Automotive Batteries are rechargeable batteries that supply electrical energy to an automobile for starting lighting and ignition. Batteries are very important for a vehicle, it does not only start a vehicle, it also serves as the shock absorber or protection for electronic equipments on board a vehicle.

There are two types of car batteries. The LM or Low Maintenance and the MF or the Maintenance Free. Low Maintenance Battery and Maintenance Free differ in the construction of its grids.

Grids are the most basic part of a car battery. The Grid of Maintenance Free batteries are normally made from Lead and Calcium, while Low Maintenance Batteries are normally made from Lead and Antimony. The grid has special significance in the Maintenance Free Battery, it hold the explanation as to why water never needs to be added to the battery, thus, the holes and filler caps can be eliminated.

Once the grid have been pasted with the active materials in the manufacturing process, they are called Plates. During the manufacturing process, the plates are subjected to a process to transform the pasted materials into chemically active materials. The negative plates contain sponge lead (Pb) and positive plates contain lead peroxide (PbO2).

Once negative and positive plates have been determined. These plates will be group together by attaching a number of similar charged plates which will be called Elements. Then plate groups of the opposite polarity will be interlaced making the positive and negative plates alternate.

Electrolyte in the car battery consists of a solution of sulfuric acid (H2SO4) in water (H2O). The solution is 36% acid and 64% water by weight. The specific gravity of the electrolyte is 1.260 which means that with equal volume, electrolyte weighs 1.260 times as much as water.

Equipments Needed to test a Battery :

1. Hydrometer – Use to measure the density of the battery solution

2. Voltmeter – Use to measure the electrical charge (voltage)  between two points.

3. Load Tester – Use to test the capacity of the battery by subjecting the battery to a control load.

4. Ammeter – Use to measure the flow of electrical current.

Specific Gravity Table

Specific Gravity                  State of Charge

1.260                                 100%

1.230                                  75%

1.220                                   65%

1.200                                   50%

1.170                                   25%

1.140                                     0%

Battery Sizes and Equivalent by PABMA and JASO

PABMA*  -      JASO*

1SNF       =       N40L

1SMF       =      NS50L

2SMF      =       N50L

3SMF      =       N70L

6SMF       =      N100L

2D           =        N120

4D           =        N150

8D           =        N200

6TN        =       PT110

6DUU5   =       DIN55

6DUU7   =       DIN72

6DUU8   =       DIN88

G65         =        MF65

G78        =         78DT

G31         =        1150K

*PABMA – Philippine Association of Battery Manufacturers

*JASO – Japanese Automotive Standards Organization