Mercedes Assistance - Flat battery

[PaulXC]

Rather embarrassingly I flattened the battery on the E500.

I was working on the car (see here drainage channels) and while doing so I raised and lowered the roof a few times to get at the areas under the hood cover.

I also had the CD installing for the digital user manual which took about 10 mins.

I didn't obviously didn't realise how much power the hood used..

Went to start the car ... and got just a feeble turn of the starter ... but no worries I had jump leads and a VW Polo to hand!

Connecting them up and got ... nothing!:fail

Got a bit worried at this point and had to call out Mercedes Assistance.

Their guy was here within the hour and jump started the car in seconds.

I think I have some duff jump leads.

 

[190]

The real question is what state of charge was the battery in before the power draws. It may not have been fully charged. Either that or the battery is on it's last legs and so has reduced capacity.

The priority now should be to get it fully charged which won't happen just by driving the car unless you are going to drive it for a very long time.

 

[PaulXC]

I was a bit surprised at how little it took to drain it.

The last time I drove it was about a week ago and I did 550 miles in that day, so it should have had a good charge.

The Merc. Assistance guy did a battery test after 10 mins of running the car but all it shows on the print out is 12.31Volts.

 

[addbuyer]

I was a bit surprised at how little it took to drain it.

The last time I drove it was about a week ago and I did 550 miles in that day, so it should have had a good charge.

The Merc. Assistance guy did a battery test after 10 mins of running the car but all it shows on the print out is 12.31Volts.

12.3v is as near to dead

 

[PaulXC]

Should I have a trickle charger on it - bearing in mind its only used at the weekends and sometimes left for a week or two.

If so what charger would the collective recommend?

 

[Tuercas viejas]

The buying decision must be based on what typoe of battery you have in the car.

If its a conventional wet, simple plate unit then any will suffice.
If on the other hand its an AGM unit, "aka" spiral coil gell cell then you must use an AGM compatible charger.
Failure do do that will result in battery failure, you will cook it and it will overheat and fume.

By the way if you do have a gell cell flat battery you CAN charge it with a conventional charger IF you hook a reasonably low charged regular wet plate battery to your flat gel cell in parallel. Then charge the pair as if you had a two pack battery set up. Then charge as a trickle.

This dampens out the charge ensuring you don't "cook & destroy" your gel cell or surface charge it.
All the best
Tuercas Viejas