Maha MH-C9000 SUPPORT / FAQ - continuation

[Turbo DV8]

When you do a "standard charge" and "standard discharge" you get a capacity for the cell. When you run the 3 - 5 cycles, you compare your discharge results with those obtained from the "standard discharge."

OK, so after all my hemming and hawing and chomping at the bit, I'm finally feeling broken, so I am actually running eight of the new AAA Eneloops on break-in, which is what I assume you mean by "standard charge" and "standard discharge". Thing is, now that it is nearing the latter half of the second charge, I notice the display shows the current "into" the cell during the charge, not the capacity obtained from the 0.2C discharge. Will the discharge capacity reading reappear when the break-in is "DONE"?

[Mr Happy]

Will the discharge capacity reading reappear when the break-in is "DONE"?

Yes

Incidentally, my experiment with the Duracell AAA cells is still continuing. I'll post another update soon.

[fireguy]

OK, so after all my hemming and hawing and chomping at the bit, I'm finally feeling broken, so I am actually running eight of the new AAA Eneloops on break-in, which is what I assume you mean by "standard charge" and "standard discharge". Thing is, now that it is nearing the latter half of the second charge, I notice the display shows the current "into" the cell during the charge, not the capacity obtained from the 0.2C discharge. Will the discharge capacity reading reappear when the break-in is "DONE"?

If you're doing multiple cycles of charge/discharge, you can press the up or down arrow key to see the results of previous cycles, just not the current cycle that is resting.

As for the break-in, you have to wait until the end unless you watch it after the discharge cycle. At this point it shows you what was discharged and you know the results without waiting for the rest and charge (18 hrs). I believe, if memory serves me correctly, the discharge amount is available through the entire rest cycle, it just disappears once the charge operation has been started.

[Mr Happy]

OK, here's my next update on the Duracell AAA cells that were behaving so poorly out of the package (see post #229).

After the break-in cycle the reported capacities were 797 807 805 804 mAh. These compare quite favorably with the 800 mAh label capacity.

The break-in charge finished this morning, and I have this evening put them on another 200 mA discharge to compare with the first one. Here are the results so far (it is not finished yet):

volts after 1 min
1.28 1.28 1.27 1.28
volts after 45 mins (130 mAh)
1.19 1.19 1.19 1.19
volts after 90 mins (270 mAh)
1.17 1.18 1.18 1.18
volts after 133 mins (400 mAh)
1.17 1.17 1.17 1.17

As can be seen the voltages are higher and are much more evenly balanced between the cells now. Once this discharge finishes I will cycle them a couple of times at a faster rate and then make another attempt at the 500 mA discharge that they could not sustain to begin with. I am quite interested to see if they can do it at all since I have little experience with AAA cells compared to the AA variety.

[Turbo DV8]

Let me reiterate up to this point. Let's take the first eight of my brand new AAA Eneloops cells manufactured in April 2008. First I discharged them on the Maha at 500 mA. Then I charged them and discharged them again at 300 mA on the Maha, and got the following mAh capacities:

763-760-750-744-769-762-773-752

(An additional charge and discharge on the BC900 gave somewhat higher figures between 849-879 mAh's, which I undestand is to be expected.)

Then it was suggested to run a break-in. At the end of break-in, which discharged at only 160 mA, the capacities were as follows:

805-785-791-785-802-779-786-786

After the end of break-in, I discharged again at 400 mA to obtain the mid-point voltages, which were as follows (at one hour):

1.13-1.11-1.09-1.13-1.15-1.15-1.13-1.13

Using the C9000 and discharging at 400 mA, you should see voltages of 1.16 or higher. Very good cells will be at 1.17 or 1.18 volts. Once they drop below 1.15, they are well on their way to being crap cells.

So, I have eight brand new Eneloops of April 2008 manufacture. They have been cycled at least three times total, plus a break-in. According to the above suggested guideline, at least 75% of my brand new Eneloops are "well on their way to being crap cells." Hmmm... man, I gotta dump these Eneloop crap!

I think my cells are fine and dandy, thank you very much. I stand by my first observation. My Maha's are reading voltages artifically low, which, among other things, can cause the Maha to prematurely terminate a discharge even with plenty of capacity under load remaining. I could now run another 3-5 cycles, but would that prove anything after already having several cycles on them, and already seemingly well balanced?


The end of my 30 day return period is approaching...

[Mr Happy]

My 200 mA discharge has finished now. Capacities were 776 787 786 785 mAh (the cells had rested for several hours after charging).

I'm going to cycle them a bit and then do a 400 mA discharge with my C9000 to give you a comparison to work with. I should have that result tomorrow. I'm learning here myself as I have not done this exercise before with AAA cells.

[SilverFox]

Hello Turbo DV8,

Very interesting...

I have a set of 4 AAA Eneloop cells that I use in my camera flash. The flash doesn't get much use normally, but when I need it I work the heck out of it.

I had charged the cells up just before Christmas. I pulled them out and ran a discharge at 400 mA on the C9000.

60 minutes into the discharge I observed these voltages.

1.14, 1.15, 1.04, 1.05.

These cells are from the original release in Japan and are about 3 years old. It looks like at least a couple of them are headed to be crap cells.

I then charged them and ran another discharge at 400 mA. This time I observed the following voltages after 60 minutes of discharge.

1.18, 1.16, 1.14, 1.14.

I now have 2 cells that are good, by my definition, and 2 that are showing great improvement. One more charge/discharge cycle should bring them back to good performance.

These are my most abused cells. I don't use my flash for months, then suddenly need to use it all the time for a day or two, then it goes back in storage. I usually try to exercise my cells with a charge/discharge cycle every 30 days. I have not done this with these cells and it shows. I will change that and include these in my monthly exercise program.

By the way, at the end of the initial discharge I observed the voltage bounce between 0.95 volts and 1.02 volts several times on the cells that showed the lower voltage under load. The other cells just saw a steady decrease in voltage and did not jump around.

We still haven't determined if the problem is with your cells or your charger. Your 2008 cells are behaving similar to my 2006 cells that have basically been in extended storage. Do you happen to have any other AAA NiMh cells? If you do, you could run a test on them and compare.

Who did you get your chargers from? I would be happy to call them and see if I could get an extension on your 30 day return so we could figure this out.

Tom

[Mr Happy]

Here are my comparison results, continuing the test on a new set of 4 AAA Duracell pre-charged from earlier posts.

After the 200 mA discharge in post #246 I gave them 3 cycles of 400 mA charge/400 mA discharge. The last 400 mA discharge has just finished.

For each of the cells, these are the 400 mA discharge readings:

cell #1: 787, 787, 786 mAh
cell #2: 800, 799, 797 mAh
cell #3: 796, 795, 793 mAh
cell #4: 796, 795, 794 mAh

I noted the voltages at the 400 mAh point of the last discharge (that was about 66 minutes). They were

1.18, 1.18, 1.17, 1.18

If I had recorded them at exactly 60 minutes the third cell would also have been 1.18. It dipped down to 1.17 just before I noted the reading.

My feeling is that there is a good degree of consistency in successive tests with my sample of the C9000, and also good consistency between these four cells.

I would also wonder, as SilverFox suggested, if you have some other AAA cells from a different source that you could do a comparison test with? It does seem somehow that your samples of the C9000 are not delivering the results that would be expected.

[Turbo DV8]

I would also wonder, as SilverFox suggested, if you have some other AAA cells from a different source that you could do a comparison test with? It does seem somehow that your samples of the C9000 are not delivering the results that would be expected.

Edited for clarity: the following tests were performed on the new AAA Eneloops.

After break-in, I did another 400 mA discharge, followed by two more cycles. Then I halted the process, as they had plenty of cycles on them already, and there was no appreciable increase. The discharge and two cycles rendered the following capacities:

786-767-768-766-781-763-769-765
790-774-777-769-786-767-774-770
790-776-779-770-786-767-775-770

Then for fun, I charged them at 300 mA plus 2 hours top-off, then discharged on the BC-900 @ 350 mA for 400 mAh, then discharged the remainder on the Maha @ 400 mA. The mid-point voltages as shown on the BC-900 at 400 mAh discharge were:

1.19-1.19-1.18-1.19-1.18-1.18-1.19-1.18

After immediately pulling them from the BC-900 and inserting into the Maha @ 400 mA drain, after a minute of settling, the "new" mid-point voltages as shown on the Maha were:

1.14-1.13-1.12-1.15-1.14-1.14-1.15-1.06

Everything's quite a bit lower, and that last one is an example of exactly the strange behavior I originally noted.

Finally, for kicks, I took the sum of the initial 400 mAh BC-900 discharge and the remaining Maha discharge capacities:

400-400-400-400-400-400-400-400
+419-402-410-396-408-391-401-397
819-802-810-796-808-791-801-797

And to compare to the final Maha cycle capacities earlier:

790-776-779-770-786-767-775-770

All within 30 mAh of each other between Maha-only discharge and half-and-half. Not bad.

Who did you get your chargers from? I would be happy to call them and see if I could get an extension on your 30 day return so we could figure this out.

Well, heck, SilverFox, if you have connections, let's just make it a lifetime warranty! (Thomas Distributing... )

If I were to try another set of AAA cells, should I try with older Hybrids or older Eneloops, both almost a couple years old by now?

[Chase2b]

I am sure I know the answer to this question, but have to ask it anyway.

If I choose a certain cycle, i.e analyze/refresh and after approx. 12 hours (still in charge mode), I decide to cancel the rest of the cycle and just want to pull the batteries out. Does just cancelling the cycle by unplugging hurt the charger in any way? Can the charger be damaged?

[Mr Happy]

The answer is what you think it is.

But in fact you don't even have to unplug the charger. Just removing a battery from a slot will reset that slot ready for a new program.

[SilverFox]

Hello Turbo DV8,

After another charge/discharge cycle, my cells ended up with mid point voltages of

1.18, 1.17, 1.17, 1.17.

I still think the problem you are seeing has to do with your cells. I think those Eneloop AAA cells should show a mid point voltage of above 1.2 volts on the BC-900.

If you have some other Eneloop AAA cells, they would be good to confirm what we are seeing.

I will contact Thomas Distributing and see if I can get a small extension on your 30 day return. No promises, but I would really like to get to the bottom of this.

Tom

[Mr Happy]

Here's a final test on my Duracell AAA cells. I've been thinking about a 6AAA cell hotwire, and I started to wonder if AAA cells were up to it. To find out, I discharged the cells that were charged yesterday at 1 amp to see how they stood up to the load.

This also has a bearing on the thought that the C9000 might show lower discharge voltages because it uses a pulsed 1 A discharge current under PWM. No PWM here, it is a flat out 1000 mA.

Without further ado, here is the discharge profile:

1000 mA discharge of Duracell white top AAA cells
Cell    |  #1    #2    #3    #4
--------+--------------------------
100 mAh | 1.19  1.19  1.18  1.18 V
200 mAh | 1.18  1.18  1.17  1.17 V
300 mAh | 1.18  1.17  1.17  1.17 V
400 mAh | 1.17  1.17  1.16  1.16 V
500 mAh | 1.16  1.16  1.16  1.15 V
600 mAh | 1.14  1.14  1.13  1.14 V
700 mAh | 1.09  1.10  1.09  1.09 V
--------+--------------------------
Totals  |  763   778   771   775 mAh

The cells have held up remarkably well it seems (look back to post #229 where they collapsed and died the first time I tried a 500 mA discharge on them).

I'm beginning to wonder Turbo DV8, the same as SilverFox, if it is your cells that are misbehaving?

[SilverFox]

Hello Turbo DV8,

I contacted Thomas Distributing and must say that they are wonderful people to deal with. They are interested in having satisfied customers, and are willing to work with you in this situation. I will PM you the details.

I am very pleased when I find "no hassle" access to decision makers, and a customer service department that is dedicated to making sure the customer is satisfied with their purchase.

I believe that this attitude has been part of the success of Thomas Distributing during its 31 + years of business. If they have what you are looking for, go ahead and get it from them because they will take care of you in the long run.

I also contacted William of Maha to see if he has anything to add to our discussion.

Tom

[coppertrail]

Hello Turbo DV8,

I contacted Thomas Distributing and must say that they are wonderful people to deal with. They are interested in having satisfied customers, and are willing to work with you in this situation. I will PM you the details.

I am very pleased when I find "no hassle" access to decision makers, and a customer service department that is dedicated to making sure the customer is satisfied with their purchase.

I believe that this attitude has been part of the success of Thomas Distributing during its 31 + years of business. If they have what you are looking for, go ahead and get it from them because they will take care of you in the long run.

Tom

+1

[willchueh]

Tom, got your email. I am happy to contribute. Having read the posts, following are the issues Turbe DV8 experienced - and my thoughts:

1) Inconsistent discharge voltage between MH-C9000 and the BC-900

The MH-C9000 and BC-900 use different methods for measuring voltage during discharge. The MH-C9000 measures the voltage under a 1000mA load, while the BC-900 measures the open circuit voltage between the discharge pulses. We chose this particular design because the open circuit voltage does not fully reflect the condition of the battery and that the under-load voltage is the figure-of-merit for real devices. For instance, a highly resistive battery might show a high open circuit voltage (measured between discharge pulses). However, as soon as the discharge current is drawn, the voltage will drop significantly. Here is an example, for a battery with 0.1 ohm DC resistance, a open circuit voltage of 1.2V will give a under-load (1A) voltage of 1.1V.

We've come across a lot of AAA batteries (well-known and off brand, new and old) that have DC resistances exceeding 0.3 ohm. Their open circuit voltage, measured between discharge pulses, actually never reach the cutoff and the discharge continues until the MOSFET is unable to draw current (due to insufficient differential voltage). The under-load voltage will already be 0.8V but the open circuit voltage will still be above the discharge cutoff. As a result, the discharge never ends!

However, under-load voltage has one drawback - it also reflects the contact resistance between the charger and the battery. In a 2-point measurement (as used in the Mh-C9000 where only two points are used to measure the voltage across the battery, one on the positive terminal and one on the negative terminal), the voltage drop includes those across the contacts as well. Since no contact is perfect, it is possible to develop a small voltage drop between the battery and the charger. Commercial battery testers overcome this problem by using the so-called "4 point measurement" while two probes carry the current and two probes measure the voltage (so that the contact resistance is not measured).

2) Non-monotonic discharge voltage (with respect to time)

It is normal to have a non-monotinic discharge voltage (and charge voltage as well) due a change in the battery resistance. This usually happens with batteries that have been sitting on the shelf for a while, and old batteries.

3) Pre-mature discharge termination

It rarely happens, but it does. Did you encounter the problem frequently? on both units? Pre-mature discharge termination is most likely due to a sudden drop in the measured voltage (such that the charger sees a voltage less than 0.9V), often due to a jiggle to the battery, noise, etc.

4) Why isn't the battery fully charged when DONE shows? Why the 2hour topoff charge?

It is a balancing act between undercharging and overcharging batteries. Maha design chargers differently depending on the target market. In the case of the MH-C9000, we favor undercharging in order to extend battery life. Typically, batteries are 93-95% charged when DONE pops up. This is when the user-set charging current stops and the 100mA top-off current kicks in. Our research showed that this termination strategy will substantially increase the life of the battery by preventing overheating. I think most folks here will agree that the MH-C9000 is a "cool" charger.

5) Pre-mature charge termination

Charge termination issues do happen, but rarely. The MH-C9000 measures the battery voltage (both the absolute and relative value, and as a function of time), temperature (absolute and relative, and as a function of time) and puts the information into a matrix to evaluate whether to terminate the charge or not. At the design level, we decided that we prefer not to overcharge the battery. Occasionally, especially with new batteries or those sitting around for a while, premature charge termination would occur. However, missed termination is extremely rare because of our design choice.

6) Capacity difference between the MH-C9000 and BC-900

BC-900, according to our measurement, tends to overestimate the capacity quite a bit (for instance, the Powerex 2700mAh capacity (1A charge/discharge) typically gets 2750mAh on the BC-900, when our laboratory-grade instrument consistently give about 2550mAh). This has to do with two things: 1) accuracy of the discharge current measurement, and 2) accuracy of the time base. The MH-C9000 has a 1% tolerance in the discharge current measurement. Furthermore, the MH-C9000 uses a quartz oscilattor time base (you can see them if you open the charger, I think there are some photos here on CPF) whereas the BC-900 uses a resistor-capacitor (RC) network as a time base which is less accurate.

I trust the BREAK-IN capacity on the MH-C9000. It typically is within 2% of the capacity measured on a calibrated battery analyzer.

I hope this answers some of the questions raised.

William

[Black Rose]

Thanks for the information and explanations Will.

Greatly appreciated

[Turbo DV8]

Thanks all, for the comments and efforts, and for contacting TD.

The MH-C9000 and BC-900 use different methods for measuring voltage during discharge. The MH-C9000 measures the voltage under a 1000mA load, while the BC-900 measures the open circuit voltage between the discharge pulses.

I still think the problem you are seeing has to do with your cells. I think those Eneloop AAA cells should show a mid point voltage of above 1.2 volts on the BC-900.

Well, actually they did ... sort of. The BC-900 display was alternating between two values, and William's explanation above may help explain what I saw. For about 80% of the time, the midpoint voltages on the BC-900 were displayed as:

1.20-1.22-1.22-1.21-1.19-1.22-1.22-1.19

Then every five or ten seconds or so, the displayed voltage dipped, for a second, to the values I gave earlier:

1.19-1.19-1.18-1.19-1.18-1.18-1.19-1.18

Am I to assume from William's comment above that the higher voltages were the BC-900 indicating OCV, and the momentary lower voltages which flashed every five or ten seconds were an indication of the voltage under the applied load? This is sort of what I figured what was happening, that's why I just gave the lower midpoint voltages. But if I were to read the higher readings that were displayed the majority of the time, SilverFox, then the cells did indeed meet the 1.2v midpoint voltage on the BC-900 you cited. (with the exception of the last cell.)

5) Pre-mature charge termination: Charge termination issues do happen, but rarely.

3) Pre-mature discharge termination: It rarely happens, but it does. Did you encounter the problem frequently? On both units?

I must be one unlucky guy, because I experienced both scenarios, on the same unit, right out of the gates! So far, each case has occurred once. At the end of the day, these occurrences will remain in the back of my mind.

I still think the problem you are seeing has to do with your cells... If you have some other Eneloop AAA cells, they would be good to confirm what we are seeing.

Before I start another prolonged run of testing, please be specific about the process and readings I should be documenting.

Do you want me to two year old Eneloops, or the other eight new ones I received with the first eight? If the two year old ones, and possibly not all see a lot of use, should I just charge them, then discharge to get the midpoint voltages? Or first do a break-in, followed by a discharge for midpoint voltages? If I run them as-is, being in various states of condition, that may make it unlikely to be able to pin a potential problem either on a specific charger of the two, or the cells.

Any other specific requests for the testing before I begin? Thanks again for the help and contacting TD.

[Turbo DV8]

I forgot to ask...

I just finished a break-in on eight regularly-cycled Duracell 1700 cells, which must be more than three years old. New, the exceeded their rating, by a large margin even considering the test was on the optimistic BC-900. After break-in, the capacities were:

1767-1756-1699-1706-1752-1725-1661-1698

If I now wanted to run a couple cycles on them and observe midpoint voltages, what current is recommended to discharge the 1700 mAh cells? Is there a rule of thumb based upon cell capacity? Half the cell capacity rating, or half the actual capacity after break-in? If so, should I round up (900 mA) or down (800 mA) from the 1700?

Also, on the AAA Eneloops, I took the midpoint voltage at 400 mAh into the discharge. That just happens to be pretty close to half the tested capacity of the cells. However, for these Duracell 1700's, should I determine the midpoint voltage at half the tested capacity from the break-in?

Finally, what midpoint voltage for AA cells are we calling the dividing line between good and not-so-good?

[Mr Happy]

Before I start another prolonged run of testing, please be specific about the process and readings I should be documenting.

Do you want me to two year old Eneloops, or the other eight new ones I received with the first eight? If the two year old ones, and possibly not all see a lot of use, should I just charge them, then discharge to get the midpoint voltages? Or first do a break-in, followed by a discharge for midpoint voltages? If I run them as-is, being in various states of condition, that may make it unlikely to be able to pin a potential problem either on a specific charger of the two, or the cells.

Any other specific requests for the testing before I begin? Thanks again for the help and contacting TD.

Are the eight new Eneloops new and unused, or new but lightly used? It may not make much difference actually, but I'm just curious.

In this thread I have been testing four AAA size Duracell Pre-charged that I believe to be "Duraloops", i.e. Eneloops in different packaging. They were purchased new in 2008 and were unused until now.

I'll quickly recap the I process I followed in case you would like to follow along with four of your cells and compare with my posted numbers.

Out of the package, I discharged the cells at 200 mA.

Then a break-in cycle with 800 mAh entered capacity (at the end of which the cells were fully charged).

After the break-in, a discharge at 200 mA.

With the now empty cells, a charge/discharge cycle using 400 mA charge, 400 mA discharge settings. Three cycles were requested, so the cells underwent:

Charge (400 mA)/Discharge (400 mA)
Charge (400 mA)/Discharge (400 mA)
Charge (400 mA)/Discharge (400 mA)
Charge (400 mA)

Lastly, I discharged the now charged cells at 1000 mA and noted the voltages during the discharge and the final recorded capacities.

This process, of a discharge/break-in/discharge followed by a few 0.5 C charge/discharge cycles is probably a good way of enervating cells that may have been sitting around for a while.

[Turbo DV8]

Are the eight new Eneloops new and unused, or new but lightly used? It may not make much difference actually, but I'm just curious.

They are the latter eight of a total of sixteen I purchased from TD along with the MH-C9000's. I originally cycled them about three times between the Maha and BC-900 (not break-in) and that's it.

I made a slight error before about the dates of manufacture of the eight AAA cells I was testing. I said all were April 2008. In fact, the first four are June 2008. All twelve other AAA Eneloops I got from TD are April 2008.

My older AAA Eneloops are from April & October 2006.

[Mr Happy]

I've got some AA cells that I'm just topping up; two older Eneloops from 2006 and two Hybriloops that are more recent. I can run a 1 amp discharge on those and record the voltage profiles if you have any AA Eneloops to compare with.

I think I also have some Duracell 1700 cells that I got with my Power Gauge charger, but unfortunately I can't remember where I put them. If I find them I could run a discharge test on those too.

[Mr Happy]

Here is my discharge test of AA cells in case you want to compare:

1000 mA discharge test of AA Eneloops 1 & 2, "Hybriloops" 3 & 4
Cell     |  #1    #2    #3    #4
---------+---------------------------
 200 mAh | 1.14  1.22  1.21  1.22 V
 400 mAh | 1.11  1.19  1.19  1.20 V 
 600 mAh | 1.11  1.19  1.19  1.19 V
 800 mAh | 1.10  1.19  1.19  1.19 V
1000 mAh | 1.09  1.18  1.18  1.18 V
1200 mAh | 1.08  1.17  1.17  1.18 V
1400 mAh | 1.07  1.16  1.16  1.16 V
1600 mAh | 1.04  1.13  1.14  1.14 V
1800 mAh | 0.98  1.08  1.09  1.10 V
---------+---------------------------
Totals   | 1876  1895  1918  1930 mAh

It looks like the first Eneloop has gone high resistance. I don't know why that should be, it has been treated much the same as the second one. I guess it shows cells can go "bad" spontaneously and that you can't take even Eneloops for granted. I will have to run a break-in cycle on that cell and see if it recovers its original performance.

[Chase2b]

Don't mean to interrupt your posts but I have a (noob) question on the C9000.
I am doing a "break-in" cycle on 4 new AA's. The rating are 2000mAh.
I entered the required data on the C9000; capacity=2000.

The first cycle took 16 hours but the batteries are at 2900 mAh. I know that some overcharging will occur, but isn't 2900 TOO much? That's almost 50% more.

Note: I did do a full discharge on the batteries BEFORE the break-in cycle.

*** Please disregard this post. I just read in the beginning of this thread that it is normal for a 1.6 x overcharge. 1.6 x 2000 = 3200.
So the 2900 definately falls into that range.

[coppertrail]

This is normal during a break-in cycle, its not what the cells are actually holding.

[Chase2b]

Just read the first post of this thread. 1.6 x overcharge is normal.
1.6 x 2000 = 3200

[Turbo DV8]

I can run a 1 amp discharge on those and record the voltage profiles if you have any AA Eneloops to compare with... Here is my discharge test of AA cells in case you want to compare.

I would love to compare. Yet, before I begin another long test on AA Eneloops, I am awaiting instruction from SilverFox on how he thinks I should proceed on the AAA Eneloops, since he is trying to determine if I have cell issues and/or MH-C9000 issues.

[SilverFox]

Hello Turbo DV8,

The pressure is on...

Let's go with your 2006 Eneloop cells.

Do 3 cycles of charge discharge on them and let's see what they do.

Are they also AAA cells?

Tom

[Turbo DV8]

Hello Turbo DV8,

The pressure is on...

Let's go with your 2006 Eneloop cells.

Do 3 cycles of charge discharge on them and let's see what they do.

Are they also AAA cells?

Tom

Yes, AAA. I didn't hear many specifics, so I'll assume 300 mA charge and 400 mA discharge rates (as before) are adequate, and that this is a preliminary routine during which I do not need to record midpoint voltages and such. I have begun. Thanks.

Question about the "rests" in various modes. In the two hour rest after the first charge in refresh & analyze mode, is that 2 hours rest still giving the 100 mA "top-off" charge? Same question in Cycle mode. Is the 2 hour "rest" actually a 2 hour top-off at 100 mA? Or does the Maha only apply the top-off charge only after a straight charge.

[TakeTheActive]

William,

I acknowledge that you 'do this for a living' and thus understand it MUCH better than us, but I don't see how the following could be true:

...1) Inconsistent discharge voltage between MH-C9000 and the BC-900

The MH-C9000 and BC-900 use different methods for measuring voltage during discharge. The MH-C9000 measures the voltage under a 1000mA load, while the BC-900 measures the open circuit voltage between the discharge pulses. We chose this particular design because the open circuit voltage does not fully reflect the condition of the battery and that the under-load voltage is the figure-of-merit for real devices. For instance, a highly resistive battery might show a high open circuit voltage (measured between discharge pulses). However, as soon as the discharge current is drawn, the voltage will drop significantly. Here is an example, for a battery with 0.1 ohm DC resistance, a open circuit voltage of 1.2V will give a under-load (1A) voltage of 1.1V...

I own both a BC-900 and a MH-C9000. I recently moved the BC-900 upstairs to my HEATED den from my UNHEATED basement. Thus, I've been able to fairly continuously monitor the progress of both while I sit here "surfing the web". I don't see any WILD swings of voltage (as in going from UNDER LOAD to OPEN CIRCUIT) on the BC-900 while it's discharging. And, I do see it revert to charge when the discharge voltage hits 0.9VDC, just like the MH-C9000.

How can I prove to myself, here at home, that the BC-900 is measuring OPEN CIRCUIT while the MH-C9000 is measuring UNDER LOAD?

Thanks!