[TenTec] Use of Battery DC-DC converter? (EX Scout Batteries)

[Dr. Gerald N. Johnson, electrical engineer]

There are a number of semi-older MAXIM step up regulator chips made for
use with external power MOSFETs that could raise the input voltage a
couple volts. Its hard to do it absolutely quietly because the voltage
rise comes from storing energy in an inductor and then dumping it to the
load and a fast fall on the charging MOSFET drain current is essential
to efficiency. This is presuming a none isolated voltage rise. If a
conventional DC to DC converter with transformer is used then isolation
can be a part of the project, but noise is still a potential problem.

The step up regulator could be shut down for receive and enabled only on
transmit. It has a diode drop when shut down, so a schottky diode would
be most appropriate (or maybe a power MOSFET).

One might also look for a commercial 12 volt in, 2.5 volt 15 amp output
DC-DC made for retrofitting a late high speed CPU chip with isolated
output. Then the 2.5 volt output would be connected in series with the
Scout power as a boost voltage.

My tests on 12 volt lead acid batteries (and their data sheets) indicate
that by the time the terminal voltage at any reasonable load reaches 11
volts there is very little energy left and trying to extract that last
1/2% of energy can do permanent damage to the battery. I class an engine
starting load as not a reasonable current.

73, Jerry, K0CQ

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