High-capacity NiMH cells -- very rapid self-discharge common?

I recently bought some cheap no-name (actually "Tenergy," whatever that is)
2600mAh AA cells on eBay. I haven't tried to assess the accuracy of their
rating, don't know how I'd do that anyway, but I'm flabbergasted by how fast
they self-discharge -- a couple days or so, sometimes almost overnight, it
seems. Tried leaving them on charge overnight, no difference. Tried
"conditioning" them in a Maha C204W, still no difference. Charged with a
Maha C401FS, individual charging circuits for each cell, still no
difference. So far they do not seem to improve with use either.

So I tried some more cheap no-name (really no-name this time, just cell info
on a pale green case) 2600mAh cells from a different eBay source. Pretty
much the same thing. From fully charged they go flat amazingly fast with no
use at all. Not actually zero-voltage flat, they'll still light a two-cell
flashlight, but flat enough that a couple of days after charging they won't
operate an old four-cell Minolta S404 for more than a few shots.

I've used no-name (or unheard-of name) NiMH cells from eBay sellers before,
with excellent and reliable results, and most of those cells are still
giving me good results after several years. But they were of lower capacity,
2000 mAh or less. So I'm wondering if fast self-discharge is a
characteristic of these newer 2600mAh NiMH cells in general, or if it's just
that cheap cells ain't what they used to be.

Neil

I have similar experiences with many NiMH cells and batteries.

I now use Eneloops for many applications.

On Jun 24, 4:36*pm, "Neil Harrington" <n...@home.today> wrote:
> I recently bought some cheap no-name (actually "Tenergy," whatever that is)
> 2600mAh AA cells on eBay. I haven't tried to assess the accuracy of their
> rating, don't know how I'd do that anyway, but I'm flabbergasted by how fast
> they self-discharge -- a couple days or so, sometimes almost overnight, it
> seems. Tried leaving them on charge overnight, no difference. Tried
> "conditioning" them in a Maha C204W, still no difference. Charged with a
> Maha C401FS, individual charging circuits for each cell, still no
> difference. So far they do not seem to improve with use either.
>
> So I tried some more cheap no-name (really no-name this time, just cell info
> on a pale green case) 2600mAh cells from a different eBay source. Pretty
> much the same thing. From fully charged they go flat amazingly fast with no
> use at all. Not actually zero-voltage flat, they'll still light a two-cell
> flashlight, but flat enough that a couple of days after charging they won't
> operate an old four-cell Minolta S404 for more than a few shots.
>
> I've used no-name (or unheard-of name) NiMH cells from eBay sellers before,
> with excellent and reliable results, and most of those cells are still
> giving me good results after several years. But they were of lower capacity,
> 2000 mAh or less. So I'm wondering if fast self-discharge is a
> characteristic of these newer 2600mAh NiMH cells in general, or if it's just
> that cheap cells ain't what they used to be.
>
> Neil

Have you put a V meter on them to see if they even charge and what the
discharge is. I can let them sit a month and still have use, but not
cheap no names. Try Eneloop are a different design, but measure what
voltage your chargers give, mine charge to 1.5v or so

"ransley" <Mark_Ransley@yahoo.com> wrote in message
news:9aac17c6-752c-4db5-933a-f7a8c4f8c6d1@56g2000hsm.googlegroups.com...


Have you put a V meter on them to see if they even charge and what the
discharge is. I can let them sit a month and still have use, but not
cheap no names. Try Eneloop are a different design, but measure what
voltage your chargers give, mine charge to 1.5v or so

________________

Good idea, I will check the charging voltages. But my Maha chargers are the
same ones I've been using with other NiMH cells for a long time, with no
problems.

As for discharge, I suppose I could get a suitable resistor from Radio
Shack, rig up a multitester somehow and plot the discharge curve -- but
that's really more tedious than I care to get into, unless there's a simpler
method that hasn't occurred to me. I used to do that 30+ years ago with NiCd
battery packs when I was flying R/C models.

Neil

"Charles" <charlesschuler@comcast.net> wrote in message
news:jfWdnQnZy48L8fzVnZ2dnUVZ_o3inZ2d@comcast.com. ..
>
>
> I have similar experiences with many NiMH cells and batteries.
>
> I now use Eneloops for many applications.

Yep, Eneloops are probably the answer. Never used 'em before, but I just
ordered a 4-pack yesterday.

Neil

"Neil Harrington" <not@home.today> wrote in message
news:8dmdnTllDsRW6vzVnZ2dnUVZ_gWdnZ2d@comcast.com. ..
>
> "Charles" <charlesschuler@comcast.net> wrote in message
> news:jfWdnQnZy48L8fzVnZ2dnUVZ_o3inZ2d@comcast.com. ..
>>
>>
>> I have similar experiences with many NiMH cells and batteries.
>>
>> I now use Eneloops for many applications.
>
> Yep, Eneloops are probably the answer. Never used 'em before, but I just
> ordered a 4-pack yesterday.

I'll predict that you will like them.

The mAH rating is highly overrated ;>)

On Tue, 24 Jun 2008 17:36:35 -0400, Neil Harrington wrote:
> I recently bought some cheap no-name (actually "Tenergy," whatever that is)
> 2600mAh AA cells on eBay. I haven't tried to assess the accuracy of their
> rating, don't know how I'd do that anyway, but I'm flabbergasted by how fast
> they self-discharge -- a couple days or so, sometimes almost overnight, it
> seems.

Are they "2600mAh" cells, or "Up to 2600mAh" cells? :-)
A set of Panasonics I bought state "Up to 2100 mAh". They are working
ok for me -- so far. But, when they go dead, Dead, DEAD , they will
still meet Panasonic's 'specifications'.

Jonesy
--
Marvin L Jones | jonz | W3DHJ | linux
38.24N 104.55W | @ config.com | Jonesy | OS/2
*** Killfiling google posts: <http://jonz.net/ng.htm>

Neil Harrington wrote:
> "ransley" <Mark_Ransley@yahoo.com> wrote in message
> news:9aac17c6-752c-4db5-933a-f7a8c4f8c6d1@56g2000hsm.googlegroups.com...
>
>
> Have you put a V meter on them to see if they even charge and what the
> discharge is. I can let them sit a month and still have use, but not
> cheap no names. Try Eneloop are a different design, but measure what
> voltage your chargers give, mine charge to 1.5v or so
>
> ________________
>
> Good idea, I will check the charging voltages. But my Maha chargers are the
> same ones I've been using with other NiMH cells for a long time, with no
> problems.
>
> As for discharge, I suppose I could get a suitable resistor from Radio
> Shack, rig up a multitester somehow and plot the discharge curve -- but
> that's really more tedious than I care to get into, unless there's a simpler
> method that hasn't occurred to me. I used to do that 30+ years ago with NiCd
> battery packs when I was flying R/C models.
>
> Neil
>
>
The good folks over at CandlePowerForums
http://www.candlepowerforums.com/vb/...d.php?t=149804 have studied
this subject extensively. Might save yourself some time and energy in
reviewing what they did before doing any analysis yourself.

Clair

On Jun 24, 5:43*pm, "Neil Harrington" <n...@home.today> wrote:
> "ransley" <Mark_Rans...@yahoo.com> wrote in message
>
> news:9aac17c6-752c-4db5-933a-f7a8c4f8c6d1@56g2000hsm.googlegroups.com...
>
> Have you put a V meter on them to see if they even charge and what the
> discharge is. I can let them sit a month and still have use, but not
> cheap no names. Try Eneloop are a different design, but measure what
> voltage your chargers give, mine charge to 1.5v or so
>
> ________________
>
> Good idea, I will check the charging voltages. But my Maha chargers are the
> same ones I've been using with other NiMH cells for a long time, with no
> problems.
>
> As for discharge, I suppose I could get a suitable resistor from Radio
> Shack, rig up a multitester somehow and plot the discharge curve -- but
> that's really more tedious than I care to get into, unless there's a simpler
> method that hasn't occurred to me. I used to do that 30+ years ago with NiCd
> battery packs when I was flying R/C models.
>
> Neil

I just meant check the voltage when they dont work, my old old cells
still charge to 1.35-4, it could be the camera, but Sanyo, Panasonic,
Duracell, Energiser are good. Running RC stuff im suprised you dont
stick with Sanyo as they are the standard of quality. Eneloops I think
are the way to go, slightly less amps but a little self discharge.

Clair Johnston wrote:
> Neil Harrington wrote:
>
>> "ransley" <Mark_Ransley@yahoo.com> wrote in message
>> news:9aac17c6-752c-4db5-933a-f7a8c4f8c6d1@56g2000hsm.googlegroups.com...
>>
>>
>> Have you put a V meter on them to see if they even charge and what the
>> discharge is. I can let them sit a month and still have use, but not
>> cheap no names. Try Eneloop are a different design, but measure what
>> voltage your chargers give, mine charge to 1.5v or so
>>
>> ________________
>>
>> Good idea, I will check the charging voltages. But my Maha chargers
>> are the same ones I've been using with other NiMH cells for a long
>> time, with no problems.
>>
>> As for discharge, I suppose I could get a suitable resistor from Radio
>> Shack, rig up a multitester somehow and plot the discharge curve --
>> but that's really more tedious than I care to get into, unless there's
>> a simpler method that hasn't occurred to me. I used to do that 30+
>> years ago with NiCd battery packs when I was flying R/C models.
>>
>> Neil
>>
> The good folks over at CandlePowerForums
> http://www.candlepowerforums.com/vb/...d.php?t=149804 have studied
> this subject extensively. Might save yourself some time and energy in
> reviewing what they did before doing any analysis yourself.
>
> Clair
Excellent forum on NiMh and self discharge rates. Thanks for the link.