwia.org/
> http://nnytech.net/
> -- 
> http://www.piclist.com PIC/SX FAQ & list archive
> View/change your membership options at
> http://mailman.mit.edu/mailman/listinfo/piclist
> 


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