"Jeff Liebermann" wrote in message
...
On Mon, 24 Dec 2012 11:28:48 -0800, "William Sommerwerck"
wrote:

http://802.11junk.com/jeffl/NiMH/Duracelll-NiMH-2050.jpg
shows that the first charge cycle results in a 1180mA-hr capacity,
while the third charge cycle increased it to 1360mA-hr or about 15%
increase. Is that what you mean by "slammed"?

No. It means hitting it hard with a high charge current.

Yuck. Why would I want to do that? If there were dendrites in NiMH
batteries like in NiCd, then perhaps it would make sense. Besides if
such a high current blast was necessary to produce a proper battery,
or to produce bigger numbers on the data sheet, the manufacturers
would already be doing it.

Where did you see this recommendation? I couldn't find anything with
Google under "NiMH slamming" variations, except under National
Institute of Mental Health. I did find this blurb that recommends
against the practice:
http://forums.dpreview.com/forums/post/25581821


"Slam" is my choice of words.

I can't give you any references, but I've repeatedly seen in the documentation
for NiMH cells, that hitting them hard is necessary to get a "full" charge.
You are repeatedly warned NOT to charge them below 0.3C, and higher values are
preferable.


I've noticed that my NiMH battery collection (flashlights, cameras,
GPS, radios, etc) spent much of their time in the charger simply
recovering from self discharge.

I've never had that problem -- as far as I can tell. I've had cells that
sat
around for the better part of year deliver 20 or 30 flashes, with rapid
recycling.

Perhaps my cameras and GPS require a higher minimum state of charge
than your flash? When I used to leave my conventional NiMH batteries
in the camera for a few months, it would usually be good for one or
two photos before complaining. I always kept a spare set of charged
NiMH with the camera in case I run out. They were also only good for
a few shots.

Most of my flashes are 500-series Canons, which are hardly wimpy li'l
critters.


http://www.stefanv.com/electronics/sanyo_eneloop.html
Scroll down to the two pink graphs near the bottom of the article. The
conventional battery is down to half capacity in 75 days, and 1/4
capacity in 150 days.

That's not what I would consider "rapid" self-discharge -- other than,
perhaps, compared to a lead-acid battery.



Incidentally, this article:
http://www.stefanv.com/electronics/using_nimh.html
covers quite a bit of ground on dealing with NiMH batteries, including
trickle charging, and a home made NiMH computah controlled charger:
http://www.stefanv.com/electronics/battman2.html
and a simplified USB powered charger:
http://www.stefanv.com/electronics/usb_charger.html
I'm tempted...

Most of my cells have been close to rated capacity. In one case, a cell was
about 20% low, and MAHA replaced it.

I didn't know that Maha made batteries:
http://www.mahaenergy.com/batteries/

I don't know if they make them, but they definitely sell them under the
PowerEx brand. Thomas sells four for about $12. Considering that a charged
2500mAh cell gives about as much runtime as an alkaline cell, it doesn't take
long to amortize the cost.


Thomas sometimes sold the C9000 for ~ $40, but those days seem over.
I have two, so I don't have to wait if a lot of cells need charging.

I'm finding prices from $50 to $140 (including tax and shipping).
http://www.ebay.com/sch/i.html?_nkw=maha%20mh-c9000&_sop=15

The eBay prices are nuts.

I was wrong. Thomas's holiday deal is the charger, a generic carrying case,
four Immedion AA cells and a plastic case for the latter, for about $52. Given
the cost of the "accessories", the charger nets at $40. This would be a very
good time to grab a C9000 from Thomas Distributing.