VOLTAGE DROP

if not too inconvenient, take it back and get them to do the same check as you, with their test gear, you witnessing.

could be a high resistance joint at the anderson (poor soldering or crimping or both.)

is your camper connected when you measure at the anderson?

Hi Muzz

I have an Anderson plug on the back as well because, like you, I found that there was a large voltage drop between the car and trailer.

I left the original wiring at the trailer plug as it is and ran a pair of 6mm cable (conductor diameter) from the front of the trailer to the fridge. Because the fridge is isolated from the house battery, I now have two separate circuits. The voltage drop went from about 3 volts to less than 1 volt.

You haven't said whether your problem is charging the battery or effectiveness of the fridge. My problem was the fridge.

Measuring the voltage at the battery may be misleading because there is an isolating diode in circuit to prevent the fridge running off the battery. You will always experience a .6 volt drop across a diode. This is normal.

As far as charging the battery is concerned, I have an Arrid Twincharge battery charger installed. It will fully charge the house battery with input voltage anywhere from 8 to 15 volts.

Good luck
Mike

Some questions that are also points along the path to find the cause of the voltage drop:

Where does the "hot wire" originate? Does it run directly from the Patrol main or second battery, via a fuse/circuit breaker to the plug?

Where does the earth come from?

What is the size of both wires?

Has the Anderson plug been assembled correctly (springs on the opposite side to the contacts, wire cleaned before crimping/soldering)?

Where are you measuring at the camper end? What is plugged in at the time (fridge, lights, batteries)?

Voltage of the camper batteries when disconnected (if the batteries have never been charged properly then trying to charge via a hot wire will take a very, very long time - if the battery is low 9.6v if the drop is 3v it may never charge)

What's the wiring like between the anderson plug on the camper to the battery (number of connections, circuit breaker, size etc)?

Hope this helps as a start.

Adrian

Muzz, this makes no sense. If you do not have the trailer lead connected to the car, the voltage at the trailer end of the Anderson plug from the battery should be exactly the same as the battery voltage. The only current being drawn on the lead SHOULD be the minute amount drawn by the multimeter which even with undersize cable to the battery, will have no measurable voltage drop.
If there is a load on the camper battery somewhere off this wiring then what you are seeing makes sense as the current drawn by this load will cause a voltage drop if the wiring is too light. Check that there is nothing loading the battery off this lead, if there is isolate it and the voltage at the plug should be the same as the battery terminal voltage. If this is the result you see you need to find where the voltage drop is being generated. It could be the wire gauge is too light or there is voltage drop across some of the connections. It won't be in the Anderson plug as you are not drawing any current through it if I understand your test method. I'd start with the battery terminal connectors as I have had problems with a vehicle main battery where the inside of the connector clamps are corroded resulting in a poor connection to the battery posts. A measurement on the battery terminals and another on the outside of the clamp might show an interesting result.
Good luck,
Ken

G'day Muzzgit,
if your internal wiring is as it was out of the factory, even if it has been uprated, this might explain the difference.

The auxilliary line goes into a switched input on the regulator which essentially isolates the wiring back towards the vehicle. While I haven't tested it, I think it will also act to minimise discharge back into the vehicle if the engine is off and power is being drawn on that circuit.

As indicated above, it also allows for switching of power to the fridge when there is power from the vehicle, but disconnects the fridge from the house battery when the vehicle is disconnected.

I suspect if a load was placed across the anderson plug, you would see zero or next to zero volts available.

If I get a chance I will test the theory on mine.

Cheers

Peter

OK. Just picked up the camper from the auto leccy.

NO VOLTAGE DROP FOUND.........on his multimeter.

BIG VOLTAGE DROP FOUND.........ON MY MULTIMETER!!!

BUGGER!!!

Another item on the XMAS prezzy list.

Thanks for your help and suggestions.