Eneloop voltage?

[Mr Happy]

I've noticed that in a few discharge studies, such as this one:

http://translate.google.com/transla...?q=%22eneloop+r%22&num=50&hl=en&safe=off&sa=G

(scroll down for the graphs), the recorded voltage during discharge is quite high, typically 1.25 V to 1.30 V and level right through most of the discharge.

This is puzzling me since none of the Eneloops I have tested on the C9000 maintain more than 1.20 V during the flat part of the discharge. I've never seen 1.25 V, let alone 1.30 V.

Does anyone else have different numbers to report? Is it because of the age of the cells (mine are all 2006 vintage), or is it a characteristic of how the C9000 measures the voltage?

 

[SilverFox]

Hello Mr Happy,

I ended up with a mid point voltage of 1.27 volts at a 0.5 amp discharge rate, and 1.24 volts at 1 amp.

After 150 cycles charging with the Energizer 15 minute charger, the mid point voltage dropped to 1.11 volts.

Tom

 

[Bullzeyebill]

Hello Mr Happy,

I ended up with a mid point voltage of 1.27 volts at a 0.5 amp discharge rate, and 1.24 volts at 1 amp.

After 150 cycles charging with the Energizer 15 minute charger, the mid point voltage dropped to 1.11 volts.

Tom

Tom, do you attribute the drop to 1.11 volts to the fast charging of the Energizer 15 minute charger, and would it be different with a charging rate of 1C, or so.

Bill

 

[UnknownVT]

If this is of any use -
I used fixed wirewound resistors and took voltage and current reading on an eneloop AA which had been discharged to probably about 1/2 capacity - I compare the eneloop directly with a Kodak Pre-Charged LSD - in post #47 of eneloop vs. Kodak Pre-Charged Voltage Maintenance

I partially discharged the same 2 batteries in the Dorcy 45lumen 1AA flashlights for about 25 minutes - probably to approx half capacity - ie: about 1/2 the runtime until the lights would not turn on again (see post #11). Allowed the batteries to rest/cool down for about 1.2 hours (as those lights run noticably warm - so the batteries were warm at end of discharge).

Readings -

Open-circuit (o-c) -
ene 1.298V; FA=10.4A; 1.293V
KPC 1.273V; FA=9.9A; 1.267V

2 ohm load -
ene 1.266V @ 0.60A
KPC 1.243V @ 0.59A

1 ohm -
ene 1.247V @ 1.17A
KPC 1.220V @ 1.14A

0.5 ohm -
ene 1.224V @ 2.09A
KPC 1.176V @ 2.01A

ending o-c -
ene 1.294V
KPC 1.267V

eneloop AA with 1 ohm load @ a current draw of 1.17A the voltage was 1.247V
- in comparison -
Kodak P-C w. 1 ohm @ 1.14A = 1.220V

These seem slightly lower than this 1 ohm load graph from this Translated Page comparing eneloop with Sony CycleEnergy and Panasonic R2 (from same website)

 

[SilverFox]

Hello Bill,

As cells are charged and discharged, their internal resistance increases. I would think that ultra rapid charging would be harder on the cells than 1C charging, but these Eneloop cells came through the 15 minute charging and are still performing better than I expected they would.

So far, it seems that if you want to kill Eneloop cells you need to over discharge them, and/or leave them on a charger with a high rate of trickle charge for an extended period of time.

Tom

 

[Anders]

Hello mister Happy.

I had similar results as Silverfox and I also ended up with a mid point voltage of 1.27 volts at a 0.5 amp discharge rate, but 1.23 volts at 1 amp.

The results is from 2007-12-21 with Eneloop marked 2006-08.


Anders