Tracing battery drain.
Discussion
Does anyone know a good methodical procedure for tracking down what might be draining the engine battery on a motorhome? I have a good multimeter and a selection of crocodile clips.
I was going to connect the meter in series between the earth cable and the battery then remove what fuses I can find (not familiar with the van) one at a time until the current drops to 0. Question is, am I likely to find the fault this way? Hwo much current draw is acceptable for the items that are always on? I'm guessing stuff like the alarm and clock will be drawing current, but not a lot.
I was going to connect the meter in series between the earth cable and the battery then remove what fuses I can find (not familiar with the van) one at a time until the current drops to 0. Question is, am I likely to find the fault this way? Hwo much current draw is acceptable for the items that are always on? I'm guessing stuff like the alarm and clock will be drawing current, but not a lot.
The normal amount of drain with everything turned off should be about 0.06 to 0.08 amps depending on what is "live", like radio memory, clock ,alarm etc.
Always wait a while for the ammeter to settle to a stable reading, some cars can take as long as 20 minutes for some ECU to go "to sleep".
Always wait a while for the ammeter to settle to a stable reading, some cars can take as long as 20 minutes for some ECU to go "to sleep".
Depends if you need to find out in a hurry, or have time to work with. If the latter just charge it up over night and pop one of the fuses. If it goes flat, replace that fuse, recharge and pop a different one.
Won't get you to exactly what's draining the battery in one go but will get you to the offending circuit.
Won't get you to exactly what's draining the battery in one go but will get you to the offending circuit.
Sorry for not responding sooner. It's not my vehicle so wont be able to embark on a long winded diagnostic. Could do with something that I can spend an afternoon on. I realised that with it being a motorhome, it has two electrical systems. I've no idea how the "leisure" and engine systems integrate, or whether this makes diagnosing the fault more difficult.
You're right regarding the two electrical systems. The basics of it are that you have a split charge relay, which when the engine is running, will charge your vehicle's battery and the leisure battery. Depending on the age of the motorhome, the power supply panel (in the accomadation area)will have a switch marked 'car', 'motorhome/caravan' and 'off'.
This is the other link to the van's battery. When this is off, it SHOULD be completely separate from the van.
Perhaps you could try locating the split charge relay and safely isolating its output to the leisure battery and disconnecting the leisure battery. This should isolate the fault to the van's own battery and circuits. From then on, it's a case of carrying out what you suggested in the first place.
This is the other link to the van's battery. When this is off, it SHOULD be completely separate from the van.
Perhaps you could try locating the split charge relay and safely isolating its output to the leisure battery and disconnecting the leisure battery. This should isolate the fault to the van's own battery and circuits. From then on, it's a case of carrying out what you suggested in the first place.
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