dlevi67

No. It just displays time (and I assume date, but I haven't been bothered to click on the stalk button) as dashes. Date and time are also dashed on the iDrive screen.

I am pretty sure of that, because this morning the car was complaining about washer liquid level (so I had a warning there), but nothing else, and the iDrive clock was showing --.--; the dash clock I did not check, as it was showing the washer liquid symbol on top!

a9rrr

This happened to me just last week.

My 530d is 10 months old, and I've noticed recently that the engine turns over a bit more slowly when starting. Then last week, having just driven about 100 miles, I didn't use the car for nearly 2 days - when I went to it, it did start, but the clock had completely lost the time, and the date was 1 day 'slow'. I went back to it an hour or so later, to see if the time/date had returned - it hadn't, but I also now had a 'Battery charge very low' warning message.

The owner's manual says that if there is a 'temporary power loss' then some functions (e.g. time & date, amongst others) will need to be reset. So I'm thinking that my battery is on the way out.

I contacted my dealer, who explained that even driving 100 miles doesn't charge the battery !!! He suspected that something might be drawing power while the car is turned off (or asleep), and pulling the battery charge down. He had the car for about 3 hours today, during which time he 'boost-charged' the battery, then checked it and pronounced it to be OK ... but he wants it back in for a longer test to see if anything is drawing power when it shouldn't be. And I'm sure that I've read previously on this forum that BMW have a 'spec' for how long you should be able to leave your vehicle for, and still have it start - I seem to think it should be something like 40 days ???

This sounds very similar to your problem, Veight - I'll post with the outcome, but it could be a week or so before I can let him have it again.

As an aside ... would any knowledgable person(s) care to comment on what the dealer is saying about driving the car NOT charging the battery. My understanding is that the battery only powers things when the engine isn't running. And it powers the starter/electronics to start the engine. Once the engine is running, the alternator 'puts back into the battery' the energy that was used to start the car, and takes over powering all of the electronics. So driving the car a reasonable distance WILL charge the battery. When I pushed him about it, he said that modern cars had so much electronics that the alternator only charged the battery a little bit, but if the battery charge was very low it could not fully charge the battery.

I'm afraid to my simpleton way of thinking, this is crap - but I will be happy to be enlightened !

Veight

Well where you got that washer liquid level warning i get a clock symbol. I know my battery level is low. I get a battery symbol too.

But the car always starts right up.

Veight

In 100 miles it probably isnt enough to fully charge your battery. Your altenator is trickle charging your battery along the way, but based on how many electrical features you have on, like the headlights etc, the amount the altenator actually sends to the battery is minimal.

This is why I bought this trickle charger from BMW but I got the one with the cigarette adaptor which was the incorrect one.

Not one word in the instructions or the box to indicate that its not made for recent BMW models with cigarette lighters that arent powered "on" when key is off. I got it to work but when the car went to sleep it stopped working. Im exchanging it tonight for one with clips.

Rudy

I've also seen the clock go to dashes for a short time so maybe see if waiting it out next time will bring it back?

dlevi67

The battery (on a 530d) has a capacity of 90 Ah (Ampere x hour). Think of it as literally the capacity to hold electricity like a liquid. The alternator generates ~170 A when it's running at peak (probably about 2800 rpm or so for the engine), so it would take roughly 0.5 hours to recharge the battery if the full alternator output were directed to recharging an empty battery and the battery were able to withstand such a rate of charging.

However:

1) As the dealer said, there's a lot of electronics and electrical components. My guesstimate is that at least 50-70 A are needed to power the various bits in average driving conditions (i.e. stereo on, nav working, all the ECUs running, fuel and steering pumps, a bit of lighting, iDrive, climate control fan...). This is "only" equivalent to 600-850W, but it reduces the capacity of the alternator to recharge the battery.

2) Unless the engine speed is high enough, alternator output will be below the 155 A max. And when it's producing less than 60-70A (below say 1800 engine rpm), the battery is being drained again.

3) There is probably a limiter on the battery charging circuit, which means maximum current into the battery is limited to 20-30 A (?), to avoid damaging the battery.

Assuming I am guessing right (the values are reasonable, but I don't have access to the technical specs of all the equipment!), it would take about 4 hours of continuous running above 2000 rpm to recharge fully an empty battery. Yours clearly had enough power to start the engine, so it would have required less, but to recharge it fully you would have needed continuous running at decent engine speed for a few hours. If you drive in start-stop traffic, it will charge a little bit and then lose it again at the next stop.

E60Sim

I think we have a 110Ah battery in our E60 530dA..

When I wash the car and dry it, I usually have the Logic 7 playing a nice CD, sometimes with the angeleyes on, sometimes for more than an hour.. The car more than 2 years old now, with 89.000 km's on clock, and we are still on the factory fitted battery!

I have got the Low battery warning a few times, after having the Logic 7 and lights on for a long time, but it dosen't happends that often..

If the alternator generates 170 Ah @ 2800 rpm's you will need to drive 200 km/h (in 6th. gear ) to generates that amount of power ! Usually a alternator is only able to generate 80% of its fully capacity, that would be 136 Ah @ 2.800 rpm's. So if you drive at a highway with 1800-2000 rpm's, on a rainy day, the alternator will have a hard job, to charge a almost empty battery...

dlevi67

Interesting - the UK specs (and my 535d) say 90Ah for V8s and I6 Diesels. I wonder if the spec changes in Nordic countries because of assumed colder weather.

E60Sim

?
Could be a reason! We bought our E60 in Stockholm, Sweden, when we lived there..

Veight

So i exchanged the so called "intelligent" BMW charger last night at my dealers with one with the clips so I can hook the charger directly to the positive and negative points under the hood.

So I unpack the charger from the plastic box, and separate the clips, and plug it in. Bang, smoke and sparks come out of the vents in the top of the box. My wife is standing there with me in the garage and she says "is it supposed to do that"? I just looked at her. Luckily I hadn't hooked it up to my car. It didnt even blow the in line fuse. But its dead, so back to the dealer it goes.

I just pulled out my heavy duty charger and i set it to trickle charge. That BMW charger was the last one my dealer had in stock so they are odering a new one for me. Its never simple.