Flat Battery
09 March 2009, 02:04 PM
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Flat Battery
Been away for a week come back and the battery is completely flat ,car had a new battery 8 weeks ago not had any problems as it has been used daily.
Charged the battery and checked voltage 12.6 which is about right
started car turned on lights / heater fan / heated rear window/spot lights everything i could revved to about 2000rpm and checked voltage 13.7 which i think again is about right
could anyone confirm that the readings i got are right or any ideas as to why the battery would go dead flat in 4 days
Is there any way to check if any thing is drawing current and causing it to go flat in such a short period of time
checked all the obvious like interior light and boot light
thanks
Gary
Charged the battery and checked voltage 12.6 which is about right
started car turned on lights / heater fan / heated rear window/spot lights everything i could revved to about 2000rpm and checked voltage 13.7 which i think again is about right
could anyone confirm that the readings i got are right or any ideas as to why the battery would go dead flat in 4 days
Is there any way to check if any thing is drawing current and causing it to go flat in such a short period of time
checked all the obvious like interior light and boot light
thanks
Gary
11 March 2009, 12:14 AM
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The figures you measured are correct, but it's only the voltage you are checking. It's the current that matters, much harder to check. (But saying that, 9 out of 10 times the alternator is OK if the voltage reading check out).
What you need to do is check the current draw from the battery when the engine is off (and every thing else). I take it you have a multimeter? You will also need croc clips for the multimeter, and a piece of wire with croc clips on each end.
Disconnect the battery -ve terminal, join the two together again with the bit of wire, wait a few seconds for the alarm to sort it's self out.
Connect the multimeter (set to the milliamp scale) the same as the bit of wire, then remove the bit of wire.
You now have the multimeter connected in series and it will be showing the current flow (depending which way you connected it, it will be a +ve or -ve number).
A rough figure for normal current draw is 20 - 25 mA, it depends on if you have an alarm, tracker, memory for radios, gauges etc.
What you need to do is check the current draw from the battery when the engine is off (and every thing else). I take it you have a multimeter? You will also need croc clips for the multimeter, and a piece of wire with croc clips on each end.
Disconnect the battery -ve terminal, join the two together again with the bit of wire, wait a few seconds for the alarm to sort it's self out.
Connect the multimeter (set to the milliamp scale) the same as the bit of wire, then remove the bit of wire.
You now have the multimeter connected in series and it will be showing the current flow (depending which way you connected it, it will be a +ve or -ve number).
A rough figure for normal current draw is 20 - 25 mA, it depends on if you have an alarm, tracker, memory for radios, gauges etc.
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