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Discussion Starter #1
I have a (almost) 4 year old Hyundai i10. Just recently the battery has been repeatedly going flat, so much so that the car won't start and I can't even use the remote central unlocking. When I turn the key to start the engine I get nothing, not even a red battery light on the dash.

To get the car working again I trickle charge the battery and it runs fine for a few 15-mile trips out for about 10-20 days. Then, again the car goes dead. The most recent time this happened I had driven the car 4 days prior on a 35 mile round trip with no problems (I'm not killing it with short journeys). Last week I took it to Halfords and they tested the battery and concluded there was no fault with the battery or alternator. I got a machine readout saying "good battery". I've checked the tightness of the terminal connections and they are good.

So this makes me think that the battery is being excessively drained whilst it's sat in the car when not in use. I've checked that all the interior/exterior lights are off. The only other thing I can think of (or reasonably expect) is a fault with the automatic door locks:

About 2 months ago whilst driving I noticed that the car sounded like it was randomly locking/unlocking all the doors. Sometimes it was continuous for 5 minutes (at 70mph) then it might be ok for the next 10 minutes, then it would misbehave intermittently for a while but less continuously, and so on. This happened on multiple journeys before I started having the problem above of not being able to start the car (However, the door issue didn't happen once on my recent 35 mile round trip a few days ago). So is it possible that the door locking fault is draining my battery when the car is not in use? Is it possible the doors are occasionally unlocking/locking when the car is not in use?

I understand that the doors are meant to automatically lock when the car drives away above a certain speed. Can this be disabled, how?

Do you have any other ideas a) why my battery is apparently "good" but unreliable and b) why the doors continually lock/unlock?

Im not currently desperate to drive anywhere during this current lockdown, so I have plenty of time to problem solve/test any pointers you may be able to give me.

Many thanks,

Richard
 

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One way to check whether current leaks during shutoff drain the battery is to unplug the negative battery terminal and leave the car for some days. Then repeat with the terminal plugged in.

Alternatively drain current can be measured with a multimeter, but due to the high currents car batteries can supply one needs to be careful AND (!) use a multimeter capable to shield the user from such currents in case of need (most cheap and some expensive ones do not).
 

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Discussion Starter #3
One way to check whether current leaks during shutoff drain the battery is to unplug the negative battery terminal and leave the car for some days. Then repeat with the terminal plugged in.

Alternatively drain current can be measured with a multimeter, but due to the high currents car batteries can supply one needs to be careful AND (!) use a multimeter capable to shield the user from such currents in case of need (most cheap and some expensive ones do not).
Thanks.

I've just measured it with a multimeter and found a draw of 300mA. So I guess this is the problem - I found a video on youtube saying anything over 50mA is not good.

I've started removing the fuses one at a time to see which one makes the reading drop - only done half so far, then it started to rain. Will do the rest tomorrow
 

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Thanks.

I've just measured it with a multimeter and found a draw of 300mA. So I guess this is the problem - I found a video on youtube saying anything over 50mA is not good.

I've started removing the fuses one at a time to see which one makes the reading drop - only done half so far, then it started to rain. Will do the rest tomorrow
It's all fixed now.

I got it looked at under warranty. They found water ingress in one of the rear doors which was shorting the circuit that controlled the central locking - this was causing the battery drain. They replaced the door lock motor and some wiring and fixed the water ingress.

That was two weeks ago and it's been fine since.
 

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Excellent!
And thanks for reporting back!

Did they say what the cause for the water ingress was?
(i.e. was it a damaged or worn part or was it some gasket/seal that wasn't fitted correctly at the factory?)
 

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Thats good to know and you did the correct testing. Funny story. I recently bought a Mazda MX5 and the battery would go flat in 3 days so I guess that's part of the reason they sold it. Found a 20 cent piece inside the CD/radio. Fixed that problem so sometimes removing the fuses is the best way to find a problem. By the way the radio works fine so no damage.
 

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Discussion Starter #7
Excellent!
And thanks for reporting back!

Did they say what the cause for the water ingress was?
(i.e. was it a damaged or worn part or was it some gasket/seal that wasn't fitted correctly at the factory?)
They said that, normally and by design, any water that lands on the window will drain into the door. The water should then be directed towards a drain hole in the bottom of the door so it can escape.

There is a part inside the door that is meant to deflect the water around the wiring in the door and towards the drain hole. This deflector part had been poorly fitted in the factory - so they repositioned it to get the water draining properly.
 
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