The battery on my M reg Fiat Punto is often flat in the morning, even
though it was fully charged the night before (according to the green
led on the battery). The only way I have been able to 'cure' this
fault is by disconnecting the battery every time I stop the engine.
Sometimes I can hear a click from a relay in the engine compartment
when I disconnect the battery and sometimes there is a little spark at
the battery terminal indicating a large current is being drawn.
However, when I measure the battery current with a multimeter it reads
Connecting and disconnecting the battery in a modern car will just about
always result in small sparks, clicking relays etc.
Your say you have 5mA current drain with everything off. This looks a
little low but is possibly accounted fo by the multimeters realtive high
restistance when measuring low currents.
If your are sure you have no current drains, e.g. the boot light is
soemtimes common cause of unexplained battery drain, then you could be
looking at battery self drain. This happens when sediment, which builds up
over time, effectively shorts the bottom of the battery plates out resulting
in internal current drain.
In my experience if this internal drain is happening then a battery left
disconnected over night will most prabably survive. However when connected
the natural car idle load will push the battery too far.
If the battery can withstand 100+ hours disconnected and still be able to
start the car then a vehicle electrical fault may be present.
Often the easiest solution is to replace the battery and see what happens.
Many battery outlets will test your current battery free of charge. The
problem here is that when you have driven to them the battery is quite well
rejuvinated by the drive and my well pass their tests. If you can take just
the battery, after 24+ hours of standing alone, then the tests results are
far more reliable.
Motorsforum.com is a website by car enthusiasts for car enthusiasts. It is not affiliated with any of the car or spare part manufacturers or car dealers discussed here.
All logos and trade names are the property of their respective owners.