MAHA C9000 killing cells?

[AaronG]

I picked up a MAHA C9000 in the marketplace recently and have charged a pile of cells with it. The problem is that five cells are now only holding a couple mAh now. It seems that the cells I ran through the break-in mode aren't making through the other side. It's happened to four different brands and models of varying ages so I wouldn't think it was the cells.

Has anyone ever had this happen before? If so were you able to fix the cells?

 

[Wrend]

Not that I know of.

I take it that you were entering in the correct capacity values for the different cells for the break in? Were the cells discharged first?

Even overcharging at this low of an average rate shouldn't do significant damage.

The current firmware version of the C9000 terminates a regular charge on the conservative side, so if your cells aren't performing like new any more, it might not charge them as fully as it would otherwise. What "C" rate were you doing regular charges at?

This is assuming your charger is working as it should, of course.

 

[Black Rose]

Has anyone ever had this happen before?

No. I've processed hundreds of cells with my C9000 and have never had this happen.

 

[vaizki]

No problems here either.. Except I wish I could program default parameters as I recharge Eneloops 99% of the time.

 

[TyJo]

No problems here either.. Except I wish I could program default parameters as I recharge Eneloops 99% of the time.

What parameters are you using, I thought the default charging parameters were considered good for Eneloops?

 

[Wrend]

Yeah, Eneloop AAs are "plug and play," unless he's talking about cell capacity settings or something. Recharging some Eneloops right now myself (as usual).

 

[AaronG]

I put in the rated capacity of the cells. One was 2500, two were 2300, one 2000, and one 850. They were campower, energizer, and Duracell white tops. They were in varying states of charge when I started. They haven't been through a power analyzer before but most of them were fairly new and seem to be holding a reasonable charge before the MAHA. Now the stored charge is 5 mAh or less.

 

[Wrend]

Only holding 5mAh worth of charged capacity is an excessively minimal amount. Are you getting a charge error or something? How long do they charge for when you charge them, and what "C" rate do you do a normal charge at?

They might have very high internal resistance so when you discharge them they drop down right away to 0.9V and the discharge terminates, yielding those low charged capacity results.

If you have a MM to test them, what is the resting voltage of the cells?

On the other hand, it might be that your C9000 just isn't working.

 

[45/70]

It could be something wrong with the charger, but it sounds to me like high IR cells. If they charge up and when you discharge, the voltage drops quickly, it's a sure sign that the cells have high IR and have seen better days. During a 0.2C discharge, a good cell should hold over 1.20 Volts for the most part of the discharge. High IR cells will drop to below 1.20 Volts almost immediately, and result in minimal capacities such as you are getting.

Dave

 

[samgab]

I've never had any issues with my C9000.

Also, remember that having 4 completely independent and independently settable channels, you - in effect - have 4 separate single bay C9000 chargers.
So try different bays... Are you getting the same problem with certain cells in every bay? Then the problem is more likely the cell. Or are the problems all occurring in the same bay? Then it could be the charger.

 

[apagogeas]

Probably high IR cells. Try to measure the IRC displayed by Maha. I had such AA cells giving 0-400Mah and all registered an IRC > 2.00. This is just one step before displaying HIGH, which according to MAHA are considered dead. You may also attempt using the Maha to actually compute the actual IR of the cells. I recall there is a post with an equation in here with instructions on how to do this. Keep in mind, these high IR cells can provide a relatively good service in low-drain devices but in any mid-high drain ones will look like dead right after charge. So, it is easy to mistakenly say a high IR cell is in good shape when used in low-drain device because it can only provide low current.

 

[AaronG]

Sorry to take so long for an update. Two small children and a full time job keep me pretty busy :huh:

So I've run a couple more cells through on refresh and analyze. 1000mA charge 500mA discharge. Rated capacity was 2300mAh. They came out 1300, 2000, 23, very low can't remember what.


I ran the 23mAh one in bay one and it came back as 1900ish. I'm starting to think bad bay. I'm going to run some more cells through bay one to see if they recover.


I'll update as I get more info :D

 

[Surnia]

AaronG, Sorry if I missed this but did you discharge the cells before you did the Break In cycle?

You mentioned they were in varying states of charge before you applied the break in cycle... I have always fully discharged my cells before running them through Break In, as it immediately starts charging the cells (without discharging them).

 

[AaronG]

Ok another update. It seems that three of the four bays are defective. Even if I select charge with a rate of 1000mA, three out of four will only charge at a very low rate (less than 24mA) . Only bay one seems to work properly. I've tried lots of different cells and three different settings to see if it made a difference. All the cells that appear defective are fine when run through bay one.

 

[samgab]

Seems very strange. But it'll be covered by warranty. Don't waste any more time with it, I suggest you just return it under warranty for replacement.