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Author Topic: I need help choosing a battery for portable operating.  (Read 17352 times)
W6UX
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« on: August 04, 2010, 11:08:22 AM »

Hi everyone,

I hope this is the appropriate forum for my question.  I will be operating portable with my FT-857D during a road trip from California to Colorado, via Nevada and Utah.  The antenna I'm bringing with me will be a 1/2 wave dipole (inverted-v) at 40 feet, fed with ladder line and tuned with an SG-239 smart tuner.  So, I should have a decent antenna for DX, assuming propagation cooperates, and will be able to work 10-40 meters, maybe even 80.

My dilemma is deciding between operating SSB at 5 watts, and using a few small AGM batteries, or getting a monster battery that weights about 60 lbs so I can run closer to 100 watts.  I'll just be operating a few hours at a time, probably 1-3 hours in a session.  I'll have a Battery Tender Plus charger to keep things topped off.

I can get a couple of AGM 12V 7.5Ah batteries from Powerwerx ($17.99 each).  At 5 watts, that should provide me at least a few hours of operating.   The SG-230 draws just 230mA.  I'd prefer to not have to lug around a heavy deep cycle type battery.

What do you guys recommend?
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AA4PB
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« Reply #1 on: August 04, 2010, 11:31:36 AM »

The SG230 draws up to 900mA (almost an amp). The actual current depends on the tuning solution and how many relays must remain closed to match your antenna. Bottom line is that it's not the best solution for portable, battery powered operation. For that type of operation you should consider either a manual tuner or one of the automatic models with latching relays that don't draw any current once it is tuned.

As far as 5W vs 100W, that's a trade-off you'll have to make. What's more important, making more contacts or not having to lug heavy batteries around?

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AA4PB
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« Reply #2 on: August 04, 2010, 11:35:15 AM »

Ooops pulled up the wrong spec sheet. The SG239 does only draw 230mA, still quite a bit for battery operation considering it is a constant drain on both Rx and Tx.
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W6UX
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« Reply #3 on: August 04, 2010, 11:40:22 AM »

Ooops pulled up the wrong spec sheet. The SG239 does only draw 230mA, still quite a bit for battery operation considering it is a constant drain on both Rx and Tx.


I plan to power the tuner with it's own 12V 7.5A battery for that reason.  So it's really down to what I use for the transmitter.  I supposed it's probably prudent to just invest another $18 in a second 7.5A battery and try the rig out at 5 watts and see how it goes.  A Yellow Top optima battery is around $130, I think, so that's kind of the other possibility I'm trying to decide.
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AE4RV
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« Reply #4 on: August 04, 2010, 12:11:43 PM »

Being used to the LDG tuners with latching relays, I forgot to factor in the current consumption of my new AH-4 remote tuner when I operated QRP on field day with a 22AH battery. Turns out the AH-4 draws 200+ mA even in stand-by mode (when I was using a tuned dipole and different coax). I was surprised to see my battery get down to 12 volts after only eight hours using an IC 703. Now I know why.

At least you remembered to factor the tuner in!

73 Geoff

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AA4PB
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« Reply #5 on: August 04, 2010, 12:27:06 PM »

You have to figure that many of the automatic tuners like the AH-4 have 20 or more relays in them. The coils probably draw close to 50mA each to keep them closed. Mgs often spec the "minimum" current, meaning that the tuning solution doesn't need any relays closed so you are only looking at the processor current (the best case). If you happen to require a tuning solution that requires all relays to remain closed (the worst case) then you could easily be looking at an amp (plus the processor current). Normally you'll be somewhere between the two, but you can't count on it.

Latching relays solve the current problem but commonly available latching relays don't have the voltage/current ratings required for more that 20W or so (again, depending on the antenna impedance). Tuners using latching relays generally are either rated for low power or a very limited impedance range.

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VA7CPC
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« Reply #6 on: August 04, 2010, 01:02:36 PM »

The LDG Z-11 Pro uses latching relays, and it's rated at 125 watts or so.  I power it with AA batteries.

 It has a reasonably wide matching range -- certainly, it will match any dipole cut _approximately_ to the operating frequency, and it handles my 40/20/15/10m fan dipole on 30m.   

It _won't_ match a 16' vertical on 80m; that's a job for the SG-230.

               Charles
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WX7G
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« Reply #7 on: August 04, 2010, 03:22:10 PM »

The FT-857D can be operated at full power using the smallest automobile battery. A few hours of normal CW operation can be had.
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K5LXP
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« Reply #8 on: August 05, 2010, 08:20:25 PM »

I'd check that 857 on the bench with an ammeter before you go sizing batteries.  If it's anything like an Icom 706 it draws over an amp on receive, and six amps on transmit at 5 watts out (no, that's not a typo- 75W in, 5W out).

I've run my 706 at 5W using a 7Ah gel but it's depleted in about 2 hours at a modest duty cycle.

There's choices between 7Ah and "heavy deep cycle" batteries.  Consider perhaps one of those ~17Ah jump start packs, and operate at say, 25W out.  That's only an S-unit down from 100W and would likely give you your desired operating time.  Plus you get the convenience of a built in charger/battery in one package.


Mark K5LXP
Albuquerque, NM
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W6UX
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« Reply #9 on: August 06, 2010, 10:51:02 AM »

I decided on a compromise between the small and large AGM batteries.  Another Ham had good success this past Field Day by wiring two 12V 12Ah batteries in parallel and it lasted them the whole contest, he claims at 100W SSB.  Now he didn't say what the duty cycle was, my guess is he was operating "search and pounce" rather than "running".  The 857D manual says it draws about 1A on receive, so with a 100% topped off battery, he'd be lucky to get 24 hours just listening, and really you figure it's more like 12 since apparently you don't want to run AGM batteries down more than about 50% (to maximize the # of cycles you can get out of them).  Perhaps he had another set of batteries and swapped them out during the contest; he didn't say.

I'll dedicate a smaller 12V 7.5Ah batter for the SG-239 tuner.

12V 24Ah should give me several hours at 5-50 watts, and allow me to boost to 100W for short DX contacts (the 857 draws 22A @ 100W); I'll be happy so long as I can get 2-3 hours, which is about the longest session I will have time for during my vacation.

I got a pack of 2 12V 12Ah batteries from Gruber Power Systems.  Their eBay store sells the 2-pack for only $37!
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KB1GMX
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« Reply #10 on: August 06, 2010, 12:49:42 PM »

I'd suggest a different antenna solution.  Either and end fed wire with a simple one band coupler or
make up a 40M dipole with coax feed and forget the SGC.  You don't say if you will be
multiband operating but if your doing 40 and 20M the dipole with coax feed is less stuff to
bring and hook up.

If you use the 40M coax fed dipole set it up as a full length 40M for 7.1 as that will cover the band.
to use it at 20M make each wire half size by folding the end back to the center insulator and moving
the end insulator to the wires new end.  It's possible to do other bands higher than 20M but you
have to work out the exact length for the overall length and the excess is just folded back and
wrapped on itself.  Usually the big issue is getting two support to hold it all up.

As to the radio you need more than twice( more like 3-4x) the battery for use as RX is a solid 1A
and TX is a real load 6A plus and the radio may not like a partially discharged battery as teh terminal voltage drops some as the battery discharges.  So for a reliable 3-4 hours use I'd be in the 30AH or
larger size battery (1 not two in parallel) and it must be rated for deep discharge use of it will
not last through a lot of discharge/charge cycles.  Also a larger battery means that 10 or 20W
operation is reasonable or usable when needed.

Make sure all your connections are very good as any resistance or thin wires means lost power.
I'd suggest Power Poles or other keyed connectors as field assembly invites the dreadded Oops.


Allison
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WZ1P
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« Reply #11 on: August 15, 2010, 12:49:00 PM »

The A123 nano phosphate battery packs at buddipole.com is a really good choice. Not cheap but the only battery that I drag around the world with me. You can run 100w for a few hours on one. Just go their website and click on 'portable power'.

73, Dan
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VE3WMB
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« Reply #12 on: August 16, 2010, 04:49:42 PM »

I agree with Mark, K5LXP.. the difference between 25W and 100w is only one S-unit but it makes a big difference in how much current the rig will draw (~5A vs ~25A). There is really no need to run 100W when operating portable. You are planning to use a decent antenna so you should be fine.

Frequently places like Walmart will have jump-start battery packs on sale. I have one that has a 22Ahr SLA in it and it is moderately heavy but still easy to tote around as it has a nice chunky handle built-in.
Mine has a built-in USB port for charging things like iPods and in a pinch I can even use it to jumpstart the car ;-)

Michael VE3WMB

I'd check that 857 on the bench with an ammeter before you go sizing batteries.  If it's anything like an Icom 706 it draws over an amp on receive, and six amps on transmit at 5 watts out (no, that's not a typo- 75W in, 5W out).

I've run my 706 at 5W using a 7Ah gel but it's depleted in about 2 hours at a modest duty cycle.

There's choices between 7Ah and "heavy deep cycle" batteries.  Consider perhaps one of those ~17Ah jump start packs, and operate at say, 25W out.  That's only an S-unit down from 100W and would likely give you your desired operating time.  Plus you get the convenience of a built in charger/battery in one package.


Mark K5LXP
Albuquerque, NM

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W8AAZ
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Posts: 323




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« Reply #13 on: August 29, 2010, 05:48:52 AM »

When I was a teen of fifteen or so, I ran bicycle mobile.  Not HT either.  Mounted old Genave crystal rig on the handlebars, 10 watt class radio. Got one of those fibreglass poles that mounted on the axle with an orange flag.  Took off the flag.  Converted the pole to a gain antenna with wire, matching coil and tuning network.  Ran coax along the frame.  Made a crude bracket and mounted a Globe Gel Cell on top of the radio.  Now this was maybe 6-12 A/H type, not real large, I forget after the decades.  But I was able to work all over the place just like a car mobile with that rig.  Ride up to high ground and work repeaters 40+ miles and simplex pretty far too.  Globe Gell cells were thereafter my choice of portable power for a long time as they were cheap as equipment pulls(replaced on a regular basis used or not) and relatively easy to charge up. Never really ran any 100W gear on batteries portable though.   
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AA4PB
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Posts: 12696




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« Reply #14 on: August 30, 2010, 05:44:22 AM »

Marketing dept specsmanship. The components in a tuner are "stressed" when matching extreme impedances. When you see a tuner with small relays and components that has a big power rating you can be sure that the impedance range is limited.

1. Small components
2. Impedance range
3. Power capability

Pick any two.
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