Bongo Fury

I have a good 110 amp leisure battery which has been in place since November 2013. I have never run anything big from it, eg a fridge. Just internal lights, DVD player, charging phones/iPad.

I had to change my SB recently. Since then my LB is showing 13.5 on the meter while the engine is running warm, 12.5 while idling cold, but drops down to 9 when I leave the meter plugged in while in work, or overnight. There is nothing but the plug-in meter running during the test.

My question is - Is my LB dying through natural causes (end of life) or could something have been caused by the SB getting low/changeover to a new SB?

Incidentally my driver side window switch has refused to work without the door being open since the new SB was fitted grrrrr! Was fine before. I know it's the wiring loom in the door - again, but what a coincidence!

When the engine is running your actually measuring the voltage of the two batteries in parallel as the SCR will have operated. The LB falling to 9v is not a good sign at all, either it isn't being charged or more likely you have a failed cell in the LB. Best thing is to take it for a run or charge the LB for several hours, then disconnect the LB and measure the voltage after about 1 hour of the battery being disconnected, if it is still around 12.6volts then that is a good sign but then you need to reconnect it and put some internal lights on to draw some current, if the voltage then falls below 12 volts after an hour it would indicate that you have a problem with the battery. During the testing don't start the vehicle at all just let the LB take the load on its own.

Thanks Geoff. When I've managed to go on a longer run and test this, I'll report back.