My alarm still keeps randomly going off and the other night it went off twice so I unlocked the car and left it unlocked.

I came down in the morning and the battery was dead flat, wouldn't start the car.

After charging up the battery to full I decided to embark upon a parasitic drain hunt to see if I could find out what is causing it.

I removed the earth clamp and put an ammeter in series and then left the car. According to the manual it should sleep after 33 mins even if not locked.

Luckily my multimeter has a datalogging function so this is the graph I managed to create from the data.

The vertical axis is amps with a unit scale of 0.2 The horizontal is time.

More Data from the log

Measured over 3929 Seconds or 65 minutes at one measurement point per second once car had settled into sleep


Average draw when asleep 0.006A

Max peak draw when asleep 0.039A

Minimum draw when asleep 0.0A Christian.


Current Cars
2011 Range Rover Vogue SE
2020 BMW M4 Competition
2019 BMW X4

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I would charge the battery fully, disconnect the battery -ve terminal, leave overnight and see what happens.
The battery drain data you have recorded seems reasonable to me, if not pretty good.
I suspect your battery itself may have a problem.

The battery is 3 months old.

Duracell AGM. Christian.


Current Cars
2011 Range Rover Vogue SE
2020 BMW M4 Competition
2019 BMW X4

My RR Blog: www.facebook.com/L322Project
or
https://www.fullfatrr.com/forum/topic61540.html

Try disconnecting the bonnet switch and bridging the terminals in the connector. I had this issue and got fed up with getting up in the night to sort it.

Charge the battery and then see what happens. Indicators should flash when you lock the car (even with the bonnet open once you've bypassed the switch).

Never had an issue with mine since I did this, and free to try to begin with. I will get around to replacing the switch one day! 05 L322 4.2SC
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Last edited by 400-ascona on 23rd Dec 2021 2:29pm. Edited 1 time in total

Caesium wrote:

The battery is 3 months old.

Duracell AGM.

I would still charge and leave overnight
Something is discharging it and it doesn’t appear to be the rest of the car.
Best eliminate it.

400-ascona wrote:

Try disconnecting the bonnet switch and bridging the terminals in the connector.

Yours must have a different type to mine as bonnet closed is open circuit and bonnet up is circuit closed on my car.

I've simply disconnected the switch for now as that tells the car the bonnet is closed all the time.  Christian.


Current Cars
2011 Range Rover Vogue SE
2020 BMW M4 Competition
2019 BMW X4

My RR Blog: www.facebook.com/L322Project
or
https://www.fullfatrr.com/forum/topic61540.html

nicedayforit wrote:

Caesium wrote:

The battery is 3 months old.

Duracell AGM.

I would still charge and leave overnight
Something is discharging it and it doesn’t appear to be the rest of the car.
Best eliminate it.

Just a thought,
If the battery is indeed ok the one circuit your data logger didn’t record is the alarm system when the alarm is active.. When you tested l presume the alarm wasn’t operating. It’s quite possible that when the alarm operates for whatever reason it instigates a current drain on the alarm circuit which is sufficient to drain the battery over a longer period.
Can you disconnect the whole of the alarm system?

That's a very good point.

Perhaps I'll repeat the testing when weather allows, with different test initiation criteria. Christian.


Current Cars
2011 Range Rover Vogue SE
2020 BMW M4 Competition
2019 BMW X4

My RR Blog: www.facebook.com/L322Project
or
https://www.fullfatrr.com/forum/topic61540.html

nicedayforit wrote:

Can you disconnect the whole of the alarm system?

nicedayforit wrote:

Can you disconnect the whole of the alarm system?

Have you checked for last alarm causes with a scanner?

Rear doors both times, left and right. Christian.


Current Cars
2011 Range Rover Vogue SE
2020 BMW M4 Competition
2019 BMW X4

My RR Blog: www.facebook.com/L322Project
or
https://www.fullfatrr.com/forum/topic61540.html

I had the same issue. Rear doors apparently causing alarm to go off. Turned out to be the sun roof switch had been hit while cleaning and it was about 2mm down from sealed. Was causing the alarm about 15m after I locked or just left it open and it locked itself. Stopped doing it after I realised!