by GeorgeTelford » Wed Jun 21, 2006 3:54 am
Hi Paul
My bad, Like Jack I read the original post to mean a manual Isolating switch, when I read your post, it seemed to mean that you would have a switch as well as the isolating diode.
Quote Paul C I don't profess to know how they work but I've been told they operate on voltage balance versus the main battery being at optimum charge at all times.
Just to clear this up, your sources are incorrect, the Isolator is a diode, basically there are 2 one way streets leading away from the middle pin, Optimum charge, hmm there is the biggey
There is an experiment I have always wanted to do to see if an Isolating diode, improve's the charging beyond 65-70 %
The reason that a battery doesnt get fully charged via an alternator are very complex ( to the point that when I have demonstrated this to some people with degree's in electronic engineering and they still cannot get their head round whats happening )
Anyway onwards, the diode has 2 known effects, one it keeps the batteries totally isolated from each other, this is because diodes only allow power one way, the other is that they use up approx .8 Volt doing it and there is the rub. for comparison isolating relays allow the batteries to see each other when the alternator is running.
An alterntor puts out 14.4 to 13.8 Volts, with an isolating diode inline, this instantly drops to 13.6 to 13.0 Volts and thats before any voltage drop due to wiring.
To summarise
1. They are the surest means of battery seperation
2. There are no "backfeed" losses beacause of the above
3. There is a voltage drop penalty