E320 battery problems

[Sve]

Hi,

I had the car (53 plate) for few weeks now and I saw a message month ago saying that the braking effect will be reduced and to start the engine. That message made me thing there is a problem with the battery, but I saw it just once and went away.

Yesterday while I was driving, all of a sudden I got "Battery protection: Convenience functions temporary unavailable". I parked the car in the morning and then in the evening when I put the key I saw message saying that the functions are back to normal. The moment I started the car I saw the above message again - "Battery Protection: Convenience functions temporary unavailable". On my back to home yesterday evening I saw that couple of functions were not available - the back window heating, the back lights, then just before get home my radio went off and didn't came up.

I parked the car and decided to see if it will start, well it didn't. I saw all the lights coming up and when I tried to crank nothing happens, except my clock went back for few hours. I started getting the same message about Reduced braking effect. I waited in the car for 15 mins and tried again and this time the car started - went for a short walk and parked it again. Unfortunately this morning it didn't start, I called my insurer to find out that I didn't have road assistance. The battery is not completely dead, the central locking still works, lights are coming but it didn't start.

So I'm going to get AA breakdown cover today hopefully they will come and confirm this is a battery.

After a quick read I was able to get battery voltage:
position one - 11.5 V
position two - falls to 10 V
when I try to start fall at around 8V

Ideally I'll be looking to get new battery today or tomorrow, the current one in the trunk is Varta, but I cannot say when it was last changed. Being driving with Bosch for many years and had no problems and I'm thinking whether should I continue with Varta or try Bosch or Exide (I see RAC Battery fit one of these). I know it should be AGM battery, not sure for the capacity, will check later the one I got because I was in a hurry in the morning.

I'll appreciate your comments.

Thanks in advance.

 

[BlackC55]

Get a Mercedes one and ask for a discount. The battery in my old ML is original at 13 years old. There is a difference between MB batteries and others.

 

[V12]

Sounds like the battery is flat but the alternator may also be dead and has not sufficiently charged the battery.

Varta make Bosch batteries and I've always had good experience with them.

AGM is only advantageous for vehicles with start/stop AFAIK.

 

[Sve]

Hi,

Thanks for your replies. V12, indeed AGM should be for start/stop but that's what most sites offers me when I type my car number.

The road assistance came and I have been told that the alternator is not charging the battery. This time the battery voltage was 13.7 on position 1, then when I crank became 12.3 and after a short 5mins drive it was 11.5 and when I parked was 10.9. After I turn off the engine I tried to crank again and it didn't start this time.

I got the car with one year warranty and alternator should be covered under that. I'm going to give them a call tomorrow and hope it is indeed covered.

Thanks.

 

[GordonTarling]

The original battery in your car will have been an AGM type and it should be replaced with the same type. Got one for my car about a year ago for around £120 fitted.

 

[Sve]

Hi,

Here's an update if (I hope not) happened to someone else.

I took the car to Brunswick garage (nearby Arnos Grove station, N11) and Andy was very kind to take care of the car. They actually took the car one day earlier than my appointment and then it was ready on the following day.

Carry out tests confirmed that the alternator charge rate was 11.9 volts and it has to be replaced.

I've been charged with 254.20 for labor (renew and diagnostic) and another 367.12 for new alternator excluding VAT. The final bill was 745.58 and the WMSGroup warranty will cover just the half of that. The battery was charged overnight and they said it's ok. I can see now that the alternator rate is constantly around 13.7-9 volts.

As I said it started with turning off any convenient functions, no back window heat, indoor lights. If you want to see the current voltage of the battery, plugin the key and turn in position 1, scroll the cluster display to miles and then press the R button three times. Once you move the key to position 2 or start the engine the voltage will change, at least it will give you some clues on what's happening.

Regards.

 

[Miao]

The original battery in your car will have been an AGM type and it should be replaced with the same type. Got one for my car about a year ago for around £120 fitted.

GordonTarling, can you explain why the car would need an AGM battery? I may need to change mine and many websites propose a cheaper non AGM type. Thanks

 

[Miao]

I have the same exact problem. The car starts with an alternative battery but I had to give it back. How can I find out that it is only a battery issue, not an alternator one like you?

 

[Dryce]

The original battery in your car will have been an AGM type and it should be replaced with the same type. Got one for my car about a year ago for around £120 fitted.

I don't think there's any reason to justify AGM as a replacement.

Just as long as the Ah and CCA values are OK a decent battery such as Bosch S5 should be fine.

 

[GordonTarling]

Original MB spec for the car was an AGM type, so why change from that unless you know more about MB electrical systems than the original designer?

 

[V12]

I would consider an AGM battery if you are doing short journeys and few long journeys.

In reality, a healthy alternator will fully charge a good 100Ah battery in less than 10 minutes after a start.

It's only abut a £40 difference so it's no big deal, that's less than half a tank of fuel...

 

[Miao]

Well, I just discovered the problem is with the alternator, not the battery, which by the way is an MB one, AGM type, made by Varta, but a smaller 70Ah. Is it something I should be surprised about and should I consider changing it? (Is it possible that the alternator was damaged from using a smaller battery?)

 

[GordonTarling]

I don't think a smaller capacity battery can damage anything, but 70Ah does seems small for an E320cdi, so maybe think about changing it soon.

 

[V12]

A 320cdi should have a 95Ah or 100Ah battery fitted (017 or 019).

A weak or small capacity battery can cause higher voltage fluctuations than a larger battery would. I don't know what the long term effects of this would be, but I have seen plenty of cars on star with fault codes in almost every control unit from either undervoltage or overvoltage.

I would definitely change it for piece of mind.

 

[Miao]

Car is back with new alternator. Garage originally wanted to do it for 1200 which is way above what I read it should cost. Settled for 860 with a Bosch alternator instead.
On the way back, I noticed that my consumption on my usual journey decreased by 20%! Is it possible that an aging alternator had such an impact?

 

[V12]

If your old one wasn't charging at all then it's one thing less for the engine to power.
Another reason for fitting a new battery, improved MPG!