Mercedes-Benz S-class W140 - Repair manual and operation

7.2.1. The rechargeable battery - the main data, shutdown and acquisition of the new battery

See also Section Check of a Condition of the Battery, care of it and gymnastics of the Head Routine maintenance

The battery installed 12 V consists of six cans containing positive and negative plates which are lowered in solution of sulfuric acid. The problem of the battery includes production of current for start of the car, ignition and for lighting, and also for other consumers of the electric power.

The battery possesses 100% efficiency at 27 °C. At -18 °C efficiency falls to 40%. Now to start the engine, it is necessary to have more than twice more energy, than it was necessary at 27 °C.

Starting power (starting current) shows ability of the accumulator to start the car in the conditions of very cold weather. It shows current in amperes which gives the accumulator within 30 seconds at -18 °C without power failure lower than 7.2 Volts (the minimum level demanded for reliable start). The this indicator, the more starting power of the accumulator is higher.

Reserve power shows time in minutes during which the accumulator gives current of 25 Amperes at 27 °C., i.e. time during which the accumulator ensures functioning of all auxiliary devices in the car at night and in the conditions of bad weather at the faulty generator.

In winter conditions at -18 °C and below the battery will be badly charged in connection with increase of internal resistance. At short trips in the winter the energy spent by the battery for start is not restored. As a result the battery works very hard, is constantly discharged and eventually fails.

In summer months after long trips the engine strongly heats up, and often happens that it is difficult to start it anew. Such "hot starts" sometimes demand as much the power how many and at cold weather, or it is more. Especially it extends to high-compression engines with large working volume and cars with the conditioner. It once again emphasizes importance of a right choice of the accumulator according to the car engine.

Acquisition of the new rechargeable battery

Probably, the most important what the buyer has to pay attention to, are characteristics of the accumulator. They are three.

The first - rated voltage, it at all batteries identical, and it is impossible to be mistaken. Upon purchase it is desirable to check the rechargeable battery a load fork.

The second - the capacity measured in ampere/hours (And / h), means, roughly speaking, the quantity of the electric power which is kept in the accumulator. Depends on capacity as it is long possible to twist a starter the engine, more precisely - how many it is possible to make attempts of start of the engine. The price of the accumulator is almost directly proportional to its capacity.

And the third characteristic - starting current (it is measured in amperes: A), i.e. the current given on a starter during start-up. On accumulators it can be specified on four different systems: GOST (on domestic), EN (the standard of Uniform Europe), SAE (the American standard) and DIN. The last, German standard, is closest to our state standard specification and on the majority of the European is put "by default" i.e. when the system of the standard is not specified. The it is more, the quicker and with a bigger force the starter will turn the engine.

It is better if you buy the rechargeable battery with those characteristics which are specified in the maintenance instruction of your car: so it will serve to you longer at the minimum expenses. It is possible to save and buy the battery of smaller capacity, but it will serve you less usual term and it is bad to cope with winter start. Having bought the battery even not much more to bigger capacity, you will not win in service life since constant недозаряд the accumulator will lead to sulphation of plates, and will lose in money. It is not necessary to be fond of the raised starting current also: you will burn a starter. Replace oil in the engine better, and problems with start will not be.

Lately the market of the country is overflowed with low-quality goods and fakes. Accumulators are not an exception. There are several signs on which it is possible with a sufficient accuracy to distinguish the original from a fake. The first and, perhaps, main thing: on the accumulator the country manufacturer and the releasing plant have to be surely specified, it is better if with the address. The second - date of production has to be specified that is very important if the accumulator which is filled in. Technical data sheet has to be attached to each battery, and here existence of the instruction is optional. It is connected with what in the West accumulators almost do not sell at retail, they are installed by experts at service stations. The third - the high-quality accumulator is inconceivable without the high-quality case, good traffic jams and smooth output plugs which are quite often greased with technical protective lubricant from oxidation and covered from above with color plastic caps.