[HomeBrew] DC isolator circuit?

[Ray LaRue]

I currently have a 14 vdc, 30 amp AC power supply wired across a bank of 
12 volt batteries to power my station from.  When on batteries only, I 
have a DC to DC voltage booster to provide full voltage to my radios.

I currently manage the battery charging manually.  But I also need some 
isolation of the AC PS from the batteries, when the AC power fails.  I 
don't want to use diodes because of the forward voltage drop.

Thus, I am looking for a circuit probably utilizing power mosfets, that 
would isolate the 14 vdc AC power supply from the bank of 12 volt back 
up batteries and also charge the batteries at a preset 13.8 vdc when AC 
powered.

I know how to do this with diodes but I don't want the forward voltage 
drop of silicon power diodes.

The low "on resistance" of power mosfets should cause little forward 
voltage drop under load.  But I've not been able to find a suitable 
circuit for I want.  I also want to include a low voltage drop "wrap 
around" charging circuit.

Has anyone done this that can lead me to such a circuit?

Your attention is appreciated.
Ray, W4BYG

-- 
It Ain’t What You Don’t Know That Gets You Into Trouble.
It’s What You Know For Sure That Just Ain’t So.
Mark Twain


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