Common Car Batteries Maintenance Tips
Over a period, a lead-acid battery loses distilled water from its electrolyte. If this is not replenished, the level eventually drops below the top of the plates, reducing efficiency.
The electrolyte is topped up using distilled or de-ionized water, sold by garages and accessory shops as topping up fluid. Tap water that may contain mineral traces should not be used.
The correct level for the electrolyte is marked on the translucent case of modern batteries. On batteries with a black case, the electrolyte should just cover the splash shield over the top of the plates or the separators between the plates.
If the battery terminals or the metal parts securing the battery are covered in acid corrosion, this must be neutralized before it eats into the metal.
Undo the battery connections and take the battery out of the vehicle and wash corroded parts of the battery holder in household ammonia, baking soda, and hot water.
When the acid is neutralized, give the exposed metal a coat of paint. Battery terminals should be cleaned to bare metal with a wire brush.
As a battery discharges, the electrolyte solution becomes weaker. The state of charge of the battery can be found by testing the specific gravity of the electrolyte with a hydrometer.
When the electrolyte temperature in the battery is 60oF that is 15 degree-Celsius, a discharged battery gives a reading of 1.110 to 1.130, a reading of 1.230 to 1.250 indicates the battery is 70 percent charged, and a fully charged battery gives a reading of 1.270 to 1.290.
However, many hydrometers will have only colored bands on the float, representing the different charge states. Where figures are given, the decimal point may not be revealed.
For accurate readings, a battery specialist uses a temperature compensation scale to allow for the electrolyte temperature of the battery, if it is above or below 60oF.
Once a week, remove the battery caps or vent cover and check the level of the electrolyte. If it is below the minimum mark, or the splash shield or separators between the plates are uncovered, top it up with distilled water.
Do not overfill it, otherwise acid may leak out of the vent holes while the battery is being charged, causing corrosion. After topping up, dry the battery with a clean cloth.
Corroded battery connections make poor contact and reduce electrical output. Remove the terminals for cleaning. If they are tight, do not use force; instead, wrap a rag soaked in hot water around the terminals. This will expand them and ease their removal.
Clean the battery posts and terminals to the bright metal with a wire brush, making sure that you keep the ds tot of your eyes. Apply petroleum jelly to discourage further corrosion.
The state of charge can be tested with a hydrometer. Insert the dip tube into the electrolyte, then squeeze and release the bulb to draw a sample of electrolyte into the tube.
Note the reading on the calibrated float riding on the surface of the sample.
Hydrometer readings should be taken only after the battery has been charged or used on the car for 30 minutes. If the readings fluctuate by more than 0.040, the cells may be faulty.
