Duracell Ni-MH manual Performance Characteristics, General Characteristics

Ni-MH Rechargeable Batteries

5PerformanceCharacteristics

5.1 General Characteristics

The discharge characteristics of the nickel-metal hydride cell are very similar to those of the nickel- cadmium cell. The charged open circuit voltage of both systems ranges from 1.25 to 1.35 volts per cell. On discharge, the nominal voltage is 1.2 volts per cell and the typical end voltage is 1.0 volt per cell.

Figure 5.1.1 illustrates the discharge character- istics of nickel-metal hydride and nickel-cadmium rechargeable cells of the same size. As shown, the volt- age profile of both types of cells is flat throughout most of the discharge. The midpoint voltage can range from

1.25to 1.1 volts per cell, depending on the discharge load. Figure 5.1.1 can also be used to compare the capacity of the two rechargeable types. Note that the capacity of the nickel-metal hydride cell is typically up to 40 percent higher than that of a nickel-cadmium cell of equivalent size.

FIGURE 5.1.1

	1.5
	1.4
(V)	1.3
	1.2
Voltage								C/5
	1.1				C/5
	1.0					Ni-Cd		Ni-MH
	.9
	0	20	40	60	80	100	120	140	160

Ampere-Hour Capacity (%)

Comparison of discharge voltage and capacity of same-size Ni-MH and Ni-Cd cells.

[Conditions: Charge: C/3 for 5 hours, Temperature: 21°C (70°F)]

5.2Discharge Characteristics: Effect of Discharge Rate and Temperature

Typical discharge curves for DURACELL nickel- metal hydride batteries under constant current loads at various temperatures are shown in Figures 5.2.1 to

5.2.3.Discharge voltage is dependent on discharge

current and discharge temperature.

FIGURE 5.2.1

	8.5
	8.0				Temperature:		45°C (113°F)
	7.5
(V)				C (2.4A)			C/5 (0.48A)
Voltage
	7.0
	6.5
	6.0
	5.5 0
		0.5	1.0	1.5		2.0		2.5
			Discharge Capacity (Ah)

FIGURE 5.2.2

	8.5
			Temperature:	21°C (70°F)
	8.0
	7.5
(V)		C (2.4A)		C/5 (0.48A)
Voltage	7.0
	6.5
	6.0
	5.5

0	0.5	1.0	1.5	2.0	2.5
		Discharge Capacity (Ah)

FIGURE 5.2.3

	8.5
						Temperature:	-20°C (-4°F)
	8.0					Temperature:		0°C (32°F)
			C/5 (0.48A)
	7.5
(V)					C/5 (0.48A)
Voltage	7.0
				C (2.4A)
	6.5				C (2.4A)
				C (2.4A)
	6.0
	5.5
		0.5		1.0		1.5		2.0	2.5
	0

Discharge Capacity (Ah)

Voltage and capacity of DURACELL DR30 Ni-MH batteries at various discharge temperatures and rates.

[Conditions: Charge: 1C to -ΔV = 60mV @ 21°C (70°F)]

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