A battery charger which could provide one tenth of the current needed to
run the amplifier could be sufficient if the amplifier was only operated
with a 10% duty cycle and the battery discharge/charge efficiency was
100%. Even in that (imaginary and unrealistic) scenario, The period of
current draw (how long you transmit), not just the duty cycle, would
have to be kept low to avoid discharging to too low a state of charge.
For example 1 second key down and 9 seconds idle might work without
damaging the battery, but 20 seconds key down and 180 second idle, which
is still only 10% duty cycle, might damage the battery. I don't know
what a typical battery efficiency is, but I do know it is not 100%.
Another consideration when using a battery to power a communications
system, is whether you intend to operate for periods when the ACs mains
power is unavailable. If you do, then you need to size the battery and
the charging system appropriately. When the AC mains power comes back
up, do you want to stay off the air for a while to let the battery get
some charge? If not, then the charger has to have the current capacity
to simultaneously run the equipment and charge the battery. So the
charger has to have a current capability greater than a power supply
that only runs the equipment would have.
I suspect that most folks who use batteries and a charger to provide the
high current needed for a big solid state amplifier are not doing it so
that they can operate when the AC power is out, but rather are doing so
because they have not found a power supply that can do the job by
itself, at a price they are willing to pay. In this case I would suggest
that the charger have a current capacity of at least 1/3rd what the
amplifier needs, and greater than 1/2 would be much better.
I use an Astron 70 and a couple of T-105s with my SGC-500. (about the
same current requirements as a Hercules II) It works pretty well. I
would not even consider using a only 20 Ampere rated power supply for
this setup.
Did Ten-Tec really recommend that for a Hercules II? It sounds like it
would be appropriate to run one of their transceivers, but not the
Hercules II.
DE N6KB
I need to replace my battery charger for my twin Trojan T-105 batteries.
Ten Tec recommends an automatic 10 amp charger but I have read on the LIST
that some have had great success with the Battery Tender (about 1.25 amp).
A&A Engineering makes nice quality 1 and 5 amp Smart Charger models.
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