My Eneloops charge to and hold a higher voltage than other LSD's

[cam94z28]

I have noticed this recently on my C-9000. At the end of charge, the voltage will rise very quickly and they will often charge to 1.50 to 1.52v, and hold at about 1.49 for several days. Other cells terminate right at 1.48, and drop over the next few hours to 1.4. I've never had another cell terminate or stay above 1.48 volts with this charger.

Does this indicate that these are strong cells? Is this a trait of proper LSD design. Other LSD brands don't show these characteristics, so they probably use a different process. My Sanyo 2500's, and 2300's don't do this either, so it's not a Sanyo thing.

 

[VidPro]

Re: Eneloops charge to and hold a higher voltage than other LSD's

why is everything so complex
they terminate higher because they are slightly more robust, so they dont go into an overcharge state as quickly.
they stay a bit higher for longer, because of the reduced self discharge itself, and mabey a bit due to the chemistry.

a weak cruddy cell, can get as high as 1.6v on termination, because the resistance is higher on the cell, the cell is not as "tight".

but really your talking such minor ammounts, that age, vibrance, use, cycles, temps and all that other stuff would change all that.

 

[cam94z28]

I think it's more along the lines of me over complicating everything.

I thought that was a sign of a good cell. Considering most of my cells are fairly new or in good shape, and none do this, the LSD chemistry must be to blame.

My Hybrids, and Kodak PreCharged have quite a bit higher discharge capacities, but I guess the Eneloops will hold up longer. They show about 1.60v on the initial resistance test on my c-9000.

 

[VidPro]

well i am taking it all in anyways, just keep the data comming.

 

[Curious_character]

Open circuit voltage (or, for that matter, voltage under load) doesn't tell you anything about the "strength" or quality of a NiMH cell. High voltage immediately after charging indicates to some extent how much the cells were overcharged. Within seconds of when you begin discharging at a moderate rate, the voltage will drop to around 1.3 to 1.35 volts regardless of the voltage off the charger.

c_c

 

[wasBlinded]

In my simple tests, the Eneloops do hold a higher voltage than the Ray-O-Vac Hybrids during a discharge cycle. This even though the C-9000 gives the Hybrids about a 100 mAh total capacity advantage. This higher voltage can be important in some electronics that are not designed specifically for NiMh cells.

 

[Curious_character]

In my simple tests, the Eneloops do hold a higher voltage than the Ray-O-Vac Hybrids during a discharge cycle. This even though the C-9000 gives the Hybrids about a 100 mAh total capacity advantage. This higher voltage can be important in some electronics that are not designed specifically for NiMh cells.

Electronic circuits designed to run from alkaline cells should be able to function with a cell voltage from about 1.55 down to 0.9 volt. Otherwise, the circuit will quit before the energy is removed from the cell. If it quits at, say, 1.2 volt, you'll be throwing away cells which have half or more of their energy remaining (depending on load). That's why virtually any NiMH cell will work fine in any device that's properly designed to function with alkaline cells. The real advantage of a higher discharge voltage is in constant-power consumption devices, such as flashlights with a switching regulator (typical of non-direct drive LED flashlights). In those devices, higher cell voltage will result in lower current consumption and hence longer run time.

I wonder if the voltage difference is due to chemistry or if the Ray-O-Vacs have a higher internal resistance. If it's the latter, the voltage difference will be greater at higher discharge rates. Unfortunately, I don't have any Ray-O-Vacs, so can't run the tests myself.

c_c

 

[wptski]

Electronic circuits designed to run from alkaline cells should be able to function with a cell voltage from about 1.55 down to 0.9 volt. Otherwise, the circuit will quit before the energy is removed from the cell. If it quits at, say, 1.2 volt, you'll be throwing away cells which have half or more of their energy remaining (depending on load). That's why virtually any NiMH cell will work fine in any device that's properly designed to function with alkaline cells. The real advantage of a higher discharge voltage is in constant-power consumption devices, such as flashlights with a switching regulator (typical of non-direct drive LED flashlights). In those devices, higher cell voltage will result in lower current consumption and hence longer run time.

I wonder if the voltage difference is due to chemistry or if the Ray-O-Vacs have a higher internal resistance. If it's the latter, the voltage difference will be greater at higher discharge rates. Unfortunately, I don't have any Ray-O-Vacs, so can't run the tests myself.

c_c

c_c:

You've stated the same thing before. Why don't you run the some tests on various AA powered devices that have a low battery alarm/icon and record at what voltage under the lolad that the alarm starts?

Voltage under load doesn't tell you anything??? Are you kidding?

 

[TorchBoy]

Voltage under load doesn't tell you anything??? Are you kidding?

+1. The Eneloops hold their voltage under load so well that Tom tested them at 10A and they still got over 1.5Ah. That tells me they're great cells.

 

[cam94z28]

+1. The Eneloops hold their voltage under load so well that Tom tested them at 10A and they still got over 1.5Ah. That tells me they're great cells.

I never would have even considered testing LSD cells that high. I do have a CBA now, but I've only tested them up to 1 amp. Maybe I'll put my Hybrids, Hybrio's, and Kodak PreCharged cells to the test.

 

[TorchBoy]

I never would have even considered testing LSD cells that high.

I can remember in the good(?) old days being told that NiMH cells couldn't provide that sort of current, that only NiCd (of the two) had a low enough internal resistance for it.

 

[Curious_character]

+1. The Eneloops hold their voltage under load so well that Tom tested them at 10A and they still got over 1.5Ah. That tells me they're great cells.

I'm sorry, I didn't say very well what I meant.

Certainly, if two cells have the same mAh capacity (total charge), the one which has a higher voltage under the same load will produce more energy than one with a lower voltage. But you can have a low-capacity cell with high voltage and a much higher-capacity cell with lower voltage which will deliver more energy. So knowing nothing but the cell voltage doesn't tell you which cell will deliver more energy.

c_c

 

[TorchBoy]

So knowing nothing but the cell voltage doesn't tell you which cell will deliver more energy.

:thinking: Do you mean knowing the instantaneous voltage under load isn't much use?

 

[wptski]

If voltage under load was meaningless, there'd be no use for a CBA-II and its graphs!

 

[chevrofreak]

My Uniross Hybrio cells will hold 1.42v for several days after being charged, but my Kodak Pre-Charged cells drop to 1.375 volts within only a few hours.

The Kodaks run substantialy longer in my flashlights, though. I think the higher voltage of the Uniross cells (and perhaps the Eneloops) would be good for use in devices that are voltage sensitive, requiring about 1.5v each.