Panasonic HHR160A Five Main Characteristics, Charge characteristics, Discharge characteristics

NICKEL METAL HYDRIDE BATTERIES - CONTINUED

Five Main Characteristics

As with Ni-Cd batteries, nickel-metal hydride batteries have five main characteristics: charge, discharge, storage life, cycle life and safety.

•Charge characteristics

Like Ni-Cd batteries, the charge characteristics of nickel- metal hydride batteries are affected by current, time and temperature. The battery voltage rises when the charge current is increased or when the temperature is low. The charge efficiency differs depending on the current, time, temperature and other factors.

Nickel-metal hydride batteries should be charged at a temperature ranging from 0° C to 40° C using a constant current of 1C or less. The charge efficiency is particularly good at a temperature of 10° C to 30° C. Repeated charge at high or low temperatures causes the battery performance to deteriorate. Furthermore, repeated overcharge should be avoided since it will downgrade the battery performance.

Refer to the section on recommended charge methods for details on how to charge the batteries.

•Charge characteristics

	2.0						Charge			: 120%
	1.8						Temperature: 20C
							Model			: HHR160A
(V)	1.6							1C
								0.33C
	1.4							0.1C
Voltage
	1.2
	1.0
	0.8
	0.6
		20	40	60	80	100	120		140	160
	0

Charge Capacity (%) (Nominal Capacity Ratio)

•Charge temperature characteristics at various charge rates

	110						1C
	100
(%)	90
	80	Charge	0.1C x 12h		0.1C			0.33C
Ratio
	70		0.33C x 4h
			1C x 1.2h
Capacity
	60	Discharge		: 0.2C to 1.0V
	50	Temperature: 20C
		Model		: HHR160A
	40
		-10	0	10	20	30	40	50	60	70

Charge Temperature

•Discharge characteristics

The discharge characteristics of nickel-metal hydride batteries are affected by current, temperature, etc., and the discharge voltage characteristics are flat at 1.2V, which is almost the same as for Ni-Cd batteries. The discharge voltage and discharge efficiency decrease in proportion as the current rises or the temperature drops. As with Ni-Cd batteries, repeated charge and discharge of these batteries under high discharge cut-off voltage conditions (more than 1.1V per cell) causes a drop in the discharge voltage

(which is sometimes accompanied by a simultaneous drop in capacity). The discharge characteristics can be restored by charge and discharge to a discharge end voltage of down to 1.0V per cell.

•Charge temperature characteristics at 1C charge

	2.0
							Charge : 1CmA x 120%
	1.8						Model	: HHR160A
								0C
	1.6
(V)								20C
	1.4							40C
Voltage
	1.2
	1.0
	0.8
	0.6
		20	40	60	80	100	120	140	160
	0

Charge Capacity (%) (Nominal Capacity Ratio)

•Discharge characteristics

	2.0
						Charge	: 1CmA x 1.2h
	1.8					Temperature: 20C
						Model	: HHR160A
(V)	1.6
	1.4		0.2C	1C	3C
Voltage
	1.2
	1.0
	0.8
	0.6	20	40		60	80	100	120
	0

Discharge Capacity (%) (Nominal Capacity Ratio)

NICKEL METAL HYDRIDE HANDBOOK, PAGE 10 August 2000