A fully charged battery only produces 12.6-7 VDC
Never hear of deal where you had something in a 12VDC vehicle setup that had to have 13VDC to work...
Only way you can get more DC voltage is using your alternator which will be producing 13.2 to 13.6 in normal mode and may jump up to 14.4-4VDC when in charge mode...
If you valve doesn't draw much DC current then maybe install another 6VDC battery in series with the 12V dc outputs and set it back to 13VDC with a resistor...
Maybe you need a newer toy haha...
Roy Ken
