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Warning - Lupo Battery drain with the car unlocked


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Friendly warning.
If you leave your car unlocked (even if the door is shut) then your battery parasitic current drain could be so high as to flatten the battery within a few days.I measured my parasitic drain current and found it to be 110 mA, whilst the car was shut but unlocked, however, it went down to 10mA as soon as I locked the car.  I think the spec says ideally  it should be lower than 20mA when the car is locked. This suggests that in a unlocked car some unit is still alive and drawing current, and as soon as you lock the car that unit is switched off.

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36 minutes ago, julietdiane said:

Friendly warning.
If you leave your car unlocked (even if the door is shut) then your battery parasitic current drain could be so high as to flatten the battery within a few days.I measured my parasitic drain current and found it to be 110 mA, whilst the car was shut but unlocked, however, it went down to 10mA as soon as I locked the car.  I think the spec says ideally  it should be lower than 20mA when the car is locked. This suggests that in a unlocked car some unit is still alive and drawing current, and as soon as you lock the car that unit is switched off.

You sure it wasn't your interior light? The Lupo despite it's relative modern'ness in the world of cars is still primitive. I can't think of any submodules that are active and drawing high current with the door unlocked.

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The interior light was in the permanent off position. You had to lock the car with the key to stop the current drain, locking it from the interior central locking switch would not stop the drain.  In the key locked state opening the boot had no effect to the locked drain current mode, however, as soon as you used the key to unlock the car (without actually opening the door) the drain would begin.

The lesson is: you are not doing the battery any good by regularly leaving it parked for long periods unlocked.

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Tbf who doesn’t lock up their car when they leave it anyway. I’d be more worried about the car or it’s contents going walkies rather than a flat battery.

However saying that I’d say there is something wrong with your car if something isn’t going to sleep simply because you haven’t locked it.

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Sorry to say this Juliet, but it has a problem. It might be something like a short.

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I think this is true. There is a timer in the convenience centre (only on S spec cars with leccy windows), which keeps the system active after unlocking. I think it's a fault though because I've experienced the exact same symptoms on a mk4 golf (S spec again). There is a relay that is activated which draws the majority of the current. Haven't investigated it any further, but when the door lock led is flashing, the current drops. The fault manifests itself as extending the timer to stay on longer and longer as the car ages. No idea why... I have a hunch it's linked to the door lock switches.

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Yes the current drops when the door lock led flashes, however, if you use the internal door lock switch (not the key) to lock the door then the led does not flash and current does not drop? This fault or design feature will have to remain a mystery. I now have trained myself to always lock the door, even when after I put the car in my locked garage and no longer have flat batteries. Last year this fault/design feature made me wrongly buy a new car battery.

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  • 2 weeks later...
22 minutes ago, KiwiYork said:

My Lupo had a brand new battery in September. I use it pretty much daily but it's been on the driveway for less than 2 weeks, and it's flat as a pancake. Anyone have any ideas? 

Aftermarket radio? 

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13 hours ago, KiwiYork said:

It has - the previous owner to me had put in a blaupunkt

Start with that.

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KiwiYork - I suggest you get yourself a multimeter and do the parasitic battery current drain check (see youtube). When you do this check taking out the radio fuse will identify if your radio circuit is the culprit.

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  • 2 weeks later...
On 3/15/2019 at 4:27 PM, julietdiane said:

KiwiYork - I suggest you get yourself a multimeter and do the parasitic battery current drain check (see youtube). When you do this check taking out the radio fuse will identify if your radio circuit is the culprit.

Cheers - will do.

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  • 4 weeks later...
On 3/15/2019 at 4:27 PM, julietdiane said:

KiwiYork - I suggest you get yourself a multimeter and do the parasitic battery current drain check (see youtube). When you do this check taking out the radio fuse will identify if your radio circuit is the culprit.

Did just that - borrowed multimeter and found a good vid on You Tube - and as Skezza mentioned it looked to me like the radio and DAB aerial (both put in by previous owner .....). Decided to pay someone to do a good check over - I was a bit concerned in case I'd missed something - and he confirmed and fixed it. All good. Cheers for your help and advice. On to bodywork which I'm much more comfortable with.

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