[TenTec] Paragon Battery Backup

[Dr. Gerald N. Johnson, P.E.]

There are multiple problems here. First "9v" nicads made for transistor
radios are more often 7.2 than 9 volts. That leaves much less head room
for the memory that probably needs some minimum voltage like 4 volts.

The first thing to do is to try a 9 volt alkaline battery and see how
long it lasts. A good (duracell or energizer) alkaline should have more
than four times the ampere hours of a true equivalent nicad for the same
volume.

There are a couple solutions, one is to make up a bigger ni-cad pack say
of AA or C or even D sized cells to hold the load longer. It would be
more profitable to use D sized Alkaline cells though they can get some
fumes out and loose connections occasionally under light loads. The
energy per penny is greatest in the D sized primary cells. Of course
they don't fit well within the radio. I see that Digi-Key sells
Panasonic alkalines with solder tabs so the fumes on the connection can
be overcome with soldered connections. A D sized alkaline pack should
last 150 times as long as a Panasonic 9v NiCad...

NiCads depending on quality tend to self discharge, perhaps sealed lead
acid might be a better stand by battery, they will self discharge at a
lower rate and larger capacity costs less in lead/acid than in nicad.

The newer cells I'm not yet familiar with for standby applications. They
can be pickier about how they are charged.

Another solution is to bring out a diode and resistor from the internal
nicad to a connector on the back of the radio and connect up a wall wart
to trickle charge the battery while the radio is off, and depend on the
nicad only to hold memory past true power outages.

I have an IC-211 that eats that backup cell too. About the same vintage
as the paragon. The root problem is that the CMOS logic promised to hold
memory with minuscule current consumption but it that vintage circuitry
doesn't do it, probably because of using linear voltage regulators and
not truly cleaning the board. One linear chip on the CMOS board will
draw enough to eat the battery while you aren't using the radio.

73, Jerry, K0CQ

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