The Problem With the Lawton Circuit

[bigfatpothead]

Well, The problem I have with it.

I read my car owners manual and it says
if I connect a trickle charger to the battery while
it is in the car and connectedto the car.
It says this will damage the rectifier in the alternator.
This is what happened, The charging system started putting out 17.5 volts with the engine running, and with the engine off and key out
the alternator discharged the battery.
so massive overcharge = boiled over battery, battery acid everywhere, blown bulbs all around,
I have replaced my alternator (94 ford escort 1.9L) and the bulbs.
What I need to do is ISOLATE my Lawton circuit from the rest of the cars wiring. I assume I can do this with a couple of DIODES.
Does anyone know of a way to isolate the circuit?

[Super God]

There are many ways to 'isolate' a circuit.  Transformers 'isolate' circuits.  You could use a switch to 'isolate' the circuit when you need to, or switch it through a relay connected to the ignition.  I hope this helps!  By the way, transformers aren't suggested, go with a switch instead!