Ignition Key flattens car battery

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Dave Chambo
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Qashqai Model: Mk.1 Qashqai - J10 (2006–2013)

Post by Dave Chambo » Tue May 11, 2021 8:07 am

I have an ongoing problem with my 2012 Qashqai. If the ignition key is left in (not turned on) when waiting for say school out (20 mins sometimes) the battery goes flat and the car will not start. When the car is jump started it runs fine for weeks until the next time i forget to take the key out. I have had the battery tested each time and it is fine. Something drains the the battery heavily when the key is left in. Computer check at the garage shows no error codes.
Dave Chambo

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Post by calnorth » Tue May 11, 2021 10:29 am

The ignition switch enables a number of systems via relays e.g Starter Motor and ECU for instance. Its a very simple switch. However, to discharge a battery within 20 odd minutes tends to indicate a battery/charging problem.

Investigating any power drain is very difficult and I'm not clear as to what garage type you attended for a Computer check. Was it a Nissan dealer.

Do you know what the battery test was exactly? Was it a capacity test for instance. Was any charging test performed?

I assume the ignition etc lights are not showing in the instruments?
Last edited by calnorth on Tue May 11, 2021 1:25 pm, edited 2 times in total.
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Post by mrugby » Tue May 11, 2021 11:26 am

So you have had the battery checked and it's ok
You haven't said if it's been tested for correct charging
It doesn't happen when the key is not inserted
And it happens when the key is in but not turned.

I'm sure no electrical contact is made with anything when the key is just inserted ,
So do we have an issue with the ignition key/barrel some how creating a short and draining the battery at a pretty rapid pace.
To drain a battery in 20 minutes is a fair old current draw.
If you are a diy person you can measure current draw using a multi meter in series with the battery lead to give you the extent of the discharge Rate.
If you are not a diy person or are not comfortable with car electrics get it to an auto electrician as you need an understanding of the system from a safety perspective.
You could test the charging system your self quite easily, with a multi meter set to volts or a charging pen from an auto store that indicates using led's the static state of the battery when the engine is off and then when you start your engine, what the charging status is.
This is a simple process to give you an initial idea.
A fully charged battery will last a whole lot longer than 20 minutes, so something is pulling juice at a hefty rate out of your battery.
The other idea would be to put a sticker in the car reminding you to take your key out hahahah.

Feed back to us when you know something,
Circuit drain is a game of calculation, knowledge and patience.
A multi meter is essential and these days, measuring voltage drop across the 2 open slots in a blade type fuse seems to be the preferred initial method in determining what circuit is the culprit..
One note of caution, modern cars have systems that don't shut down straight away when you switch off the ignition, a bit like your computer having to close various programmer before it shuts down. Generally there is a waiting time before you should disconnect a battery. Even different qashqai models have different waiting times. Normally doors, should be closed, lights off etc to stop the cars computer crashing.
On my J11 theirs a whole section on this in the repair manual, including the requirement to scan for fault codes after re-connection incase you have a bug in the boot up process.
Please bring back old fashioned plugs and points i say lol

Take care,


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Post by BobM » Tue May 11, 2021 7:22 pm

If you have your headlamps turned permanently as like on a Volvo then they will stay on until you remove the ignition key from the lock, might be that
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Post by Qashowner » Wed May 12, 2021 12:26 pm

Draining an 85 amp hour battery in 20 minutes, something is going to get very hot, even headlight main beam would take 40 minutes or so, I would suspect the battery is not holding charge and need replacing.
Past cars Mercedes B Class, S Class, E Class Estate, E Class Coupe, G Wagen, 260E interspersed with Peugeot 406 and Audi Coupe.

Dave Chambo
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Qashqai Model: Mk.1 Qashqai - J10 (2006–2013)

Post by Dave Chambo » Tue Oct 12, 2021 3:13 pm

Thanks everyone for your input. I am an electrician and was looking to see if anything known was out there before I get the mulitmeter out. Looks look I will have to disconnect the battery and insert the meter on a high amps range and see what the drain is with the key in. And then remove fuses to see what circuit the drain is on.
The drain must be quite high and above some of the fuse ratings suggesting it is a short somewhere. The battery was tested at Halfords. They used a battery efficiency tester and it came out very high. Ho hum..chipping away.
Dave C

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Post by MrSweetE90 » Tue Oct 12, 2021 10:11 pm

Great advice above, I had a similar issue with my 330d and it was actually just the battery, I had tests done on the battery which passed absolutely fine, voltage seemed fine but if I left the car ignition on just for a little while the battery would be too dead to crank.

Personally I would check for a parasitic draw which a chap previously mentioned and it's something I also done. Just remember to leave the doors, bonnet open with the door latch manually pushed back in and the bonnet switch taped down so you can then let the car go to "sleep" which as far as I'm aware takes no more than 30 mins.

With the multimeter connected in series on the negative terminal you can check for a parasitic draw. However, I wouldn't advise pulling fuses as that may wake the car back up during testing. Use this method instead, it's faster.

As I say I did all this myself and despite the battery passing tests it still was the culprit.
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Post by gloucester » Wed Oct 13, 2021 3:02 pm

Welcome to this forum.

How old is the battery?
(2015 Nissan Qashqai Tekna DIG-T 1.2 sold 15/6/18) ~ 2018 Suzuki Ignis SZ5 - 2018 Yamaha MT-07

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