> In my case, I was looking to charge a gel cell that runs some radio gear.
> I didn't want the battery charged unless the car was running, so that once
> the key was off, the radios would run till the gell cell ran down, but NOT
> the vehicle battery.   It also dosen't suck to have better regulation.

Hi Dave(it is Dave, isn't it, just with a new handle?)

Why not just use a relay to connect the batteries whenever the voltage is
over  some preset voltage? I've seen this method used quite successfully
in commercial products.

Or you could use two back-to-back PMOSFETs if you didn't want to use a relay.

Cheerful regards,

Bob

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