In market, there are really no
good charger than what you describe
below.

But it seems too expensive if reach
the specification of yours. discharge
5A? Charge 5A is easier than
discharge 5A. So, simplifying you
plan seems unavoidable.

Through too long time trying and
step by step solving, I have one
pic charger running on my table.
realiable and playable. Those big
ic manufacture's charger ic, none
of them really work! most funny thing
is those 15min/one hour charger,
they are just battery killers or 1/3-charger.
For example one simply problem they missed:
contact resistant of battery holder is all time changing!




----- Original Message -----
From: "Philip Pemberton" <philpem@dsl.pipex.com>
To: <piclist@mit.edu>
Sent: Friday, December 23, 2005 9:07 PM
Subject: [PIC]: PIC based NiMH charger


> Hi,
>   After having yet another NiMH charger die on me (at least this one gave
me
> a firework display before it gave up), I started thinking... what about
> building a battery charger... The question turned to "What should I use to
> control it" - the answer inevitably ended up being "a PIC".
>
>   Has anyone built an "intelligent" NiMH charger out of a PIC? What I'm
> thinking about building is something with these specs:
>
>   - Reflex (aka burp, negative pulse, ...) and Constant Current Fast
charging
>   - Charge current variable from 50mA to 2A
>   - Discharge pulse current variable from 100mA to 5A
>   - Timing variable from 30 minutes to 8 hours
>   - Onboard voltage-vs-time data log (I need an excuse to use one of those
>     FRAM chips that's been cluttering my junkbox for ages)
>   - Charges 1 to 4 NiMH cells
>   - PC link to download data log, view charger status, upgrade firmware
and
>     tweak algorithm timing
>   - 16x2 LCD display
>
>   As far as current regulation goes, I was going to use an opamp with a
> push-pull driver stage to do both charging and discharging. A DAC will be
> used to produce a +/- 2.048V signal that'll be fed to the opamp to select
the
> charge/discharge voltage.
>
>   What I'm thinking about is something along the lines of an ICS1702, but
> implemented in a far more versatile way... That said, it seems Galaxy
Power
> have vanished, so ICS1702s might be a little hard to get anyway...
>
>   Anyone got any comments on this? Is it worth bothering implementing
Reflex
> charging, or should I just stick to constant-current with voltage-delta
> termination?
>
>   Yes, I know this could potentially turn into a REALLY expensive project,
> but I've had two chargers die recently, and I'm sick of spending good
money
> on something I'm not even sure is charging the batteries properly... At
least
> if I build my own, I get to play with the algorithms and make DAMN SURE
it's
> charging them properly.
>
> Thanks,
> --
> Phil.                              | Acorn RiscPC600 SA220 64MB+6GB
100baseT
> philpem@philpem.me.uk              | Athlon64 3200+ A8VDeluxe R2
512MB+100GB
> http://www.philpem.me.uk/          | Panasonic CF-25 Mk.2 Toughbook
> ... Anything not nailed down is a cat's toy
> --
> 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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