This is from page of the manual.
Battery BAT-09: Five super-capacity A-size Nickel Metal-Hydride cells. Charger AC Charger: T70 – Standard charger / USA 110VAC T70E – 220VAC European standard prong Car Charger: CH04 – Vehicle cigarette lighter type plug Charge Time To charge a completely dead battery, place meter on charge for 12 hours. Charging a battery with a partial charge will require less time. Extensive overcharging can reduce battery life. Run Time 8 hours with NO modem or backlights. 5 hours with modem on 25% of the time. Battery Test To test the battery, press the battery key. The LCD will display the battery voltage and an accumulated on-timer. The nominal battery voltage is 6.0V and the normal operating range is 5.0 to 7.0 volts. Since the battery voltage does not drop linearly with use, it is not a good indicator as to the remaining life of the battery. The accumulated on-timer tracks the total amount of time the meter has been operated since the timer was last reset. To reset the timer, press the decimal point, then the battery key. Use the timer in conjunction with the battery voltage to determine when the battery needs to be recharged. Remember to reset the timer each time the battery is charged. The meter will beep and display a warning when the battery voltage is getting low. The meter will turn off automatically when the battery reaches 5.0V. The DisplayMax 5000 WILL NOT give incorrect readings due to low battery. Automatic Shutoff To conserve battery power, the meter is programmed to turn off after 5 minutes of non-use (no keypad entry). The timer can be set to 10 minutes by pressing .10 ENT (decimal, 1, 0, ENT) or disabled by pressing .00 ENT (decimal, 0, 0, ENT). To set back to 5 minutes, press .05 ENT (decimal, 0, 5, ENT). Note:
