In article ,
Richard Clark wrote:

On Thu, 26 Oct 2006 00:22:01 GMT, ml wrote:

I was thinking of getting a jado fuel cell, it puts out 100w (about
8amps ?) @12vdc

Hi Myles,

Fuel Cell??? That is a pretty pricey option.

More than likely it is 100WH (Watt-hour, not Watt) rated.

wanted to power a 2m rig at low power 5w out it falls w/in the spec's
of the jado but i wanted a buffer

Well, a 5W transmitter is not going to load it too heavily, but you
have to figure that 5W out is a 10W demand on the battery. This means
your battery will work 8 - 10 Hours continuous (you don't sit on the
key, do you?).

at first i thought of a battery using the full cell to charge the
battery during receive since tx is brief but how do i calculate

A battery - fuel cell - battery?

how big a battery i need?

At least 100WH, undoubtedly more.

Why charge a fuel cell with a battery? Why not cut out the middle man
and just run battery operation?

i also wondering if perhaps a capacitor or a few of them might also
do the trick and if so how to size them

Not unless you can assemble a couple hundred Farads (note the complete
absence of pico, nano, or micro in that Farads). The short version is
DON'T GO THERE.

73's
Richard Clark, KB7QHC

thanks to all that replyed\
Tom , you changed my equation, combustion generators and solar are not
options or the question, it was a rather obvious choice but thanks
not sure where everyone got their spec's from and pricing but your
numbers are off and most likely i'd get a sample unit free , tom i
also wouldn't be using it's charging canisters but sstraight into the
tank

the jado i mentioned list price is around 2k$$ and i can get it for
less list and it is 100w it lit my 75w light bulb pretty steady and
bright

Question:
i thought since my key down isn't steady that might be enough juice to
then charge top off'' the battery but i didn't know how to size it

i'd have x amps (or ah) from fuel cell x ammount of draw think my rig
pulls 5amps? tx, x ammount capacity from batt,, so after say a min of
key down the battery would be y drained, given a big enough battery
Y (drain)would need to be small enough such that the 12/8amps out of the
Jado fuel cell would be able /fast enough to top it back off

question is what is that value how do i calculate how big a battery i
need at the know constants?



Rich the reason i thought of cap's was both the short key down time and
the article in cq of this new powersupply that uses a few 5farads it
got me thinking if it could be modified to do dc to dc regulation
rather than 120v ....maybe i was pushing it, then i thought of
supercapacitors i dunno