[TenTec] Battery Powering Hercules, PLEASE READ, Important info 4 U.

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

JEFF S JOHNSON wrote:
> 
> As for battery power to a rig. Is it possible to put two batteries in
> series and run the 24 VDC into a voltage regulator circuit like that
> found in a common power supply. This way we could have 13.8 VDC > regulated as well as longer battery charge.
> 

Probably not longer battery charge. The linear regulator typical of most
power supplies in that situation would be just a hair over 50% (maybe as
much as 60% when the 24v battery dropped down to 23 volts) so the added
energy of the second battery would be almost all wasted in the regulator
as heat. Going to a switching regulator would save lots of energy at the
cost of being potentially noisy.

It would be better to go to a boost regulator and run from a single 12
volt battery and use the boost regulator to hold the output voltage up
to 13.8 until the battery was down to maybe 11 volts (at which point the
voltage versus time curve is just about turned vertical anyway). The
bugaboo is still switching noise that can be a bother to shield and
filter for use with a radio.

The linear regulator in a power supply can be protected from battery
back feed by connecting a diode from the regulated output to the
unregulated input of the regulator. Cathode to the unregulated. That
keeps the regulator from being back biased. Still doesn't protect the
world from unwanted crowbar operations that tend to short the battery
with resultant fireworks. Its imperative that the battery charging and
load circuits be protected by substantial DC rated fuses or circuit
breakers. And that the battery be ventilated outside, not near radios.

73, Jerry, K0CQ

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