Auto Electrician with Caravan Experience

Magnus,

I have run 10 mm square cable to the rear of my vehicle to an Anderson plug, so I have negligble drop at the trailer connection. Dual battery system in the car.
However, the cable to the van battery is less tha 6 mm auto or about 4 mm square and there is a charging diode in the circuit as well. Two problems here. a) The voltage that actual ends up at the battery to effect charging from the vehicle and b) the current capacity of the cable if the deep cycle battery is partially discharged.
I want to consider using some sort of device like the Arrid Twin Charger to boost the voltage at the battery terminals. I also would like to install a simple expanded scale voltmeter inside the van to allow monitoring of the state of battery discharge.
By way of the charging diode, the fridge can only be powered by 12 V from the car. Again, the cable to the van introduces a voltage drop which may lessen the effectiveness of the fridge especially in outback summer temperatures.
I am looking for someone that understands these problems and can advise how best to deal with them within my budget and then do quality work within the limits of recabling the van.

Magnus,

It is a three way fridge (Electolux). When stopped (camped) it runs on 240 V ac or on gas. Only runs on 12 V dc while on the move.

Rosscoe,

Have been down this road. Have used 3 way fridges for years and never been successful in getting them to operate as more than a cooler on 12 volt.

Have managed to get them to run on gas while in transit but stopped doing so as it wasn't worth the hassle. Especially when the fridge was mounted on the drawbar of the trailer!!! They work really well on gas on the move.

As we only spend 6 to 8 hours max in transit I just live with the defrosting. We have never lost food as the fridge stays quite cold but not as cold as on gas or 240.

I use a large scale meter to show amp draw and amp charge while using lights and the solar panel. Reads one to 5 amps.

Was using a digital voltmeter from Jaycar to monitor battery state. First one was destroyed and the second one led me to think I had battery problems. Turned out it was reading a full half volt out. That is the difference between a recharge and taking no action on a deep cycle battery.

Now use a multimeter to test battery. Have two so I can check them against each other. Two were only slightly more costly than the digiutal voltmeter in any case.

As was pointed out to me on this forum, measuring State of Charge on the fly is not of much use in any case. Some battery sites on the net suggest as much as 24 hour resting before measuring an unloaded SOC of a battery. I make do with the 12 or so hours from lights out at night to the next morning and now measure with the multimeter.

Hope you are able to get good help from the Sydney contact. Best of luck in getting it all sorted.

Cheers

Magnus

Hi Magnus,
Thanks for the comments.
I think it's a matter of maximising the performance on 12V. I don't think it's ever going to be as good as it is on gas.
Re checking the state of the battery, you're correct about letting it rest before you check. The voltmeter in the van is just another way of keeping an eye on things. I also carry a digital multimeter and a Hydrometer.
I have purchased a low cut off relay but haven't installed it yet because of "the bounce" effect of the battery. It does have a by-pass switch though which should allow me to use my shouder mounted computer to make a final decision as to when the discharge level is getting critical.

Regards,

Rosscoe

Bob,

Thanks for your input. I've been refered to a company in Nowra who does work for the mob I purchased the caravan from.
Given the traffic between where I live in Wollongon and Rydalmere at the moment I'm opting for Nowra.

I don't blame you