The cover and the case of the PROBE MF PREMIUM battery is made of polypropylene co-polymer, which is a high impact resistance material. The two pieces are heat sealed together to ensure extreme resistance during operational conditions of the battery.

The battery terminals are made of a specially hardened lead alloy to ensure good mechanical resistance to torque and external above.

The specific gravity of the battery electrolyte is in line with international standard requirements to ensure a good cranking performance at different climates. As the battery is discharged the specific gravity of the electrolyte decreases and the reverse occurs when the battery is recharged. The PROBE MF PREMIUM battery has a built-in visual hydrometer on the cover which shows the battery state-of-charge at a glance.

Shown below is the overall chemical reaction that takes place in the battery cells on charging and discharging .
Notice that the reaction is reversible.

PbO2		Pb		2 H2SO4	Discharge Charge	2 PbSO4		2 H2O
Positive Plate		Negative Plate		Electrolyte		Lead Sulphate (both plates)		Water

The sulphuric acid in the electrolyte is consumed during the discharge and it is regenerated back to the electrolyte during the recharge.

This mass transference process causes the specific gravity variations in the battery and the built-in hydrometer reacts to these variations giving an indication of the battery's state-of-charge.