I agree with the comment on the maxim nimh charger chip. The trickle
current I just way too high! I have to keep a watchful eye for full
charge then quickly kill the charger else my batteries get really hot!
Anyone know a workaround for this?

------------------------------------------------------------------------
Daniel Chia

"Genius is one percent inspiration and ninety-nine percent
perspiration."

     - Thomas Edison

E-mail: danielcjh@yahoo.com.sg
MSN: danstryder01@yahoo.com.sg
ICQ: 37878331
------------------------------------------------------------------------


> -----Original Message-----
> From: piclist-bounces@mit.edu [mailto:piclist-bounces@mit.edu] On
Behalf Of
> Steve Halla - LEAP
> Sent: 11 May 2005 04:21
> To: Microcontroller discussion list - Public.
> Subject: Re: [PIC] Backup Battery
> 
> Respectfully, pause charging allows even NiMH to develop a detectable
> voltage peak prior to overcharging.  read NASA to find out that they
have
> used pause charging on NiMH cells (up to 300V packs) on crew recovery
> vehicles.  With conventional approaches like Maxim and Benchmarq, you
are
> correct in saying that NiMH cells can be complicated to charge quickly
and
> completely.
> 
> Steve Halla
> 
> ----- Original Message -----
> From: "Dave VanHorn" <dvanhorn@dvanhorn.org>
> To: "Microcontroller discussion list - Public." <piclist@mit.edu>;
> "Microcontroller discussion list - Public." <piclist@mit.edu>
> Sent: Tuesday, May 10, 2005 4:08 PM
> Subject: Re: [PIC] Backup Battery
> 
> 
> > At 02:53 PM 5/10/2005, Steve Halla - LEAP wrote:
> >>I believe that we may be making battery charging too difficult.
> >>
> >>Heat is the single worst cause of battery failure and poor
performance.
> >>To minimize the heat on charge build up (for any battery), pause
charging
> >>is the most effective way to make a simple charger.  Ni cells can
all be
> >>easily charged with constant current with an LM317, terminate at
peak
> >>voltage. Both SLA and Li can be charged to their respective fixed
> >>voltages, and still be safely pulse charged to provide 87-93%
nameplate
> >>capacity.
> >
> > NIMH is a very complicated chemistry to charge, especially if you
want to
> > do it quickly, and not damage the cells.
> >
> > Charging to peak voltage, will get you a false early termination on
cells
> > that have sat for a while.
> > Read the data sheets at Panasonic and Sanyo, they will give you a
good
> > start, and have a look at Galaxy power's chips.
> > The maxim "nimh" chip will cook most NIMH cells because it's
constant
> > trickle current is way too high.
> > Some NIMH cells will TOLERATE C/10 trickle, others specify ZERO
trickle.
> >
> > --
> > 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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