Hi, Ron - more specs on the power source you want to use, would be
good.  If you always have AC power present, that's one thing - if
charging from a solar panel etc., that's different.

For lead-acid's you don't necessarily need to control the charging by
the PIC - can use a pretty simple voltage-based charging system;  or
just trickle charge constantly (less efficient though.)  Typically
charge at 14.6V or so for fast charging and at 13.8V for "float"
charging i.e. you can put a 13.8V power supply output across the
lead-acid deep cycle battery "forever" with no problems - READ them thar
data sheets for current limiting info, though, you will hurt batt's by
charging them too fast - you want to current limit as well as voltage
limit.  If you do this on a PIC, the info on how others've done this
with other IC's is good knowledge <G>

National's LM317 works (A pair can give you current limiting and voltage
limiting.)  See their LB-35 for some info also on doing it cheaper
(Linear part so it can dissipate some heat, also the battery will tend
to warm somewhat but that's lots less than the linear regulator will
heat!)

http://www.repairfaq.org/ELE/F_Battery.html (GOOD info there),
http://www.repairfaq.org/ELE/F_deep_cycle.html,
http://fribble.cie.rpi.edu/~repairfaq/REPAIR/F_aapsfaq.html have some
info.

Pick the battery first, look at the data sheets, before designing the
charger <G>

For monitoring, look at Sigma Delta (or Sigma-Delta) techniques, in the
archives, I'm sure James has a link on piclist.com also.

  Mark

Ron Hackett wrote:
> Hi,
>
> I'm looking for a (simple) circuit that would enable a PIC to monitor and
> charge it's own battery (prefer lead-acid, but would also consider ni-cad).
> If anyone can provide a link to this sort of thing, I would greatly
> appreciate it.
>
> Thanks...  Ron

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