Re: [SARES] on rechargeable batteries

Ralf,

What is the brand of these AA batteries and charger?  Is there a web site that I can read about them?
 
 Thanks Ralf for coordinating all this!
 
 Tae

----- Original Message ----
From: Andreas Ott <andreas@naund.org>
To: Ralf Erickson <wa6cqa@sbcglobal.net>
Cc: SARES LIST <sares-list@sunnyvaleares.org>
Sent: Wednesday, May 31, 2006 9:33:23 AM
Subject: [SARES] on rechargeable batteries

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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