Clock / Date / Dial Reset Upon Start-up - Battery or other?

[X-S-Z]

When I bought my Z4M I had suspicions about the battery so I made sure the previous owner undertook a battery test at the local garage as well as a diagnostic check. Things have been fine since until after Christmas.

I left the Z4M for 3.5 weeks over Christmas while I went on holiday. I came back and it started OK but the clock, date and dials all reset to zero and then the dials (rpm etc) came back to life and to their normal idling position. Things are OK after a bit of a run and reset but I am finding with low / weekend usage that this problem keeps occurring again and again.

I suspect the battery, however there is enough charge to start the car so why not enough to maintain the date etc? Does anyone have any experience of this?

I am happy to proceed with replacing the battery (and have read about standard / AGM types so need to check what I have tonight). I'd like to put a trickle charger on it but the car is kept in an underground car park with no access to a power supply. I could fit a solar charger but again it is underground and very little power would be provided from fluorescent lighting that is on presence indication and a timer.

Any other thoughts?

 

[Rialas]

Your battery sounds fine. 3.5 weeks is pretty good going on our cars. Other high end cars may last 2 weeks without a trickle charge.
After 3.5 weeks your battery had dropped enough to be border line, and as you turned the starter, the voltage dropped further hence reseting your clock. Even though there was "sufficient" power to start the car.
Just my theory.

 

[Rialas]

Any other thoughts?

Battery isolator.

 

[X-S-Z]

Any other thoughts?

Battery isolator.

Isolate the battery to save its charge when I leave the car for extended periods? Obviously this will disable all electronics and power in the car so manual key locking / entry would be required and the car will have no alarm / security system. Not desirable really.

 

[Rialas]

I agree..not ideal... but you'll eventually kill the battery if you keep on leaving it for long periods without a trickle charger. Is using the key to manually lock the car that much of a hardship? It was the norm not so long ago.

How about an isolator and a heavy duty wheel-clamp for security.

 

[Adamski]

Alas I think all Zeds suffer from this, don't think this is an M issue. My 3.0i needed to be started every 2-3 weeks for a battery charge. Anything longer and the car wouldn't be as keen to start.

Like you, my car is kept in an underground car park, so a trickle charger is out of the question.

I would try to give the car a run every two weeks. Even if its just a half hour gentle drive


Sent from my iPhone using Tapatalk

 

[X-S-Z]

Alas I think all Zeds suffer from this, don't think this is an M issue. My 3.0i needed to be started every 2-3 weeks for a battery charge.

I NEVER had this issue with my 2004, 3.0i SE that I had for 5 and a half years...

 

[X-S-Z]

So I 'dug' out the battery last night and I was suprised at how much of a challenge it was to get to bare terminals on the battery so a point where you could changeover. Regardless I had a good dig around and didn't break anything.

I have a black AGM battery (I hear the Bosch S6 is a good replacement - where is the best place to get one?) which I suspect to be the original battery. What is the 'design life' of these batteries? I am not convinced it is 'dead' but certainly on its way so may consider a replacement shortly. I also noted some lead-acid corrosion around the negative terminal, I am not sure whats causing this with it being a sealed battery but I am going to clean it out thoroughly and hope to find some insulated washers to put at the bottom of the negative post.

I also had a good dig around the underground carpark and I am toying with the idea of breaking in to a lighting circuit to acquire a 230V AC supply... (I am a Chartered Electrical Engineer so please no safety, etc chat - I am qualified!) what trickle charger or battery conditioner would people recommend? I've heard good things about CTEK but I note they're rather expensive and have quite a few variants.