Maha MH-C9000 SUPPORT / FAQ - continuation

[SilverFox]

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

[Black Rose]

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.

[willchueh]

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.

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

William

[Turbo DV8]

Typically, batteries are 93-95% charged when DONE pops up.
William

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

William

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.

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...

[coppertrail]

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?

[Turbo DV8]

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?

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.

[Mr Happy]

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.

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?

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.

[Mr Happy]

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?

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.

[Turbo DV8]

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.

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.

[Black Rose]

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.

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

[Mr Happy]

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.

The top off charge is applied during the two hour rest period after charging in Cycle mode, so I think it likely it is applied during R&A mode too, but I have not used R&A mode to find out for sure.

[Black Rose]

The top off charge is applied during the two hour rest period after charging in Cycle mode, so I think it likely it is applied during R&A mode too, but I have not used R&A mode to find out for sure.

Guess I should have relied on the paper manual that came with my charger instead of the easier to access but outdated PDF version from the Maha site

[mikevelarde]

Mr. Happy:

When I chance upon the discharge capacity of a cell during the 120 min. rest before the final 16 hour 0.1C charge to the cell.

Can I safely assume that the discharge capacity is very near the available capacity after the 16 hour final charge of 0.1C ??

mikevelarde

[Mr Happy]

Mr. Happy:

When I chance upon the discharge capacity of a cell during the 120 min. rest before the final 16 hour 0.1C charge to the cell.

Can I safely assume that the discharge capacity is very near the available capacity after the 16 hour final charge of 0.1C ??

mikevelarde

Yes, you can. That same number is what the charger will report after the final charge completes. However, if the cell started out in very poor condition it may take more than one break-in cycle to bring the cell up to maximum capacity, in which case the available capacity may have increased even further after the second charge.

[Turbo DV8]

Here are the results of my 2006 AAA Eneloops for three cycles @ 300 mA charge and 400 mA drain:

Cycle #1: 772-775-770-762-770-761-767-771
Cycle #2: 782-777-771-771-778-764-777-781
Cycle #3: 782-777-772-772-778-765-776-781

I think they were in pretty good shape from the get-go. What's next, boss? Discharge at 400 mA and get midpoint voltages? Midpoint of 800 mA, or as close as possible to half the actual capacities above? The latter would be kind of buggy to do with eight cells so close in capacities, though. I already tried to be so perfect with the other cells and I went berserk as I was concentrating on one cell, another one zipped right past it's half way point right under the radar! The BC-900 is definitely nice in that respect of displaying the info for all four bays at simultaneously.

[Mr Happy]

Here are the results of my 2006 AAA Eneloops for three cycles @ 300 mA charge and 400 mA drain:

Cycle #1: 772-775-770-762-770-761-767-771
Cycle #2: 782-777-771-771-778-764-777-781
Cycle #3: 782-777-772-772-778-765-776-781

I think they were in pretty good shape from the get-go. What's next, boss? Discharge at 400 mA and get midpoint voltages? Midpoint of 800 mA, or as close as possible to half the actual capacities above? The latter would be kind of buggy to do with eight cells so close in capacities, though. I already tried to be so perfect with the other cells and I went berserk as I was concentrating on one cell, another one zipped right past it's half way point right under the radar! The BC-900 is definitely nice in that respect of displaying the info for all four bays at simultaneously.

Well, you have got lots of cells to work with. I discharged some Eneloop clones at 1000 mA back in post #253. You could discharge some of yours at the same rate and compare voltage profiles with mine, or we could wait and see what test SilverFox suggests you try.

[Turbo DV8]

I discharged some Eneloop clones at 1000 mA back in post #253. You could discharge some of yours at the same rate and compare voltage profiles with mine, or we could wait and see what test SilverFox suggests you try.

Since SilverFox has implicitly stated he would like to pinpoint whether the strange observations I observed earlier are cell related and/or charger related, I am waiting for further instruction from SilverFox. Pressure...

I can't say I am anxious to discharge my pampered AAA Eneloops at over 1C, though!

[Mr Happy]

On the Eneloop AAA data sheet there are discharge curves at 160 mA, 800 mA and 1600 mA. They show a mid-point voltage at 800 mA of about 1.24 V, and at 1600 mA of about 1.19 V. I have to say I have never managed to see voltages as high as that on the C9000. My 1000 mA discharge corresponds very closely to Sanyo's 1600 mA discharge curve.

However, their tests are conducted at a temperature of 25 C, and my room temperature is much more like 20 C, which would make a difference.

[SilverFox]

Hello Turbo DV8,

Let's try this...

Charge at 600 mA and after the 2 hour top off charge let the cells rest, in the charger, for about 30 minutes.

Now, discharge at 400 mA. Note the voltage at about 30 minutes into the discharge (in the range of 29 - 31 minutes should be fine).

Tom

[Turbo DV8]

Hello Turbo DV8,

Let's try this...

Charge at 600 mA and after the 2 hour top off charge let the cells rest, in the charger, for about 30 minutes.

Now, discharge at 400 mA. Note the voltage at about 30 minutes into the discharge (in the range of 29 - 31 minutes should be fine).

Tom

Okay. I'll have to discharge again first, as they've already been charged at 300 mA and trickling overnight. The manual was not at all clear that the final cycle of "Cycle" mode adds a final charge. The manual just says, "Performs a charge-discharge cycle for a programmable number of times." I took this comment to mean that at the end of the third discharge cycle, the cells would be left drained, just as in "Discharge" mode. I'll try to get this done before I go to work this evening. If not, it may be a day or two before posting results, as I am having surgery Tuesday morning.

[Mr Happy]

Somewhere in the small print I think the manual does say that a final charge is performed at the end of Cycle mode. I was curious about this myself at the weekend and looked it up.

[crofty]

I can confirm the top off charge is applied in R&A also.

It would be nice to have a complimentary C9000 manual compiled by CPF members that gives these types of details. Maybe I`ll make a start if I get time and knowone beats me to it.

[Black Rose]

The manual was not at all clear that the final cycle of "Cycle" mode adds a final charge. The manual just says, "Performs a charge-discharge cycle for a programmable number of times." I took this comment to mean that at the end of the third discharge cycle, the cells would be left drained, just as in "Discharge" mode.

I've used the cycle mode numerous times to add charge/discharge cycles to my problematic cells to help wake them up.

At the end of the last "cycle", it does perform a final charge.

I'll try to get this done before I go to work this evening. If not, it may be a day or two before posting results, as I am having surgery Tuesday morning.

Good luck

My wife had gall bladder surgery last Friday, so I'm home for part of this week taking care of her.

[Turbo DV8]

Let's try this...
Charge at 600 mA and after the 2 hour top off charge let the cells rest, in the charger, for about 30 minutes. Now, discharge at 400 mA. Note the voltage at about 30 minutes into the discharge (in the range of 29 - 31 minutes should be fine).

Results just in:

1.16-1.17-1.14-1.16-1.16-1.15-1.15-1.15

What's next? Do the same thing on the first set of eight 2008 cells that gave me grief earlier?


Doc called tonight and changed the slicing and dicing from AM to PM tomorrow. Great, an extra four hours I can fret with the sense of impending doom! If it weren't for the food and drink restriction after midnight tonight, I would practice sensible pre-op protocol...

[SilverFox]

Hello Turbo DV8,

Those results are very respectable for cells that are a few years old.

Yes, run the other cells again. These are newer cells and I would hope that they would perform better than your 2006 cells.

It looks like the charger is working pretty well. Now let's see if the newer cells fall into place.

Tom

[fireguy]

My C9000 has a date code of 0H0Da.

I had a NiMH that I thought might have had a reversal. It was in a flashlight that got left on. I noticed that it was on and extremely dim. I put it in the C9000 and started a charge. One cell started to charge fine but the second had a voltage showing as 0.08. The capacity never went about 0 mAh. I removed it and put it in under Break-In and it did start to charge, jumping up to around 1 volt within a few seconds. I'll have to see how this cell behaves afterwards - maybe it was almost empty and the low-rate of charge for break-in was what it needed? I was trying to charge at 500 mA the first time. My guess is that this cell is likely toast.

The second thing I've noticed is that my C9000 never shows HIGH. I did have one old cell that it just wouldn't recognize. Out of curiousity, I popped in an alkaline to see what would happen and it started to charge. I removed it right away, though. I wonder if the newer C9000's have had their tolerances changed and sometimes an alkaline will pass through the checking? It was a brand new battery, so maybe a used alakaline would fail?

[EngrPaul]

I'm losing some digit segments on my charger.

Example:

1.238

Now appears as

1.23H

[Turbo DV8]

I'm looking at the manual, trying to find any hidden nuggets I may have missed, and it seems that with Cycle mode offered, the Refresh & Analyze mode is redundant. According to the manual, they both do the identcial routine, except the Cycle mode lets one program more than one cycle. But why clutter tha display with a Refresh & Analyze mode when one can simply use the Cycle mode and set the number of cycles for "1"?

[pobox1475]

Please delete...

[TakeTheActive]

I'm losing some digit segments on my charger...

What Date Code?

Where and when did you buy it?