All the Motorola FRS radios (that I'm familiar with) use three AA cells.
All of their literature states that alkalines or Nimhs *must* be used.
According to Motorola, NiCads are not acceptable.

jak

"Dave Martindale" wrote in message
...
(Old Nick) writes:

I have a couple of little Uniden walkie-talkies, that take 4 X AAA
cells. They chew out the cells fairly fast, so I bought NiCds. No go.
The radios appear to have trouble dealing with the lower voltage. I
reckon they are trying to grab max volts to get Tx power up, and
probably should have had an extra battery. Rechargeable ALkalines
worked fine, but as you say deteroriate rapidly.

Sounds like the radio is poorly designed. Alkaline cells start at 1.5
volts, but drop pretty much continuously in voltage as they are drained.
Depending on the load, a device needs to operate properly down to 1 V
per cell (light load) to 0.8 V per cell (heavy load) in order to get
most of the energy out of alkalines. So a properly-designed radio
powered by 4 alkaline cells should tolerate 6 V in, but work properly
all the way down to 4 V. NiCd and NiMH cells provide about 1.2 V over
nearly their entire discharge time, over a wide range of load. Thus,
4 cells will provide 4.8 V and the radio *should* work fine.

If the radio doesn't work on NiCds, and the NiCds were in fact all good,
then it just doesn't operate properly at 4.8 V. If it works at 6 V but
not at 4.8 V, it will start working OK on alkalines, but stop working
when the alkalines are still half-full.

Sorry. Question. Are NiMH cells better in this regard? I am ringing
battery houses, and one guy said they were. I assume this would be
because they have lower internal resistance. Is this so? I got the
impression the guy knew more about _batteries_ than I do, but less
about electrical theory G

NiMH is not better than NiCd in this respect. NiMH actually have higher
internal resistance than NiCd, though still far below alkalines. If
NiCds don't work, NiMH aren't likely to either.

Next G. One shop had several AH capacities, at different prices
(actually they were the only ones to explain this, and will get my
custom). Are there any advantages/disadvantages to getting the lower
capacities, if this means they get discharged better etc?

Lower capacity cells may just be older. But they may also have lower
internal resistance. You can't really tell without measuring. I
wouldn't pay much of a premium for exceptionally high capacity.

Dave