Battery Life with ACC switch on... How many amps - How long?

E

EdButler

Senior member
 Sheffield
Hey All,

Basically i think my battery is on its way out... The car is a MY03 but with only 30k so i think its been garaged for a lot of its life.

Whilst fitting my cruise control and AUX (30-40 mins max) i had the radio on (Carver) and the interior lights on. The engine bay was buzzing so i assume the Fuel pump and coilpack draws some power also. Id have said that it was drawing 15 Amperes max (i darent use the multimeter in case of frying it)!? The battery should hold ~8x that much juice assuming its ~80ah!! Is that a fair assumption?

Anyway needless to say that the car completely failed to turn over afterward. A voltmeter over the battery terminals gave me an almighty 8.2V!! :rofl:

So does anyone have any experience of Accessory power usage and whether this is normal or not? Are the batteries sealed, because they look it...

Cheers guys/gals :thumbsup:
 
If it was dark were your headlights also on, they might drain it quickly.

The fuel pump is in the tank, however the buzzing could be HID ballasts or the ignition system. The cold weather is particularly cruel to batteries and if it is only used for short journeys this is the time of year it will be likely to fail.

I'd have a go at charging it up disconnected from the vehicle overnight.
 
If you had the ignition on (reference the comment about the coil pack drawing some) then the entire cars electorics system is on 'full', not in it's low current state when it sleeps. Take an old battery, probably not fully charged, draw current from it for an hour and then ask it in this cold weather to spin an engine probably needing a few hundred amps and it's no suprise it flattens it. Incedentally once a battery is slightly discharged it loses it's edge the voltage drops and the current draw surges. On Jeeps winching as we flatten batteries it 's not uncommon to melt 500 amp relay switches. :thumbsdown:

That said your battery should not really drop to the 8v and given the battery is 6 years old could be getting past it.

Do as Adam suggest and put it on a long charge. ideally using a proper conditioning charger and see how it goes.
 
Cool, cheers for the advice guys... Will give it some warm tlc out of the way of all this snow :)
 
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