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4.4 Battery information
General: The PI4100 is supplied with a rechargeable battery pack made up of six matched
nickel-metal hydride (NiMH) AA size cells. Included in the pack is a temperature sensor which connects
to the charging circuit to prevent charging when the temperature is too high or too low. When the pack
reaches the end of its useful life, as indicated by a decreasing number of measurements possible per
charge, it is recommended to replace it with an identical pack from the factory.
4.4.1 Charging the battery:
To charge from the AC line (mains): Locate the supplied charging power supply (Input, 100 -
240 VAC; output 12 VDC regulated, 2 A), Connect its output to the 4100 charge input (see figure 4) and
connect its input to the AC line using the supplied power cord. Charging now begins and will be
completed in three hours or less. If the 4100 is turned on during this time, charging still proceeds at the
same rate and a blinking word CHARGE appears on the display. When charging is completed the
display shows BATT and a voltage near 9.0 V while the charger is connected. When the charger is
disconnected the voltage drops to a value near 8.3 V.
To charge from vehicle power (12V nominal only), for example while traveling between
monitor points: Connect the 4100 charge input directly to vehicle power using the supplied cable with
lighter plug (the plug has a fuse, 3A, 8AG). The current drain is approximately 1.0 A with the 4100 off
and 1.3 A with the 4100 on. A complete charge reduces the vehicle battery's available capacity by about
three ampere-hours if the vehicle engine isn't running, not a large loss. Note: During charging the
charging circuit generates significant interference at multiples of approximately 400 kHz..
When to charge the 4100 battery: The battery voltage appears on the display at the upper right
when the unit is on. Although voltage is known to be generally not a good indicator of remaining
operating time, it can indicate when the battery is nearing depletion. When a battery is first used after a
charge the voltage may be near 8V; it drops steadily with use to about 7.2V, where is changes little until
the battery is nearly depleted. Voltage then begins to drop at an increasing rate, and at 7.0V about one
hour of operation remains. This is a good time to plan to recharge. The front-panel BATT LED blinks as
a warning when the voltage falls below 6.6 V, at which point only a little operating time remains. During
charging the voltage reading is replaced by the word CHARGE blinking.
Non-operating charging: When the 4100 is not in use the battery self-discharges and its voltage
drops; if the voltage goes below 6.0V charging becomes difficult. Therefore, if the 4100 is not to be used
for a long period, charge it fully before putting it on the shelf, and recharge after not more than three
months of non-use. The battery manufacturer recommends storage at normal room temperature, avoiding
heat or cold.
Charging temperature: The charging circuit allows charging only at ambient temperatures
between approximately 5C/41F and 40C/104F.
Charge maintenance: If the charging supply is left connected for much longer than the normal
charge time, charging will automatically restart when the voltage drops to 7.6V and restore a full charge.
Continued operation with the charger connected for a long period may shorten the life of the battery.
Battery life: The manufacturer states that the expected life is 500 charge-discharge cycles or two
years. End of life is indicated by shortening of the operating time between charges.
4.4.2 Loose-cell battery:
A battery holder for six individual AA cells is supplied with the 4100. It can use rechargeable
nickel-metal hydride cells, which can be recharged in the 4100. It can also use primary (non-
rechargeable) cells. Non-rechargeable 1.5V Lithium AA cells will give a reasonable number of
measurements. A strip of tape may be needed around the holder to keep loose cells from popping out of
the holder.
Warning: Do not connect a charger while using non-rechargeable cells.
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