Michael Black wrote:
"jtaylor" ) writes:
When I was little(r), almost all small portable radios used 9-volt
batteries. There were some, of course, that used AA's (or even 1 AA; I had
an am portable with 1 AA cell that we snuck into school when
something-or-other REALLY important to schoolboys was going on), but now I
don't have & don't know of any radio that uses 9V batteries.

Why were they needed in the first place? The 9-volt package has a lot more
package and a lot less mWatthrs in it. Was it because of the voltage - did
the existing solid-state tech not work so well at 3V?


One thing to keep in mind that it's easier to get audio power out of an
audio amplifier if it runs off a higher voltage. And those old radios
were all about driving speakers. A 9volt batter gave the higher voltage,
but didn't require a bunch of AA cells that would take up far more space.
(Take apart a 9v battery, and you'll find actual cells inside, sometimes
small packs in plastic other times what look like smaller AAA cells.)

With recent products, they could go to a lower voltage because the
products are driving headphones. So that MP3 player runs off an AAA
cell because it doesn't need to provide much output power. Same
with Walkman's of twenty years ago, no speakers just headphones.

Motors needed lower voltage, forty years ago we had a lousy cheap
tape recorder that had a 9v batter for the amplifier and some C
cells for the motor, but required more power, so Walkmans and portable
CD players moved to multiple AAs.

One thing that has happened, as digital electronics has become a staple,
is they've gotten better at making devices that run at lower voltages
(alongside making things use less current). Which means that thirty
years ago, if an MP3 player had been practical, it likely would not
have been able to run off one AAA cell, but now they can.

Michael

The batteries inside a 9 volt battery are "Quad A" or AAAA batteries,
1.5 volt. There are 6 of them inside a 9 volt case.

Harold