Echometer Company
Model – M Manual
Phone: (940) 767-4334
5001 Ditto Lane
Page
22
Fax: (940) 723-7507
Wichita Falls, Texas 76302, U.S.A.
E-Mail:7 - Battery and External Power Information
The Echometer Model M instrument will operate from the self-contained rechargeable battery or from a power cord, which
is plugged into an automobile cigar lighter or is connected to an external 12-volt battery.
A sealed, rechargeable, lead cell, 2.5 amp/hour internal battery is used in the Echometer Model M instrument. The battery is
similar to a 12 volt sealed automobile battery. The battery charger provided with the unit permits charging the battery from
an AC power outlet. Either a 110 VAC or a 220 VAC unit can be specified at the time of ordering. The battery charger will
charge the battery at a rate of 500 ma until the battery is almost fully charged then it will trickle charge at a 25 ma rate. The
red light on the charger is ON when the charger is charging at high rate. When the charger is in trickle charge mode the light
is OFF. Approximately 7 hours are required to charge a fully discharged battery. Continuous charging does not damage the
battery.
When operating with the cigar lighter power cord, a low battery will be partially charged by an operating automobile system
in 5 to 10 minutes and will be completely charged if the car is driven for four hours.
The battery should be charged when the operating voltage printed on the header of the strip chart drops to about 11.3 volts.
The battery can be charged more often if desired. Best operating performance will be obtained with battery temperatures
from 0 to 120 degrees F (-15 to +50 C). The battery has less capacity and voltage at lower temperatures.
Temperature oF
Temperature oC
Battery Life, Hours
104
40
4
77
24
3.5
32
0
3
-4
-20
2
The battery should be charged when the operating voltage printed on the strip chart drops to about 11.3 volts. Charging
more often will improve battery life. A message to charge the battery is printed on the strip chart when the voltage drops to
11 volts. The amplifier current drain is 330 ma. The amplifier, chart drive, and print head current drain is approximately
800 ma. A fully charged battery in good condition should perform more than 200 tests before the battery will require
recharging. The battery is rated at 2.5 amps/hour.
Long storage periods without charging will severely reduce service life. An unused, fully charged battery will discharge in 6
months at 113
o
F, in 15 months at 77
o
F (20
o
C) and in 50 months at 23
o
F (-5
o
C). A discharged battery deteriorates rapidly.
Experience has indicated that the battery should be recharged at least monthly using the AC charger. Charging the battery
before it is fully discharged will result in longer battery life.
Battery Sulfonation
A very deeply discharged battery may not accept a charge normally. The red light on the AC charger does not come on
when the AC charger is attached. After a period of time, up to 6 hours, the red light will come on indicating that charging
has started. After 7 hours the red light will go out indicating the battery is charged. In some cases a battery will not accept a
charge and will require replacement.