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Thread: What is the highest capacity NiMh AA?

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    Default What is the highest capacity NiMh AA?

    I'm just curious here, I know we've kind of hit a wall in terms of capacity for NiMh, and, some have actually started having a lower capacity. Who makes the absolute highest capacity (in real life, not on the label) NiMh AA?

    I have a small handfull of Duracell 2650's that measure reliably at 2.8ah in my BC700. But I had to pick them out of hundreds of lower capacity batteries. Do any other batteries meet or beat that?
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    Flashaholic* TorchBoy's Avatar
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    Default Re: What is the highest capacity NiMh AA?

    Are you looking at the charging capacity or the discharging capacity? 2.8 Ah sounds a bit high, even with fussy selection from a population of hundreds.
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    Default Re: What is the highest capacity NiMh AA?

    As per the "charge/test" mode on my BC700 at 700/350ma. They are few and far between, but I get consistent results if I test them over and over. Most of the rest of the "2650" batteries are in the 2.5x or 2.6x range in the same test.
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    Default Re: What is the highest capacity NiMh AA?

    Quote Originally Posted by TorchBoy View Post
    Are you looking at the charging capacity or the discharging capacity? 2.8 Ah sounds a bit high, even with fussy selection from a population of hundreds.
    lacrosse chargers overrate at least 10%

    and they start the discharge just after the charge so can count on a little overcharge state of the battery

    from my tests, duracell 2650 give around 2450-2400mAh after 24 hours from the charge at 1A of load

    the best in the same condition are the sanyo 2700 with 2550mAh of average (but they have a higher self discharge)

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    Flashaholic* TorchBoy's Avatar
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    Default Re: What is the highest capacity NiMh AA?

    Quote Originally Posted by davidefromitaly View Post
    lacrosse chargers overrate at least 10%

    and they start the discharge just after the charge so can count on a little overcharge state of the battery
    So you think the high figure could indeed be a discharge figure skewed by those two factors?
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    Default Re: What is the highest capacity NiMh AA?

    Quote Originally Posted by davidefromitaly View Post
    lacrosse chargers overrate at least 10%
    Says who?

    Quote Originally Posted by davidefromitaly View Post
    and they start the discharge just after the charge so can count on a little overcharge state of the battery
    That I'll give you, but it is very, very miniscule.

    Also I'm more curious about ratings as the battery MFG would rate them, with about a C/5 discharge.
    I got a fever and the only prescription is more cowbell.

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    Default Re: What is the highest capacity NiMh AA?

    What I would do is let them rest after charging. Want to simulate real world capacity.

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    Default Re: What is the highest capacity NiMh AA?

    From what I've read, it's the PowerEx 2700mah or Maha 2700mah AAs. The reason you see many brands making "lower" capacity cells is probably because they are Low Discharge cells, so they don't lose their charge over a month's time like most NiHMs.
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    Default Re: What is the highest capacity NiMh AA?

    Quote Originally Posted by BatteryCharger View Post
    That I'll give you, but it is very, very miniscule.
    [Ahem] "Says who?"
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    Default Re: What is the highest capacity NiMh AA?

    Quote Originally Posted by TorchBoy View Post
    [Ahem] "Says who?"
    I think we all understand and agree that a small overcharge stored in the battery temporarily is not going to be (and CAN'T be) more than a handfull of mAh.

    Never heard of anyone else accusing the LaCrosse charger of being inaccurate besides the lack of a wait period between charge and discharge.
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    Default Re: What is the highest capacity NiMh AA?

    I'm sure someone on CPF will have tested that - I'll see if I can find something to link to. But how would a battery store an overcharge, even temporarily?
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    Default Re: What is the highest capacity NiMh AA?

    Quote Originally Posted by TorchBoy View Post
    But how would a battery store an overcharge, even temporarily?
    That's exactly why it's so small. It has no place to store anything extra besides some high voltage.

    Now, claiming the charger brand is "10% off" are some pretty substantial claims that I've never seen backed up before. If anybody has evidence to the contrary I'd love to read it.

    The fact is EVERY "machine" that tests batteries is going to give a slightly different result, so it's really hard to say which one is telling the truth. That's not to say a $30 BC700 is the most accurate thing in the world...

    It's kind of like horsepower ratings, if you take your car to a dynomometer, you'll get a slightly different horsepower result depending on which dynomometer you use.
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    Default Re: What is the highest capacity NiMh AA?

    Quote Originally Posted by BatteryCharger View Post
    ...
    Now, claiming the charger brand is "10% off" are some pretty substantial claims that I've never seen backed up before. If anybody has evidence to the contrary I'd love to read it.

    The fact is EVERY "machine" that tests batteries is going to give a slightly different result, so it's really hard to say which one is telling the truth. That's not to say a $30 BC700 is the most accurate thing in the world...

    It's kind of like horsepower ratings, if you take your car to a dynomometer, you'll get a slightly different horsepower result depending on which dynomometer you use.
    ...
    Quote Originally Posted by willchueh View Post
    ...
    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.
    ...
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    Default Re: What is the highest capacity NiMh AA?

    thanks to bones, thats the post i refer, and more, all the test we see on the net the ones made by lacrosse are higher than other... so is possible that nobody say nothing? lacrosse read more than 2000mAh on eneloops while all other chargers read 1850-1900... we need a detective to understand that the lacrosse overrate?


    Quote Originally Posted by TorchBoy View Post
    I'm sure someone on CPF will have tested that - I'll see if I can find something to link to. But how would a battery store an overcharge, even temporarily?
    a nimh battery have a oversized negative electrode, it work like a reserve in case of overcharge or overdischarge. the overcharged state selfdischarge in few hours. this reserve can be around 10% on high cap cells up to 50% to special batts like standby cells or high temp cells...

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    Default Re: What is the highest capacity NiMh AA?

    Quote Originally Posted by davidefromitaly View Post
    lacrosse read more than 2000mAh on eneloops while all other chargers read 1850-1900...
    I've had as high as 2116 mAh on my MH-C9000 testing Eneloops with a few charge cycles on them, using the break-in mode.

    Quote Originally Posted by davidefromitaly View Post
    a nimh battery have a oversized negative electrode, it work like a reserve in case of overcharge or overdischarge. the overcharged state selfdischarge in few hours. this reserve can be around 10% on high cap cells up to 50% to special batts like standby cells or high temp cells...
    OK, that's interesting. That's quite a significant amount. Any idea how heat affects that? When the cells are overcharged they'll be hot, which will improve performance until they cool down.
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    Default Re: What is the highest capacity NiMh AA?

    well, the lacrosse "overrates" compared to the c9000, but it's the c9000 that actually underrates. it uses a 1v cutoff instead of the .9v industry standard, and has a reputation for undercharging LSD cells due to termination on max V instead of -dV.

    when the c9000 says "done" it really means "almost done, I have to do a trickle top off charge for another 2 hours now"

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    Default Re: What is the highest capacity NiMh AA?

    Quote Originally Posted by davidefromitaly View Post
    lacrosse read more than 2000mAh on eneloops while all other chargers read 1850-1900... we need a detective to understand that the lacrosse overrate?
    10% that is not.

    Quote Originally Posted by Ragiska View Post
    well, the lacrosse "overrates" compared to the c9000, but it's the c9000 that actually underrates. it uses a 1v cutoff instead of the .9v industry standard, and has a reputation for undercharging LSD cells due to termination on max V instead of -dV.

    when the c9000 says "done" it really means "almost done, I have to do a trickle top off charge for another 2 hours now"
    Oh snap!

    Like I said, no matter what machine you use they're all going to give you a different number, and so is every individual battery. Even if you want to call it "labratory grade" you will find variation between manufacturers and individual cells.

    It doesn't matter if the machine is totally wrong, if you're only comparing results against the same machine. (IE my 2.8ah batteries came out of the same machine that names most as 2.5ah)
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    Default Re: What is the highest capacity NiMh AA?

    Quote Originally Posted by Ragiska View Post
    well, the lacrosse "overrates" compared to the c9000, but it's the c9000 that actually underrates. it uses a 1v cutoff instead of the .9v industry standard, and has a reputation for undercharging LSD cells due to termination on max V instead of -dV.
    It uses 0.9 V under load (you might be thinking of the first firmware, which was changed, oh, about 3 years ago, and used a non-standard 1.0 V unloaded). In SilverFox's charger comparison the MH-C9000 scored second best. In the test, for all chargers, "cells pulled as soon as charge end signaled". So no top up, charge finished on max V, and it still got second best result.
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    Default Re: What is the highest capacity NiMh AA?

    Quote Originally Posted by TorchBoy View Post
    It uses 0.9 V under load (you might be thinking of the first firmware, which was changed, oh, about 3 years ago, and used a non-standard 1.0 V unloaded). In SilverFox's charger comparison the MH-C9000 scored second best. In the test, for all chargers, "cells pulled as soon as charge end signaled". So no top up, charge finished on max V, and it still got second best result.
    official specifications say 1.00v

    where is .9v documented?

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    Default Re: What is the highest capacity NiMh AA?

    Quote Originally Posted by Ragiska View Post
    official specifications say 1.00v
    Hm, you're right. How strange. Looks like it was never updated.
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  21. #21

    Default Re: What is the highest capacity NiMh AA?

    My C9000 when discharging is using 0.9V under load as a cut off.

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    Default Re: What is the highest capacity NiMh AA?

    I have also observed my MH-C9000 discharge down to 0.9 volts.

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    Default Re: What is the highest capacity NiMh AA?

    Quote Originally Posted by TorchBoy View Post
    Hm, you're right. How strange. Looks like it was never updated.
    As far as I know, the manual that comes with the C9000, as well as the .pdf one, has never been changed to reflect the updates to the charger. It is the same one that was provided with the very first C9000's.

    Dave

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    Default Re: What is the highest capacity NiMh AA?

    I compared the present web site version with one on my computer dated 2006 and they have the same revision/print number.
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    Default Re: What is the highest capacity NiMh AA?

    Quote Originally Posted by TorchBoy View Post
    I've had as high as 2116 mAh on my MH-C9000 testing Eneloops with a few charge cycles on them, using the break-in mode
    for what i know, the maha is quite accurate (maybe 2-3% of difference that is nothing), so 2116 for a eneloop or your maha is damaged or your eneloops aren't original. have you done a self discharge test? try to test the batteries after 30 days from the last charge

    break-in overcharge the battery ok but 2116 is too much...

    i'm just curious

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    Default Re: What is the highest capacity NiMh AA?

    Quote Originally Posted by davidefromitaly View Post
    so 2116 for a eneloop or your maha is damaged or your eneloops aren't original. ...

    break-in overcharge the battery ok but 2116 is too much...
    It is curious. In slot order for that break-in: 2092, 2115, 2100, 2116. When they were new I think they got scored an average 2008. Maybe it's about time to test them all again.
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    Default Re: What is the highest capacity NiMh AA?

    Quote Originally Posted by davidefromitaly View Post
    break-in overcharge the battery ok but 2116 is too much...
    At the risk of contributing to going OT, which I am often guilty of , I just thought I'd mention that when I broke in my first batch of 20 eneloops, the capacity was ~2100mAh. I attributed this to having discharged the cells first @ 100mA, rather than 400, or 500mA before starting the break in. The capacity was about 100mAh higher than most everyone else was getting, and I noted it in a post somewhere.

    These cells were about 2 years old when I obtained them (date code 8/2006). I had been researching (OK, playing) with the reduction of large crystal formation in standard NiMh cells at the time. I didn't know if eneloops had this problem, but figured a very slow discharge before the break in wouldn't hurt anything, especially since they had been in storage for ~2 years. After obtaining 100-150mAh higher capacity than most everyone else was getting, I concluded that this did make a difference, and eneloops can suffer from large crystal formation to some degree when stored for long periods.

    Anyway, I just wanted to point out, that it is possible for new eneloops to achieve ~2100mAh on the Maha C9000. It may require that the cells be fairly new, or a very slow discharge may be necessary first to do so, but it is possible.

    Dave

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    Default Re: What is the highest capacity NiMh AA?

    I think SilverFox has mentioned that capacity on new NiMH cells can increase slightly after a bit of cycling.
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    Default Re: What is the highest capacity NiMh AA?

    Quote Originally Posted by TorchBoy View Post
    I think SilverFox has mentioned that capacity on new NiMH cells can increase slightly after a bit of cycling.
    Yeah, it's pretty well known that standard NiMH cells don't achieve their maximum capacity for 25-50 cycles. I have no reason to doubt that LSD cells would be any different. I was just saying that you can get ~2100mAh on the first "break-in" on a C9000. Of course, it's also possible to get readings, as you have, after that. With new cells that have been in storage until you get them though, I doubt it's possible to get more than 1900-2000mAh, unless you do a slow discharge first.

    Dave

  30. #30

    Default Re: What is the highest capacity NiMh AA?

    Quote Originally Posted by 45/70 View Post
    As far as I know, the manual that comes with the C9000, as well as the .pdf one, has never been changed to reflect the updates to the charger. It is the same one that was provided with the very first C9000's.

    Dave
    The original C-9000 momentarily disconnected the load to measure voltage, so it was discharging to 1.0 volt (as I recall) with no load. Newer ones leave the load connected, so they're measuring the voltage under load. Besides the drop due to cell internal resistance, there's an additional drop due to contact resistance. That's probably why they lowered the cutoff.

    A problem with the original scheme was in measuring cells with high internal resistance -- I discovered this when measuring some of the notorious Energizer cells. It would show the cell capacity to be much higher than a straight constant current discharge -- or operation in a flashlight -- would.

    I have both an older and newer one. The indicated cell voltage during discharge is noticeably lower on the newer one because of the different method.

    c_c

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