Maha MH-C9000 Charger Analyzer

© Brooke Clarke 2007
Maha C9000 AA/AAA Charger Analyzer


Background

When attempting to test the eneloop Ready To Use Sanyo AA batteries the Maha - C777Plus Charger/Analyzer could not properly test them.  It's gone back to the factory for repair.  But even if it's working properly the initial small charge makes the discharge capacity measurement wrong.  This is especially imnportant when testing shelf life on the eneloop cells.  The MH-C9000 is designed to only work with single cells, not packs like the 777.   Also there are 4 test positions each of which can hold either a AA or AAA cell and each test position is independent of the others.  There is a common LCD for all four test positions that can be pointed to any of the four channels.

Although this is a charger analyzer for AA or AAA cells, but I don't see why it could not also work with C or D cells, i.e. any single cell rechargable battery that was Ni-Cad or Ni-MH.

Along with the C9000 a 4 pack of the Powerex 2.7 AH AA cells was ordered.  The first application for the C9000 is to discharge all four cells to see how much charge is in them   So far there's no obivious date code on the blister pack or cells to give an idea of how long it's been since they were charged.  The cells are made in Japan.

New Cell

When a new cell is installed in one of the channels the display asks for the Mode.  The options are:

Discharge

This is a pure discharge and nothing else.  With four cells installed the LCD cycles through each of the four test positions and reports the number of minutes that channel has been discharging, the current cell voltage and the mAh the cell has delivered.   When finished next to the channel number is "DONE".  The display cycles through each channel and through minutes volts and mAh.  It does NOT charge after the discharge.
The results are:

 1
 2
 3
 4
Tmin
 9
 10
 9
 8
Volts now
 1.2
 1.2
 1.2
 1.2
mAh
 128
 133
 137
 126
The cells were essentially dead as received.
To go on to another mode each cell needs to be removed from the C9000 and reinserted to start a new mode selection.  This is a very good thing, unlike the C777 that does an automatic charge.

Break-in (aka Forming)

This mode is recomended for new cells and after 30 charges on existing cells.   After selecting Break-in mode and pressing ENTER the next screen asks for the battery capacity, in this case 2700 mAh, once that's set and ENTER pressed the Break-in starts (it's 8:40 pm 1 Nov).
Next there is a 16 hour charge at 0.1 C (270 ma ending at 12:40 pm 2 Nov.).
After a few hours the cell voltage is at 1.4 and holding, but more and more mAh are going into the cells.  LCD shows Current Progress Charge
After about 700 minutes the cell voltage is 1.49, 2.845 mAh. - Note it takes more than C to charge a battery.  How much more is a measure of efficiency.
A one hour rest time (ending at 1:40 pm 2 Nov).
1.46 to 1.47 Volts & 3910 to 3915 mAh
Discharge at 0.2 C (should take 13.5 hours and end at 3:40 am on Nov 3)
1.14 V @ 2588 to 2607 mAh ended more like 6:40 pm
A one hour rest time (ending at 4:40 am Nov 3).
A 16 hour charge at 0.1 C ( ending at 8:40 pm Nov 3).
3 Nov 2007 -811 minutes, charging @269 ma, 1.49 V 3293 to 3308 to  mAh
When finished around noon 3 Nov 2007:

Batt #
 1
 2
 3
 4
minutes
 318
 319
 317
 321
Volts
 1.46
 1.46
 1.46
 1.46
mAh
 2597
 2588
 2595
 2607

Maha says that down to 2500 is acceptable for the "2700" rated batteries and that's other makers also use the same method of rating capacity.

Things That Could be Better

A way to change the defaults.  For example now I'd like to charge and discharge at 200 ma but when a new battery is installed and charge selected the current has a factory default of 1000 ma.
A way to keep alive the settings when the power fails, not so much the utility fails but either the wall wart or the plug into the C9000 gets disconnected.  I can fix this with a simple add-on box.


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