C9000 discharge not complete?

[bcwang]

So I got my new 0G0IA C9000 charger and have been playing with it. I actually have two to test with and both exhibit the same behavior. I started noticing that all my cells tested with very low capacity values. It would have been too much a coincidence that all my cells went bad.

all tests at 1amp discharge rate
tenergy 2500 - 1500-1600 mah
kodak 2500 - 1800-2000 mah
powerex 2500 - 2100-2200 mah
quest 1600 - 1000 mah
eneloop fresh out of package - 1200-1300 mah

I retested some of the cells at 500mah discharge and results were the same.

I watched carefully and note that the discharge terminates when the cells drop below .9 volts. This would be right but then I wonder if the voltage readings are even accurate. Frequently, slot1 will show .97v or around there while discharging at the same time the other slots are showing 1.15v. However, at the end all slots discharge to about the same level as I can swap the batteries around after discharge, and they all end within a minute of insertion.

Now why do I think the discharge isn't going to a low enough level? Well for one, these cells all tested near capacity in my bc900. Using the C9000 results in a much lower capacity reading. Secondly, after discharging the eneloop cells with the C9000, I proceeded to charge them up again at 1amp. When the 4 cells finished, the charger had inputted around 1800mah into all 4 cells.

Other C9000 owners, do you see the same thing? This is my first experience with 0G series units, my previous 0F units were much much closer to the bc900 in results.

 

[SilverFox]

Hello Bcwang,

Perhaps you could run another test and report back with your results...

Take your Eneloop cells. Charge them at 1000 mA. When the charger says "Done," wait 2 hours before removing the cells. You should now have fully charged cells.

Remove the cells, wait for 30 minutes, then stick them back in. Select discharge at the default 500 mA rate. Tell us what you get for a discharge capacity.

I have some Tenergy 2600 mAh cells that test out to 1800 mAh and some Powerex 2500 cells that test out to 2300 mAh, so your results are not totally beyond belief. Your Eneloop cells should come in slightly over 1900 mAh.

Tom

 

[GaryF]

My averaged results on cells with C9000, discharging at 500ma:

2390 - Powerex 2500
2670 - Sanyo 2700
1965 - Eneloop 2000
2040 - ROV Hybrid 2100
1960 - Fujifilm 1900

So to me, your numbers look low. I do tend to leave the batteries in for an hour or so after the charger says done - nothing real consistent or planned, I just don't watch it closely for termination.

I've been pleasantly surprised by the Powerex 2500's, as these were batteries I had forgotten in a headlamp for a year or so. They were completely dead when found, but came back after a forming charge and seem to be good cells, with a low self discharge for regular NiMH batteries.

 

[BrianChan]

C9000 charge and discharge not complete.

My charger works exactly the same as you described bcwang. Honestly I'm a bit disappointed with this charger. I have a OGOE02. I wished I had the older version which gives a fuller charge when it says 'done', not the current one when 'done' doesn't really mean 'done' and I have to wait another 2 hours for a full charge. To obtain the numbers other members have posted, you have to wait for 2 hours after the charge is complete. Since you are using a new unit you don't have much choice.

I have actually spent some time observing the charger during charging. My eneloops got around 1850mAh charge capacity too, and that's from a fully discharged cell. Another thing I have noticed is that no matter what charging rate or type of cell I put in, the charger always terminates the charge at 1.47v. Charging stops because the cells have reached 1.47v, not because it's full! I tried reinserting fully charged cells into a charger and set a different, lower charging rate and it stops at 1.47. I reinserted the cell again and set a ridiculous 200mA charge rate, and yes, it stopped charging at 1.47v. In another instance I tried taking fully charged cells out, waited for the voltage to drop to 1.45 and reinserting it again to charge, at 0.2C, it stops at 1.47 too. Tried inserting cells at 1.46v and they stopped at 1.47v. This is contrary to what William said that the -dV signal takes a few minutes to be detected. From what I have observed the voltage is capped at 1.47v. I have tried this around 20 times with various cells and came to this conclusion.

I have read in some older posts that the old units have the ability to charge beyond that. If they solved the missed termination problem just by capping the voltage at 1.47v during charging, I think that's not really solving the problem. People who like to fast charge like me end up with undercharged cells.:thumbsdow

The only way for the new units to go beyond 1.47v is to go into the test menu of the charger. I'll start a new thread on this.

 

[bcwang]

Hello Bcwang,

Take your Eneloop cells. Charge them at 1000 mA. When the charger says "Done," wait 2 hours before removing the cells. You should now have fully charged cells.

Tom

Additional info: the original post were values obtained using cycle mode, refresh mode, and plain discharge mode. I tried all of them and results are similar. Tom, I remember some post saying the 0G series c9000 top off during the 2 hour rest period in refresh and cycle mode, so if that's the case I should have a full charge however the capacity still shows very low.

I did additional testing:

Eneloop sitting for over 2 hours on c9000 after done signal. Took it off and waited overnight. Put into C9000 and discharge at 500mah, capacity is 1806mah. Took a second eneloop that I topped off in the C808M and put into the C9000 at 500ma shortly after finishing in C808M, capacity is 1876mah. Took a powerex 2500 mah fresh off the C808M charger in maintanence mode, measured 2263mah.

So it does look like things are ok on the discharge side of things. I guess the problem is the refresh and cycle modes don't get the battery fully charged before giving a reading on the capacity.

 

[Power Me Up]

Eneloop sitting for over 2 hours on c9000 after done signal. Took it off and waited overnight. Put into C9000 and discharge at 500mah, capacity is 1806mah. Took a second eneloop that I topped off in the C808M and put into the C9000 at 500ma shortly after finishing in C808M, capacity is 1876mah. Took a powerex 2500 mah fresh off the C808M charger in maintanence mode, measured 2263mah.

So it does look like things are ok on the discharge side of things. I guess the problem is the refresh and cycle modes don't get the battery fully charged before giving a reading on the capacity.

Those figures are still rather low for Eneloops...

It might be worthwhile for you to contact Maha and see if they can help you - you might just have a faulty unit. Maha are good for supporting their customers.

Before you do that, try checking the contacts on the charger - if they're dirty, it could cause the discharge to terminate early. I'd be surprised if this was actually the cause of the problem though if your results are consistent across all slots...

 

[TorchBoy]

Re: C9000 charge and discharge not complete.

Another thing I have noticed is that no matter what charging rate or type of cell I put in, the charger always terminates the charge at 1.47v. Charging stops because the cells have reached 1.47v, not because it's full!

My AAA cells typically stop at 1.46V, so I don't think your theory is quite correct. However, on the top up charge their voltage increases to 1.51V, so it doesn't look like peak voltage was reached before termination. It does look like it's using something other than -dV.

 

[bcwang]

Those figures are still rather low for Eneloops...

It might be worthwhile for you to contact Maha and see if they can help you - you might just have a faulty unit. Maha are good for supporting their customers.

Before you do that, try checking the contacts on the charger - if they're dirty, it could cause the discharge to terminate early. I'd be surprised if this was actually the cause of the problem though if your results are consistent across all slots...

I've actually got a second unit that I tested as well to see if it was a faulty unit, but both perform the same.

 

[Mitch470]

I've actually got a second unit that I tested as well to see if it was a faulty unit, but both perform the same.

Just go with the LaCrosse BC-900 Version 33 which is available now from Amazon for just $ 40.

 

[bcwang]

I've already got a bc900. In fact, I probably have way too many chargers.

I don't like how the BC900 heats up cells so much especially when charging 4 cells. I also don't like how it can't do a simple discharge and stop so I can measure performance of my other chargers.

But the point is I want to see if this trait is a defect in my version 0G0IA or if all the 0G show similar behavior. I'm getting mixed answers so far.

 

[GaryF]

I'll run a few cycles on my Eneloops over the next few days and report the results doing the 2 hour wait vs removing when done, and also the total mAh if the charge cycle, which is a number I've not paid close attention to. My C9000 is a 0G0B01, which is what I received from Thomas Distributing around the end of September. Again, it may take me a few days to run the tests I want to try.

 

[GaryF]

Here are my results on a pair of AA Eneloops in the C9000. All charges were at 1000 mA, discharges were at 500mA, with about 1 minute wait time between charge completion and beginning the discharge cycle. Cell 1 was always in slot 1, cell 2 was in slot 4.

Cycle 1 – batteries were topped off and left in the charger for 4 hours after "Done". Total mAh input is unknown for this first cycle.

Cell1---Cell2
1973----1974 mAh Out – Discharge

Cycle 2 – Batteries were charged and removed promptly at "Done" signal
Cell1---Cell2
1797----1834 mAh In - Charging
1879----1881 mAh Out – Discharge

Cycle 3 – Batteries were charged and removed promptly at "Done" signal
Cell1---Cell2
1792----1855 mAh In - Charging
1859----1865 mAh Out – Discharge

Cycle 4 – Batteries were charged and left in for 5-6 hours after "Done" signal
Cell1---Cell2
1781----1845 mAh In - Charging
2005----2009 mAh Out – Discharge


Conclusions…

Cells left in the charger for 2 or more hours after the "Done" signal show about 5-8% more capacity than cells that are removed immediately.

Surprisingly, on every test discharge cycle, the cells put out more mAh than the charger registered going in on the corresponding charge cycle, even when the cells were removed from charging promptly at the "Done" signal. My first thought was that the charger was erring on either the charge or the discharge calculation. On further reflection I realized that voltage probably comes into play, and that the batteries spend most of the charge cycle above 1.3 volts while spending most of the discharge cycle below 1.25 volts. If we could see the total Watt Hours it would give us a better comparative figure for charge vs discharge.

 

[bcwang]

Well I just had a false discharge termination. Was discharging 4 cells, most terminated around 1200mah but one finished around 300mah. I thought that was odd so I stuck it back in, and it did another 900 or so mah before it finished. Strange how that happened.

 

[Power Me Up]

Well I just had a false discharge termination. Was discharging 4 cells, most terminated around 1200mah but one finished around 300mah. I thought that was odd so I stuck it back in, and it did another 900 or so mah before it finished. Strange how that happened.

Interesting - I've seen something similar with my 0FAB02 unit - often with "crappy" cells, it'll terminate the discharge on some or all of the already inserted cells when a new cell is inserted. I've never seen it happen on my newer 0G0B01 units and only when the cells are crappy - i.e. when they don't actually hold a decent voltage under load - I'm guessing that somehow it incorrectly reads the voltage under load instead of offline like it normally does. (For those new to these discussions, the 0F units measure the voltage offline during discharge whereas the newer 0G units measure it under load - at least for my units - maybe they've changed things again with the latest revision...)

 

[Burgess]

very interesting info in this thread.


_

 

[jkraus]

I have only used the break in mode in my 0G0D01 revision. To my surprise, my brand new Sanyo 2500s never exceeded discharge capacities of 2380 mAh. In fact, two of the six are below 2300 mAh - even after 2 repeats. Rotating between bays did not make any difference. I repeated the charge in the Maha 204W charger (overnight) and the discharge capacities (as measured with the C9000) were identical.

Other cells (Energizer 2500 mAh) also scatter between 2380 and 2280, with one excelling at 2440 mAh.

I tickled 1805 mAh out of an old 1850 mAh energizer cell.

I am also wondering whether the discharge underestimates the capacity or whether the batteries are just not that great. After all, the differences in capacity estimates are independent of cutoff.

 

[bcwang]

Well I can't even break into 2300mah territory with any of my 2500mah cells on my 0G0IA unit, so you're doing pretty well.

 

[TorchBoy]

That's why I love Eneloops - they almost always exceed the rated capacity, not fall short by a couple hundred mAh. The last run I did they got over 2100mAh.

 

[bcwang]

I got 1806mah and 1876mah with my eneloop batteries and my 0G0IA charger.

 

[TorchBoy]

Four possibilities that I can think of off the top of me head...

1. The Eneloops are bad.
2. Your MH-C9000 is bad.
3. Your test procedure is bad.
4. Any combination of the above.

Know anyone close by who has another MH-C9000 that you could test some of your cells on?