I - current.

IEC - International ElectroChemical Commission.

Immobilized Electrolyte - An electrolyte made motionless by use of a gel additive or AGM separator. See also Gel-Cell Battery and Recombinant.

Impedance (Z) - The total opposition that a battery offers to the flow of alternating current. Impedance is a combination of resistance and reactance.

Initial Drain - The current that a cell or battery supplies when first placed on load. Also referred to as starting drain.

Insulator - A material — such as rubber, some plastics and glass — that is highly resistant to conducting electricity.

Internal Resistance (Ri) - The opposition to direct current flow within a battery, which causes a drop in closed-circuit voltage proportional to the battery's discharge rate.

International ElectroChemical Commission (IEC) - A worldwide organization that establishes standards in the electrical and electronic fields.