On 02/16/11 10:15 am, raypsi wrote:

snip

... I built a flooded lead acid charger. I only bought one part the
IC UC3906, I already had a solderless breadboard, the resistors and
capacitors in my junk drawer
The hardest part was figuring the resistor values and how to make
those values, and that was easy.
The heatsink fan came from an old CPU fan heatsink, and I mounted the
pass transistor to that heatsink fan.
I think that the UC3906 was the best think since sliced bread

I've seen schematics and board layouts for SLA chargers based on the
UC3906. VK3EM's uses SMT components, while N5BIA's uses discrete
components -- but both are only for charging currents of 2A or so.

For what current did you build yours? If high-current, what pass
transistor(s) did you use?

N5BIA offers a kit, and I was wondering whether this could be beefed up
to handle 25A by adding 12ga wire to all the charging-current traces and
substituting higher-current pass transistor(s). I'd have to recalculate
the resistor values to suit a flooded battery, of course. And what about
using a P-channel MOSFET device, such as the STP80PF55 that the "Micro
M+" uses?

"Perce"