flat battery

[bodminman]

Hi there,
if I were to disconnect the battery, leave the car for 2 weeks and then reconnect it again all is well. But if the battery were to remain connected then it will be flat in approx 48hrs. I have switched off all lights etc, I make sure that the heating etc is also off and still the bugger goes flat!

Is it a job for a auto electrician?

Thanks

_______________________________
lynda, moderator

please note forum rule 20

 

[Stivino]

Something must be draining it. That needs to be checked with an ammeter.

 

[holmslaw]

Had exactly the same problem once. It was caused by the interior boot light not switching off. Wait till its dark and pull down the rear seat backs to see if the boot is illuminated.

 

[Ron Gamma]

you don't say what type of vehicle it is.

if it has an alarm system then this will be the probably cause. The average car alarm/immobiliser will flatten a good battery in about 2-3 weeks with the vehicle not in use. it will do it more quickly if the alarm keeps being activated.

the fact that you are only lasting a few days before going flat could indicate the above problem but linked to short journeys during the winter giving the battery insufficient time to recharge from the alternator with all of the lights & heater running.

if it is safe to do so then lock the car with the key only and don't arm the alarm for a few days. this should prove if it is the alarm or another electrical item.

if it is the alarm causing the problem then you can get around it by purchasing a £20 solar charger from maplin. it sits on the dashboard in daylight and trickle charges the battery. if the car is stored out of daylight then halfords sell a "battery saver" trickle charger but it requires a 13amp socket near the car. it is also about £20.

 

[greengrass]

Funny I had that on my cortina several yrs ago and it turned out to be the alternator. I was told where the old dynamo vehicles had a separate 'voltage regulator and cut out ' the alternators have them build in to regulate the flow as required. It may be faulty so draining the battery. Check out holmslaw's theory if it's off then have the alternator checked at your local car shop, most have testers that simulate 'load' to the battery at the same time testing the state of the alternator.