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Rewiring the Battery Supply

Dec 2013: Most of the description here is out of date with the fitting of a lithium battery. It is retained for historical interest.

As changes to the Applause have been made, they have caused me to make changes to the main 12 V wiring. Adding the State of Charge Meter has caused me to simplify the connections to the house battery to a single cable for each pole and to make use of Clipsal Connector Blocks L7R (red) and L4T35 (black) as distribution points.

The Elektroblock does not measure total battery current because the solar power manager is wired independently (though I could change this), as are two 240 V inverters).

Investigation of the rather high voltage drop between the house battery and the fridge (0.68 V) showed the cause to be the large distance between house battery and starter battery, and the consistent use of negative return wiring rather than using the vehicle chassis as negative return. Normally best practice, the negative return cable for the fridge was approx. 22 m in length when running off the house battery and the cause of most of the voltage drop. While keeping the negative return wiring in place, I have grounded the negative pole of the house battery to a local chassis point (the rear wheel arch, as shown here in a photograph) and the negative line at the fridge to a separate local chassis point. The voltage drop at the fridge has been reduced to 0.15 V. Further detail can be found at the discussion of changes to the fridge installation. One result of the change is that the Ducato alternator now supplies a few amps more to the house battery when operating.

I have replaced the main wiring between the house battery and the Elektroblock with welding cable. Two x approximately 2.1 m of this 38 mm² (better than 2 AWG) cable are used. The voltage drop for a 30 A current draw is reduced from 0.3 V to 0.05 V.

At least for the present, I will keep the wiring for the solar regulator unchanged. This and the new current shunt allows the house current meter to monitor both the current consumed (via the Elektroblock, not including the infrequently used inverters) and the total current input to the battery. The difference is the current input from the solar panels.


More recently I have also added a trunk cable (twin sheathed 6 AWG) from the battery board to the front of the vehicle in the cab roof space above the driver. This heavy cable has a Jaycar 60 A fuse inline (gold holder type SZ2060 and 5AG gold fuse type SPF1978) at the battery end.


The cable is run up the wall cavity behind the cooktop and along the track for the vehicle sliding side door to the Technical Cupboard above the fridge. There it enters a 32 A DIN Rail 230 V AC circuit breaker (from Jaycar) and then across the van in the cab ceiling and under the microwave oven to a junction on the front wall of Cupboard 1.

Circuit breakers made by Clipsal are rated to 48 V DC. I expect the Jaycar one to be similar, so it should be fine for the 12 V application here.

On its way from behind the range hood to the Technical Cupboard, the trunk cable wiring passes behind the cover to the sliding side door track.


Technical Cupboard


The Technical Cupboard above the fridge is used to store tools, parts, and similar supplies for the Applause. It also is a convenient place for small electrical items and power leads etc.

Changing the wiring to the Omni-Step freed up a 12 V power cable that could be routed into the Technical Cupboard. With a 5 A blade fuse inline, this pair has been used for the LED cab light and the lighting in the cupboard.

Mounted in the Technical Cupboard, the circuit breaker on the trunk line provides some protection for the wiring. It is also a convenient switch for all that is powered from it: three cigarette lighter sockets for mobile phone and battery chargers, two Hella type 4917 surface mount sockets for the TV and any other heavier amperage item fitted with Hella type 4914 plugs, and anything connected to the junction on the front wall of Cupboard 1.


12 V Wiring


Battery in its box with revised wiring. The temperature sensor for the solar regulator is on the negative terminal.


Battery power board mounted on the wall with cables connected.

technical cupboard (63 kB)

The cupboard above the fridge is the "technical cupboard".