The leisure battery is draining of power whilst we’re driving - or stationary with the engine on. When we switch off the engine the drain stops. It’s about a 12 Amp drain, so pretty serious! The vehicle has a Smart Alternator. Can anyone suggest any reasons why this might be happening?
Leisure Battery Drain Whilst Driving
- Thread starter StuartB
- Start date
Depends what you are looking at , ours standing in the sun will show 14 volts, but as soon as you start it up it will drop to 13, because starting it up has the effect of joining the batteries together so brings the hab down to engine power, but it's only on the dials.
As soon as you stop the hab starts going up again as the solar kicks in.
The fridge is off. Radio is off, air con off. Just a phone and a Garmin Sat Nav plugged in the cab - nothing on in the hab.
Have you checked your starter battery is ok?
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It started fine this morning. I had it on hookup at home for a couple of days before leaving and both batteries were fully charged. It’s only now that we’re driving that the leisure battery charge is plummeting at ~12 Amps. After about 4 hours we’ve 20% - lost 40 AmpHours.
We don’t have any solar, unfortunately. It’s an uncontrolled discharge from the leisure battery of around -12 Amps.
Just a guess but maybe the alternator isn't working. Our car uses 8 amps when engine is running, found out when the alternator failed.
I'd disconnect the leisure battery next and see what that does.
I'd disconnect the leisure battery next and see what that does.
OK, I’ve done that and it’s stopped the drain on the leisure battery, which is great! Not too sure where the vehicle is getting its electricity supply from now. Hopefully the alternator, but I can’t check the status of the vehicle battery when driving….
If it has a smart alternator and the constructor has only installed a split charge relay the current could be flowing out of the leisure battery, rather than into it. If the constructor hasn’t fitted a B2B/Booster you probably need one.
The difficulty created by smart alternators is that they are set up to keep the engine battery voltage low, often about 12.3V. This leaves room for the alternator to recover power that would otherwise be wasted when slowing down or braking. However if the engine and leisure batteries are linked by a simple split charge relay the ECU (Engine Control Unit) can read the higher charged leisure battery and shut the alternator down. The higher charged leisure battery may then empty itself into the engine battery.
Edit. This link may help to explain the problem.
The difficulty created by smart alternators is that they are set up to keep the engine battery voltage low, often about 12.3V. This leaves room for the alternator to recover power that would otherwise be wasted when slowing down or braking. However if the engine and leisure batteries are linked by a simple split charge relay the ECU (Engine Control Unit) can read the higher charged leisure battery and shut the alternator down. The higher charged leisure battery may then empty itself into the engine battery.
Edit. This link may help to explain the problem.
Aux Battery Charging With Smart Alternators | 12 Volt Planet
A guide to the benefits of using battery to battery chargers to overcome split charging problems caused by smart alternators on modern Euro 5 & 6 vehicles.
www.12voltplanet.co.uk
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