Maha MH-C9000 unimpressive charger?

I bought a MH-C9000 because it seems to be the most recommended charger in these forums. And after playing with it for a couple months, I have decided it's 'charge' function is quite lackluster. While the other functions are okay, the 'charge' functions is just not so good. My $8 MQN05U clearly does a better job charging.

I don't want to say the MH-C9000 is bad, but for a $50 charger, it's charging is really not that good. And the problem is it's method of termination. Basically the C9000 terminates it's main charging at 1.48 volts, then follows with a 2 hour top-off charge. The problems is that as the batteries start getting full, the voltages rises fairly fast, but it rises FASTER on a cooler battery than it does on a warmer battery. So if charging 4 fairly equal batteries, the C9000 will stop charging on slots 1 and 4 before it stops on slots 2 and 3. This makes the batteries somewhat unbalanced. The top-off charge will reduce this unbalance somewhat. But the end results are still not as good as my $8 Sanyo charger.

Comparing the C9000 charging to my MQN05U charging...
If the batteries are removed from the C9000 after 'DONE' appears and before 'top-off', then the batteries (both AA and AAA) will be undercharged and unbalanced.

If the batteries are left on the C9000 for full 'top-off' then AA batteries will still be somewhat undercharged and still a little unbalanced, and AAA batteries will be failry balanced but OVER-charged.

I don't want to say the MH-C9000 is a bad charger, but a $50 charger that leaves the batteries either overcharged or unbalanced, it really is NOT THAT GOOD!

Quite frankly there are several cheap chargers, with seperate channel for each slot, that will do a better job than the MH-C9000!

I'll have to agree with you to some extent, bleagh. For simply charging cells there are a few chargers that are better. For example, if I'm charging 6x AA cells for my ROP, I charge them on C9000's, but before I load them, I sometimes "top them off" with my BC900.

That said, I think the main purpose of the C9000 is as a maintenance tool/analyzer. The break-in, refresh, discharge/capacity check, and cycling functions being "best in class" for these purposes. And as for charging, I don't consider it to be all that bad. It does have 19 rates for example.

Dave

bleagh said:

So if charging 4 fairly equal batteries, the C9000 will stop charging on slots 1 and 4 before it stops on slots 2 and 3. This makes the batteries somewhat unbalanced.

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Hi bleagh

Interesting. I know that cells removed from the C9000 immediately after the -dV cut-off causes the "DONE" indicator to activate are indeed slightly undercharged. However, I had not heard that cells in the 1 and 4 position will be different from those in the 2 and 3 position. Do you have data to support this? I would like to see how different the capacities are. That being said, perhaps I should just try it myself!

My only complaint about the C9000 is that the "DONE" indicate kicks in at the end of -dV. I would prefer a flashing "DONE" at the end of -dV cut-off, and a solid "DONE" at the end of the 2 hour top off.

Cheers,
BG

In my current location, taking battery temps near end of charge cycle using laser, slots 2 and 3 and 5-6 degrees (F) higher than slots 1 and 4. And slots 1 and 4 always say 'DONE' several minutes before slots 2 and 3. (I do NOT have a fan blowing on the charger.) And yes at this point the batteries are quite imbalanced.

Allowing the full 2 hour top-off does reduce the imbalance quite a bit. And likely nothing to be concerned about at that point. But even then it is STILL not as good as my $8 Sanyo charger!

Am I nitpicking? Why yes I am!
But when I play near $50 for a charger I want it to be BETTER than some cheap $8 charger I picked up, or at least as good. But as a charger, it simply is not as good as my $8 MQN05U.

Hello Bleaqh,

When you discharge the cells charged on your MQN05U what capacity do you get and what is the difference from slot to slot? When you measure the temperature from slot to slot, what values do you get?

When you do the same with the C9000 what values do you get?

Tom

bleagh said:

And yes at this point the batteries are quite imbalanced.

Click to expand...

What's the difference between total capacity of cells in slots 1-4 and 2-3 in mAh? (assuming you stop the charge when "done".

What batteries are you charging? I don't think I have seen mention of the brand, type, age and condition of the batteries so far in the thread.

Um, I have NOT taken temps of the betteries when charging on the MQN05U. I have always charged with the battery cover on, and based on it's method of termination I don't think is much of and issue.

vali said:

What's the difference between total capacity of cells in slots 1-4 and 2-3 in mAh? (assuming you stop the charge when "done".

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I have never actually stopped the charging on the C9000 right after 'DONE', but always let it finish the top-off. And quite frankly I don't feel the need to do such.

But based on several observations, I feel quit certian that IF I did such the batteries would be quite imbalanced. These observations include:

Battery voltage always rises faster in slots 1 and 4 than in slots 2 and 4 (both 'break-in' and 'charge' modes).

Battery temps are always higher near end of charge in slots 2 and 3 than in slots 1 and 4 (both 'break-in' and 'charge' modes).

With 4 sets of pretty new Eneloop AA vatteries, keeping each package as a group of 4. Slot 1 always finishes first, slot 2 always finishes second. Slot 1 always reports the least amount of charge, slot 2 always reports the next least. And just going from memory (I didn't right it down), slot 1 reports anywhere from 30 to 60 mAH less than slots 2 and 3.

So slot one has the lowest temp, voltage rises the fastest, stops charging first, and reports the lowest mAH.

I think if you can keep the temps between the slots more even, that it would be much less of and issue. Maybe have a fan blow directly on the batteries?

Mr Happy said:

What batteries are you charging? I don't think I have seen mention of the brand, type, age and condition of the batteries so far in the thread.

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Ok, I'll explain what I have done and maybe it will explain better my conclusions (or maybe not!).

A while back I bought a new MAHA MH-C9000 and 16 new AA Eneloops and 16 new AA eneloops. My goal was simply to do a 'break-in' on the C9000, 'charge' on the C9000, and charge on the MQN05U, discharging each time on the C9000. I wrote down the capicity reported by the 'break-in' (but not the discharge after it) and the capacity reported by the discharges after charging on both the C9000 and the MQN05U. Then I wanted to use these numbers to order and number my Eneloops from low capacity to high capacity.

I did basicly the same with both AA and AAA Eneloops, the only real difference is I use AAA more so I started with them. I did read a thread about slot 1 stopping charging first AFTER I had finished with the AAA eneloops, so I watched the AA stuff a bit more and posted some of my observations in my previous post.

So when I finish the AAA charging/discharging I had 3 sets of capacities (from C9000 break-in, C9000 charging, MQN05U charging). I then numbered each set from lowest to highest (1-16). When comparing these order numbers (1-16) between the different sets I couldn't see anything that stood out. So for the AAA Eneloops I just averaged the order numbers (the 1-16) and used that to order and number my AAA Eneloops. Good enough for me.

About the only thing I noticed with AAA Eneloops is that the 'charge' put in almost as much as the 'break-in' and quite a bit more than charging on the MQN05U. And considering that the full 'top-off' puts in 25% of the capacity of a AAA eneloop, I feel that both the 'break-in' and the 'charge' on the C9000 overcharge a bit.

But then I did the AA Eneloops, and thing were a bit different! First, after 'charge' and full 'top-off' on the C9000, the capacities were not only well under the 'break-in' capacities, they were also a bit under the MQN05U capacities. But the real kicker was how poorly the order numbers for the C9000 charging capacities lined up with the other two sets of order numbers!

For example, I numbered the C9000 'break-in' capacities 1-16 based on capacities (low to high). Then I numbered the MQN05U charging capacities 1-16 (low to high). Then comparing the 1-16, I noticed one was off by 5 and another was off by 3, and all the rest were within 2 or less (usually less). But when I compared the C9000 charging with the C9000 break-in, 8 were off by 4 or more. And when I compared the C9000 charging with the MQN05U charging, 6 were off by 3 or more.

In other words, the order from the C9000 break-in was fairly close to the order from the MQN05U charging. But the order from the C9000 charging was not that close to either of the others. And in comparing the numbers that were most out of line, and slots 1 and 4 were lower and slots 2 and 3 were higher. And when subtracting the C9000 charging capacities from the C9000 break-in capacities, slot 1 and 3 always have a bigger difference than slots 2 and 3.

It seems about the only thing consistant when looking at the differences was that with a given set of batteries, slot 1 and slot 4 would always have a bigger difference than slot 2 and slot 3 when subtracting 'charging' on the C9000 from 'Break-in' on the C9000.

I'm pretty sure somebody else can do some better testing than what I did. But it does seem quite clear to me that the MH-C9000 has temp differences between the slots (outside slots are cooler than the inside slots) and that this temp difference causes unbalanced charging (when charging 4 batteries).

It should also be noted that because temp differences does seem to affect the MH-C9000 charging, that different testing enviorment will likely provide different results. For example my charging was done in a cool room with good air circlation, but no fan blowing directly on the chargers. A fan blowing directly on the batteries while charging in the MH-C9000 may even out the temps, and give more balanced charging (but would also likely decrease the total charge put in the batteries a bit).

It is not that the MH-C9000 is inaccurate, in fact it seems quite accurate. The problems is in the MH-C9000 method of termination. It terminates charging at 1.48 volts. But it seems that the rising voltages of an Eneloop is quite tempurature sensitive. And as such the voltage of a cooler battery rises faster than that of a warmer battery. And the batteries in the outside slots are often cooler than the batteries in the inside slots. So the batteries in the outside slots reach 1.48 volts sooner and receive less of a charge.

The inbalance will likely be less of a problem when charging just 2 batteries, as long as they are either charged in the inside slots (2 and 3) or the outsides slots (1 and 4). I would recommend charging in slots 2 and 3 as they will be somewhat more resistant to room airflow and therefore maybe somewhat less temp differance for a more even charge.

Actually, that DOES make sense to me.
The lower the (ambient) temperature, the higher an eneloop's voltage when charging.
Conversely, the higher the (ambient) temperature, the lower the eneloop's voltage when charging.
So a lower temperature would make it hit that 1.48V cutoff earlier, so it would have received less charge.
The higher the temperature, the lower the voltage when charging, so it would receive more charge before hitting that 1.48V cutoff point.
See the graph on the left from the new AA eneloop datasheet:


So to ensure a proper charge with the C9000 one wouldn't want to cool the cells, and rather; keep the ambient temperature fairly warm.

I've consistently noticed that slot 1 on my C9000 terminates prior to other slots even with good batteries like eneloops. This thread is a good explanation why.

Don't want to derail this thread, but I have to ask..........I wonder if the LaCrosse chargers have the same issues.

The La Crosse chargers use a different termination method, so they should not have this issue.

Really though, if you leave AA batteries on for the full two hour 'top-off' it's nothing to really worry about.
If I used it for AAA I would likely stop it after only maybe one hour of the 'top-off'.

bleagh said:

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If the batteries are left on the C9000 for full 'top-off' then AA batteries will still be somewhat undercharged and still a little unbalanced, and AAA batteries will be failry balanced but OVER-charged.

...

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According to my measurements they're actually charged close to but less than their full potential. I think this is because of their higher internal resistance than the AAs. It's my understanding that the C9000 uses the same current rate but changes the duration and/or frequency of the current pulse to change the average charge rate.

While coming close, but being just short of the charged capacity potential of the AAA cells under an average "top off" charge rate close to 0.1C/h, you're not going to do significant damage to the cells, even after many charge cycles.

Test info: http://www.candlepowerforums.com/vb...UPPORT-FAQ-continuation&p=3674635#post3674635

Got me thinking so I checked the 4 new eneloops that I have charging at this time. I'm not getting your results with my new charger. I went to my records and check on each batch that I have charged and I can't find any clear indication that the slots are consistently getting the same results as far as capacity or time is involved. I will keep monitoring them as I continue to use this charger as I am keeping detailed records of all the charging and I am keeping track of each individual battery.

Interesting thread that I just read (being new to CPF). Thanks!

All right, am I going to be the first one to note that nowhere in this discussion so far does anyone state what charge rate he is using on the C9000? It seems obvious to me that the temperature rise, and hence any imbalance between inner and outer cells which may eventuate, is going to be strongly dependent on the charge rate. MaHa is at pains to note that charging either below 0.3C or above 1.0C is "not recommended" with this charger, but it is perfectly possible to manually set the charging rate well below 0.3C for an AA, or well above 1.0C for an AAA. Perhaps our original poster would be good enough to state what charge rate he has used? Anyone else?

All right, am I going to be the first one to note that nowhere in this discussion so far does anyone state what charge rate he is using on the C9000?

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Or any actual measured values... It's just speculation of what could potentially happen.

I wouldn't worry about it.

...

I charge at 0.5C/h and let them go through the full top off, leaving cells on the charger for a total of about 5 hours to help balance them. Based on my testing results, I do not think that doing this overcharges the AAA cells.

Ending the charge more conservatively and then topping them off at such a low rate should be good for the cells and improve their lifespan over more fully charging them quickly.

As you point out, charging at faster rates would most likely cause more of a temperature imbalance.

If it's any additional consolation, Eneloop cells that I've matched using the break in function and made series cell sets out of and then discharged at 100mA before recharged at 0.5C/h are often within 1mV (0.001V) of each other during the full range of their useful capacity, even after they're "empty." You can't get much more balanced than that.

Re: Maha MH-C9000 impressive charger!

bleagh said:

I don't want to say the MH-C9000 is a bad charger, but a $50 charger that leaves the batteries either overcharged or unbalanced, it really is NOT THAT GOOD!

Quite frankly there are several cheap chargers, with separate channel for each slot, that will do a better job than the MH-C9000!

Click to expand...

I certainly would like to know what other chargers do a better job as my friends have happily used the C9000 in professional situations for several years without issue. I just last night duplicated your exact situation with an new C9000 0L0EA and 4 AA & 4 AAA new Eneloops and measured them off with my Fluke and cannot duplicate your findings.

I did find that the two inner batteries seemed warmer to touch but the capacity measured afterwards was not of a significant deviation value across all my test cells!

I find the Maha C9000 a very impressive charger indeed!