On Mon, 24 Dec 2012 14:39:56 -0800, "William Sommerwerck"
wrote:
"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 think I've decoded the effect. It's a cure for "voltage
depression", where the NiMH battery decides to operate fairly
normally, but at a somewhat lower voltage. The usual culprit is over
charging. I've had it happen to me and almost tossed a set of good
batteries. The recommended fix is to cycle charge the batteries a few
times and it should recover. However, the not so graceful fix is to
discharge the battery, and then to a radical quick charge, being
careful not to overcharge it again. Allegedly, this avoids having to
cycle charge the battery several times, probably at the expense of
battery life.
http://en.wikipedia.org/wiki/Memory_effect#Voltage_depression_due_to_long-term_over-charging
See voltage depression section near the bottom of the page:
http://www.stefanv.com/electronics/using_nimh.html
http://www.greenbatteries.com/nibafa.html#NiMH%20memory
Most of my flashes are 500-series Canons, which are hardly wimpy li'l
critters.
I'm not familiar with the flash, but I suspect is does not have the
continuous high current load of a camera with it's focus and aperture
motors grinding away for many minutes.
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.
Well, it's rapid enough that I was recharging almost everything I
owned every 3 months or so. If it were only one device, I wouldn't
complain, but it was a mix of GPS, flashlights, cameras, phones,
walkie-talkies, FRS radios, clocks, etc.
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.
Well, the plan was to save money by using rechargeable batteries. I
usually buy Costco Kirland AA batteries:
http://www2.costco.com/Browse/Product.aspx?prodid=11285539&whse=BD_115&topnav=bd off&cat=21810&hierPath=68474*91765*&lang=en-US
at about $0.30 each. Sanyo Eneloop NiMH batteries are costing me
about $3.00 each. So, if the NiMH battery lasts 10 charge cycles, I
break even. So far, that's been the case, so for cost savings,
rechargeable wins.
However, that has NOT been the case for convenience. I can leave an
alkaline AA battery in my various devices for many months, and not
have a self discharge problem. I find myself carrying spare alkaline
batteries for these devices just in case the battery decides to
discharge itself. Extra points for devices that suck power when
turned off. Therefore, for convenience, conventional rechargeable
NiMH is a problem. The low self discharge batteries are a big
improvement and may just solve the problem. I'm not keeping score,
but I'm definitely not recharging anywhere near as often as when I was
using conventional NiMH batteries.
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.
Good price, but the web pile is back to $52 (including shipping) and
without the AA cells and plastic case:
http://www.ecrater.com/p/11476696/maha-powerex-c9000-aa-aaa
--
Jeff Liebermann
150 Felker St #D http://www.LearnByDestroying.com
Santa Cruz CA 95060
http://802.11junk.com
Skype: JeffLiebermann AE6KS 831-336-2558