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Like many people I guess my MINI was left for a few days over the xmas period and suffered a flat battery.
My car has the alarm and minidisc player and was built
mid Novemeber
Also like many others the car had unlocked itself
before the battery died. My guess is that this is a failsafe
mechanism to allow access to a dead car.
Seeing as it took The emergency service people 8 hours
to come out I decided to take matters into my own hands,
removed the battery and gave it a good charge.
Once the battery was re-installed I decided to measure
the residual current drawn from the battery using my ammeter
(which can go up to 20A)
Seeing as I saw 13A momentarily when the car is locked,
then you would blow the fuse doing this on most ammeters.
There is an easy way around though which I shall describe in
a minute.
Observations
1) ECU seems to shut down after a couple of minutes (NOT 16)
but then goes through a continuous cycle of shutting down
and waking up.
Current sequence is approx
1) 0.9A for 1 minute
2) 0.8A for 30 seconds
3) 0.7A for 1 minute
4) 0.2A for 1 minute 30 seconds
and so on. It was still following the sequence an hour
after the car was locked up.
This averages to about 400mA, which would flatten the battery in 4-5 days
My guess is that the once the ECU shuts down, the spurious
c-bus pulse from the radio wakes it up. It then goes away
and thinks about something (like why its been woken up),
and then goes to sleep again, only to be woken up later
on.
If I removed fuse F27 (the radio) then the current
settles pretty quickly to a constant 20mA. If your car does not have the alarm, it will be lower than that.
This would be a little higher if you have a fixed
radio fitted, but I would expect to see no more than
50-100mA
You can make these measurements yourself if you have
and ammeter that can read up to 1A
1) Disconnect the battery -ve cable.
2) Use some 20A automotive wire to bridge the connection
3) Connect up the ammeter between the -ve cable and the
-ve terminal of the bettery
4) lock the car
5) remove bridge cable (with ammeter still connected)
6) observe current
7) reconnect bridge cable (or risk blowing ammeter fuse)
and unlock car -
8) remove F27 (2nd radio fuse)
9) repeat above procedure for measurements
WARNING - if the ammeter becomes un-connected
while the car is locked and you have the alarm, it
will go off. It can only be stopped if you reconnect the
battery cable and unlock the car.
So until you get your new radio fitted, you can remove this fuse to avoid a flat battery.
Incedently, my fuel consumption has now improved by 3-4mpg
now the alternator is not constantly having the charge the battery.
My car has the alarm and minidisc player and was built
mid Novemeber
Also like many others the car had unlocked itself
before the battery died. My guess is that this is a failsafe
mechanism to allow access to a dead car.
Seeing as it took The emergency service people 8 hours
to come out I decided to take matters into my own hands,
removed the battery and gave it a good charge.
Once the battery was re-installed I decided to measure
the residual current drawn from the battery using my ammeter
(which can go up to 20A)
Seeing as I saw 13A momentarily when the car is locked,
then you would blow the fuse doing this on most ammeters.
There is an easy way around though which I shall describe in
a minute.
Observations
1) ECU seems to shut down after a couple of minutes (NOT 16)
but then goes through a continuous cycle of shutting down
and waking up.
Current sequence is approx
1) 0.9A for 1 minute
2) 0.8A for 30 seconds
3) 0.7A for 1 minute
4) 0.2A for 1 minute 30 seconds
and so on. It was still following the sequence an hour
after the car was locked up.
This averages to about 400mA, which would flatten the battery in 4-5 days
My guess is that the once the ECU shuts down, the spurious
c-bus pulse from the radio wakes it up. It then goes away
and thinks about something (like why its been woken up),
and then goes to sleep again, only to be woken up later
on.
If I removed fuse F27 (the radio) then the current
settles pretty quickly to a constant 20mA. If your car does not have the alarm, it will be lower than that.
This would be a little higher if you have a fixed
radio fitted, but I would expect to see no more than
50-100mA
You can make these measurements yourself if you have
and ammeter that can read up to 1A
1) Disconnect the battery -ve cable.
2) Use some 20A automotive wire to bridge the connection
3) Connect up the ammeter between the -ve cable and the
-ve terminal of the bettery
4) lock the car
5) remove bridge cable (with ammeter still connected)
6) observe current
7) reconnect bridge cable (or risk blowing ammeter fuse)
and unlock car -
8) remove F27 (2nd radio fuse)
9) repeat above procedure for measurements
WARNING - if the ammeter becomes un-connected
while the car is locked and you have the alarm, it
will go off. It can only be stopped if you reconnect the
battery cable and unlock the car.
So until you get your new radio fitted, you can remove this fuse to avoid a flat battery.
Incedently, my fuel consumption has now improved by 3-4mpg
now the alternator is not constantly having the charge the battery.
