After lots of internet searching, I found a small step up voltage converter on Ebay. The unit has a variable output, and a range of input voltages. The Dodge is still running on the original 6 volt system, which when charging is giving about 7.5 volts charge from memory ( It's a while since I checked ). The converter was tested in the workshop with a 7.45 volt input from a car/motorcycle battery charger, and under no load, the voltage converter was set to give about 13.5 volts out. When this was connected up to a 12 volt battery to charge, the voltage dropped to 13.3 volts at between 0.5 and 1AH charge rate. I'll have to make final adjustments to the output voltage once it is connected to the Dodge electrical system. I will also be fitting switches to turn it on and off, and also isolate it from the radio battery. The unit was built into a small case and plywood mount to fit it into the truck somewhere.

Before taking the truck back after the DLI show, I've done a little internal wiring. I've taken a 12v power feed from the BC-375 transmitter across the top of the rear doors, and down into the Meteorological Panel. From there it splits with one feed going to the small panel light switch and the other feed is regulated to top up the charge of the 2 volt battery running the clocks. This will mean I can charge them from an internal supply, rather than having to bring in a charger. I've just ordered a step up voltage converter so I can charge the 12 volt radio battery from the Dodge's 6 volt electrical system while driving. This will save me having to constantly lift the battery in and out for each event. I'll fit this next time I have the truck home.