Checking the acid level in the battery

The Focus is factory-installed with a largely maintenance-free battery. Of course, the service life of modern batteries is highly dependent on the conditions of use: every start of a cold engine, driving mainly for short distances with numerous stops at traffic lights and traffic jams, every additional consumer of electricity (air conditioning system, heated windshield and rear window, air blower in the cabin, etc.) subject the battery to more stress than regular long-distance driving. However, modern batteries last between three and five years.

If you must then opt for a less convenient open-cell spare battery, we advise you to check the battery fluid level from time to time. The battery fluid consists of sulfuric acid diluted with distilled water. High ambient temperatures or a defective voltage regulator reduce the amount of water in the battery acid. During long periods of parking, the battery automatically discharges itself. This can also lead to a lack of water, as well as deep discharge due to an external current consumer (for example, a refrigerator box connected to the cigarette lighter). Always top up with distilled water only - just like boiled water, tap water contains conductive salts and other minerals that are harmful to the battery.

In maintenance free batteries, the evaporated liquid condenses over the cells and drips back into the battery.

Stages of work

The acid level must at least reach the MIN·mark on the housing (the top edges of the plates should be well covered).


Top up if the acid level is too low. To do this, unscrew the plug or wring it out with a screwdriver.

Add the liquid level of a charged battery to the top line (about 15 mm above the plates) distilled water.

Top up a heavily discharged battery only until the plates are covered - when charging, the acid level rises significantly. If necessary, after charging, add liquid to the upper mark with distilled water.

Never overfill the battery or acid will come out of the plugs or side vents. This causes corrosion or acid crystals to form on the surface of the battery and around its location. Carefully remove the salt crystals with a brass brush and then wash the surfaces with plenty of water. Remember to disconnect terminal 31 first (negative pole) battery.