Battery charging

[Mark F6233]

The C class has been stood for quite a few months. Battery is flat. Question is can I charge the battery while it is still all connected to the car thus preserving the radio code etc or due to the charging voltage/current does it need to be disconnected completely.

 

[markjay]

What year is the car?

Newer C-Class with Stop/Start and AGM batteries are not so straightforward to charge when they go flat.

Otherwise you can use a trickle charger to recharge the battery overnight while the battery connected to the car.

 

[190]

Which generation of C class ?

In the manual for my W204 there is a maximum safe charging voltage specified which I think is 14.8 Volts. As long as that limit is not exceeded it's OK to charge with the battery insitu. No modern regulated charger is likely to exceed that voltage. As a guide chargers with the biggest charging amps tend have the highest voltage but if regulated should still be safe. Regulated trickle chargers certainly won't be a problem but if the battery is truly flat then it may take several days to charge fully.

Current isn't an issue. Consider what the alternator will push out if needed.

 

[Stratman]

Get yourself one of these. They have settings for small and large batteries (car/bike), AGM batteries and recondition, and come with a set of leads which you can wire permanently to the battery and have an easy accessible connection point for charging. You can leave it connected for an extended period to float charge too, as it's a 'smart' charger.

No, they're not the cheapest. Yes, I have one and am glad I paid for quality.

Link to MXS 5 on Ctek website

 

[Smart320]

+1 for Ctec

 

[Mark F6233]

Thanks guys, my charger is quite old, I will check its output. The car had a new battery last Nov, since then it's only ever been out the garage a few time. Hence it's taken more out than put back. The car lights up but no juice to start. I just did not want to do any harm leaving the battery connected.
The car is a W203.

 

[toolman1954]

Hi,
How flat is your battery? You really need to check the voltage with a multimeter, If you do not have one, get one, a "cheap and cheerful" will do as long as it is just used for DC volts.
So, check the battery voltage, if it is less than about 7 volts, then no modern trickle charger will charge it up, even if you leave it charging for a month of Sundays. It needs a voltage of about 7 volts to kickstart the charging, and if it does not see the voltage, it will just do nowt.
You have 2 options, get ( beg, borrow ) an old fashioned 4-6 amp charger, these simple chargers will charge up a battery from flat.
Otherwise piggback another good battery in parallel, positive to positive--- negative to negative and this will provide the 7 volts necessary to get your battery charging, using a modern trickle charger. Even a motorcycle battery will do for this.
Another option of course depending on the age of your current battery is just to buy another battery.
Charging battery off the car in these circumstancesis a far safer option, just keeping it topped up is fine on the car.
Losing the radio code etc, are small minor problems easily fixed.

Steve

ADD .... Looks like my post was beaten by yours, take out of it what you will.
Old charger is good ! No new battery needed. Get yourself a multimeter.

 

[Deleted member 126969]

I have a couple of Ctek chargers. One is pretty much permanently connected to the Westfield as it gets little use, the other gets used for keeping spare batteries in a good state as well as keeping the Jeep topped up from time to time. I recently bought an AA branded charger to fit permanently to the Jeep, but it didn’t do the job. It shuts itself down after a while and let the battery go flat. I’ll be getting another Ctek for that I think, great chargers..