Battery Isolator Test

[RV-Ron]

Sent: 9/1/2004 12:38 AM

Does anyone know how to test a battery isolator?

Thanks

[Cooneytoones]

From: cooneytunes
Sent: 9/4/2004 12:01 AM

If it's a solid state battery isolator the way it works is, separates two or more batteries using dioads that are one way check valves. Each battery receives current FROM the alternator,but the batteries are never connected in parallel. When the coach battery is being discharged, a diode keeps the starting battery from being discharged with the aux. battery. Current can only flow from the alt. When you start the engine, the isolator controls current flow to both batteries, charging both as needed. Now that that's out of the way. If your sure you hooked it up correctly. There are three different types of Alt. and each one is wired a little differnt to the isolator.
Test teminal A (engine off) reading may be 0 to 12 volts
test terminal 1 on isolator (engine off) should ready vehicle battery voltage
terminal 2 (engine off) should read Aux. or coach battery voltage
terminal e (engine off) should read 0
Now with the engine running and Alt. charging
terminal A should read 14.8 to 15.2 volts
terminal 1  2  & E should read .8 to 1 volt less that would be 13.8 to 14.2
The A should be approx. 15 volts The 1 & 2 posts should read 13.8 to 14.2  if the A post reads 13.8 to 14.2 the regulator is sensing the Alt. output rather than the main battery
It's important to have the right gauge wires for length or run and the Amp out put of the Alt. You loose about .8 volts with any diode, the Alt. should compensate for that, but if your wire is too small  for the length it has to run, you can melt the wire or have to much resistance for the right voltage to flow. Most problem with Solid State isolators are stuck or open diodes and only fix is replace isolator. Hope that helped ...Timmy