Maha MH-C9000 SUPPORT / FAQ Thread

[TorchBoy]

I agree with NiOOH. This is very strange behavior. Continual charging should heat the cells up.

How much heat will there be? 0.33C for a 1000mAh cell is 330mA. At 1.5V is 0.5W. Next question, how much of that 0.5W will convectional, conductive, and radiative cooling remove? The cells are warm, yes? But not hot because they are being cooled as they go. MHO is that they are being charged, and maybe damaged in the process.

I suppose there is a certain irony in us having the best flashlights and the crappiest cells...

The two AAA cells that I managed to put through the break in finally finished so I discharged them at 400mA and got 615 and 619 - the same as in the break in 0.2C discharge. But now I can't recharge them because they both read HIGH (again). Yes, I can dig out another charger to give them a bit of cycling (discharging on the C9000 to get capacity readings) but like jusko said, this charger is supposed to be good at this sort of thing.

Forgive me if it's a stupid question but why is it checking impedance on break in mode? This is the mode we'll be using if we want to rejuvenate stubborn cells. I should be able to use it for this, even if the cells are too poked to charge normally.

I've even contemplating putting a resistor across the battery terminals during the impedance test.

 

[TorchBoy]

Hello Verge,

The standard IEC charge is 16 hours at a 0.1 C rate. The standard discharge for capacity is at 0.2 C. This usually results in a 5 hour discharge (300 minutes), however it looks like your cells had more than their rated capacity. This means that it took over 5 hours to complete the discharge.

Tom

I've noticed, like others, that these cells (AAA in my case) discharge very slowly when nearing the end of their discharge, and this can cause much longer discharge times that the 5 to 5.5 hours expected. Is that because the C9000 ramps down its discharge rate to ensure fully flattened cells by 1.00V or because of the alleged high impedance of the cells?

 

[SilverFox]

Hello Ian,

The impedance check is to rule out charging Alkaline cells.

Most of the heat that is produced during the end of the charge comes from a chemical reaction within the cell. I am not sure how you figure the wattage equivalent for that.

I have no idea why the current drops at the end of the discharge cycle. I am sure it has something to do with the programing, but I don't understand it at all.

Tom

 

[digitor]

I have no idea why the current drops at the end of the discharge cycle. I am sure it has something to do with the programing, but I don't understand it at all.

Tom

Earlier in the thread, willcheuh wrote:

I think I've a good explanation for you. During both charging and discharging, the voltage is read "offline" which means they are taken with the current off.

Say your battery has a higher than usual resistance. When the current is on, it might cause the battery voltage to drop (treating the battery as a virtual resistor - this is really not the case it's best simulated by a resistor and capacitor in parallel). This voltage drop can cause the charger to unable to pull the set current as the voltage becomes too low (the circuit is only designed to reach set current when battery voltage is >0.9V).

The Good news is capacity calculation is always made with the "real" current. The software does an integration of current with respect to time every two sceonds. So your capacity reading is still accurate.

William

I think this is the explanation.

Cheers

 

[SilverFox]

Hello Digitor,

Welcome to CPF.

Yes, I read that, however, I still don't completely understand the need for it...

Tom

 

[digitor]

Hello Digitor,

Welcome to CPF.

Thanks! I've been reading hard since I ordered my C9000 just before Christmas, hopefully they'll be in Oz in a week or so.

Yes, I read that, however, I still don't completely understand the need for it...

Tom

An unintended effect I guess, but that seems to be why the discharge current tapers off for some cells towards the end.

Cheers

 

[jusko]

Hello Tom,

I have done 2 tests per your request in post #237.

1. Two "Super 2000" AA with min. 1900mah. Always show "HIGH" with whatever modes of C9000. Charged in another charger at 500ma for some 5+ hours. Discharge capacities were 1530mah and 1562mah. This result was quite reasonable given the cells are 6 or 7 years old. I have 4 pieces of this cell that all show "HIGH" in C9000 but chargeable in other chargers.

2. Two "REX Ultra 700" AAA with min 650mah. One shows "HIGH" and the other causes the LCD on and off. Charged in another charger at 200ma for some 4+ hours. Discharge capacities were 506mah and 471mah. I have 8 pieces of this cell, 5 show "HIGH", 3 cause the LCD on and off. They are also 6 or 7 year old and I know they are of inferior quality.

I agree with another user that the impedance check should be relaxed or at least be neglected in the break-in mode, so that some old batteries can still be charged.

But the most bothersome problem is missed termination. I have experienced several times and more with a fan, that even new and good quality cells such as the Eneloop and Uniross Hybrio missed termination. I would say this C9000 is not performing consistent and stable enough.


jusko

 

[SilverFox]

Hello Jusko,

Thanks for checking that for me.

If cells are considered "dead" when they can only provide 80% of their original capacity, or less, your cells are very close to being "dead." It is interesting that the other charger will charge them...

I agree that the missed termination issues are more important, but find the impedance rejection issue "interesting."

Tom

 

[TorchBoy]

Re: Maha MH-C9000 SUPPORT Thread

Using the CYCLE mode, why do I see a "0 mAh" capacity on the screen? What happened to the saved battery capacity?

A CYCLE is consisted of:
Charge > 1 Hour Rest > Discharge > 1 Hour Rest (repeats for programmed number of times)
The discharge capacity is saved into the memory at completion of discharge but cannot be reviewed until that cycle is completed (after the 1 hour rest). During the rest, a zero capacity is displayed.

During this period, all previously completed cycle data can be viewed, but not the most recent cycle. It will become available after that particular cycle is completed.

Cycle data can be accessed anytime after completion of the first cycle by using the "UP" and "DOWN" keys.

I've just tried using CYCLE mode for the first time and after the hour rest period (WHY??? ) I pushed the UP and DOWN keys to read the capacity of the cycle... and got "5 5MAH". Yes, that's a space in the middle. Where did the middle digit of the capacity figure go to? That digit normally displays just fine.

(Did a search for all sorts of things but I haven't seen this problem mentioned anywhere.)

I'm beginning to have issues with this thing's issues.

 

[meeshu]

Most likely a LCD and/or a LCD driver/decoding circuitry problem.

Someone else in another thread is also having LCD display problem (faint characters).

 

[TorchBoy]

Thanks meeshu. I found that other thread, and maybe it's the same thing - perhaps it was a 1 and just a couple of segments weren't showing. If it happens again I'll take a photo like "too" too.

 

[SilverFox]

Hello Ian,

I have also seen one case of a dropped digit. I don't remember the exact circumstances, but it was not repeatable. I do remember it was on a 3 cycle run, and on cycle 2 one of the slots displayed dropping the second digit from the right.

I have not seen it since, but I also have not done that many cycle tests.

Tom

 

[TorchBoy]

Thanks Tom. Interestingly, mine is repeatable, as shown in the photo I took this time. https://www.candlepowerforums.com/posts/1820138&postcount=9

Any comments, William?

 

[willchueh]

Does the power up LCD test normal (i.e. all symbols show correctly and digit display cycle from 0000 to 9999)?

William

Thanks Tom. Interestingly, mine is repeatable, as shown in the photo I took this time. https://www.candlepowerforums.com/posts/1820138&postcount=9

Any comments, William?

 

[TorchBoy]

The last time I powered up I didn't notice any problems at all. That slot has now finished cycle 2 and it shows the capacity for that cycle as 519mAh, with the centre digit perfectly clear, but the first cycle figure is still "5 5". How weird.

Edit: No problems with startup routine.

 

[summerwind]

Will,
i think it's fair to say we have put the demand on you, and in return you have answered practically every question and concern.
my question is now, will the C9000 be getting revamped in the near future?

 

[summerwind]

any news?

 

[digitor]

At last! My C9000 shipped today from the Australian distributor - it should arrive tomorrow.

It'll be getting a good workout for the next few weeks, first I plan to work through all my older cells, to see if I can sort out some reasonably well matched sets for use as backups for my flashguns.

Cheers

 

[jusko]

No way for old cells. I first also thought that the C9000 can revive my old cells, but it can't. It just can't charge old cells in whatever modes, including the BREAK IN mode . It just keeps showing HIGH or the LCD on and off. It is designed for good and healthy cells only.

 

[verge]

My MH-C9000 did great BREAKIN job on my old Kodak 1600mAh (4xAA) and 1700mAh (4xAA) batteries.