Battery / Electrics Issue

[ppw]

Hi Guys,

I am having some probs with something draining the battery. Last month the car (2.0 TDi Sport) was not run for about 4 days - went to start car and nothing. Tested battery showing about 11.1V so thought better be safe than sorry and bought a new battery.

Yesterday (thurs) after not being run since sunday exactly the same problem (battery so low that the central locking, ignition lights were not even showing). Jump started immediately off a mate's Mondeo TDi. Now the weird thing is that after running for only 2 - 3 mins. I was able to stop and start the car 5 times in succession. That does seem odd in that the battery was so dead that no ignition lights, reset radio / trip etc but after only 2 mins of idle was able to start / stop 5 times. Left on trickle charge overnight last night and fired up 1st time this morn.

Showing on the meter at 12.8 Volts when engine running.

The only thing that i can think of though is that it is possible the aftermarket powered ariel adaptor / amplifier for the aftermarket head unit *may* have been fitted to a perm (not ignition) live - anyone had experience of this running a drain current.

Cheers in advance
Paul

 

[Viking]

When was the aftermarket head unit etc. fitted? Just recently or a while ago?

Other possibilities are that there's an internal light staying on when you close the doors (boot etc.) or something like that.

 

[ppw]

Aftermarket HU was fitted back in July, although cant really say that the car has ever stood still for more than a day since then.

Checked all interior lights - nothing staying on past the usual few secs.

Daily commute is about 50 miles so not a short journey.

 

[idmorris]

Hi ppw

I had virtually the same problems on my Alhambra. It turned out to be a aftermarket head unit that was pulling about 900 milli amps (0.9 amps) when the car was switched off. I put the SEAT headunit back in and, if my memory is correct, the drain current was only about 30milli amps (0.03 amps) and the battery drain problem went away.

Like me you didnt have any problems in the warmer weather because of the way the battery works. As this small (well actually quite large in power off state) drain current was discharging the battery, the battery's terminal voltage was decreasing. Now as the air temperature get lower the battery's electrolyte (acid) increases its electrical resistance, this also lowers the battery's terminal voltage. And the last little snippet is that when you switch on the ignition the electrical load placed on the battery is again going lower the batterys terminal voltage. Sorry!!

A way to check drain current is to disconnect the neg battery terminal, connect an ammeter (black lead to battery, red lead to disconnected battery cable) Take reading. Then do same with your aftermarket unit disconnected.
Not trying to teach you to suck eggs but beware of shorting yourself /any circuits out....keep all the lead metal bits away from the body of the car.

One last bit, you say that you have 12.8v when engine running. Ive always checked battery voltage when engine revved to about 2000-2500 rpm as this checks the alternator regulated output. I usually look for something about 13.5v (ish)

Anyway hope that lot helps.