Pin 9 feedback to tow car

Mar 4, 2019
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Does anyone worry about this? I have leisure battery which is usually better than car battery. Batteries are paralleled through pin 9, and also pin 10 with ignition. I do not have habitation relay and I can run my fridge 12 v anytime. I prefer to do this when driving to keep gas for camping.
I have measured leisure battery feeding current back to car:
1. Starting car, 20 amp surge back.
2. High car load (lights, fan, usb, glow plugs) Leisure battery supplying up to 10 amps.
Alternator charging or turning on the van fridge 12 v stops most feedback. But there is often circumstance when leisure battery is draining back to car:
1. When stopped and fridge on gas.
2. WAECO car freezer in stationary car, leisure battery will be putting into this.
What to do about it?
1. Don’t like the idea of diode in pin 9 supply, voltage drop.
2. Relay up pin 9 to power only when alternator charging. (This may be illegal although I have no electric stability on this van)
 
Nov 11, 2009
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Even when travelling in Europe in summer I found that the caravan fridge was able to maintain the food cool during the daytime driving, then on EHU, or gas for overnight stops. Cannot really see why you need to complicate the electrics. But your changes would not be illegal as Im not aware of any legislation that affects the system, even with ATC.
 
Mar 4, 2019
49
12
10,535
Visit site
Does anyone worry about this? I have leisure battery which is usually better than car battery. Batteries are paralleled through pin 9, and also pin 10 with ignition. I do not have habitation relay and I can run my fridge 12 v anytime. I prefer to do this when driving to keep gas for camping.
I have measured leisure battery feeding current back to car:
1. Starting car, 20 amp surge back.
2. High car load (lights, fan, usb, glow plugs) Leisure battery supplying up to 10 amps.
Alternator charging or turning on the van fridge 12 v stops most feedback. But there is often circumstance when leisure battery is draining back to car:
1. When stopped and fridge on gas.
2. WAECO car freezer in stationary car, leisure battery will be putting into this.
What to do about it?
1. Don’t like the idea of diode in pin 9 supply, voltage drop.
2. Relay up pin 9 to power only when alternator charging. (This may be illegal although I have no electric stability on this van)
Forgot to mention this feedback became more of an issue when I recently upgraded pin 9 to 6mm cable. Hardly any feedback thru pin 10 with 2.5 mm (maybe 1.5?)
 

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