Maha MH-C9000 SUPPORT / FAQ - continuation

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Mr Happy said:
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.
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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.
 
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.
 
Here is my discharge test of AA cells in case you want to compare:

Code: 
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.
 
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.
 
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Just read the first post of this thread. 1.6 x overcharge is normal.
1.6 x 2000 = 3200
 
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Mr Happy said:
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.
Click to expand...

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.
 
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
 
SilverFox said:
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
Click to expand...

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.
 
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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:
willchueh said:
...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...
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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! :)
 
Hello Turbo DV8,

The first few charge/discharge cycles are designed to bring the cells back up to decent operating condition. No special care or observations are required during this part.

I seem to recall that the top off charge is applied in the cycle mode, but I don't know if it is applied during the refresh and analyze mode. There may be information on this in one of the C9000 threads, or you can run a test and see if the voltage climbs during the rest periods. If the voltage increases during the rest period, the cell is being topped off.

Tom
 
When I run the R&A on my cells, I always leave them in for the extra 2 hours, but I've never monitored the voltages.

I should toss a set of my Eneloops that have been sitting for 6+ months on an R&A cycle and see what happens.
 
Turbo DV8 said:
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.
Click to expand...

2-Hour top-off charge is applied in all modes except in DISCHARGE and BREAK-IN.

William
 
willchueh said:
Typically, batteries are 93-95% charged when DONE pops up.
William
Click to expand...

willchueh said:
2-Hour top-off charge is applied in all modes except in DISCHARGE and BREAK-IN.

William
Click to expand...

Interesting. So, if during break-in there is no top-off, and the cell is only charged to 93-95% of actual capacity when "DONE", then the capacity determined during a break-in is not an accurate capacity. But in this case, I do not understand your comment earlier:

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

How can the break-in capacity be an accurate representation of a cells' capacity if it only charges to 93-95% due to not topping-off in break-in mode?

EDIT: Never mind! Brain fart kept me from considering that break-in is terminated by time at 16 hours, not voltage. Therefore, no top-off needed. Duh...
 
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Let's take refresh/analyze mode for example. When charge is complete, let's say the cells are 93% full and show 1900 mAh for eneloop AA cells.

Am I to assume that when the 2 hour top off charge is complete, I have 2+ Ah in my cells?
 
coppertrail said:
Let's take refresh/analyze mode for example. When charge is complete, let's say the cells are 93% full and show 1900 mAh for eneloop AA cells.

Am I to assume that when the 2 hour top off charge is complete, I have 2+ Ah in my cells?
Click to expand...

Not near my manual now, but if I recall, the R&A mode charges the cell, discharges, then charges again. Since William states that the R&A mode will apply the two hour top-off between the first charge and discharge, then the accrued discharge capacity should already take into account the energy added by the two hour top-off after the preliminary charge. That's the way I am reading it, anyway.
 
Turbo DV8 said:
Interesting. So, if during break-in there is no top-off, and the cell is only charged to 93-95% of actual capacity when "DONE", then the capacity determined during a break-in is not an accurate capacity. But in this case, I do not understand your comment earlier:
I trust the BREAK-IN capacity on the MH-C9000. It typically is within 2% of the capacity measured on a calibrated battery analyzer.
Click to expand...
How can the break-in capacity be an accurate representation of a cells' capacity if it only charges to 93-95% due to not topping-off in break-in mode?
Click to expand...
It is because the break-in process charges the cell as close to 100% capacity as is possible. During the break-in charge, a current of 0.1C is applied for 16 hours. This applies a total charge of 160% of the cell's capacity, which saturates the cell with as much charge as it can reasonably be expected to hold. Essentially the break-in charge does not need a top-off because it is built into the charging process.
 
coppertrail said:
Let's take refresh/analyze mode for example. When charge is complete, let's say the cells are 93% full and show 1900 mAh for eneloop AA cells.

Am I to assume that when the 2 hour top off charge is complete, I have 2+ Ah in my cells?
Click to expand...
When the cells are more than 95% full, the charge acceptance for further charge current is very low. That means that even if you feed 200 mAh into the cell, the whole 200 mAh is very unlikely to stick. Maybe only half of it will actually be stored.

This is why it is very difficult to charge batteries to 100% in a short time. Once the batteries are nearly full they convert a lot of the charge current to heat, which means you have to drop the charging current and take it slowly to avoid overheating the cells. The only possibility is to apply a small charge over a long period and be patient. This is what the C9000 does. There is no other way to go about it due to the way batteries behave.
 
Mr Happy said:
During the break-in charge, a current of 0.1C is applied for 16 hours. This applies a total charge of 160% of the cell's capacity, which saturates the cell with as much charge as it can reasonably be expected to hold.
Click to expand...

Yeah, that light bulb turned on for me just as you were composing your reply! I added a "brain fart" disclaimer to my post! Thanks.
 
Turbo DV8 said:
Not near my manual now, but if I recall, the R&A mode charges the cell, discharges, then charges again. Since William states that the R&A mode will apply the two hour top-off between the first charge and discharge, then the accrued discharge capacity should already take into account the energy added by the two hour top-off after the preliminary charge. That's the way I am reading it, anyway.
Click to expand...
Williams response didn't seem to directly answer the question you had about what happens in the rest periods.

I believe the top off charge is only applied after DONE is displayed, so it would not be applied at the 2 hour rest period following the first charge in R&A mode.

SURVEY SAYS: WRONG :D
 
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