NiMh Battery Shoot Out

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The most important factor determining cycle life is charging. Any amount of overcharge will shorten cycle life. Sanyo writes in their technical papers on NiMH cells that charging with -dV termination will shorten cycle life by about 20% compared to charging with 0dV (peak voltage detection). This is providing that the voltage drop that will triger shut-off is 10 mV per cell or less. Many chargers are not sensitive enough to detect this and will continue charging until 20-30 mV per cell is detected. Depending on the current you are chargin at this can cause excessive heating and increase of internal pressure. I estimate that the average fast "smart" -dV charger charging at something like 1000 mA with -dV termination shortens the cycle life by at least 30-40%. Many people don't care about it. Indeed the cells are more likely to be replaced by newer higher capacity ones before the end of their life. For heavy everyday users it may matter however. The problem is that some cells cannot take the abuse of a typicall fast -dV charger as we could see from Koala's pictures. I wouldn't consider something that heats my cells to 50C and above safe. Venting not only destroys your cells but is potentially very harmfull. See this electrolyte leaking. This is a very concentrated hydroxide solution. It causes burns upon contact with skin
 

SilverFox

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Hello Billson,

On single cell test I terminate at 0.8 volts and report to 0.9 volts.

On multi-cell tests I terminate at 0.9 volts per cell.

Tom
 

SilverFox

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Hello Rdshores,

I have some data from tests already done. I will be posting those test results shortly. It will not be as extensive as the AA tests, but should be a good sample.

Tom
 

rdshores

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SilverFox...
Thanks for the reply...I was curious because I have some 750ma Titanium AAA cells that only seem to test at 600ma on my BC-900. I know the Titanium 2400 AA cells are good, so I was wondering if the Titanium AAA were too.
 

SilverFox

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Hello Rdshores,

I know nothing about the Titanium AAA's.

600 mAh doesn't sound too bad for a discharge rate of 0.5 amps. To get to the 750 mAh, I think you need to discharge at about 0.15 amps.

What discharge rate were you using on the BC900?

Tom
 

rdshores

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SilverFox:

Written on the cell label is:
Standard Charge: 15 hrs at 75ma
Fast Charge: 5 hrs at 225ma

Therefor I left the BC900 set on the default 200ma charge setting, which gives 100ma discharge when doing the refresh cycle. I didn't think I should go up to 500ma charge rate.
 

SilverFox

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Hello Rdshores,

In that case they don't seem to be doing very well. Are they consistant from cell to cell?

I will have to check my data on other brands of AAA cells to see if any of the other brands do any better.

Tom
 

rdshores

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TESTED WITH LA-CROSSE BC-900

POWERIZER 750MAH AAA
CELL A 517MAH CHARGED:500MA REFRESH CYCLE
CELL B 541MAH CHARGED:500MA REFRESH CYCLE
CELL C 582MAH CHARGED:500MA REFRESH CYCLE
CELL D 570MAH CHARGED:500MA REFRESH CYCLE

TITANIUM 750MAH AAA
CELL A 447 MAH CHARGED:500MA REFRESH CYCLE
CELL B 580 MAH CHARGED:500MA REFRESH CYCLE
CELL C 412 MAH CHARGED:500MA REFRESH CYCLE
CELL D 569 MAH CHARGED:500MA REFRESH CYCLE

NEXCELL 800MAH AAA
CELL A 737 MAH CHARGED:500MA REFRESH CYCLE
CELL B 772 MAH CHARGED:500MA REFRESH CYCLE
CELL C 788 MAH CHARGED:500MA REFRESH CYCLE
CELL D 790 MAH CHARGED:500MA REFRESH CYCLE

LA CROSSE 700MAH AAA
CELL A 657 MAH CHARGED:500MA REFRESH CYCLE
CELL B 656 MAH CHARGED:500MA REFRESH CYCLE
CELL C 683 MAH CHARGED:500MA REFRESH CYCLE
CELL D 693 MAH CHARGED:500MA REFRESH CYCLE
 

SilverFox

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Hello Ted,

Welcome to CPF.

They sure look like them, but there are some very good copies out there. While they may look like Sanyo's, the question is do they perform like Sanyo's? Perhaps you could send an email to the seller to find out more information.

If you need the cells for a critical application, I would get them from an authorized dealer to be sure of their performance. If you just need them for fooling around, try them out and report back to us.

Tom
 

tedSmith123

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Thanks for that SilverFox, seller is from HK so very likely they are just copies. I suppose if they are real Sanyo, he would have made it clear. Anyway, I will shoot them a mail to confirm.
 

Bullzeyebill

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tedSmith123, delete your second paragraph, and open a new thread in this forum, asking the same question. Go to POST in the header at the top of this forum, and open your thread.

Bill
 

greenlight

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Cheers to SilverFox for compressing his graphs to loadable size! I'm not sure what to do with all the data, but at least I can read it now.
 

pcmike

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Tom,

Per KevinL's recommendation I would like to check with you regarding Titanium 2600 mAh cells. Would they be considered 'high drain' and 'high current?' Are they capable of a 5A draw? Thanks!
 

pcmike

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Tom,

This is my first foray into rechargeables and I'm trying to select some good high current, high drain batteries for flashlight use (they need to be able to do 5A really well) and for general home use (in a GPS, in a Canon 420EX flash, etc). After looking over the different graphs I believe a good choice would be the Sanyo 2500mAh industrial cells; however I may be reading the graphs wrong, who knows. Would you concur? Are these a good choice for high current, high drain, high capacity cells? Also, by any chance do you or anyone else know if three of these fit fine in the Elektrolumens 3AAtoD holders? Thanks again!
 

SilverFox

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Hello PCMike,

At 5 amps the top performers were (in no particular order):

Titanium 2400
Sanyo 2500 HR 3U
Jetcell 2400
AccuPower 2600
Energizer 2500
and the Ansmann 2300 were a bit behind, but strong.

Unfortunately I did not measure how the cells fit into the various adaptors.

Tom
 
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