Unfortunately, identifying if your have a failed leisure battery isn't easy. So you have to check what isn't the problem.
The first thing we would do ourselves is to check that the SCR is infact supplying a charge to the leisure battery. There should be 2 fuses protecting the circuit. The first will be near the van battery's positive terminal and the second should be close to the leisure battery's positve terminal. You need to check that both fuses haven't blown.
2 of our SCRs are intelligent units and only kick in a few moments after the van has started as the initial charge goes to the van battery. If someone else starts the van and you stand with your ear near the unit, you can hear it click on. But this won't be the case with the 3rd SCR as that operates automatically as the van's alternator charging circuit operates that.
We have a voltmeter and the initial lesiure voltage test is to check the battery's voltage at rest. Then start the engine and see if the volt meter shows a higher voltage once the engine is running for a few minutes. If it shows a higher voltage the leisure battery is receiving a charge.
We bench charge the battery every couple of evenings as we don't do enough miles for the van alternator to replenish the day's useage. If you keep drawing out more than you put back, then the battery will soon be empty - flat. If we spend 4 hours on the glass and our pump draws 3,5amps per hour, then we have drawn 14 amps from the battery that day.
It takes us about 10 minutes each way to drive home and back to the job the following morning. If the alternator is charging the leisure battery at 8.00 amps per hour, then we have only replaced 2.7amps back into the battery while driving.
Our 3rd van does an 18 mile round trip every working day, and a 25mile trip every second weekend. That van's alternator just manages to keep it's leisure battery reasonably fully charged, so only needs a top up every couple of weeks or so.
If you do regularily bench charge your leisure battery and it's a few years old then just replace it. If it's not old and you don't top up the charge, then the battery was probably just flat.
We can't test a leisure battery in the same way as we test a car battery. With a car battery it is fully charged with the filler caps removed, then put under load. If the water in the cells starts bubbling, then you have a duff battery and the solution is to replace it. Unfortunately most leisure batters are sealed and aren't designed to discharge under load like a starter battery is.
