NiMh voltage?

AnthonyL wrote:

The internal resistance issue is the explanation I was given when my
camera refused to work and I was on the point of throwing it out. I
kept buying higher rating Energiser rechargeables only for them to
fail to get the camera working. Sanyo Eneloops were then recommended
because of their low internal resistance and the camera has worked
perfectly for the past 3 years. I now rarely use anything else.

Thanks for that; googling gave me this article,
with details on what you're saying:

http://www.stefanv.com/electronics/sanyo_eneloop.html

from 2006. The author also goes on to test and discuss
other, similar, batteries that subsequently came to market.

http://www.stefanv.com/electronics/l...discharge.html

BugBear

In article ,
says...

On 27/10/2013 04:55, Daniel W. Rouse Jr. wrote:
"Martin Brown" wrote in message
...

[snip...]

The advantage of AA cells is you can buy them most places.

I keep my once used AA cells for use in other low current drain
applications where terminal voltage is non-critical. I do use and get
decent life out of my NiMH in a Pentax istD but I have matched the sets
and periodically weed out failing cells. I carry a set of alkaline spares
too as high self discharge is a problem with most NiMH.

Not only too high a self discharge, but also how the charger does a charge
on the NiMH batteries. Some chargers make them burning hot to the touch,
while others do not.

Fast chargers tend to run the batteries seriously hot. That is the price
you pay for high charging currents. I try not to do this since battery
chemistry tends to be more nearly reversible when done slowly.

A good fast charger should never take the battery outside of its rated
operating conditions but a cheap and nasty one probably will.

I think the hotter the charger makes the battery, the less it lasts not
just in a single charge, but overall for the number of charges.

I haven't done the experiment but I also believe that fast charging
accelerates the loss of capacity.

Not sure if this is a Fry's Electronics only brand, but I've had mixed
results with Lenmar branded NiMH AA batteries. Some lasted for much
longer than AA alkaline. Others lasted less than 1/4 the time of a AA
alkaline. On the other hand, Lenmar AA (and AAA) are very cheap in price
to replace even if one or more batteries become defective.

In the UK Aldi/Lidl supermarkets sometimes have unexpectedly good low
self discharge NiMH batteries (already charged when supplied) on offer.
They are much cheaper than better known brands and almost as good. The
batch I got were all in a red finish and still going strong.

The odd cell does go duff with time developing a high internal
resistance and needs weeding out. You have to test terminal voltage
under load to find them. Open circuit the voltages are all very similar.

That's good information--I hadn't thought of Aldi as a source for
batteries, next time I go in I'll have to see if they have them in the
US.

On Sun, 27 Oct 2013 18:57:48 -0400, nospam wrote:
: In article , Robert Coe
: wrote:
:
: : I think the hotter the charger makes the battery, the less it lasts
: : not just in a single charge, but overall for the number of charges.
: :
: : yep, heat is *bad*.
:
: I have a feeling (not backed by any actual knowledge) that it may be more
: complicated than that. I have a Radio Shack charger (two actually: one at home
: and one at work) that leaves the charged batteries too hot to touch. I usually
: stand them up on a formica counter to cool for 15 or 20 minutes before putting
: them away. But the batteries seem to accept the treatment, as I haven't seen
: any degradation of their performance over time.
:
: But while those chargers work fine on Radio Shack and Enercell batteries (the
: latter a brand sold by RS), they refuse to charge "Impact" batteries (which
: are a B&H house brand, I believe). The model claims to be a "high speed"
: charger, and it does seem to do its job relatively quickly. My suspicion is
: that the charger knows (or thinks it knows) which batteries can stand the high
: heat of being charged that way and which ones may not.
:
: high speed charging means pumping a lot of current into the battery to
: charge it quickly, which heats it up. that reduces its useful life.
:
: if you charged them at a normal rate, they wouldn't be hot to the touch
: and they would last a lot longer.
:
: some chargers can report the actual capacity of the battery, and you'd
: see that decreasing over the lifetime of the battery.
:
: are you in that much of a rush that you need high speed charging?

Yes. At least I was until very recently, when I bought a lithium battery pack
and spare battery. For a long photo shoot I was charging 48 NiMH AA's. So yes,
charging speed was important to me.

Bob

In article , Robert Coe
wrote:

: are you in that much of a rush that you need high speed charging?

Yes. At least I was until very recently, when I bought a lithium battery pack
and spare battery. For a long photo shoot I was charging 48 NiMH AA's. So yes,
charging speed was important to me.

jeezus. how the hell did you keep track of them all?

did you at least get an 8 cell charger? i don't know if they make 16
cell ones but they probably do.

On Tue, 29 Oct 2013 21:03:17 -0400, nospam wrote:
: In article , Robert Coe
: wrote:
:
: : are you in that much of a rush that you need high speed charging?
:
: Yes. At least I was until very recently, when I bought a lithium battery
: pack and spare battery. For a long photo shoot I was charging 48 NiMH
: AA's. So yes, charging speed was important to me.
:
: jeezus. how the hell did you keep track of them all?

Carefully. When getting ready for a shoot, I tried to make sure to charge each
set of four exactly once. :^}

: did you at least get an 8 cell charger? i don't know if they make 16
: cell ones but they probably do.

I have three 4-cell chargers. I keep one at work and two at home.

Bob