C9000 slot 1 not charging evenly compared to the other 3 slots

I decided to start a new thread on this, to carry on from the discussion in http://www.candlepowerforums.com/vb...charged-with-Maha-C9000&p=3347131#post3347131

My 1 year old C9000 (OJxxxx) recently started terminating the charge on slot 1 early, about 80-90mah less than the other slots, no matter which way around I put the cells. The other slots were pretty close. The reputable online shop where I bought it agreed to an exchange, and said they'd seen this a few times.

So I bought a new C9000 (OKxxxxx) to use while getting the first one replaced (which I haven't done yet). The new one consistently charges about 30-40mah less in slot 1, no matter which way around I put the cells.

Has anybody else had this problem and had it fixed? I'm not super happy for it to be considered "normal" it seems like a design fault or manufacturing fault to me. I don't like having to wait for the 2 hour topup charge to finish to know the cells are more evenly charged, sometimes I need to pull them out once DONE appears.

I've been in contact with somebody on another forum who also had a C9000 (unknown batch number), which was charging noticeably less in slot 1. After testing, the same online shop replaced it with an OKxxxxx, but his new one has exactly the same problem, its about 60mah less when charging in slot 1.

I've heard the theory is related to heat, but the other outer slot (slot 4) doesn't have this problem. The only thing I've determined so far is it terminates on max voltage ie 1.48v rather than temp. I know temp can affect the voltage though, so am considering doing a charge with a powerful fan aimed at the cells, to try to keep their temps similar.

Any ideas??? Anybody got a C9000 that charges slot 1 the same or different to the other slots?

The problem only seems to happen for me when the cells need at least 1000-1500mah to be charged in. If its less than 1000mah the difference is minimal.

bbb74 said:

I've heard the theory is related to heat, but the other outer slot (slot 4) doesn't have this problem. The only thing I've determined so far is it terminates on max voltage ie 1.48v rather than temp. I know temp can affect the voltage though, so am considering doing a charge with a powerful fan aimed at the cells, to try to keep their temps similar.

Click to expand...

I think this is the clue. What make and model of batteries are you charging?

The C9000 employs a variety of tests for charge termination, but for many cells, especially good modern ones like eneloops, it will stop charging when the cell voltage reaches 1.47 V. With eneloops this method of charge termination happens every time without fail. Some older technology cells have a different chemistry and they don't quite reach 1.47 V. With these older design cells the charge will be terminated on the negative delta-V signal below 1.47 V and this usually takes longer to be detected. If you happen to have some cells that are on the borderline, then it is possible that some cells will terminate on negative delta-V and other cells will terminate on max V of 1.47. It could be that this is what you are seeing.

I don't know exactly why slot 1 would be different, but it could be because the temperature gets slightly higher in that slot. Cell voltages increase a little with increasing temperature and that might push the cell up to the 1.47 V mark. If all the cells are eneloops then it could be that the first cell reaches maxV sooner, again because it is slightly warmer. But my C9000 does not behave like this, so I'm not sure what is going on.

Mr Happy said:

I think this is the clue. What make and model of batteries are you charging?

Click to expand...

4 x Imedion 2400 AA
4 x Eneloop AA (the 1500 cycle ones)
4 x Powerex 2700 AA
4 x Vapex Instant 2500 AA

All sets of cells treated identically since coming out of the packet, as they are being tested against each other in my test thread.

The C9000 employs a variety of tests for charge termination, but for many cells, especially good modern ones like eneloops, it will stop charging when the cell voltage reaches 1.47 V.

Click to expand...

Actually its 1.48 when it terminates. Thing is it always hits 1.48v first on slot 1, so it terminates earlier. All of the cells terminate "correctly" by max-v, its just no matter which cell is in slot 1, it will hit 1.48 first. Usually it feels cooler in slots 1 and 4, compared to slots 2 and 3, and the problem does not affect slot 4.

The higher the temperature, the LOWER the voltage:
http://www.eneloop.info/fileadmin/EDITORS/ENELOOP/DATA_SHEETS/HR-4UTGA_data_sheet.pdf
[URL]http://www.eneloop.info/fileadmin/EDITORS/ENELOOP/DATA_SHEETS/HR-3UTGA_data_sheet.pdf
([/URL]see the chart at bottom left part of the datasheet)
So if slot 1 is terminating first, that indicates that perhaps slot 1 is cooler than the others.

Hi, I've been corresponding with bbb74. With my new replacement charger that the local distributor has replaced under warranty (Code 0K0EA) these are the sorts of figures I'm getting for a good set of LSD (either eneloops or GP recyko) taken out of baby monitor before they were flat, therefore should all be discharged to same degree.

Slot 1, 2, 3, 4: 613 655 652 638; 1426 1515 1489 1479; 1314 1393 1369 1359; 986 1034 1011 1010; Slot 1 in bold.

As you can see there is a consistent pattern of slot 1 terminating first and slot 2 terminating last. There is always roughly a 5-6% difference in charge between slot 1 and slot 2.

I think this is not coincidence but due to some sort of design factor.

I am disappointed that the replacement unit does this just the same as the 1st unit. I am not sure whether to pursue this any further as I'm not sure the replacement would be any better.

Sorry to drag up an old thread, but it seems better to tack this into the end of this than a new one.

I'm seeing the same thing with my newly purchased (i.e. September 2013) MH-C9000. My revision number is 0M0FA

I have just finished charging 4 x PowerEX 2700 mah batteries. Here's the results shown at the end of charging:

Slot 1: 2325
Slot 2: 2444
Slot 3: 2502
Slot 4: 2453

As you can see, slot 1 is the lowest, by over 100mah. This happens every time I charge these 4 PowerEX batteries, regardless of what order I put them in, slot 1 is always lower.

I emailed Maha about it, here's the correspondence:

Hi,

I recently purchased a c9000.
I notice that slot 1 often doesn't put as much charge into the batteries as slots 2-4. I also notice on forums quite a few people have noticed this.

If I leave the batteries in for 2 hours to top off it evens up the batteries, so it's not a big deal, but I wondered if it was a known fault on certainly product runs? Is it worth returning to my supplier (recharged.co.nz) or is it just part of the product?

For example here's the amount of charge put into 4 AAA's @ 800MAH before I received "DONE" on each:

Slot 1 636
Slot 2 664
Slot 3 678
Slot 4 669

I receive similar results for AA's, Slot 1 often gets ~100MAH less than the other slots.

Thanks!
Tim

Their Reply:

Thank you for contacting Maha. This is normal due to the temperature differences between slot 1 and 4 from slot 2 and 3. Slot 2 and 3 have two batteries adjacent to them while slot 1 and 4 only has one adjacent battery. I would recommend putting a mini fan over the charger if you would want equal temperature distribution.

So they say it's normal...
Do other people see this issue too, as badly as I do? 30-40mah I wouldn't worry about, but over 100mah every time with AA's seems excessive. I know the top-off charge will balance it out (and it does, the readings from a discharge confirm this) but I still worry.

Should I?

Thanks!

tjh said:

...I still worry.

Should I?

Thanks!

Click to expand...

I wouldn't worry about it. It's really not a major issue. Due to the lower temp in position one the cell in that slot terminates charge a little earlier as the voltage gets up slightly higher. But it all balances out in the end as you mentioned, and 100mAh difference in a set of >2000mAh cells is not of major concern, IMO. Just label your cells and mix up which slots you put them in if it bothers you, or do as Maha suggested and use a fan. Personally, I don't bother with that. I have eneloops that are rated for >1500 cycles, so I'm not losing any sleep over a minor difference like this, slot to slot. It's still a vast improvement over most of the chargers on the market. Sometimes we can get so concerned over the minutiae that we forget about just using the cells for what they're for and recharging them and using them again. They're not that fragile.

Thanks samgab.

It's nice to have some reassurance by someone who knows what they're talking about. A fellow Kiwi as well.
(Ok, I'm Australian, but I live in Napier these days)

Oh cool, another (sort of) local CPF'er. Welcome to CPF! Bear in mind that my comments are just my opinion, there are bound to be other C9000 users who disagree with me, and are really bugged by the slot 1 discrepancy... I just think there are more pressing things to worry about more

My slot 2 stopped charging all together though it will discharge, my c9000 is out of warranty

John.

Hello Tjh,

Welcome to CPF.

Keep in mind that the amount of charge that goes into a cell while interesting is not all that significant. What counts is the amount that comes out.

Tom

Hello John,

It may be worthwhile to contact Maha to see if there is anything they can do for you. At times their customer service goes beyond expectations...

Tom

Hi
i have exactly the same problem with my c9000 (0M0HA) slot 1 is always getting lower result compared to other 3 slots.. I charge my eneloop AAA 800mah to 300ma, eneloox xx AAA 950mah to 400ma and my eneloop AA 2000mah to 700ma. By the way the charger and batteries isn't warm when charging/discharging
If it isn't a defect but temperature difference, can someone give me an advice in order for me to resolve this issue? Has anyone tried the mini fan over the charger?
Thanks!

This happens on my C-9000 as well. I use only Eneloops and the latest charged set reads 1430mA input in slot 1 with slots 2-4 at 1520mA +/- 15mA on each. There must be something with the design.

18650 said:

<snip>...There must be something with the design.

Click to expand...

Well, my C9000 certainly does not exhibit such symptoms. Can you tell us the "code" (lot number) on yours? Mine is: OLOJA.

I have run BREAK-IN and REFRESH/ANALYZE procedures on 88 brand new Eneloop AAA cells, and 68 brand new Eneloop AA cells, while keeping records of each mAh capacity result, and I can see no statistical anomaly associated with slot 1.

I wonder how many others are experiencing this "problem" with their slot 1? If you are, please let us know. Although the differences in charging capacity that are being reported so far, seem to be fairly small, I do not think that they are in any way normal. Perhaps Powerex has some solution (repair, fix?) to offer.

Rosoku Chikara said:

Well, my C9000 certainly does not exhibit such symptoms. Can you tell us the "code" (lot number) on yours? Mine is: OLOJA. I have run BREAK-IN and REFRESH/ANALYZE procedures on 88 brand new Eneloop AAA cells, and 68 brand new Eneloop AA cells, while keeping records of each mAh capacity result, and I can see no statistical anomaly associated with slot 1. I wonder how many others are experiencing this "problem" with their slot 1? If you are, please let us know. Although the differences in charging capacity that are being reported so far, seem to be fairly small, I do not think that they are in any way normal. Perhaps Powerex has some solution (repair, fix?) to offer.

Click to expand...

0K0DA. It's especially noticeable because I have three sets of (4) Eneloops used for my camera and flashes that get charged and drained together at the same time all the time.

Let's be clear here.

You only notice it on the charge put in. If you do a full refresh/analysis, they're even.

But, I wonder if it's even just because of the top-up charge.

tjh said:

Let's be clear here.

You only notice it on the charge put in. If you do a full refresh/analysis, they're even.

But, I wonder if it's even just because of the top-up charge.

Click to expand...

OK, that would explain why I have never noticed it. I don't pay any attention to my cells when simply recharging them.

I use them mostly as "groups" (mostly 4 cells together), and after considerable cycles have passed, I had intended to re-analyze them as such "groups," and check to see if the capacities within each "group" are still reasonably well matched, and measure whether or not their average overall capacities may have changed from when I first measured them (when brand new).

I will have to pay attention the next time I am charging. However, the question remains: do all current MH-C9000s behave this way? If so, I would have thought that I might have heard more about it before now. (What little I had heard in the past, I had always assumed was an isolated problem with a few units, since mine seems normal. If this is a widespread issue, I would hope that MAHA is aware of it, and tht they are planning to do something about it.)

Once again, is everyone seeing this phenomenon?

Well, I got to thinking, and I do have some data on some past CHARGE procedures. Back when I first got my C9000, I wanted to test all of my old (non-LSD) Panasonic Evolta cells. I was performing a DISCHARGE, BREAK-IN, DISCHARGE, and ANALYZE, and I got some "strange" results. This led me to add an additional DISCHARGE, CHARGE, and ANALYZE to those procedures. (I needed to use the CHARGE function because I wanted to "see" and record that voltage number that flashes briefly at the beginning of the CHARGE procedure.) Anyway, this means that I have CHARGE data for 20 AAA cells.

So, 20 cells means five uses of the charger with four cells each, and here is how the four slots measured up for those five times:

Slot 1 had lower readings than "normal" 2 out of 5 times. Slot 2 was 4 out of 5, Slot 3 was 3 out of 5, and Slot 4 was 1 out of 5.

The problem is that these were all old and mismatched cells, so it is difficult to say just what is "normal" capacity for them. I decided to consider the final ANALYZE capacity rating for each cell to be "normal" for that cell, and then compared that capacity to the CHARGE capacity. So, in the case of Slot 1, its "lower readings" were an average -6 mAh below normal, and its "higher readings" were an average of 58 mAh above normal. (Slot 2 = -39 mAh and 134 mAh, Slot 3 = -15 mAh and 69 mAh, and Slot 4 = -17 mAh and 8 mAh)

Of course, the problem is that given the condition of these cells, it is very hard to know what is really "normal," and in fact, there was considerable variation between the two capacity figures generated by the first ANALYZE and the final ANALYZE procedures. So, this data is not very conclusive, but it certainly did not show any trend towards my Slot 1 charging at less capacity than the other three slots.

Does anyone else have any better data than this?

tjh said:

Let's be clear here.

You only notice it on the charge put in. If you do a full refresh/analysis, they're even.

But, I wonder if it's even just because of the top-up charge.

Click to expand...

What do you do to fix or come up a solution to charge the cells evenly? Do you consider putting a fan?