By the time most of us reach the stage in life where we can afford or desire to own a Mercedes ‘A’Class or another model, we will be well versed on the problems, that can be caused and associated with poor battery condition and failure.
Batteries these days generally have a longer life than was previously the case, are smaller and when in good condition do a fantastic job, starting the car on demand along with providing power to all the services that drivers of modern cars take for granted

We tend to under estimate what exactly we are demanding from the battery but if we stopped just for a moment to think about all of the services in our cars that are now electrically operated, all from that one battery we would pay more attention to it.
Go back a few years’ cars had one wiper blade, screen washers were hand operated, radio and audio equipment was non-existent, mirrors were adjusted by hand,
Air conditioning was non-existent in cars and heated seats were a thing of the future.   

But what about battery care, do we really look after it?
Well you can extend its life by ensuring none-essential services such as air-con, fans, audio equipment, headlights etc are all switched off, at least while starting a cold engine, all draw valuable power and all of it is coming direct from the your battery.

And it is worth lifting the floor pan just now and again to take a look at the battery. Are I hear you say  “but I get my car serviced at a good garage, they always do the good job” I would take a look anyway it doesn’t cost anything. How old is your battery? When its starts moving towards the three years old mark it ‘s time to start saving your pennies, you are going to need one in the near future, albeit the original battery fitted in the car always tends to last longer than its replacement. Built in life perhaps?  After all battery Manufactures don’t want them to last forever or they would go out of business.

I hope I have convinced you just to have a look, to see that the terminal connections are clean and free of verdigris, a build up of green and white granules; which if left, will corrode all metal parts it comes into contact with, including the very terminals themselves and in turn will prevent power from the battery effectively reaching the most demanding, component, the starter motor, which needs a lot of power to do its job.

 Then of course there’s the acid level have you checked the battery or should we just   leave it to the Garage? Well the ‘B’ Service is done every twenty four months approx, and the ‘A’ every twelve, this period of time represents nearly one third of the life expectancy of the average car battery, so don’t rely on the garage. Check every three months or so, do it every other time you check your tyres for pressure, thread depth, cuts and abrasions, another subject, another day.

If the acid level doesn’t cover the plates, which are the dark coloured fins you can see when you look into the top up holes of the battery then the battery requires to be topped up with distilled water but don’t overfill, remember all fluids need room to expand as the conditions get warmer and the ‘A’Class battery is for all intents and purposes in the cockpit
A special water bottle can be obtained which prevents overfilling but take care to ensure it fits into the filler holes the one I’ve got is no longer any use, it won’t fit in the holes of the ‘A’Class battery. 
I was surprised to see for the first time ever that the battery fitted to my ‘A’Class has an over flow pipe, what concerns me now is where does it spill out to, remember this corrosive acid we are talking about, be assured it will rot almost everything it come into contact with including the upholstery of the car seats, so keep a disposable cloth handy, avoid getting acid on your skin and remember don’t use a naked flame or smoke any where near your car battery. 
 
Topping up, the plates should be covered by about an eighth of an inch, or up to the marker and this is best done at regular intervals and not left to the point where the battery is nearly dry, as they dry out so they buckle which causes long term damage to the battery and affects the overall performance.
The battery being made up of 6 cells needs all six to provide the twelve volts of power required for all of the accessories fitted in the ‘A’Class, so don’t just check one cell and hope check all six.
If you get an indication at any point, by sluggish starting or poor lights with low engine speeds, that the battery is in difficulty then get it checked, your battery specialist will be able to test each cell independently using a meter he will tell you if any of them are failing, alternatively he can apply a high load test which will show the state of the battery. 
If all your battery needs is re-charging then top it up with distilled water prior to re-charging or you will almost certainly make the situation worse and remember a trickle, or low charge over 12 or 24 hours is better than a boost charge over only a few hours.
If battery problems persist check the tension of your alternator belt, followed by your alternator, a good auto electrician should be able to check the output using a meter.

Replacement Batteries can be purchased at most good garages and car accessory shops, not all will fit them for you, so check first.
Make sure you obtain the correct specification battery for your model of ‘A’Class generally diesel models have a higher rated battery than petrol so check.
In my experience it is worth paying that little bit extra cash to get a quality product, which should carry at least a two year warranty only remember keep the receipt.
A new battery will not require topping up as often but as its get older it certainly will, so keep and eye on it. And if you are relying solely on your garage then occasionally check up on them.