I agree, Galaxy Power chips are the best, the problem is that they do not 
manufacture them any more.  They still provide their algorithm, as software, 
for use in any micro.

A simple pause charge/peak detect algorithm works quite well.  There are 
several pieces of open source code avilable, I will include an example in my 
reply tomorrow.

Steve
----- Original Message ----- 
From: "Dave VanHorn" <dvanhorn@dvanhorn.org>
To: "Microcontroller discussion list - Public." <piclist@mit.edu>; 
"'Microcontroller discussion list - Public.'" <piclist@mit.edu>
Sent: Wednesday, May 11, 2005 11:44 AM
Subject: RE: [PIC] Backup Battery


> At 09:14 AM 5/11/2005, Daniel Chia wrote:
>>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?
>
> Sanyo "C" type cells are rated to tolerate C/10 trickle.
>
> Cheap chinese cells would be especially bad with this. They tend to have 
> problems with electrolyte, catalyst, and seals.
>
> Too much electrolyte leaves too little air space, raising the pressure to 
> the venting point.
> Once vented, the vents don't always re-seal.
>
> Too little electrolyte reduces performance in gross amp-hours.
>
> The catalyst helps the H2 and O2 recombine, but it's expensive.
> Less catalyst, and you can end up with a pressurized can of rocket fuel.
>
> Vents can be either non-functional (see above) or leaky, allowing the H2 
> to escape, leaving very reactive O2 in the cell, ready to react with 
> anything it can find, and not usually in a good way.
>
>
> In general, I would not advise the maxim charger chips.
>
> Galaxy power's chips are much better, as long as your system meets their 
> assumptions (simple, uncomplicated,  no large variations in discharge 
> current while charging, or ideally no discharge while charging at all., 
> etc.
>
>
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