Maha MH C9000 with older cells. Experts needed!

[larcal]

Hi All,

NLee, a frequent reviewer at Amazon, says that he has not been able to charge AA cells that were several years old on his Maha MH C9000. Such cells still had a 1000 ma/hr capacity as measured on his LaCrosse and were chargeable on his laCrosse. He thinks because these older cells have a level of resistance that the Maha rejects due to some kind of safety reason. Obviously this would be a real bummer, but I like the Maha otherwise. Question- Is this true?, or maybe his was defective?

Thank You
Larc

 

[Russel]

The Maha MH-C9000 performs a internal resistance test on cells before it begins charging. If cells fail that test then the cells have a very high internal resistance and should be recycled. Some people believe that that is a waste and that the cells can still be used in low current draw devices. While that is true, high IR cells may still perform OK in low current draw devices, I personally think that is a waste of time. The high IR cells I have experimented with were unreliable and of poor performace. The cost of good high performance NiMH cells like Eneloop, and many other LSD cells, is so low that I don't see any reason to bother with substandard cells. So, I wouldn't consider the fact that the C-9000 rejects cells of high internal resistance a bad thing. It is actually a very nice feature.

 

[Russel]

You may find this thread of interest.

"HIGH" cells with C9000

 

[TakeTheActive]

...NLee, a frequent reviewer at Amazon, says that he has not been able to charge AA cells that were several years old on his Maha MH C9000. Such cells still had a 1000 ma/hr capacity as measured on his LaCrosse and were chargeable on his laCrosse. He thinks because these older cells have a level of resistance that the Maha rejects due to some kind of safety reason...

Good old NLee the Engineer also gives the C9000 a 'Bad Rap' for 'too many button presses' and recommends LT 0.5C Charge Rates. :shakehead

But, on the point of HIGH Internal Resistance, yes, the C9000 will reject those cells (Please read: Interpreting Maha MH-C9000 Impedance Check Voltage). For safety, I don't agree - IMO, it's just a 'Design Decisision'. Like the decision where the La Crosse chargers won't even attempt to charge a cell below X.X VDC (I'm guessing it's around 0.5VDC, but I'm not sure).

I own both - a BC-900 v33 purchased in Dec 2006 and a C9000 0H0AA purchased in Dec 2008 - and I feel that they compliment each other well. I find that I like the C9000 best for VIBRANT cells and the BC-900 best for *CRAP* cells (and sometimes VIBRANT AAAs). I also prefer the REFRESH Mode on the BC-900 over the C9000 because it 'knows' when to stop.

...Obviously this would be a real bummer, but I like the Maha otherwise. Question- Is this true?, or maybe his was defective?

If the C9000 is the ONLY AA/AAA charger you own, yep, it's a 'problem' if you're one of the 'Frugal Types'.

The Maha MH-C9000 performs a internal resistance test on cells before it begins charging. If cells fail that test then the cells have a very high internal resistance and should be recycled. Some people believe that that is a waste and that the cells can still be used in low current draw devices. While that is true, high IR cells may still perform OK in low current draw devices, I personally think that is a waste of time...

You may find this thread of interest.

"HIGH" cells with C9000

+1 :twothumbs

 

[Mr Happy]

There are two reasons why the C9000 does what it does.

The first is that it allows it to reject alkaline cells mistakenly inserted. You or I would not do that, but someone, somewhere, will.

The second is that if high resistance cells were to be charged at high currents they could get excessively hot and damage either the cells or the charger. Granted they might be charged at lower currents but then the charger design would be more complicated and it would be harder to detect the end of charge signal.

Since such high resistance cells are really beyond saving, Maha have apparently opted for the simple solution of rejecting them. If you can invest in a C9000 you should be interested in getting good performance from your batteries. Once the C9000 rejects them it is time to recycle them and move on.

(As I mentioned in another thread, I have encountered some of the crappiest of crap cells, like they record as little as 25% of the label capacity and won't hold a charge for more than a week. But even these cells have not been rejected. For cells to read high I think they must have been overcharged so much that the electrolyte has dried out.)

 

[McAllan]

For AA cells it's probably about right rejecting them. If it rejects them they're probably not worth using.
But for AAA I think it's a bit too restrictive. You can't demand the same Ri for an AAA as for an AA cell. Infact those AAA cells I've had that it rejected still worked just fine. OK capacity and no severe self discharge. They just had to be charged in another charger.

The cause is that the C9000 got no way to differentiate an AAA from an AA. Search the site and see internal pictures.

 

[larcal]

Wow! these excellent answers really kept me up reading back posts last night.Learned a lot. Having forgot some high school electricity it had not occurred to me that high resistance would result in a large voltage drop and the attempts to lower this resistance/renew the cell by a deeper discharge then the charger can do is interesting. I think i read that lacrosse 700 does deeper discharges then the 9009 or the Maha tho why this is so is unclear since they all use a pulsed charge and go down to 100ma.
I am not an extremely frugal or excessively green kind of guy. However, I am rural enough that buying anything is inconvenient and additionally, I have of late unfortuanately become something of a doomer. Just can't help it. So tend to buy more then I need in present and therefore my main abuse of these cells would be non use for stored cells and partial use for others because flashlight use is critical but seasonal. Do you guys think the high resistance problem comes from such light use/self discharge or from simply the opposite--ageing by high # of cycles? I realize Lsd cells is the way to go but even so....
Happy to read that Mr. Happy has had no rejections with even the crappiest cells, tho the experience of others differs so that's odd. Perhaps the Maha is a little too sensitive on this, will just have to try it. If the rejection happens at a resistance level that would still allow a few hours of useable led light if charged on a less sensitive charger then clearly it's set to high. Yes, get a second charger but the La crosse burns up and other's are kind of dumb.
Anyhooo, wanted to thank everyone for there help. Really getting myself in trouble now that work hours have been reduced. Great forum tho.

 

[larcal]

By the way, if anyone really wants to run a La Crosse off 12v (thus avoiding energy loss of inverter) this dc/dc converter should work, tho pricey at $57.00. Need 4amp, 3 volt input. Powerstream PST-DC z0305. Input 8-24v, output 3v 5 amp dc. 85% efficient.

 

[Mr Happy]

Happy to read that Mr. Happy has had no rejections with even the crappiest cells, tho the experience of others differs so that's odd.

There are different kinds of crap. The kind of crap I usually encounter is when NiMH cells have been left on the shelf too long without any kind of maintenance. In that case the cells self-discharge to such a low voltage that the internals become chemically degraded and become unable to store a charge. (This is a problem with standard NiMH cells, but is not so much a problem with Eneloops.)

The other kind of crap happens when cells have been charged and discharged too many times, especially if they have been overcharged by poor quality chargers. This kind of crap is different and may lead to rejection by the C9000. However, crap is crap and whether the cells have reached a natural end of life or if they have been abused to death by mistreatment the cure is the same: recycle them and buy new ones.

NiMH cells do not last forever. However quickly you kill them you still get many more uses out of them than alkaline cells.

 

[Bones]

I tend to think that the criteria utilized by the Powerex MH-C9000 to reject high-resistance cells isn't overly stringent.

I have two Sanyo chargers that I believe were engineered with specific regard to the Eneloop, being the MQH03 and the MQN05, and I have yet to encounter a cell that the MH-C9000 rejects that they will accept, and vice-versa.

So, whatever criteria is being used by the MH-C9000 to reject high-resistance cells is closely paralleled by both the MQH03 and the MQN05. And since this criteria directly effects the longevity of the cells that are also manufactured by Powerex and Sanyo, such as the Eneloop and the Imedion, I presume the temptation would be to tweak the criteria to reject fewer cells rather than the converse.

 

[TakeTheActive]

For AA cells it's probably about right rejecting them. If it rejects them they're probably not worth using...

I disagree. :thumbsdow

...But for AAA I think it's a bit too restrictive...

I agree. :thumbsup:

As I've posted in MANY other threads, it all depends on YOUR needs.

I've personally 'categorized' my cells into:

1. VIBRANT
2. *CRAP*
3. HIGH
4. MODE
5. TRASH

I have no 'High Demand' / Life Threatening applications, so, I'll use cells from #1 and #2 in any HIGH CURRENT application (i.e. Digital cameras / GPSs / MP3 Players). Cells in #2 and #3 will go into 'Non-Critical' applications (i.e. MP3 Players, digital clocks / thermometers, 'Reach-For-It' flashlights). Cells in #4 will go into 'Don't Care' applications (i.e. Remotes, 'older' digital clocks / thermometers). Currently, some cells just entering #5 are going into some 'Infrequently-Used' remotes - I'd rather find a DEAD NiMh :sigh: in an 'Infrequently-Used' remote than a LEAKING ALKALINE!

...The cause is that the C9000 got no way to differentiate an AAA from an AA...

You can't expect a 'Machine' to do *ALL* of your thinking...

 

[VidPro]

Hi All,

NLee, a frequent reviewer at Amazon, says that he has not been able to charge AA cells that were several years old on his Maha MH C9000. Such cells still had a 1000 ma/hr capacity as measured on his LaCrosse and were chargeable on his laCrosse. He thinks because these older cells have a level of resistance that the Maha rejects due to some kind of safety reason. Obviously this would be a real bummer, but I like the Maha otherwise. Question- Is this true?, or maybe his was defective?

Thank You
Larc

AA cells with 1000ma, let me agree with anyone who points out "it's Dead Jim" give it up and get some batteries that work.
cant believe paying some $50 for a charger to have it tell you the cells are dead, and to refuse to believe it :naughty:
coulda used a $20 charger and had enough money leftover for at least 8 good cells to use on it instead.
if they are forking over good money for a charger, then need a dumber charger too to work with the bad cells, then you have to fight rejection, and getting self discharge, and limited use, and poor series discharging, then add up the persons time . . . then try and cycle them around a few times, test for a few more days, a bit of break in charge, a little this a little that, and the pain misery and loss from it are never ending. I wont mention that for 25c you can have a leaky alklline and be done with it
all that stuff goes away when you get some enloops to replace these MISERY batteries , and those will last so long you will forget about the expendature quick enough.

I think i have spent about 6months out of the whole of my life dealing with cruddy ni-mhy batteries , couldnt Let GO, misery loves company

 

[McAllan]

You can't expect a 'Machine' to do *ALL* of your thinking...

A lot of other chargers do. There's different connection sets for AAA then for AA (at least at one end).

Have you had any OK performing AA that the C9000 had rejected? I haven't but I have had some couples of AAA. Sorry I don't have any technical to include other than my personal experience with it.

 

[TakeTheActive]

AA cells with 1000ma, let me agree with anyone who points out "it's Dead Jim" give it up and get some batteries that work.
cant believe paying some $50 for a charger to have it tell you the cells are dead, and to refuse to believe it :naughty:

---SNIP--- (lots more good stuff...)

Hey! 1000mAh is LOTS of power for a 'seldom-used' remote! :thumbsup:

Like I said earlier, I'd rather deal with a DEAD NiMh than a LEAKING Alkaline.

...Have you had any OK performing AA that the C9000 had rejected?

Sure!

But..., define "OK". It can mean a LOT of DIFFERENT things to a LOT of DIFFERENT folks! :thinking:

Us "Frugal Folks" really don't mind the move from "*CRAP*" to "HIGH" (or "MODE"). We just casually switch to our 'non-discriminating' OTHER "SMART Charger/Analyzer" and continue on our merry way...

 

[larcal]

Thanks for the clarification Mr. Happy. Apparently your belief is that AA's that are abused by being stored to long are not rejected (tho they may have other defects) whereas cells that are heavily used will develop this high resistance. So in my case that is encouraging.

Perhaps TTA did not mean to list categories that way?. You use #2-"crap" in high drain stuff?, and "mode" is a category/

Certainly it is not worth it to try and keep cells going forever. Junk is Junk. But will I have 4 AA's rejected by C9000 that I could still get another couple hours of useable light from in my 4 cell led headlamp if charged on a dumb charger?. Then it is not a feature but a problem. And if this happens because such cells were simply on a shelf for 3 years that's an additional issue tho I gather eneloops have solved that.
I recall Silverfox saying a 250ma load would probably not cause so much voltage drop that it was unuseable(with a c9000 rejected battery). Tough to measure the draw of one of my small work flashlights.

Bones, it seems the opposite to me. Why is the economic temptation not to tweak the rejection level higher so you throw them out and buy more cells? I do agree that some level of rejection is a good thing, tho, for the avoidance of high heat issue that Mr. happy mentioned.

Salute to you all.

Larc

 

[Turbo DV8]

I have two Sanyo chargers that I believe were engineered with specific regard to the Eneloop, being the MQH03 and the MQN05, and I have yet to encounter a cell that the MH-C9000 rejects that they will accept, and vice-versa.

Just an observation comparing my Duracell Mobile Chargers and the C9000. I have several LED candles that have old, non-LSD 2400 mAh AA cells. I am sure the twelve cells are mostly "crap" at this point, but due to the low current of the LED candles, they can still power them twelve hours all night, every night, for about three weeks, which is good enough for me. I wouldn't dream of using them in any other application, though.

Anyway, regarding rejection thresholds ... my Duracell Mobile Chargers will only occasionally reject one or two of the cells (flashing red LED shortly after insertion) and even then I can usually get them to be accepted by removing and reinserting them. But the C9000 will reject nearly every one, every time. It's not a big deal, since I have many other charging options, but whether a cell should be considered "crap" for any given user depends a lot on the application, so I do personally feel the threshold on the C9000 is on the overly "cautious" side. I mean, if the cells can be charged to a respectable degree safely, let the user do it, for Pete's sake, and then let the user decide if the level of performance from the cells is acceptable for his application.

 

[Mr Happy]

To put this in context, owners of chargers that will accept high resistance cells should try charging alkaline batteries in those chargers. You or I would not make that mistake, but many people out there would. And if you do get a charger to accept an alkaline battery then it will probably burst and make a big mess of your charger.

I have not tried this with many chargers, but I have tried it with the C9000. I found that the C9000 seems to be right on the threshold of being able to refuse alkaline cells. If it was any less sensitive it seems like it would fail to reject them.