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Essential element on any motor vehicle, the battery ensures the starting of the engine, but also the power supply of the different electrical circuits. If some batteries are said to be maintenance-free, others claim a minimum to ensure a certain longevity.

Text & Photos C. Petitjean

Practical advice

● A battery that has been left discharged too long is degraded by the formation of lead sulphate crystals on the plates. Think from time to time to give him a maintenance charge.
● Do not reverse the polarities of the battery. On European cars, the - is connected to the mass of the vehicle and the + to the circuit. The negative terminal is also smaller than the positive.
● In case of electrolyte contact with skin or clothing, rinse immediately with plenty of water.

An accumulator battery stores electrical energy during the charging of the alternator, to restore it as needed. On the car, she plays a buffer role. In case of accidental discharge, the full energy can be renewed by an external charger connected to the mains.

Anatomy

In a sealed plastic tank, closed by six plugs, and containing the electrolyte (dilute sulfuric acid solution), bathe plates connected to the external terminals + and -. By opening the caps, the level of the electrolyte and the alternation of the positive plates of brown color and the negative ones appear. In charge and discharge, a chemical transformation changes the nature of the plates and the concentration of the electrolyte. This enriches the acid with the load, which increases the density. The discharge leads to the formation of water, so the density decreases. The control of this density with the help of an acid scale gives information on the state of charge of the battery.

His characteristics

On a battery are indicated three characteristic values. For example: 12 V - 50 Ah - 420 A.

The voltage is measured between the terminals. 12 V DC is a nominal value that can range from 11 to 14.4 V between the start and end of charge.

The capacity, expressed in Ampere-hour (Ah) is the amount of electricity stored by the battery that it can restore in 20 hours. A capacity of 50 Ah allows a flow rate of 2.5 A during this time.

The starting powerThis is the current that can be supplied by the fast discharge battery at -18° C. Here 420 A.

The interview

The periodic check is to check the level of the electrolyte by opening the six battery caps or by lifting the plastic strip that groups them together. The acid solution should cover the plates by about one centimeter. The level is complete only with demineralised or distilled water, especially not with acid.
● To control the concentration of the electrolyte, use a scale-acid, or densimeter. By squeezing the rubber bulb, liquid is drawn successively into the six compartments. The apparatus is graduated from 1.1 to 1.3. A density of 1.1 corresponds to a battery almost discharged; a value of 1.28 at a good state of charge. In practice, three areas are used: green = good; white = medium; red = discharged or doubtful battery.
● A voltmeter placed between the two + and - terminals will measure the available voltage. It is 14.4 V for a charged battery.
● Improper contact, due to oxidation between a lead terminal of the battery and the cable terminal, can cause a failure. The tightening is done by pinching with a bolt tightened by a key of 10. The pod, often sulphated, must be cleaned internally to the emery cloth or with a special tool, as well as the terminal. After reassembly, a thin layer of grease will prevent the formation of climbing salts that cause sulphation.
● When using a charger, the charging current must not exceed one-tenth of the battery capacity. If it is 45 Ah, the charge will be 4.5 A for ten hours.

Battery features

Battery features

The characteristic elements of a battery: 12 V is its nominal voltage. 50 Ah is his ability. 250 A (or starting power) is the maximum current that it can provide punctually.

Check the level of the electrolyte

Check the level of the electrolyte

Periodically, open the caps and, if necessary, fill in the electrolyte level by adding distilled or deionized water 1 cm above the plates. Never add acid.

Test each compartment

Test each compartment

Test each compartment by taking a small amount of electrolyte with the scale. The weighted float rises more or less in the pipette. Here the yellow zone indicates an average load.

Check by voltmeter

Check by voltmeter

Another mode of control, the voltmeter connects to the terminals of the battery respecting the polarities. Switched on "DC voltage", it indicates 12,5 V, confirming the previous test.

Recharge a battery

Recharge a battery

To charge a battery, connect the charger clips to the battery terminals. Set the load to one tenth of the capacity. The bubbling of the electrolyte indicates the end of charge.

Clean pods and terminals

Clean pods and terminals

This pod starts to oxidize and its electrical contact with the terminal may be bad. This special tool, which functions as a reamer, cleans the terminals and terminals.

Deoxidize the terminals

Deoxidize the terminals

If the terminals are slightly oxidized, a brush stroke with medium-hard strands is enough to make them clean. For this operation, you can leave the battery on the vehicle.

Fix the battery

Fix the battery

On the other hand, any battery left from its housing on the car must be reassembled at the reassembly by one or two fastening lugs. Attention, this fixing is a point checked to the technical control.


Video Instruction: Battery Care and Maintenance Tips -EricTheCarGuy