What is the highest capacity NiMh AA?

[BatteryCharger]

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?

 

[TorchBoy]

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.

 

[BatteryCharger]

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.

 

[davidefromitaly]

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)

 

[TorchBoy]

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?

 

[BatteryCharger]

lacrosse chargers overrate at least 10%

Says who?

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.

 

[MarioJP]

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

 

[jcw122]

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.

 

[TorchBoy]

That I'll give you, but it is very, very miniscule.

[Ahem] "Says who?" :nana:

 

[BatteryCharger]

[Ahem] "Says who?" :nana:

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.

 

[TorchBoy]

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?

 

[BatteryCharger]

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.

 

[Bones]

...
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.
...

...
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.
...

 

[davidefromitaly]

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?

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...

 

[TorchBoy]

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.

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.

 

[Ragiska]

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"

 

[BatteryCharger]

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.

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! :laughing:

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)

 

[TorchBoy]

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. :twothumbs

 

[Ragiska]

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. :twothumbs

official specifications say 1.00v

where is .9v documented?

 

[TorchBoy]

official specifications say 1.00v

Hm, you're right. How strange. Looks like it was never updated.