The use of primary or secondary cells depends on how the product was
engineered Primary cells start out at 1.5V and are considered at the
end of life at around 0.5V. To engineer a device where the power supply
voltage varies either a DC/DC converter or LDO (low drop out) voltage
regulator. It takes a great deal of engineering to run a radio with a
DC/DC onboard. Not impossible, but you need to watch where the
harmonics of the DC/DC end up. The LDO is quite simple, but not very
efficient.

The secondary cells start out at around 1.25V and are considered at end
of charge around 1V. If you are charging the batteries in the device,
the voltage per cell can be around 1.5V. [It all depends on how fast
you charge them.] This yields a range of 1.5V to 1V per cell. What most
engineers would do is go for the LDO, with the output near the 1V/cell
limit. Thus many products that spec primary cells work just fine with
secondary cells with one caveat: the cheaper devices have no
undervoltage lockout to protect the secondary cells from a deep
discharge. Some products use battery holders for each type of cell so
that the product knows what kind of batteries are being used.

Nicads and NiMH have lower impedance than alkaline cells. You often
find them specified for products that have high current surges. [Photo
flashes, motor winders, etc.]

NiMH has a higher self-discharge than nicads. I used to really hate
NiMH, but have finally gone that route once the Rayovac 15 minute
chargable cells came out.

Getting back to your original question, the answer is "it depends."



RJ wrote:
When I got the digital camera,
I had to get the NIMH batterys and the charger.
then I said;
Why buy alkalines any more ?
and I switched my radios to NIMH batts too.

Now here's food for thought;
A pair of alkalines measure 3.1 v
A pair of NIMHs measure 2.4 v 2.6 v

Would the lower voltage affect the performance
of any of these "3 volt radios" ?

????


rj