Duracell Ni-MH manual Basic Cell Construction, Cylindrical Cell Construction

Ni-MH Rechargeable Batteries

4Battery Construction

DURACELL standard-sized nickel-metal hydride batteries are constructed with cylindrical and prismatic nickel- metal hydride cells. DURACELL nickel-metal hydride batteries are a sealed construction designed for optimal perfor- mance and maximum safety. The batteries are manufactured to strict quality control standards to ensure reliability and consumer satisfaction and offer such features as:

•High energy density — Minimizes battery volume and weight

•Wide voltage range — Meets operating voltage requirements of 3C devices

•Thin profiles — Innovative wall-less design

•Advanced interconnect — Self securing, voltage- keyed interconnect provides a highly reliable battery- to-device contact

•Durability — Manufactured with LEXAN® and LUSTRAN® polycarbonate high impact and flame retardant polymers

•UL listing — Independent approval of battery use in devices

LEXAN® is a registered trademark of the General Electric Company.

LUSTRAN® is a registered trademark of the Monsanto Company.

4.1 Basic Cell Construction

The electrodes in both cylindrical and prismatic cell configurations are designed with highly porous structures which have large surface areas to provide low internal resistance which results in superior high rate performance. The positive electrode in the cylindrical

nickel-metal hydride cell is a highly porous nickel-felt substrate into which the nickel compounds are pasted. Similarly, the negative electrode is a perforated nickel- plated steel foil onto which the plastic-bonded, active hydrogen storage alloy is coated.

4.2 Cylindrical Cell Construction

The assembly of a cylindrical cell is shown in Figure 4.2.1. The electrodes are separated by the sepa- rator which is a synthetic, non-woven material that serves as an insulator between the two electrodes and as a medium for absorbing the electrolyte. The electrodes are spirally-woundand inserted into a cylindrical nickel- plated steel can. The electrolyte is added and contained within the pores of the electrodes and separator.

The positive electrode is connected to the metal lid with a tab. The cell is then sealed by crimping the

top assembly to the can. The top assembly incorporates a resealable safety vent, a metal lid and a plastic gasket. A heat-shrink tube is placed over the metal can. The bottom of the metal can serves as the negative terminal and the metal lid as the positive terminal. The insulator and gasket insulate the terminals from each other. The vent provides additional safety by releasing any excess pressure that may build up if the battery is subjected to abusive conditions.

FIGURE 4.2.1	Metal Can
		Separator
			Negative Electrode
			Heat Shrink Tube
			Positive Electrode
			(-) Negative Terminal
			Insulator
			Positive Tab
			Metal Lid
Safety Vent			Cosmetic Disk
(+) Positive Terminal			Gasket

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