Maha MH-C9000 SUPPORT / FAQ - continuation

[DT 123]

I never paid attention to the charging results while doing a break-in. Now I did the first time and it confused me. I did a 2000 break-in and the charging results after 16 hours differed by 10 mAh. This is a difference of about 3 min @200mA. Where does this difference come from?

Will each slot be charged slightly differently (since they are independent)?
Does this effect also discharging? Or does this not matter in normal mode since the C-9000 is counting the pulses and then it doesnt matter in which slot the cell was inserted?

[SilverFox]

Hello DT 123,

Each channel is independent, so you can expect variations. They are usually close, but not exact.

Tom

[samgab]

I did some more testing with the Fluke:

setting	slot	displayed rate	min	max	avg	% of Displayed rate
200	1	197	2	1910	174	88%
200	2	198	2	1869	170	86%
200	3	197	2	1868	169	86%
200	4	197	2	1839	166	84%
200 Average		197	2	1872	170	86%
500	1	494	2	1923	438	89%
500	2	495	2	1886	426	86%
500	3	494	2	1886	428	87%
500	4	494	2	1855	425	86%
500 Average		494	2	1888	429	87%
1000	1	990	2	1923	875	88%
1000	2	989	2	1883	862	87%
1000	3	988	2	1887	863	87%
1000	4	988	2	1855	850	86%
1000 Average		989	2	1887	863	87%
2000	1	1980	22	1923	1755	89%
2000	2	1981	21	1884	1718	87%
2000	3	1983	21	1891	1727	87%
2000	4	1976	21	1855	1695	86%
2000 Average		1980	21	1888	1724	87%
Grand Average			7	1884	796	87%
setting	slot	displayed rate	min	max	avg	% of Displayed rate
-100	1	-99	3	-996	-88	89%
-100	2	-98	3	-977	-86	88%
-100	3	-100	3	-998	-87	87%
-100	4	-99	3	-986	-86	87%
-100 Average		-99	3	-989	-87	88%
-200	1	-199	3	-1004	-180	90%
-200	2	-197	3	-986	-174	88%
-200	3	-200	3	-1007	-182	91%
-200	4	-198	3	-994	-180	91%
-200 Average		-199	3	-998	-179	90%
-500	1	-499	3	-1004	-452	91%
-500	2	-494	3	-985	-447	90%
-500	3	-500	3	-1007	-457	91%
-500	4	-496	3	-994	-450	91%
-500 Average		-497	3	-998	-452	91%
-1000	1	-999	-7	-1003	-916	92%
-1000	2	-990	-7	-985	-898	91%
-1000	3	-1001	-8	-1006	-918	92%
-1000	4	-992	-7	-993	-904	91%
-1000 Average		-996	-7	-997	-909	91%
Grand Average			0	-995	-407	90%

The readings are all in mAh. The negative readings are for discharge, and positive ones are for charge.

[samgab]

Charts for the discharge results:

[DT 123]

Why did you compare to the displayed rates? You are assuming that that rate is used for the calculation of the total amount?
The C-9000 is showing the rate only every 60 sec - do we know whether the present current is shown or the average current of the last minute?
Since the test running time was longer than one minute - did you average also the display rates?

But it was a very interesting test. First of all since for charging slot #4 had the lowest current, but for discharging it was slot #2.
Any idea what could be the reason for that?

[samgab]

Why did you compare to the displayed rates? You are assuming that that rate is used for the calculation of the total amount?
The C-9000 is showing the rate only every 60 sec - do we know whether the present current is shown or the average current of the last minute?
Since the test running time was longer than one minute - did you average also the display rates?

But it was a very interesting test. First of all since for charging slot #4 had the lowest current, but for discharging it was slot #2.
Any idea what could be the reason for that?

I compared the unit's displayed rate, because that is the charge rate that it is saying it is charging or discharging at. I wanted to compare that to the rate it was actually charging at.
I tested one bay at a time, so I was getting the unit's rate much more frequently than every 60 seconds. And I checked it multiple times before taking down a reading to confirm that it is a stable, non-changing reading. The rate displayed doesn't really change it stays pretty much constant.

The differences are most likely because the C9000 is not a precision item of lab equipment.
It is just a consumer battery charger/analyser. They use multiple components inside that probably have quite (relatively) large margins for error, and tolerances.
The Fluke 87V, on the other hand is a precision piece of equipment.

I don't know the exact reason why one particular bay would be higher than the others whilst lower than the others for discharging (that would require disassembling the unit and testing each component separately), but I'd say generally it's because each slot is independent from the others, and some different components are used for charging than for discharging. So it would make sense that how one compares to the others in charging wouldn't necessarily correlate to how it compares to the others when discharging.

[DT 123]

I still think that something is wrong with the test/data. If you found out that the displayed rates are differing in average by 10% by your measured rates then this would finally mean that the C-9000 is giving us for charging & discharging results which are 10% too low. This means that when the c-9000 is measuring a capacity of 2000 then in reality it should be 2200 mAh. But this cannot be true. This also doesnt match to the 2% capacity accuracy while doing the break-in.

[Wrend]

The capacity measurement is calculated differently, from what I remember. If you read the current rate on the C9000 and time out how long its on there, it won't match up with the capacity because of this difference.

The capacity measurement, especially on the break in function, is accurate.

[DT 123]

Because of the 10% (?) 'service break'. As far as i remember we should multiply by 0.9. But even then i get different results:
#1:
shown current: 194mA * 16 hour * 0.9 = 2794 mAh. The c-9000 shows me 2824.
#2:
shown current: 244mA * 16 hour * 0.9 = 3514 mAh. The c-9000 shows me 3592.

Rounding because of display: 0.5 mA * 16 hour * 0.9 = 7.2

[samgab]

I still think that something is wrong with the test/data. If you found out that the displayed rates are differing in average by 10% by your measured rates then this would finally mean that the C-9000 is giving us for charging & discharging results which are 10% too low. This means that when the c-9000 is measuring a capacity of 2000 then in reality it should be 2200 mAh. But this cannot be true. This also doesnt match to the 2% capacity accuracy while doing the break-in.

As Wrend said, the displayed discharge amount (mAh) is calculated differently than the discharge rate (mA) and is accurate (within 1-2%).
The capacity calculation is based on the actual current rather than the set (or displayed) current so capacity calculation remains accurate.
According to Will Chueh of Maha, "The MH-C9000 has a 1% tolerance in the discharge current measurement."
Also from Will: "The displayed charging/discharging rate does not include a ~10% off-time. For example, when you set current to 2.0A, it will charge at 2.0A for 90% of the time and rest for 10%. Of course, the capacity reported includes this effect." The ~ means "about", so it isn't necessarily precisely 10%, as shown by my testing.
A way to test the capacity accuracy in comparison to the displayed rate yourself is to use a stopwatch. Discharge a fully charged AA at a set 1000mA for exactly 1 hour and check the readout for capacity vs it's rate.
I did this with 4 eneloops and the result for slots 1-4 was 915, 907, 920, 911 mAh displayed, respectively. On par with my test results.
The C9000 discharge rate (mA) display though, read 999, 990, 1002, and 992 respectively.
Each unit might differ by a little bit, because it's not a calibrated instrument, but a few mAh here or there aren't a major concern.

[DT 123]

I did some cycle tests after a break in with some of my older cells:

Varta 1600, Cycle @ 800/500 mA

		#1	#2

Break-In	1284	1336
Cycle 1		1257	1292
Cycle 2		1212	1250
Cycle 3		1209	1249

Ansmann 2500, Cycle @ 1000/500 mA

		#1	#2

Break-In	2001	2020
Cycle 1		1928	1953
Cycle 2		1870	1886
Cycle 3		1843	1867


GP 1800, Cycle @ 1500/400 mA

		#1

Break-In	1245
Cycle 1		1200
Cycle 2		1197
Cycle 3		1182

Shouldn't the cycle improve the capacity of a cell?
Is it an accident that the capacity dropped each time (from cycle to cycle) and the cycle results are still within the range to be seen as the same?
For the GP i would think so. But what could be the reason for the drop from cycle 1 to cycle 2 for the Varta & Ansmann cells?

[SilverFox]

Hello DT 123,

Interesting trend...

At the rate things are going, your cells may be used up in another 10 - 20 cycles. Perhaps you should run another test of 10 cycles and see if things turn around or continue to decline.

Tom

[DT 123]

I started another cycle test. Results continue to drop or reach a stable value. I started also another cycle test with some older Sanyo Twicell 1600 & some newer LSD Panasonic Infinium 2000. The tests are still going on, but what I get was not was I was really waiting for:

Varta 1600, Cycle @ 800/500 mA	|	Ansmann 2500, Cycle @ 1000/500 mA
				|
		#1	#2	|	#1	#2		
				|
Break-In	1284	1336	|	2001	2020
Cycle 1/3	1257	1292	|	1928	1953
Cycle 2/3	1212	1250	|	1870	1886
Cycle 3/3	1209	1249	|	1843	1867
Cycle 1/10	1238	1273	|	1808	1843
Cycle 2/10	1191	1227	|	1807	1832
Cycle 3/10	1192	1231	|	1789	1820
Cycle 4/10	1190	1224	|	1766	1807
Cycle 5/10	1193	1213	|	...	...
Cycle 6/10	1189	1218	|	...	...

Sanyo Twicell 1600, Cycle @ 800/500 mA

		#1	#2	#3	#4

Break-In	1402	1267	1177	1230
Cycle 1/3	1286	1209	1030	1153
Cycle 2/3	1258	1196	996	1121
Cycle 3/3	1249	1200	969	1132


Panasonic Infinium 2000, Cycle @ 1000/500 mA

		#1	#2	#3	#4

Break-In	1893	1933	1947	1913
Cycle 1/3	1872	1910	1930	1893
Cycle 2/3	1835	1888	1899	1861
Cycle 3/3	1838	1885	1894	1864

You mean that certainly most of the cells are already dead.
I have to add that all cells had not more than 20-50 charging cycles before these tests.
But I am pretty sure that some of them were killed by letting them in an Ansmann energy 8 charger(@trickle) for too long. So certainly they dried out? But then again - shouldn't I get then from the beginning the low results?

The only real increase I reached at cycle 1/10 for the Varta cells. But these cells were the only ones who rested long enough between 2 cycles and got finally 2 times the top off charge - once after the last charging at cycle 3/3 and then again for the first charge at cycle 1/10.
None of the cells did become too hot while charging.

So - why there is the drop between cycle 1 and cycle 2 for all of the cells?

[SilverFox]

Hello DT 123,

Good question... I don't know the answer.

However, I can speculate that it may involve variables with electrolyte changes, internal cell resistance, and temperature. I can say that fresh new cells behave differently than aged cells. One of the issues with using loose cells as a battery is matching them. Aged cells need to be viewed over several cycles until their performance characteristics are stable. Fresh cells are much more stable once you get past the initial break in.

Tom

[tobrien]

just bought a C9000 for $44 off of Amazon through their "warehouse deals" thing. description said "very minor packaging flaws/damage" but that the item is in excellent condition.

i can't wait to join this C9000 club

free two-day shipping too, since I'm an Amazon Prime member

[DT 123]

@Tom:
After doing some cycles I was curious what results a new break-in would show:

Ansmann 2500, Cycle @ 1000/500 mA

		#1	#2

Break-In	2001	2020
Cycle 1/3	1928	1953
Cycle 2/3	1870	1886
Cycle 3/3	1843	1867
Cycle 1/9	1808	1843			
Cycle 2/9	1807	1832
Cycle 3/9	1789	1820
Cycle 4/9	1766	1807
Cycle 5/9	1756	1802
Cycle 6/9	1749	1787
Cycle 7/9	1739	1782
Cycle 8/9	1723	1772	
Cycle 9/9	1708	1758	
Break-In	1802	1856

Instead of improving the cells I lost 10%. The capacity dropped with every cycle.
Measuring the ICV I get values between 1.7 & 1.8 - finally not that bad. I always thought that older crap cells will have values of 2 or higher. Isn't that so?

How do old end-of-life cells behave if you treated them well? Will the internal resistance also increase or will only the capacity drop?
If I want to judge the cells then I have at the moment 3 criteria:
- capacity
- self-discharging
- ICV (internal resistance) which seems to be connected to the voltage under load (the higher the ICV the lower U while discharging). Is this true?

[Mr Happy]

Instead of improving the cells I lost 10%. The capacity dropped with every cycle.
Measuring the ICV I get values between 1.7 & 1.8 - finally not that bad. I always thought that older crap cells will have values of 2 or higher. Isn't that so?

How do old end-of-life cells behave if you treated them well? Will the internal resistance also increase or will only the capacity drop?
If I want to judge the cells then I have at the moment 3 criteria:
- capacity
- self-discharging
- ICV (internal resistance) which seems to be connected to the voltage under load (the higher the ICV the lower U while discharging). Is this true?

It is not to be expected that repeated cycling of cells will improve them, only recover them from poor condition. Once cells have been recovered, they then enter the normal wear and tear cycle in which each cycle uses up a bit more of the battery and brings it closer to the end of its life.

There is no way to say what the ICV of any particular cell will be. It depends entirely on the specific cell.

Usually the internal resistance of cells will increase as they age and the capacity will drop. Both things are signs of cells wearing out.

Yes, the internal resistance of a cell is directly connected to the voltage under load. The higher the internal resistance the lower the voltage.

Since the capacity of your cells is going down so measurably with each cycle it seems they are really almost used up. They are at 68% of their label capacity which is rather low.

[SilverFox]

Hello DT 123,

Crap cells are a very interesting study. Some behave just like you are seeing. I think Mr Happy hit it on the head. The internal resistance is only part of the equation. When the electrolyte is compromised, or the electrodes dried out, the capacity just seems to fall off.

I recycle cells when their capacity drops below 80% of their initial capacity. Others keep using cells as long as they hold any charge at all.

I have some NiMh cells from 2005 that are still at 85% of their initial capacity. I keep thinking it is time to retire them, but they keep on working. I take very good care of them and that care seems to result in long life and good performance.

Tom

[N162E]

Hello DT 123,I recycle cells when their capacity drops below 80% of their initial capacity. Others keep using cells as long as they hold any charge at all.
Tom

+1

[finfin]

I wanted to consult the sages and determine what action to take on cells that show discharge capacities that are 60-70 percent of the manufacturers label? Should I continue to refresh (with a discharge in between) or move straight into a Break-in mode? These are cells that have been in service for a few years with usually nothing more than dropping them in the charger and walking away. These particular cells are 750 mAh and 900 mAh AAA cells. After a couple of refreshes I am seeing about a 4 percent (of labeled capacity) increase for each cycle.

[finfin]

Sorry for reposting, but I could not see where to subscribe to this thread without reposting.

[finfin]

Sorry for reposting but I needed to subscribe to the thread. Then there was some sort of problem. Don't know how many of these posted.

Hmmm. Can't delete these.

[SilverFox]

Hello Finfin,

Welcome to CPF.

If you see improvement on multiple Break-In runs, you can keep running the Break-In function. It has the best chance to recover lost performance.

Tom

[N162E]

I wanted to consult the sages and determine what action to take on cells that show discharge capacities that are 60-70 percent of the manufacturers label?

Time for new ones. They have served you well and paid for themselves many times over. If you keep them they may get mixed in with newer cells and degrade run times of your lights or other battery operated goodies.

[N162E]

Delete

[N162E]

Delete

[shelm]

Hi, is it possible to discharge Alkalines (cheap 1.5V AA, from the supermarket) on the C9000, and does this make sense at all?

Which discharge rate should i choose?

We certainly dont want to harm or damage the C9000 by doing so. Thanks for some thoughts!

[finfin]

Why not just put them in a flashlight to discharge them?
Why discharge them at all?

[uk_caver]

Why discharge them at all?

It can be interesting to find out the capacity (and cross-cell capacity consistency) of cheap cells.

[Mr Happy]

Hi, is it possible to discharge Alkalines (cheap 1.5V AA, from the supermarket) on the C9000, and does this make sense at all?

Which discharge rate should i choose?

We certainly dont want to harm or damage the C9000 by doing so. Thanks for some thoughts!

You can, but it would be best to choose a low discharge rate like 100 mA. Alkaline batteries don't respond well to high discharge rates and they will give you very poor capacity results.