ml wrote:
In article ,
Tom Ring wrote:

ml wrote:
omitted) it's quite meets
code, very small, very light dosn't pollute or stink

seemed rather sexy the jado can also be powered from small cartridges
making the unit selfcontained and very portable, however this isn't a
requirement of mine but cool benni

the only con for me, seems to be a)not totally going to give me 100w
at full load b) i wish the unit was more than a puny 100w the larger
units i would have to pay full list for and are therefore outta reach


so solath and experiment

Ok, I have applied a simple power budget to what you stated your
original desire was, as opposed to your cut down 2m 5W system.

Using a rig I own, an FT-897, on HF.

Assume 90% receive at 1 amp.
Assume 10% transmit at 15 amps with 100 watts output, (measured as
opposed to the 22 amps claimed in the docs)

This gives 2.4 amps average consumption. (Check my math, the doctor did
a lot during my pre-op today)

1 week is 168 hours which gives us 403 ampere hours.

100AH deep cycle batteries are around 100 each (or less), So that's
about $400 for all the batteries you need for a week without sleep.

A modern top of the line charger, such as produced by Schumacher, is
less than $100, does automatic desulfation, will charge at 50 amps or
greater, and weighs about 6 pounds.

So now we are at under 500 dollars for an emergency power for any ham
that needs to run an HF rig for a whole week.

I just don't see why you want to use the fuel cell, it makes no sense.

tom
K0TAR
tom, am i to understand you had some surgery today? if so, i hope all is
well with you and taking the time to write is appreciated

i am guessing roy's calculation of the total ampre hrs needed is closer
to being correct, but it's 5am and i kinda don't know how to calculate
that so i dunno as stated in my earlier post i don't have the formulas
so i can't act to confirm but i nod my head and presume it's all correct
based on roys math

you are correct about what the rig is doing mine is exactly simular i
would calculate based on 20amps

re your last comments on why i would want a fuel cell, it should be very
clear in all my many posts

5480 watt-hours of battery is more $$ and large than i have practical
room for

i can get the fuel cell for practically nothing and i just thought it
might be able to offer some useful power to top off a battery to
provide some b/u power why not? and also be a fun experiment it runs
quiet , clean and i can get all the fuel i want free always, i would
never be able to get fossel fuels in a blackout or other emerg

so now i inch a drop closer knowing how many what hours my original
abandoned goal would draw , however my current stated goal is to just
power my 5w tx output(draws4amps) 2m mobile rig

and try to calculate how much the battery would be drained in a 1min
tx and then see if the 12v 7amps comming out of the jado would recharge
it fast enough i believe that is what must be calculated for just not
sure how do it, unless you still say a 7amp battery is still 'ok'

my goal was to be able to calculate

so a 7amp battery(or what ever is needed optically this seems like a too
low a #)) w/a 1min 4amp load would be ??%drained
then based on manuf spec's for the battery we could calculate how much
power &time would be needed to top it back off

then it would be simple enough to see if the output of the jado is
sufficient i think thats all thats needed i think that's simple
but i dunno how to calculate it
thanks all i really wanted to do

If your rig draws 4 amps (I assume that's on transmit; it would be an
awful lot of power for a modern receiver), and the fuel cell can put
out 7 amps continuously albeit at slightly reduced voltage, and I
assume it can put out 4 amps at less of a reduction, why are you
worried about it? Unless you are VERY long-winded with your
transmissions, a small 7amp-hour sealed lead acid battery would give
you a couple hours operating time even if it wasn't being continuously
recharged. I'd actually opt instead for some voltage stabilization at
the fuel cell output: a buck-boost regulator would do it. If you
trust the fuel cell to do its job, then trust it. If you don't, then
provide a backup. So what I read between the lines you've written is
that you're going to get this fuel cell, but you don't really trust it.
You don't even trust it to come close to what are apparently its
published ratings.

Pretty much all the formulas you need to figure all this stuff out:
power = voltage times current (watts = volts * amps)
energy = power times time (joules = watts * seconds)
-- total energy needed = sum of (each current times the length
of time that current is drawn)
amp-hours = amps * hours = amps * seconds / 3600sec/hr
battery energy storage in watt-hours = amp-hour rating * volts
(assuming full charge)
battery energy storage in joules = amp-hour rating * volts * 3600
sec/hour
capacitor energy storage = (initial charge voltage)^2 * capacitance / 2
joules = watt-seconds = volts^2 * farads / 2
watt-hours = joules/3600 = volts^2 * farads / 7200

Where is it that you can get a license without knowing at least this
much? Why so much trouble with the concepts of power and energy
calculated from current, voltage and time? (Why is this posted to an
antennas newsgroup?)

Cheers,
Tom