hi

was wondering if someone had some thoughts on this and might be able to
help me 'calculate' the value i need

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

it's not totally regulated, at full output the volts dip a bit

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

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
how big a battery i need?


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 sure the pro's /cons' of battery vs cap's


naturally if i used the caps' i'd prob get a dc to dc regulator

any help appreciated

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

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

ml wrote:


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

I got the pricing from jadoo's site for the unit plus 6 container combo.
And you will still need something to refill.

On the battery, when we used to VHF contest with a light (600W)
generator and power supplies, we would put a 25AH battery across each 15
amp supply and we could draw 40 or 50 amps on CW/SSB peaks with no
issues. So you would probably be well served by one of the 7AH UPS
batteries from a place such as Batteries Plus. They cost about $25 and
are about 7"Lx2"Wx4"H.

tom
K0TAR

In article ,
Tom Ring wrote:

ml wrote:


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

I got the pricing from jadoo's site for the unit plus 6 container combo.
And you will still need something to refill.

On the battery, when we used to VHF contest with a light (600W)
generator and power supplies, we would put a 25AH battery across each 15
amp supply and we could draw 40 or 50 amps on CW/SSB peaks with no
issues. So you would probably be well served by one of the 7AH UPS
batteries from a place such as Batteries Plus. They cost about $25 and
are about 7"Lx2"Wx4"H.

tom
K0TAR

gosh, i sure do appreciate everybody's help, sincerely, but alas, i
still have no concise way to calculate what size battery or cap i need

but i can add a few things, even thou it's sorta a different topic
many here seem concerned about the size of the canisters and refilling
them, this is not a concern as the unit will be feed directly off a
large Hydrogen tank, not the little canisters i do not need to
calculate how long the unit(jado) will run at load vs fuel supply this
is already a known constant and published thats the easy part

the unit does 12v unregulated at about 7amps if you hit 7amps for long
voltage goes down to 10v so i will add some regulator if needed

when i said my radio(2m mobile) will be ""putting out 5w on low pwr""
i ment 5w rf output not current draw sorry

so rich since your calculation was for ah what would it be for for
the correct above spec's?? amps or 100w (no ah)?

i would have to have a battery big enough to be -drained little enough
so that the jado would be able to recharge it during the rx time(least
load) from what tx drained the battery obv if the battery is too
big then the jado wouldn't be able to recharge it or float it

right now i have 2 G27(parallel) and i float them at less than 1amp

naturally when i say recharge i don't mean from anything other than a
slight drain as in normal tx /rx

so the question become how do i calculate that? and would a ultra cap
fit in ?

i thought it would be kinda simple, gut wise i can guess but what i
was hoping for here was a more precise calculation of what would do
the trick

again thanks all for taking the time to respond , i always learn
something


ml

ml wrote:

gosh, i sure do appreciate everybody's help, sincerely, but alas, i
still have no concise way to calculate what size battery or cap i need

Please pardon the dumb question, but if you have a 100 watt fuel cell
why do you need a battery?

73, Jim AC6XG

ml wrote:

issues. So you would probably be well served by one of the 7AH UPS
batteries from a place such as Batteries Plus. They cost about $25 and
are about 7"Lx2"Wx4"H.

tom
K0TAR


gosh, i sure do appreciate everybody's help, sincerely, but alas, i
still have no concise way to calculate what size battery or cap i need


I thought my statement was clear, but I will repeat it -

"So you would probably be well served by one of the 7AH UPS batteries
from a place such as Batteries Plus. They cost about $25 and are about
7"Lx2"Wx4"H." Float that across your fuel cell and you will be fine.

Of course, if the fuel cell doesn't put out at least 13.5 vclts with
your rig on receive, a "12 volt" float battery won't have enough charge
in it to speak of. Then it would be back to capacitors and the
interesting problem that they would bring along. Such as a 0 volt
charge current that could possibly be damaging to your fuel cell.

This whole thing seems a very expensive way to have not very good
portable power. You have never stated why you must have a fuel cell.
Would you care to enlighten us?

tom
K0TAR

On Thu, 26 Oct 2006 09:37:27 GMT, ml wrote:

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

Hi Myles,

It is a matter of three things:
1. Amp-Hour or Watt-Hour capacity;
2. Demand for Amps or Watts;
3. Duty ratio.

Based on your specification for a 5W rig (I assume it is a hand held,
a small mobile would be more like 20-35W) and an efficiency during
transmit of 50-70%, then your demand would be at least 10W during
transmit. Receive would require some baseline power, my guess would
be 2W, maybe less. If you listen more than you talk by a factor of 5,
then you could count on an average demand of 2W.

Divide this 2W into the Watt-Hour capacity (I will assume 100WH) and
your power source should last two days continuous use (do you plan on
sleeping?) or 50 hours of on time over any more extended period. That
is, if you sleep 12 hours, you can stretch the service time out to 4
days. If you operate only 2 hours a day, you can stretch the service
time out over a month an a half.

73's
Richard Clark, KB7QHC

Always wanted a 1 FARAD (or bigger) capacitor!
Where can you buy one?? (Short of buying a
"Charged "one, I.E. Storage Battery)? Oh
well only 6 Months to April First!
Jim NN7K


Richard Clark wrote:



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

Jim - NN7K wrote:
Always wanted a 1 FARAD (or bigger) capacitor!
Where can you buy one?? (Short of buying a
"Charged "one, I.E. Storage Battery)? Oh
well only 6 Months to April First!
Jim NN7K


http://www.radioshack.com/search/ind...ad%20capacitor


73, Jim AC6XG