Maha MH-C808M charger terminates charge prematurely.

[Turbo DV8]

I have an MH-C808M battery charger. It seems to not fully charge cells under a certain condition. I am in the process of using it to charge eight Powerex 11Ah D-cells prior to discharge/capacity testing. I charged all eight simultaneously, leaving them in the charger upon termination for maintenance charge as I capacity tested each cell one by one. I pick a "done" cell and run it through it's discharge capacity bench test, which yields full rated capacity. Then I reinsert the discharged cell (0.9v - 1.0v) back into it's slot between the other "done" cells for charging. This is where the trouble starts. The charge on the reinserted cell terminates too soon, at about 1.25 volts, instead of the usual 1.45+ volts or so. Instead of taking the usual 12 hours or so to charge on soft charge, it terminates within a few hours, and the second capacity test bears out the fact that the cell has not received a full charge. It has done this twice so far, on separate cells.

What is going on? I am wondering is my unit defective, or is the microprocessor having difficulty dealing with charging a dead cell between other "done" cells on maintenance charge? Maha's Alex told me some time ago that although the manual states to charge from left to right, there is no technical reason why the cells cannot be charged in any order. Please advise. Thanks.


Ron

 

[Anders]

Hello Turbo DV8.

You wrote: "Instead of taking the usual 12 hours or so to charge on soft charge,"

Charging with less than 0,1 C is not a good thing to do on any charger.
The charger have trouble to find the end of charge.

My suggestion is to not use the "soft" mode and let the cells cool down before you do it again, maybe your results are different then?



Anders

 

[SilverFox]

Hello Ron,

Very interesting...

The C808M works best at the default settings. When you select soft charging or conditioning, it seems to apply that to all of the slots. When you are inserting and removing cells while it is in the middle of the program, it seems to get confused. I don't think the "mode" has a full reset until everything has been removed and the lights go off.

I agree with Anders, you should charge at the default rate.

Try this...

Unplug your charger, then plug it back in. Don't touch anything, but continue to charge and test as you were doing before. Let us know if the problem continues.

Tom

 

[wptski]

Tom:

I remove/insert cells while others are charging in Normal/Soft Modes all the time with no problems at all!

 

[Anders]

Hello Bill: Do you charge D cells 1100 mAh or with similar capacity with the soft mode?

I always use the default settings with my C cells (5,5 A) and with AA cells if i am in a hurry. I use the soft mode with cells lower than 2500 mAh.

Anders

 

[SilverFox]

Hello Bill,

Interesting...

I rarely use the soft mode, and usually am charging in batches. I may have to give this a try and see what happens.

Tom

 

[dekelsey61]

I have the Maha C808M charger and have charged the powerex D sized 11000Mah batteries in the soft mode all the time with no problems at all. I also can take out any of the batteries at any time and the charger continues just fine.
Dan

 

[SilverFox]

Hello Dan,

Thanks.

Tom

 

[SilverFox]

Hello Ron,

It appears that others are doing the same thing you are doing and not experiencing any problems. I would suggest you contact Maha. There may be something wrong with your unit.

Tom

 

[wptski]

Anders:

I don't have any "D" cells but use some 3.5Ah and 5.5Ah "C" cells but not that many where I'd be pulling them as others finish.

 

[Turbo DV8]

Thanks for the input. It seems to have only done this twice so far. When I reinserted the cells which did not fully charge, they indicated one segment on the meter, then continued to charge slowly for the full 12 hours, terminating correctly. This suggests that these cells did not charge at all the first time. They did activate the meter once inserted, but must have gone straight to "DONE" shortly after I left the room. And the 1.25 volts must have been a surface charge gained from the Maha maintenance charge mode. Since others have never run into this problem, the question now for me is does it happen often enough to be worth returning it. So many times, in striving for perfection, I have returned a product only to receive back something worse or with another problem altogether!

I agree that I could safely use the 2 amp rate on these high capacity cells, but I guess I am just old school when it comes to charging rates. And as far as AA and AAA cells, nobody will ever convince me that the 1 amp rate is "soft" charging an AA cell, or 333 mA is "soft" charging a AAA cell! All the talk about charging at 0.5C or greater to ensure proper termination only applies to those who purchased Maha's defective-by-design C9000, Rev. A! :duck: