Would radio on for 3 hrs run battery flat?

[SmoothBall]

Hi,
Was cleaning the car at the weekend with the radio turned on. Volume was quite high so I could still hear it with the windows up. It was turned on for three hours, and the engine wasn't running.

Afterwards, the battery wouldn't turn the starter motor when I turned the key in the ignition.

I had a similar problem a few months back. (See here.)

Also, about once a fortnight, perhaps once a week, I get the "Convenience features temporarily unavailable" warning in the dashboard. It goes away after a minute or two of the engine starting. I presume this is because the battery's charge is a little low, but is replenished after a few minutes of the alternator recharging it.

I spoke to two MB dealers: one said it's not unreasonable for the battery to be flat after three hours of radio play; the other said it could be a dodgy cell/might be on the way out. Both tried to sell me a 'battery test', one charging £20, the other charging £60 for the privilege.

It's a 2003 W211. I bought it second-hand in 2007, and have never replaced the battery; I don't know if the previous owner did, but I suspect not. The battery's nearly eight years old, in that case.

What are people's thoughts on the condition of my battery? Does it sound like it should be replaced? Are there other aspects that I'm overlooking? All and any advice would be welcome.

 

[Troon]

If you're getting the message, the battery is on its last legs. Listening to the radio for three hours shouldn't drain down a W211 battery to the point of not being able to start the car. Even at a very high 10A draw (120W), that's only 30Ah from the full ~90Ah capacity.

In your shoes, I'd look at replacing both batteries — the pre-facelift W211 also has an auxiliary battery under the pollen filter. Paying to have an 8-year old battery tested when it is already misbehaving seems like a waste, as the problem is unlikely to lie elsewhere.

 

[SmoothBall]

Hadn't realised the capaity was 90 Ah. Your figures do indicate that three hours of radio shouldn't have been a problem.

You mention an auxiliary battery—what's its purpose? What does it power that isn't powered by the main battery? I wonder why the main battery couldn't handle those items also.

Also, where do I find the auxiliary exaclty? I'm not familiar with the location of the pollen filter. (One of the MB dealers did mention the auxiliary battery, but said it was located under the driver's seat! I'm pretty sure there are no pollen filters in under there! You have to wonder about these dealers sometimes. :neutral

 

[television]

3 hours of loud music will drain the battery, the louder you have it the more the drain.

The consumer message, there is an update for this, but if the car does not get many long runs, the batteries will never be full. A good charge every two weeks on the main battery should solve it all

 

[Colin_P]

I have a car radio in my wood workshop, and it's running off the old battery I pulled out of my car. I usually get around 20 - 30 hours out of it before needing to charge it. That's using cd's a lot of the time which use more power than just the radio. I usually have the volume up quite loud too, as there is a fair amount of background noise from the lathe or bandsaw. The battery I'm using wasn't dead when I replaced it - my alternator packed up on a Friday afternoon 600km from home and buying a new battery once the existing one was flat was cheaper than booking the family into a B&B for the weekend while trying to source parts in the middle of no-where.

If I'm working on the car or in the garage, I have the radio in the car on, and have often had it playing for three or four hours and have never had an issue with the battery not being able to start the car.

So if three hours kills your battery, then the battery is on it's way out.

 

[SmoothBall]

Hi Malcolm,
While the volume was louder than what you would comfortably sit and listen to while inside the car, there weren't gangs of hooded teenagers wondering where the rave was at.
I agree that the louder it is, the greater the drain, but Troon's figures above don't tie with a radio completely draining a battery. Even at his pessimistic estimation of a rather high current of 10 A (or in power terms, 120 W—which is rather a lot for a radio to pump out), three hours only amounts to a third of the capacity of the battery.
I do concede that the battery probably wasn't at full charge, as I don't do many long runs, mainly city hops. But still, my gut feeling was that the battery should have taken three hours of radio play in its stride.

Colin P's experience seems to also lend weight to the battery not being able to hold as much charge as it should; perhaps it is on the way out.

 

[television]

Do you have the comand or the basic audio 10, the main thing is the 211 has a much more complicated electrics system than a 203. My 230 had a similar set up and I could not run the radio for an hour before the consumer message would come up, the car cannot go to sleep with the radio on.

I would give the battery a good charge once every 2 to 4 weeks, just using the car for short runs pulls more current than can be replaced by the alternator, it takes ½ hour for the car to go to sleep, pulling some 8 amps for quite some time

 

[SmoothBall]

Do you have the comand or the basic audio 10

Mine's got the Audio 20.

...it takes ½ hour for the car to go to sleep, pulling some 8 amps for quite some time

Wasn't aware that the car went to 'sleep', and can only guess that that entails systems winding down and switching off. Hard to believe that takes a half an hour. Whatever is it doing? Singing itself lullabies?

 

[television]

Mine's got the Audio 20.


Wasn't aware that the car went to 'sleep', and can only guess that that entails systems winding down and switching off. Hard to believe that takes a half an hour. Whatever is it doing? Singing itself lullabies?

The time is a bit shorter with the Audio 20, the cars holds information for some time in case its going to be driven again, these circuits include the SBC brake system.

If you sing a lullaby it could stay awake longer

 

[SmoothBall]

Ha ha! How did you know my singing induces frightened wakefulness rather than deep slumber?

 

[television]

Ha ha! How did you know my singing induces frightened wakefulness rather than deep slumber?

Because most of the Irish have lovely voices, soft and nice