Re: [SARES] on rechargeable batteries

One other point.  Foe those of you who read the Elecraft site, Elecraft
points out that some high-capacity NiMH's are larger than 'standard'
diameter.  This was aimed at people trying to cram oversized cells into
their internal battery cases.  I know that all of the Powerex (Maha)
are in spec.

Neal

--- "P. Stewart" <pstewart99@yahoo.com> wrote:

> A good summary Andreas.  Although not a focus of the group buy, do
> you have any comments about lithium ion batteries?
> 
> Thanks, Phil 
> ---------------------------------
> Andreas Ott <andreas@naund.org> wrote: Hi,
> 
> I am a huge friend of rechargeable batteries but would like to point
> out
> that they are not always a drop-in replacement for alkaline
> batteries. It
> is important to understand the differences in battery chemistry so
> that
> you can get the most mileage out of them.
> 
> On Sun, May 28, 2006 at 03:40:53PM -0700, Ralf Erickson wrote:
> > Here is the info from Seth:
> ...
> > For those that missed my email on this subject let me give you a
> short 
> > version.  This is from lessons from Katrina.  If we have a large 
> > earthquake we may be operating 2 or more weeks.  If that happens we
> will 
> > probably not be able to get more AAA batteries so we must make the
> ones 
> > we have last.  So my idea is that I should have enough NI-MH
> batteries 
> > to last 2 days.  Also I should have the chargers to be able to
> charge 1 
> > days worth at a time so I am not changing them during the time I am
> 
> > trying to sleep.  >From experience I should be able to run all day
> with 
> > 2 sets for my radio of fairly heavy traffic.  This works out to 12 
> > batteries a day and 24 for 2 days.  Also I should have 3 chargers.
> 
> When homebrewing rechargeable battery sets for your radio, please
> keep
> in mind that the NiCd and NiMH cells have a nominal voltage of 1.2V
> per cell versus the standard 1.5V of Alkaline AA cells. Most of the
> AA
> alkaline battery holders for HTs that I have seen are 'designed' and
> have connections for the voltage of multiple 1.5V cells, i.e. 6 cells
> will produce 9V in the alkaline pack but only 7.2V in the NiMH pack
> configuration. So please make sure that your radio can accept
> rechargeable
> batteries in the regular alkaline battery holder. The more cells you
> have
> in your battery holder the bigger the difference in voltage between
> the
> two battery types.
> 
> It is also well known that charged NiMH cells have a high discharge
> rate
> when stored (compared to other cells). One needs to keep this in mind
> when storing fully charged batteries for emergency communications
> needs.
> Reports are that it is best to charge them full right before you use
> them but in an emergency the power might be already out when you need
> the batteries. Always use a charger that is desinged to handle the
> battery type.
> 
> I have been using rechargeable AA cells with limited success in a
> digital
> camera that was designed for alkaline cell voltage. The camera always
> thinks it's low on battery as the voltage is only 4.8V over the 4
> cells
> where it would expect 6V if it had alkaline batteries. To the
> contrary, my
> MP3 player has a setting in its software menu to switch between
> alkaline
> and rechargeable battery to calibrate its battery low indicator. It
> runs
> very well on NiMH cells.
> 
> 73, andreas  de K6OTT
>
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