Battery: stop car. Leave engine running. Wait for message to disappear. Then Drive off.

[DITTRICH]

I had parked up, turned the engine and a/c off, and was listening to the radio for about 40 minutes.
Wife turns up, gets in, and I fire up the engine (radio still on) and move off.
After 10 seconds of getting out of the carpark, the dreaded amber battery stop message above appears. I pull over, engage park with engine running, and wait 10 minutes. Message does not go away.
Points to note:-
1 It isn't possible to rid of the message - eg to transfer to the trip display and watch the alternator engaging and charging the battery.
2 I reason that since the car works and the car believes the battery is charging it should be possible to complete the 20 mile journey back home'
3 I complete the journey back home, keeping an eye on the engine temperature to make sure the poly v belt is OK. I checked later and it was fine.
4 I used eco mode and made sure all the consumers were off during the journey.
5 Eco mode gear changes seemed to be very smooth and the activation/deactivation of "D" was less frequent and totally smooth.
6 On arrival in the underground parking, after checking the poly V belt, I switched off, waited 30 seconds and switched on again.
7 Fault cleared, car appeared normal. switched off again after 2 minutes.
Hypothesis: starting the car on a 6 year old battery with the radio on etc, dragged down the voltage sufficiently to trigger the warning. Once the voltage was down, the message got "stuck". After driving back, switching off/on it righted itself i.e. the alternator WAS charging, so maybe the car knows this for real, not just believing its OK.

To be honest I sort of reasoned that the battery was at fault, but did not want to turn off the battery in case the car would not start again.
Moral: If the car says battery low: stop and charge, check how the car behaves, and if OK, carefully drive home with all consumers off.
Cars these days try to be too clever, and are economical with the truth on the display panel

 

[ernie]

I had parked up, turned the engine and a/c off, and was listening to the radio for about 40 minutes.
Wife turns up, gets in, and I fire up the engine (radio still on) and move off.
After 10 seconds of getting out of the carpark, the dreaded amber battery stop message above appears. I pull over, engage park with engine running, and wait 10 minutes. Message does not go away.
Points to note:-
1 It isn't possible to rid of the message - eg to transfer to the trip display and watch the alternator engaging and charging the battery.
2 I reason that since the car works and the car believes the battery is charging it should be possible to complete the 20 mile journey back home'
3 I complete the journey back home, keeping an eye on the engine temperature to make sure the poly v belt is OK. I checked later and it was fine.
4 I used eco mode and made sure all the consumers were off during the journey.
5 Eco mode gear changes seemed to be very smooth and the activation/deactivation of "D" was less frequent and totally smooth.
6 On arrival in the underground parking, after checking the poly V belt, I switched off, waited 30 seconds and switched on again.
7 Fault cleared, car appeared normal. switched off again after 2 minutes.
Hypothesis: starting the car on a 6 year old battery with the radio on etc, dragged down the voltage sufficiently to trigger the warning. Once the voltage was down, the message got "stuck". After driving back, switching off/on it righted itself i.e. the alternator WAS charging, so maybe the car knows this for real, not just believing its OK.

To be honest I sort of reasoned that the battery was at fault, but did not want to turn off the battery in case the car would not start again.
Moral: If the car says battery low: stop and charge, check how the car behaves, and if OK, carefully drive home with all consumers off.
Cars these days try to be too clever, and are economical with the truth on the display panel

The radio per se doesn't take a lot out of the battery, but the display does. So...if you must sit with the radio on, turn off the display. Ask me how I know! Another point to note, these 205 batteries don't have a lot of reserve once they're older.

Ernie

 

[Dickster]

Exactly. My SL55 displays the red battery warning light every time I start it. I press the menu button on the steering wheel and it goes out until the next start. It’s been like this years.

I’ve tested the batteries, and charging and all is good so I don’t worry about it.

 

[Gnominateur]

If you want to be nice to the battery, I think eco mode is not a great idea, because that leans on the battery more to save fuel... Just my instinct though.

Also, when the car is running, I don't think you're at risk of depleting the battery by using your usual conveniences -- per my understanding, you could disconnect the battery in most cars while the engine is running and everything would continue receive power.

I never used a 2017 205 but the 2019 one I had, as long as you didn't turn the car off and exit the driver side and then lock it, the car was not really "off". The engine was off for sure, but pretty much all the electronics were still on. So you could trigger the low battery warning by simply leaving it unlocked overnight.

I remember once I had it at the paint shop to fix up some scratches and the fellas at the workshop left it unlocked. The next morning, I got a Mercedes Me alert telling me the battery charge was low. Idling the car for a few minutes fixed that. Car was only a year old at the time so didn't seem like it was a dying battery.

If that happens again, it might just be a sign that you should get a new battery. I wouldn't want to wait until I need roadside recovery to swap that out.

 

[johnsco]

-- per my understanding, you could disconnect the battery in most cars while the engine is running and everything would continue receive power.

I do NOT recommend disconnecting the battery with the engine running - unless you want to risk blowing a lot of your sensitive electrics.
Without the battery your electrical system is subject to the unregulated and unsmoothed output of the alternator, which may be significantly higher than the 12-to-14 volts dc for which it is designed.

 

[johnsco]

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[Gnominateur]

I do NOT recommend disconnecting the battery with the engine running - unless you want to risk blowing a lot of your sensitive electrics.
Without the battery your electrical system is subject to the unregulated and unsmoothed output of the alternator, which may be significantly higher than the 12-to-14 volts dc for which it is designed.

I was just explaining a point, not making a suggestion.

 

[NJSS]

"6 year old battery" - I think it's time to fit a new battery ?

You might also consider fitting a Battery Monitor with an appropriate app. on your smart 'phone. I have four of these, and they have proved to be useful.

NJSS

 

[johnsco]

I was just explaining a point, not making a suggestion.

My comment was "just in case" anyone might try this.

 

[Deleted member 126251]

"6 year old battery" - I think it's time to fit a new battery ?

You might also consider fitting a Battery Monitor with an appropriate app. on your smart 'phone. I have four of these, and they have proved to be useful.

NJSS

The battery in my wife’s car (B class) is now going on 8 years old and still going strong (car is infrequently driven) . I recently had to replace the 5 year old battery in my SL (also infrequently driven). Go figure.

 

[flowrider]

My SL consumer battery is nearly 6 years old and works fine, the previous battery was its original and lasted 12 years. I have just changed the starter battery which I believe was the original from 2004!