Aren't rechargeables for high current applications?

In article ,
Dave Cohen wrote:

Most people seem to be aware of alkalines having a higher internal
resistance then either NiMH or NiCD.
Since literally millions of people are happily using NiMH in their
cameras, it might occur to you that you have a problem with the camera.
My guess would be it's unduly sensitive to the lower voltage of NiMH,
but one would need to do further testing.

I'd also tend to suspect that this is a factor. My wife's fairly
recent point&shoot cameras have a three-way adjustment for the battery
voltage - for NiCd/NiMH, alkaline, and lithium-primary cells. Setting
it properly makes a big difference in the camera's willingness to use
the batteries. If left on the "alkaline" setting, and loaded with
freshly-charged high-quality NiMH cells, the camera will (mistakenly)
report low-battery after only a few flash photos when the cell voltage
drops below around 1.3 volts. The cells still have oodles of charge,
but the camera mistakenly believes that they're alkalines on their
last gasp of power.

It's also possible that Rich simply had some lousy NiMH cells. I've
certainly seen (and bought, alas!) some that were about as useful as
road gravel. They lost almost 10% of their charge per day. After
several attempts to use them, and a week-long condition/analyze
exercise using a Powerex MH-9000 charger, I decided to just toss 'em
in the recycle bin - they were more hassle than they were worth.

My impression is that the steady "marketing war" for the highest rated
capacity has resulted in NiMH cells which have a very severe tradeoff
for their capacity - very high self-discharge rate. There seems to be
a very real engineering compromise - those hydride alloys which allow
for the greatest charge capacity, also tend to have the weakest
ability to hold onto the charge.

--
Dave Platt AE6EO
Friends of Jade Warrior home page: http://www.radagast.org/jade-warrior
I do _not_ wish to receive unsolicited commercial email, and I will
boycott any company which has the gall to send me such ads!

On Fri, 5 Dec 2008 12:14:35 -0800 (PST),
wrote:

There are cheap Chinese knock-off batteries that go to great lengths
to look a lot like Duracells or Energizers.
At a quick glance, they look the same. However, even new, they can't
even get a camera to turn on. Internal resistance is that high.
Probably bottom of the barrel carbon/zinc batteries masquerading as
alkalines.

I've seen some of the cheap counterfeit Duracells. Holding them
in your hand, they're noticeably lighter than real Duracells, and
I'm sure that they aren't really even alkaline AA cells. I think
that most of the people that buy (or bought) them were for use in
portable CD players, where the very low current requirement allows
them to fool naive purchasers.

On Fri, 05 Dec 2008 21:05:49 GMT, David J Taylor wrote:

I gather a lot of the D cells have AA's inside.

I thought that most D Ni-MH cells were made like that?
At least, all I've ever seen.
Reputable makes.

That's been true for many of the C and D NiCd batteries sold to
end users by reputable stores. Some of the stores such as Radio
Shack belatedly added higher capacity sintered plate C and D cells
after selling only the low capacity cells for many years. They cost
and weigh more than the low capacity cells, where AA, C and D cell
NiCds all have the same capacities. This is probably also the case
for the C and D NiMH cells, but as I no longer have any use for
rechargeable C and D cells, I haven't been checking them out. When
I did use high capacity NiCd D cells years ago, even relatively
sophisticated chargers could take well over a full day to recharge
fully depleted D cells. Caveat - I never opened any of the low
capacity C or D cells so I don't know if real AA cells are inside,
but whatever *is* inside has the capacity of an AA cell.

"Rich Gripes"

FWIW, I'll never waste my money on NiMH's again.

** Wot a total ass.


I bought a "smart" charger that came with 4 NiMH's once,


** Here it comes - a whole load of bull with not one single *checkable*
fact in sight.


and was kind of impressed.
Unfortunately, my camera (a Fuji) has a terrible current drain when
it's off, presumably to keep the RTC up.

** Total ********.


So, I'd pick up the cam,
turn it on, and the NiMHs were dead.

** Camera problem - a few of the early models were unusable with
rechargeable cells due to automatic PSU shut down at just under 1.2 volt per
cell.

The same cameras only extracted a fraction of the energy capacity of an
Alkaline cell too.


So I trashed the whole lot, bought a couple of AA alkalines, and
they're still going after almost a year.


** So the camera had no " off " current drain issue at all.

Wot a liar.


BTW, I've never heard of alkalines having a "high internal resistance" -
IME, they're almost as hot as Nicads.


** Complete and absolute ********.

The *initial* internal resistance of an Energizer or Duracell AA alkaline
is about 5 times higher than a NiCd.

After some period of use, the ratio goes out to 10 to 30 times higher.

Huge difference.



...... Phil

John Doe wrote:

(Crossposted, please feel free to trim)

Since the worth of a NiMH rechargeable battery is determined by how
many alkalines you avoid buying and disposing of, what's the point of
low leakage current NiMHs?

In other words. Why would you care if the NiMH still has a charge after
one year?

In low standby power applications of course. It's a pain replacing
batteries in remotes and the like every few months.

Graham

John Doe wrote:

Do you insult people in person like you insult people over the
Internet, Phil?

You thought that was an INSULT ?

You ain't seen nothing yet !

Graham

(Dave Platt) wrote:

I'd also tend to suspect that this is a factor. My wife's fairly
recent point&shoot cameras have a three-way adjustment for the
battery voltage -

Are you talking about a "switch" or do you know what's going on
inside of the camera?

for NiCd/NiMH, alkaline, and lithium-primary cells. Setting it
properly makes a big difference in the camera's willingness to use
the batteries.

Same question as above. Looks like you are talking about what's
going on inside of the camera, but I doubt it.

If left on the "alkaline" setting, and loaded with freshly-charged
high-quality NiMH cells, the camera will (mistakenly) report
low-battery after only a few flash photos when the cell voltage
drops below around 1.3 volts. The cells still have oodles of
charge, but the camera mistakenly believes that they're alkalines
on their last gasp of power.

And what happens? Does the camera stopped working?

You are looking at an incorrectly adjusted voltage level indicator
(when you use rechargeables but don't correctly set the camera).
That is meant for you the user, it should not affect operation of
the camera.



--
The first big front wheel rollerblades.
http://www.flickr.com/photos/27532210@N04/3056505603

"J. Clarke" wrote in message ...
Rich Grise wrote:
On Fri, 05 Dec 2008 01:33:23 +0000, John Doe wrote:

Since the worth of a NiMH rechargeable battery is determined by how
many alkalines you avoid buying and disposing of, what's the point
of low leakage current NiMHs?

In other words. Why would you care if the NiMH still has a charge
after one year? Doesn't that negate the value of being able to
recharge the battery hundreds of times? Why not use an alkaline if
it needs to last for one year?

Or, is ordinary/current NiMH leakage current problematic even for
high current uses, and battery makers are trying to correct that?

FWIW, I'll never waste my money on NiMH's again. I bought a "smart"
charger that came with 4 NiMH's once, and was kind of impressed.
Unfortunately, my camera (a Fuji) has a terrible current drain when
it's off, presumably to keep the RTC up. So, I'd pick up the cam,
turn it on, and the NiMHs were dead. So, I'd get the next pair off
its shelf, slap the discharged pair in the charger, and be on my
merry way. Then, freshly charged, bu thaving sat for a couple of
weeks, they were dead. Finally one day, I had no charged NiMHs -
I "charged" 4 of them, and NONE OF THEM would make the camera go.

I mean, pulled them right out of the charger, put them in the
camera,
and nothing, like their shelf life was zero.

Sounds to me like you have a crap charger.

This was my first thought as well.
It is not easy to find a good reliable charger. I went through a couple and they
all had some kind of deficiency.
My last one from ELV elektronik (Germany) was not cheap, looks really sophisticated
yet after a few uses I found it won't even detect one of the almost brand-new NiMh
and I know that accu is good. Many of the wall-warts are crap, too.

Previous charger was also supposed to be good, even supported cycling.
Yet it would drive some accus into severe overheating, obviously failing to detect
the accu has been charged.

The only way to know for sure is to design one on your own. But who has time.

M

On Sat, 06 Dec 2008 01:14:07 GMT, John Doe wrote:

I'd also tend to suspect that this is a factor. My wife's fairly
recent point&shoot cameras have a three-way adjustment for the
battery voltage -

Are you talking about a "switch" or do you know what's going on
inside of the camera?

Cameras almost always implement battery "switches" via menu
options.


for NiCd/NiMH, alkaline, and lithium-primary cells. Setting it
properly makes a big difference in the camera's willingness to use
the batteries.

Same question as above. Looks like you are talking about what's
going on inside of the camera, but I doubt it.

Same answer as above.


If left on the "alkaline" setting, and loaded with freshly-charged
high-quality NiMH cells, the camera will (mistakenly) report
low-battery after only a few flash photos when the cell voltage
drops below around 1.3 volts. The cells still have oodles of
charge, but the camera mistakenly believes that they're alkalines
on their last gasp of power.

And what happens? Does the camera stopped working?

You are looking at an incorrectly adjusted voltage level indicator
(when you use rechargeables but don't correctly set the camera).
That is meant for you the user, it should not affect operation of
the camera.

If well designed it *will* affect the operation of the camera.
Some old cameras probably had "dumb" battery warning indicators,
relying only on observant users to power off the camera and swap
batteries. But that was then, and now it's different for most
cameras. Battery voltages fluctuate with usage, dipping more when
zooming the lens, focusing, writing to memory cards and especially
when recharging the flash's capacitors. Cameras can perform many
different types of operations when the batteries are fairly close to
the minimum operating voltage (a range, not really a point, due to
component tolerances). This is the point where a well designed
camera will shut down, because at this point if one more picture is
taken, there may not be enough energy left in the batteries to
complete saving the picture to the memory card, and this could trash
the card, even though many other operations could still be safely
performed, such as changing menu options, changing shutter speeds
and f/stops, even reviewing previously taken images.

Other devices also intelligently shut down at different voltages.
Many PDAs not only let you specify the battery type used, they also
have utilities that let the user redefine the voltage points where
battery warnings are given, as well as what voltage level initiates
the shutdown of the PDA. I'll leave this as an exercise for the
authors of the CHDK hack to implement - assuming of course that they
haven't already done so.

ASAAR caught 22.com wrote:
John Doe wrote:
(sorry, Jack didn't introduce author)

for NiCd/NiMH, alkaline, and lithium-primary cells. Setting it
properly makes a big difference in the camera's willingness to use
the batteries.

Same question as above. Looks like you are talking about what's
going on inside of the camera, but I doubt it.

Same answer as above.

You have called me clueless several times in another thread, Jack, but
my question here is going over your head. Yes of course a camera copes
with lower voltages, but that's not the question. This is the question,
in the other words... When you use a switch to tell the camera whether
it's running off of disposables or rechargeables, does the camera do
more than just properly display the remaining power?

And what happens? Does the camera stopped working?

You are looking at an incorrectly adjusted voltage level indicator
(when you use rechargeables but don't correctly set the camera).
That is meant for you the user, it should not affect operation of
the camera.

If well designed it *will* affect the operation of the camera.

That doesn't answer the straightforward question seven lines above,
Jack, because you don't know what I'm talking about.

snipped a long answer to a question that wasn't asked