[TenTec] Hercules II Power Source

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

That 10% limit applies to gel cells only as far as I know. Wet cells
will accept and deliver bigger currents. The electrolyte doesn't
circulate to accept charge rapidly in the gel cell, that's a limitation.

There are deep cycle gel cells as well as wet cell deep cycle batteries.
The wet cell batteries generally have a greater capacity per volume,
though they do need more care in adding distilled water regularly.

Gel Cell batteries make up for their freedom from watering by requiring
more care on load and charging currents.

Every connection to a battery needs to through a fuse or circuit
breaker, either one rated at DC. AC circuit breakers and fuses may not
open reliably on DC. A full charged deep cycle battery may produce a
couple kilo amps short circuit, which makes 100 amp wire smoke or glow.

The battery charger will have diodes in its circuit to prevent any
loading of the battery when the charger is off, the power supply won't
and the power supply voltage may need some fine adjustment to set the
proper operating point for the battery.

You can determine that proper operating point by watching the charging
current (with no loads on the battery). The battery current should just
taper to zero in a few hours. If the charging voltage is high for the
specific gravity, the current won't go to zero. If the charging voltage
is low for the battery, the battery won't develop a full charge. So to
get the best results it necessary to adjust the voltage a bit
experimentally unless the battery maker has specified a precise voltage
and you have a meter that is as precise to set the charger voltage.

Charging through a diode is a little counter to setting a precise
voltage because the diode drop depends on current to some extent. Better
if the diode is bigger.

The crowbar on the power supply and a battery aren't compatible. The
crowbar can be fired by stray RF and hooked across the battery even with
fusing at the battery it may be the last time that crowbar functions.
Unfortunately the normal failure mode for the SCR is to melt shorted.
The internal leads may then melt open, sometimes.

Charging voltage for a deep cycle is closer to 13.8 volts than 12.8
volts. That 12.8 volt value is after the battery has set several hours
after charging.

Its about 10:30 PM in Iowa, the high temperature today was 38 which
began to melt the snow. The turkey, chicken, and cookies are all gone.
I've been working on measuring 6m receivers. Need to fix some more test
equipment tomorrow.

What shows 0 ohms to a simple VOM may be an open circuit for RF. It
won't hurt to put a .01 or larger disc ceramic capacitor across the
power supply output terminals, and then to ground the negative solidly.

When the battery voltage is down a bit and the linear is producing less
than the normal output its easier to overdrive it and it may be
worthwhile to settle for 1000 watts instead of 1200 to keep the quality
up.

73, Jerry, K0CQ

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