Hi all can anyone help I can’t seem to see anyone having the exact issue I have.2009 L322
Came to the car one evening and it wouldn’t unlock called AA they couldn’t fix and were going to recover the next day. I arrived at the car the next day with the spare key as a test and it unlocked so took it home. Changed batteries in both keys.
I Left it unlocked in a secure garage luckily as the next day,black dash smart key not found no electrics other than interior lights,wipers worked indicators did but no column noise. I disconnected the battery left it 24 hrs re connected it then all was back to normal. Remote worked keyless start worked radio etc. part way through the drive I had to stop and reverse then the rear view camera went off dash went off heater controls but just before it did warnings came up saying camera fault. I brought it home switched it off and tried to start immediately but wouldn’t.smart key not found came up and the emergency start holding the key against the lower dash wouldn’t work on either key. I’ve left it a few days,disconnected The battery again re connected leaving it a few hrs but still black dash etc won’t lock and now won’t emergency start so struggling to get to a garage Anyone any ideas or has had this before ? Thanks

I wonder if the BMS is operating correctly ?
These have been known to fail. But to begin with, I think I'd clean the contacts inside the male and female plugs forming the BMS connection.

I did this recently. To be on the safe side, I first disconnected the negative battery terminal. I believe the procedure for this can be found in the Wiki. To clean the contacts you might use a universal contact cleaner. I used Normfest contact cleaner as this has a brush built into the nozzle to allow you too agitate the fluid to assist with the cleaning process.

Worked for me. And as a no cost process must be worth a try.

Once you've done this and if you have a Gap IID, I'd recommend going for a run whilst recording live values for battery charging voltage, current and estimated state of charge. The resulting chart will fluctuate significantly, but in general it should show a battery voltage not less than 12v.




Should the resulting chart not show the expected activity, then consider replacing the BMS.
This is a simple task consisting of replacing the negative lead to the battery. And much less costly than a new alternator - which may be something to think about should fixes thus far not bring a resolution.

It may also be that your battery is past its best. If state of charge drops off quite quickly once charging stops, then your battery may be suspect.

If you don't yet have a Gap tool, then I would recommend it.
I would also recommend acquiring a BM2 battery monitor if you've not already. Typically under £25 from Amazon. Nothing like as powerful as a Gap IID of course. But cheap enough and does provide continuous visibility of some of the metrics relevant to the condition of your battery.

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