Blood pressure is usually expressed in terms of the systolic pressure (maximum during one heart beat) pressure over diastolic pressure (minimum in between two heart beats) and is measured in millimeters of mercury (mmHg), above the surrounding atmospheric pressure (considered to be zero for convenience).
Corrosion on the terminals is due to hydrogen gas being released from the acid in the battery. It mixes with other things in the atmosphere under the hood and produces the corrosion you see on the terminals. Generally, if the corrosion is occurring on the negative terminal, your system is probably undercharging.
Sparks can also be caused by any electrical or moving device. Warn bearings may do so. Battery chargers, isolating relays etc, should never be installed in battery enclosures. Such battery ventilation is vital. Battery ventilation is vital â venting details . The battery enclosure must enable fresh air to enter at its base.