W211 Battery Charging

matthew k

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I wonder if anyone has advice on charging my battery. I've had the 'convinience' warning coming up for a while now for the first few miles of use. I put this down to local use and a tired battery. I've actually let my tax and insurance lapse this months as I'm not using the car for a while so I'd like to charge the battery.

Is there anything in particular I should know, does the battery need to be disconnected beforehand? I must say this is my second W211 and they do seem hard on batteries. Thanks
 

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buy a ctek and just follow the instructions .simples .
 

Tony Dyson

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You can leave the battery connected to the car providing the charge voltage doesn't exceed 14.5v and if it's not a Smart Charger stop charging when demand falls off to near zero on your charge indicator.
 
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matthew k

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You can leave the battery connected to the car providing the charge voltage doesn't exceed 14.5v and if it's not a Smart Charger stop charging when demand falls off to near zero on your charge indicator.
Ok thanks, so charging in situ isn't going to dry anything? It's an estate so I need to work out how to get access, not sure.
 

AMGeed

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If you are getting the convenience features message often, check the voltage of your aux battery under the pollen filter. Seems lots of E class owners forget or don't know about this second battery. If its on the way out it can give that message as well as the main battery.
Tayna sell a Varta aux battery for under £45 delivered, half the price of a Fiamm OEM.

As above, no problem to charge either battery insitu. Neg terminal connected first and removed last.
 
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matthew k

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If you are getting the convenience features message often, check the voltage of your aux battery under the pollen filter. Seems lots of E class owners forget or don't know about this second battery. If its on the way out it can give that message as well as the main battery.
Tayna sell a Varta aux battery for under £45 delivered, half the price of a Fiamm OEM.

As above, no problem to charge either battery insitu. Neg terminal connected first and removed last.
The aux battery was changed in the last 3 years by Mercedes I think. The car has been sluggish to start. Thanks for the information, I'll charge it today.
 

mioba

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Cold weather identifies weak batteries immediately.
If your having starting issues its the main battery.
What brand of battery have you in there now and how old is it.
 
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matthew k

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Cold weather identifies weak batteries immediately.
If your having starting issues its the main battery.
What brand of battery have you in there now and how old is it.
It's a Verta Mercedes one I think, not sure how old it is. Agreed the cold weather reduces the battery's capacity and increases the torque required. I've charged it, and it seems to crank up normally. I'm sure it's on it's last legs though!

There does seem to be some cheap (agm) replacements available on Ebay, I'm not keen on spending £300! :)

Would something like this do? https://rover.ebay.com/rover/0/0/0?mpre=https://www.ebay.co.uk/ulk/itm/312754900991
 

Tony Dyson

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matthew k

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Check your battery dimensions and post configuration against something like this which I think would be a like for like replacement for your existing? if you're not sure the existing one is at the end of it's useful life get it load tested to confirm first?

https://www.tayna.co.uk/car-batteries/varta/?ordering=&A-15=Varta Start-Stop&A-10=AGM&A-22=95
Thanks, and actually you make a good point, it could be my alternator!!! There is a bit of slight flickering from the interior lights at idle, humm, I wonder?
Om642 148,000 miles
 

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Quite often I don't use my E class for over a month, so after about 3 weeks I put it on charge using a standard 5 amp charger.
6 to 8 hours will bring the charge rate down to under 1 amp, so I then disconnect. Never had a problem.
If you need a battery then Tayna are great on price & service.
 
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matthew k

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Ok, so I've started the car a week later, (in my drive not using it at the moment) and it really struggled. When it started after a couple of minutes idling it stuttered for a second, and is running normally now, I'm sitting in it, letting it warm up.

So is this typical knackered battery stuff, or do I have a battery draining issue? After ten minutes idling I turned it off and it span up easily, this suggests to me the alternator isn't the issue? Thanks!!
 

sonic

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From what you say sounds like the battery is starting to loose its capacity, particularly as its starts after warming up. Have you a charger? If so leave it on charge overnight & try starting it in the morning?
 
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matthew k

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From what you say sounds like the battery is starting to loose its capacity, particularly as its starts after warming up. Have you a charger? If so leave it on charge overnight & try starting it in the morning?
Yeah, and maybe two weeks of disuse has finished it off. I charged it a week ago, and it was very sluggish. I'll try starting it tomorrow, I just have a dread of slow drains, I know how hard they are to diagnose.
 

sonic

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Yeah, and maybe two weeks of disuse has finished it off. I charged it a week ago, and it was very sluggish. I'll try starting it tomorrow, I just have a dread of slow drains, I know how hard they are to diagnose.
The first cold weather always finds a weak battery.
 

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If it helps i put a new battery on a w211 and 2 weeks of short trips to work put the convenience functions light on. It was winter time also. I was charging mine once a month.
 


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