Download Checking the batteries and Charge Circuitry

MIPRO MA707PA
Checking the batteries and Charge Circuitry
This should only be done by a qualified Electronics Technician!
Voltages inside the MA707PA could be dangerous or deadly!
1. Equipment needed.
 #2 Phillips head screwdriver to remove the battery covers.
 DVM, or any DC voltmeter.
2. Preparing to test.
3. Disconnect the power cord from the 120VAC wall socket and from the MA707PA
rear power socket.
4. Turn both of the MA707PA power switches off.
5. Remove the 2 battery covers with the #2 Phillips screwdriver.
6. Remove the 2 batteries while keeping the wires connected to the battery terminals.
NOTE; If the wires are too short, then you will need to separate the rear case from the
front cabinet to free up wires that may be snagged inside the cabinet.
a. To gain access to the inside, remove the 10 case screws.
b. Carefully separate the rear case from the main cabinet.
c. There are wires that connect to circuit boards that are mounted on the rear
panel, and they are in turn connected to a circuit board on the bottom of the
main/front cabinet. DO NOT STRESS THESE WIRES.
d. Cut the wire tie that holds the wire bundle together to gain some working
slack in the wiring.
e. Free up the battery wires that are twisted and stuck into the track on the
bottom of the rear panel to free up the wires to enable enough slack to remove
the batteries from the rear cabinet.
f. Reassemble the MA707 front and rear cases.
7. Measure and record the voltages of the two batteries while they are connected to the
MA707 while the power is still OFF and NOT connected to the 120VAC. Both
batteries should be about ~12.7vdc. (This is a measurement taken after the batteries
have been removed from a charging source [Unplugged from the 120VAC wall
power, and the power switch is “off”.] and batteries are given a chance to settle for
about 30 minutes.)
8. Measure the voltage across the two batteries and record. Measure from the positive
terminal on one battery to the negative terminal on the other battery. Should be about
25-26vdc. (This is a measurement taken after the batteries have been removed from a
charging source and given a chance to settle for about 30 minutes.)
9. Plug the MA707 into the wall power120vac from the wall power socket and connect
the power cord to the MA707PA.
10. Push in the round AC Charging button (#10 below) located on the rear panel about 3”
down from the top on the left side. This will allow the 120vac power to connect
electrically to the internal power supply in the MA707.
11.
12. The “Rocker” style power switch, (#11 below) should still be off.
13.
14. The only light that should be on is the red LED that is located just above the 120vac
socket on the rear panel. (#15 below)
15.
16. Steady red LED indicates the batteries are fully charged or they are not drawing much
current from the charge circuitry and the charge circuit senses the batteries are fully
charged.
17. Blinking red LED indicates the charging circuitry senses a load and is charging the
batteries.
18. Measure the voltage across the 2 batteries now that it’s connected to the power.
19. With a good charge circuit and known good batteries, (Batteries close to fully
charged) you should read about 29vdc across the two batteries. (+ terminal on one
battery to the – terminal on the other battery) The red LED should blink for a short
time and then become steady.
20. At this point, the voltage reading across the individual batteries may vary slightly but
should total about 29vdc.
21. If you check your battery voltages while the MA707PA is plugged into 120vac wall
power, and you have both the round 120vac power switch pushed in, (see step #11
above) and also have the Master Power Switch turned “on”, (See step #13 above) you
will have different measurement results than with the master switch “off”.
a. MA707PA Master power switch on, but all modules turned off, (CD, wireless,
etc) measuring across the 2 known good batteries that are at or nearly at a full
charge, you should still read about ~29vdc.
b. MA707PA Master power switch on, measuring across the individual
batteries, you’ll get much different readings. Measurements of ~12.8vdc on
one battery and ~14.2vdc on the other battery are not uncommon.
c. Always turn the Master Power switch off when charging. (Step 13, location
indicator #11)
22. If your batteries have been used and need to be charged, Master power switch (Step
#13 above indicator #11) turned off, and AC power button pushed in,(Step 11 above);
a. In an MA707PA with a normally operating charge circuit and with known
good batteries, the measurement across the 2 batteries while charging could
range from 22vdc to 28vdc.
b. The red LED above the AC power cord jack should be flashing.
c. Depending upon the condition of the batteries, it may take up to 24 hours to
regain a full charge. (Normally 8hrs.)
d. After charging and while still connected to 120vac, you should measure
~29vdc across the 2 batteries and see the red LED solid. (Not flashing)
23. However, if you have batteries that are failing in a fashion where they will no longer
hold a charge, and they are not causing the charge circuit to draw any current, the red
LED may stay solid.
a. In that case the measurement across the batteries will read 29vdc across the 2
batteries, but that voltage will get lower (0vdc to ~11vdc) within seconds once
the 120vac power is removed from the MA707.
24. You can also have a battery that shorts internally and no matter how long it is on the
charger, the red LED will continue to blink. They may read about 25-29 volts across
the 2 batteries while they are charging, but once the power is removed from the
MA707, the voltage on 1 or both batteries will quickly go down.
25. If you don’t have a new set of batteries to confirm these measurements, then a battery
load test meter may be required.
26. The current part number for the Sealed Lead Acid Batteries of the MA707PA is
D5741. (12V 5Ah.)
NOTE; These measurements should only be performed by a qualified electronics
technician. Voltages inside the MA707PA can be dangerous or deadly.