Maha MH-C9000 charger impressions

I got delivery on a Maha MH-C9000 battery charger yesterday.

I thought I'd start a fresh thread for my own and others initial and ongoing impressions of this device.

These will be my personal impressions, for specs and such see:
http://thomas-distributing.com/maha-mh-c9000-battery-charger.php
http://www.mahaenergy.com/store/viewitem.asp?idproduct=423

Out-of-Box experience.

For a 4-AA/AAA charger, the main unit is quite large, though not heavy for its size. The wall wart, by contrast, is quite small for its rating (12V 2.0 A--accepts international input power). Initial impression is of reasonably solid build quality.

The LCD display is large and very brightly backlit, and very high contrast at optimum viewing angle. The viewing angle for maximum contrast is not straight up, but biased about 30 degrees forward of vertical. While loss of contrast is substantial, it is easily readable far off optimum, as the characters are large.

Battery mount seems pretty solid. A simple metal bail props the back up off the supporting surface, probably to help air flow for cooling. In general some real attention to cooling seems to have gone into the design, and in my first day nothing I've done has made any part of the charger or its wall wart get even a little warm. (have to do a max charge rate four-channel test sometime--not done yet).

I tried the discharge function (discharges battery at specified rate to 1.0V, then holds display of mAH obtained) on some NiMH batteries on store for a few months. This took much longer to completion than you'd think, because while at higher voltages (above perhaps 1.20) the discharge rate is very close to that requested by user keying, the rate below 1.2 drops steadily to quite low values. It took about ten hours to finish the task at a 200 mA specified rate on a battery which provided about 900 mAH. Fortunately the displayed cumulative discharge is the integration of the observed rate, not of the specified rate uncorrected.

For such a complex charger, the instruction leaflet is quite brief. It actually lacks many of the technical details available on Thomas Distributing's website or supplied by Maha Engineering on the Candlepower forum, but provides adequate function description and usage guidance.

Actually controlling it so far seems easy. When you insert a battery, you are prompted to select a mode from a plain-language list of five. The names are pretty suggestive of what they do, and the leaflet gives simple suggestions on when you might wish to use each.

After selecting mode, if more user input is needed (for example charging rate) it is clearly prompted for, with a simple up-down arrow to select higher or lower rates.

On the minus side, the fact that each slot is completely independent means you must enter mode and data separately for every single battery inserted, which might strike you as a bit tedious for routine charging.

On the plus side, the button entries are immediate and give positive display feedback. I felt none of the "is it hearing me?" annoyance that is a famous problem with another charger.

My initial impression is that this charger is likely to be my choice for initial battery break-in, for capacity measurement, and for suspect battery analysis and recovery. If further use confirms that battery temperature remains well controlled and pre-mature and late termination are rare, then it may well become my default charger for routine use. For travel use it seems very bulky.

I intend to post further impressions in this thread. I invite others to post their observations on this model here, or to ask questions we early adopters can answer.

--
new 350D user July 1, 2005
BC-900 owner for several months
MH-C9000 owner for 12 hours

..last week. I would generally agree with your out of the box analysis. However, I like the individual programmable battery positions as it gives me the most flexability in rehabing AAA and/or AAs.

I also bought a brand new octet (that is eight for those of you in Slapout, AL) of the SANYO 2700mHA cells. This was my chance to test out the "break in" feature of this unit.

I set the function up and let it run. It took almost two days. At the end of the two days all four of my cells were within a few percent of each other in capacity. I repeated the function for the other four batteries with very similar results.

All during the break in I checked the unit for heat. I did not detect any warming. I did have the unit propped up on its stand...more for better viewing of the contsant information read out than for thoughts of heat dissipation.

I have also used the unit for a rapid charge of a quad (that is four batteries for those of you in Slapout, AL) of the same SANYO batteries. All during the 2000 ma charge I checked the unit for heat and again found none.

This is a fablous device. My main use for AAs is for my CP-E3 Canon flash battery pack. So, I wish it had 8 slots so I could take care of a full battery pack in one exercise. I guess I could always buy another one.

Then what would I do with my Lacrosse? ;-)

--
CDL



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Dennis Lathem said:

I have also used the unit for a rapid charge of a quad (that is
four batteries for those of you in Slapout, AL) of the same SANYO
batteries. All during the 2000 ma charge I checked the unit for
heat and again found none.

Click to expand...

That is really impressive. 8 amperes going into the batteries and the charger not getting hot. There must be at least one switching supply in there, maybe even one per channel.

I suspect a switching supply in the wall wart as well. The thing is amazing small and cool-running for its capacity.
--
new 350D user July 1, 2005

archae86 said:

That is really impressive. 8 amperes going into the batteries and
the charger not getting hot.

Click to expand...

IIRC the MAHA "intelligent" chargers use a microprocessor-controlled pulse charging system, where a pulse of current is applied to each cell, one cell at a time, instead of a steady current applied to all the cells simultaneously. Therefore, the total current used by the charger is just a bit more than the charge current of one cell.

--
Jim B. :> )

JimBtoo said:

archae86 said:

That is really impressive. 8 amperes going into the batteries and
the charger not getting hot.

Click to expand...

IIRC the MAHA "intelligent" chargers use a
microprocessor-controlled pulse charging system, where a pulse of
current is applied to each cell, one cell at a time, instead of a
steady current applied to all the cells simultaneously. Therefore,
the total current used by the charger is just a bit more than the
charge current of one cell.

--
Jim B. :> )

Click to expand...

Erm... no... The effective charging current is time-average--so even if the pulses were 25% duty cycle, they would then have to be 8 Amperes on each battery during the 25% on time to get the 2000 mA average charging current. Actually I suspect the duty cycle is much higher than 25%, though I lack a scope with which to check it. Anyone watching who has both a scope and one of these things--please chime in with the actual duty cycle.

But whatever the duty cycle may be makes no difference at all to the time-average total current required.

--
new 350D user July 1, 2005

Sanyo 2700mAh are very good batteries. I tested multiple sets with LaCrosse and all of them were above 2700mAh.

As for 8-slot charger. Maha has several models although without measurement functions. Do you really need a 8-slot measuring monster? ;-)

LaCrosse is not getting worse with purchase of another one charger. How about to use it as a travel charger?

Dennis Lathem said:

..last week. I would generally agree with your out of the box
analysis. However, I like the individual programmable battery
positions as it gives me the most flexability in rehabing AAA
and/or AAs.

I also bought a brand new octet (that is eight for those of you in
Slapout, AL) of the SANYO 2700mHA cells. This was my chance to
test out the "break in" feature of this unit.

I set the function up and let it run. It took almost two days. At
the end of the two days all four of my cells were within a few
percent of each other in capacity. I repeated the function for the
other four batteries with very similar results.

All during the break in I checked the unit for heat. I did not
detect any warming. I did have the unit propped up on its
stand...more for better viewing of the contsant information read
out than for thoughts of heat dissipation.

I have also used the unit for a rapid charge of a quad (that is
four batteries for those of you in Slapout, AL) of the same SANYO
batteries. All during the 2000 ma charge I checked the unit for
heat and again found none.

This is a fablous device. My main use for AAs is for my CP-E3
Canon flash battery pack. So, I wish it had 8 slots so I could
take care of a full battery pack in one exercise. I guess I could
always buy another one.

Then what would I do with my Lacrosse? ;-)

--
CDL



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Pbase Supporter

http://www.photobama.com/

Click to expand...

--
Rumpis )

how fast do your 2500-2700 batteries discharge when left unused on a shelf from an initial fully charged state?

I'll try to do this test as soon as I get Maha 9000. BC-900 is bit unconvinient for this test because in discharge mode it does not store the reading. In refresh mode it shows the last reading but begins the cycle with charging.

Also, I need to leave one set of fully charged batteries approximately for a month. Now the lower discharge rate maybe is just perception.

exe said:

how fast do your 2500-2700 batteries discharge when left unused on
a shelf from an initial fully charged state?

Click to expand...

--
Rumpis )

While the MH-C9000 has been giving me apparently flawless termination on quite a mix of AA NiMHs with a reasonable amount of recent use, I have seen less good results on two sets of NiMH AAA which I had left unused for perhaps three years.

For one set, apparently they flunked the "is this a real battery of a type I want to charge?" test.

I say apparently, as the way the MH-C9000 announces this outcome is by doing nothing at all--not even turning on the backlight, which is the first thing you notice when inserting a first battery normally. (I tried to use the discharge function to test remaining capacity not to charge, a fairly heavily used Lithium AAA cell--this also flunked, which I am sure is the intended behavior).

For another set of long-unused NiMH AAAs, the charger failed to terminate even after about 3C of charge (2000 mAHrs on a 700 rated AAA).

I'm not blaming the charger for the second problem--this presumably means that the battery condition after long shelf life did not provide the voltage drop termination signal which this charger (and most others) uses as its primary termination signal, and the charging rate I chose (300mA), meant the battery never got hot enough to trigger the backup thermal termination.

Also to be fair to the charger--the instructions expressly suggest using the breakin cycle on cells which have sat unused for more than three months. This probably will let me rescue the ones which failed to terminate. However, I'd have to charge the unrecognized ones in a dumber charger first even to try this.
--
new 350D user July 1, 2005

I don't have the maha (yet!) but found the same thing when tried some NiCads that had been in the drawer for years. Two sophisticated full microprocessor, dv, temp, independant etc etc chargers would not recognise them on the nicad setting, but once they had been charged in an older no longer used timer charger they did show up in the intelligent chargers. They could no longer hold any significant charge though after that length of time even after repeated cycling... too old.

Charge termination failure problem is discussed in:
http://candlepowerforums.com/vb/forumdisplay.php?f=9

archae86 said:

For another set of long-unused NiMH AAAs, the charger failed to
terminate even after about 3C of charge (2000 mAHrs on a 700 rated
AAA).

Click to expand...

--
Rumpis )

Rumpis said:

archae86 said:

For another set of long-unused NiMH AAAs, the charger failed to
terminate even after about 3C of charge (2000 mAHrs on a 700 rated
AAA).

Click to expand...

--
Rumpis )

Click to expand...

Thanks, Rumpis, for the pointer,

The CPF termination failure thread is an informative thread, though the posts do vary quite a bit in quality.

Since my AAA comment post, I have initiated a brand-new set of Kodak 2300 AAs. As they gave quite low and varied capacities after the "break-in" or forming charge run, I set them up to cycle five times at a 1200 mA charge, 500 mA discharge rate. The two center slots terminated the first charge run (perhaps because they got hot enough to trigger thermal termination) but the outer two continued on past 10,000 mAHr (well past 4C). As the charge rate was 1.2 Amperes, they got pretty warm, but did not visibly damage the outer jackets (it was just two of four batteries, and the spacings are generous on this charger). This is particularly interesting, as all four cells terminated promptly on the first charging cycle (which followed the second 1.6 C slow charge in the break-in cycle). As reported by several CPF folks, termination failure seems more likely on charging discharged batteries than recently charged ones.

At the moment I'm putting the Kodaks through another breakin cycle, hoping to age them to a state where they generate an adequate termination signal.

Premature and late termination of fresh batteries is hardly unique to this charger, but it does seem at least somewhat more prone to termination failure than one would wish.

Awkwardly, we are advised that higher charge rates generate a bigger negative delta-V termination signal, and are thus more likely to terminate properly. But, of course, the higher the charging rate the worse the over-temp resulting if termination failure does happen after all.

For the moment, I think I'll limit my charging rates to 1A unless I expect to in the room and watching quite near the expected termination time.

--
new 350D user July 1, 2005

..I was charging some older 2000 mHa Powerex cells. I had previously charged them and then discharged them. I had the charge rate at 500 mH. Three of the four cells went more than ten hours and pumped about 6000 mA into the cells. One cell terminated in the expected amount of time with about 2300 mH.

I have been reading the thread over at candlepower and I am concerned.

I will have to watch this thing when charging at rates less than 1000 mHa. I also have a question in to Thomas Distributing about what the manufacturer is telling them.

I have no specific information, but hopefully if there is something amiss there will be a recall for replacement.

--
CDL



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I gave a brand-new four-pack of Kodak 2300 mAHr AAs the break-in cycle. They gave low and widely varying first-discharge (after 16 hours of 0.1C charge) capacities (from 54 to 68 percent of name-plate), so I resolved to give them 5 cycles, using a 1200 mA charge rate. But the outer two failed to terminate (after greater than 4C), so I discharged the set and did another break-in cycle followed by a discharge.

At this point the set had been cycled five times.

Mindful that too low a charging rate can generate too small a termination signal to be acted on, I chose the maximum 2000 mA charging rate.

This time the center (hottest) two terminated prematurely (at about 1750 mAHr), while the outer 2 terminated about 2590 mAHr (1.13C, a little bit early for maximum capacity, but really quite a good point). Continuing the center pair after cool-down in the outer slots at 2000 gave a pretty good termination at cumulative about 2385 mAHr.

I concluded that under my conditions the center two of four had gotten hot enough to trigger premature termination--possibly by heat sensing, possibly through another mechanism.

So the next cycle I chose to charge the outer two slots at 2000 and the inner two at 1600. This gave reasonable but probably slightly premature termination in the outer two slots, and a definitely premature termination in one of the two inner slots. As the premature inner slot terminated in the middle of the three-minute period in which the outer two did, it seems likely to have been temperature-induced.

In summary, the combination of the Kodak 2300 mAHr AAs and the Maha MH-C9000 is awkward to manage between the two undesired outcomes of premature and failed termination, at least early in the life of the cells. As the cells are no longer unused, I can't usefully repeat the trial in other chargers to help clarify the degree to which they may have termination difficulty there.

As my most recent failures were on the side of premature termation and somewhat undesirably hot cells, I'll try somewhat lower current next time--perhaps 1400 mA.
--
new 350D user July 1, 2005

Is this charger fan cooled? I was under the impression that once you were past over 1.5A charge current you needed fan cooling to prevent overtemp slowdown during the charge? But then some chargers have more air around each cell (so are larger) to try and avoid a fan.

technicsplayer. said:

Is this charger fan cooled? I was under the impression that once
you were past over 1.5A charge current you needed fan cooling to
prevent overtemp slowdown during the charge? But then some chargers
have more air around each cell (so are larger) to try and avoid a
fan.

Click to expand...

On the Maha Powerex MH-C9000 there is no fan cooling either of batteries or of the charger electronics.

The charger is much larger than most chargers in its category. The main charger body seems to suffer little heating--probably helped by what observers on the Candlepower Forum have interpreted on circuit board photos as individual DC-to-DC convertors for each slot. If true this would greatly reduce conversion loss heating of the charger body from other schemes.

The cell spacing is greater than most AA chargers--about 0.97 inch center-to-center. Nevertheless, at 2.0 Ampere charge rates the cells nearing termination get hot enough to be painful when gripped firmly more than about 5 seconds. As observed, they also seem to provide enough heat to induce false termination of the center cells (which must get the most heat from their neighbors). Even with my 2.0 Ampere four-cell trial, I got no visible damage to the cell outer layers (unlike my sad experience with the infamous Everready 1-hour charger, which bubbled or split at least one cell in each of the three different sets I exposed to it before discarding it).

In the future, I think I'll avoid rates above 1.4A in the MH-C9000 unless I am using only the outer two slots for charging. I'll avoid such high rates altogether unless I am either in a hurry, or have batteries which won't terminate properly at lower rates.

--
new 350D user July 1, 2005

thanks very much for the info, and the valuable results

Earlier I mentioned that my MH-C9000 made no response at all to the insertion of an old long-shelved AAA NiMH.

I can't tell in such cases whether it just does not notice the cell being plugged in, or notices, performs some test, and deems the cell unworthy, but think it is the latter.

I have a case I consider much more troublesome now. I have a new 4-set of Maha 2000 mAHr NiMH AAs which came in the same shipment with the charger. I did break-in (2 cycles) a week or so ago and set them aside. A couple of days ago I discharged them, and set aside again. When I decided to charge them, the charger did not respond to the last two inserted.

Later it accepted one of the cells, but the last cell was not accepted until an edge slot became available.

Today, after the same fully-charged cells had all sat for a day or so, I plugged them in to test recognition. Two of the four were recognized in the test slot (number 3). The two which were not were recognized in slots 1 or 4, but not in either 2 or 3.

So for this particular cell, the variation from slot-to-slot in recognition threshold crossed its present state. I'm not so alarmed at the mismatch--they can't be perfectly matched.

But I am surprised and troubled that a two-cycles fresh NiMH would be anywhere close to a recognition threshold.

At first I thought perhaps the slots in question had died, but immediately after the first recognition failure, without powering down the unit, it recognized a veteran recently exercised AA NiMH.

At this stage I'll say I really like the discharge and break-in cycles of this unit, but am getting more concerned about its use for routine charging. The "failure to recognize" thing would be exceptionally bad for a travel charger--where one might not have backup.
--
new 350D user July 1, 2005

Just got my MH-C9000 last week. Have analyzed and refreshed several sets of AA's with good results. Then a few days ago I tried to refresh 4 AAA's that have not been used for many months. 3 of the 4 were recognized. But, like you, the one I put in slot 4 was not recognized. At the time I just thought it must be bad. I set it aside and put in another AAA and it worked OK. After reading your post I see I will have to experiment with the "bad" AAA and see how it responds in other slots.

The charger is pretty impressive so far. I feel like it was worth the money as long as there is not an issue with some batteries in some slots. I really want to completely trust the unit but now you have raised a some doubt.

--
Don Rose
http://www.donrose.net

I just received my MH-C9000 today... I've only seen one cell so far that failed to be recognized, but this was a several year old NiCd cell... However, I've been reading things about this charger that are kind of disturbing... Not recognizing cells is probably minor in comparison of those who've reported situations where the end of charge and/or detecting the voltage peak at the end of a charge...

I purchased the charger knowing of these types of problems... The main reason I purchased the charger is for it's ability to do a discharge test. I do not intend to use this charger as my primary means of charging batteries... At this point, I would be hard pressed to recommend this 'charger' as a all purpose charger... Until and unless Maha/Powerex fix some of the apparent problems that people are seeing with this charger, I would not recommend it to the casual rechargable battery user.

As far as the overall feature set of this charger... I like it, and personally even if I run into some of the more minor problems that have been reported with this charger, I will not regret my purchase, however this is because I really purchased it simply because I can do four simultainous discharge tests with it... this feature alone is basicly worth the price... Could it be better? YES.

If you have concerns about this, I highly suggest the following thread at the candle power forums site... there is at least one person who works for MAHA who has been observing and answering questions... One question that seems in need of answering... what exactly does the carger look for to determin if there is a valid cell inserted? I suspect it's mostly just looking for a specific voltage range at the terminals, but maybe there's more to it...

Here is the FAQ/support thread...

http://www.candlepowerforums.com/vb/showthread.php?t=145727

Don Rose said:

Just got my MH-C9000 last week. Have analyzed and refreshed several
sets of AA's with good results. Then a few days ago I tried to
refresh 4 AAA's that have not been used for many months. 3 of the 4
were recognized. But, like you, the one I put in slot 4 was not
recognized. At the time I just thought it must be bad. I set it
aside and put in another AAA and it worked OK. After reading your
post I see I will have to experiment with the "bad" AAA and see how
it responds in other slots.

The charger is pretty impressive so far. I feel like it was worth
the money as long as there is not an issue with some batteries in
some slots. I really want to completely trust the unit but now you
have raised a some doubt.

--
Don Rose
http://www.donrose.net

Click to expand...