The battery on my 99 petrol Astra was flat on Saturday am. Had it and the alternator checked and they are both fine. I'd be very grateful if anyone could suggest any likely causes of the drain or what I can do to pin down the source. Have checked that there are no internal lights staying on and there are no other obvious signs of anything that might be causing this.
Jerry
Most likely suspects are internal lights (especially boot lights) leaving the indicators on giving parking lights, radios, gps units, anything aftermarket, alarms, leaving keys in ign., bonnet, boot or door ajar
establish a meter connection to show if the battery is draining, if it is then try removing fuses or disconnecting things like the alternator till it stops draining (alternators can work and charge ok but still drain the battery) I once even came across a starter motor that drained the battery (how, I didn't investigate, but changing the starter cured the fault)
Mrcheerful
Very many thanks Mr C - I have a multi-meter but don't know how to use it to check whether the battery is draining. Is it easy to do? Any guidance much appreciated, to state the obvious!
you need a meter with an amps range on it of at 5 amps or thereabouts, connect the meter on amps scale to the lead and its mating battery terminal, lift off the battery terminal (this is easier said than done, you should do it this way as when you connect the battery there may be a significant current draw just for a moment, and if it goes through the meter you may damage the meter) , a tiny drain (0.03 amps) is normal, anything significantly above that shows a fault. Probably the first suspect would be to disconnect the alternator, if that shows no change then start pulling fuses/disconnecting things
OK, thanks again!
Jerry
One last thing - I checked the drain and it was .3mA so I assume that was the clock, alarm etc. After charging it for about 6.5 hours today it registered 11.5volts. Halfords didn't do a load test so I'm guessing that the 5 hours it was on charge gave it a surface charge: does that make sense?
If your battery only reaches 11.5 volts immediately after charging, then your battery is knackered. Your drain sounds normal. So try another battery
Batteries often go intermittent as the plate paste falls out with age. It might test ok but still be duff which it sounds to me it is.
MotorsForum website is not affiliated with any of the manufacturers or service providers discussed here. All logos and trade names are the property of their respective owners.