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[K7RKO]

I'd appreciate some advice on the best portable power source for portable HF operating at 100 watts... I have an FT-891 and would like to make sure it's getting the 13.8 Volts and 23 Amps it needs. 

I do not want to use a generator.  Operating conditions are away from a vehicle.  Any insights on LiFePO-4 batteries and solar panels (or other alternatives) would be most welcomed.

Thanks, and 73.
Paul
K7RKO

[K5LXP]

Quantify the power requirement in Ah.  Also know what voltage range is acceptable for the equipment in use.  A budget number would be useful too as lithium solutions can be kind of spendy.  Solar sounds good on paper until you have to haul it out into the sticks, and it only takes one cloud to ruin the show.  While you can buy and try a given solution you might save a false start or two by having some specific idea of what you expect the system to do for you.

Mark K5LXP
Albuquerque, NM

[K0UA]

Most people use a Bioenno Li pack either the 15 amp hour one or the 20 amp hour one depending on how long you want it to work, and also depending on the mode that you intend to use. Of course you can always reduce power some to save energy. Some will also pack a small 20 to 30 watt  fold up solar panel along too to extend the time. How long do you want to transmit at the 100 watt level?  You can transmit a lot longer at 50 watts, and a lot longer yet at 25.  And a whole lot longer on SSB than any digital mode, But the number of contacts might be better on CW for a given power level. Even the type of operation you anticipate using will make a difference.  Are we talking about packing on your back or driving up and walking the equipment to a picnic table.  More information is needed for sure here.

[KD9LFW]

I run a IC-7300 portable (yes, it's big & heavy but I can't afford a second portable radio yet) with a 20Ah LiFePo battery. It's a heavy setup but, with a well-made backpack, it's doable for a few miles. I've run the 20Ah battery at 100W for three hours and still had plenty of capacity left (in the battery, not in me). Were I to do it again, I would consider getting a 10Ah battery to save money and weight. I realize that I don't really need to run 100W on SSB but can easily get by running 50W or even less and so can get by with a smaller battery.

[AC2EU]

Last field day I used a 75 watt solar panel, solar charger module,  and a 130 AH deep cycle battery .
Ran an old IC735 for two days with power to spare.
The battery was under continuous charge during the day, so there was lots of power to run after dark.

[K7RKO]

Thanks for the info.

I've been doing a few POTA activations with an FT-891, a Bioenno 12V 20Ah battery and a 20 Watt solar panel.  My goal is to extend operating time.  Sounds like upgrading the solar panel is a good first step.

73 and Happy New Year
Paul

[KU3X]

 ................ My goal is to extend operating time.................. 

Want to extend operating time? Cut your power back to 50 watts out ! That's only a 3db decrease in output power and hardly noticeable  on the receive end.
I have an FT991A and had an FT897D, both need 13.8 volts to achieve its rated output power of 100 watts. Using a fully charged lead acid battery, both radios would only put out 70 to 75 watts.
Big solar panels yield higher output current. Using one is a great idea. I used one for field day but I was only running 5 watts. I used a 24 volt solar panel, it kept the battery topped off the entire time the sun was out.

The best suggestion I can offer you is to use an efficient antenna. Don't use some coaxial fed antenna that advertises, "With a good tuner you can work all bands!" Snake Oil !

Barry, KU3X

[KU3X]

Oops!  Typo.....24 watt solar panel, not 24 volt.

Barry

[G4AON]

<snip>I do not want to use a generator.  Operating conditions are away from a vehicle.  Any insights on LiFePO-4 batteries and solar panels (or other alternatives) would be most welcomed.

Another vote for lithium iron phosphate batteries. They are far safer than lithium ion batteries, the big downside is initial cost, but if chosen wisely should be a similar cost over their expected lifespan.

I use a 68aH LiFePO4 battery for “car portable” use where the radio and laptop are used from within the car. The battery is lighter than a lead acid one, but at 7.8Kg, is not ideal to carry any significant distance.

My radio is either an Icom IC7300 or 9700, the laptop runs from a 12V to 19V psu. Operating is mainly in VHF contests with logging on the laptop. Duration is typically 6 hours.

73 Dave

[W9IQ]

Do keep in mind that the size of the solar panel needed is heavily dependent upon the season and location at which it is operated. The insolation (energy per square meter per time e.g. kWh/m²/day) varies by location and season. Most solar panel power ratings are under ideal irradiation conditions (1000 watts/m²) so some location and seasonal specific calculations are often in order to ensure that you will achieve the desired operating time.

- Glenn W9IQ

[AE0Q]

I have an FT-891 and would like to make sure it's getting the 13.8 Volts and 23 Amps it needs. 

The Bioenno LiFePO4 batteries are 13.2 at no load, my 40AH battery drops to 13.0 under load when transmitting at the 100w setting (TT Eagle on SSB or CW) for a few hours, contest style.  When portable I don't have a separate wattmeter so am not sure what the actual RF output is at 13 vdc.

If using a solar panel and charge controller with lots of sun you would have higher voltage, but it might drop when transmitting since it would be a big setup for a few hours of portable operating to supply 23 amps from the panels.

Glenn AE0Q

[NO9E]

See my post under "Honda generators". I use FT-891 with LiFePO3.

Want to extend operating time? Cut your power back to 50 watts out !

Thsi is not a very good advice. Reducing power by 50% reduces the peak current by the square root of 0.5, or only 30%. Reducing the power to 25W reduces the current only 50%.

Ignacy NO9E

[KU3X]

See my post under "Honda generators". I use FT-891 with LiFePO3.

Want to extend operating time? Cut your power back to 50 watts out !

Thsi is not a very good advice.

Ignacy NO9E

There is absolutely nothing wrong with cutting your power in half. I did not say by cutting your output power in half you will draw half the amount of current ! BUT....by cutting your power in half you will save on current drain. The person on the receive end of the transmission will hardly know the difference in signal strength.
I've been doing that for many years.
If one wants to make sure they are getting the full 100 watts out of the FT891, then get the booster from MFJ that will take 11 volts and boost it up to the full 13.8 volts. What did you gain by doing so?
You now have your 100 watts output but watch how fast your battery will die?
Put two hams side by side in a park both operating FT891's. One ham is running his radio at 50 watts out and the other at 100 watts by using the MFJ booster. Guess which ham is going to pack up and go home first?
Barry

[KK6RPX]

See my post under "Honda generators". I use FT-891 with LiFePO3.

Want to extend operating time? Cut your power back to 50 watts out !

Thsi is not a very good advice.

Ignacy NO9E

There is absolutely nothing wrong with cutting your power in half. I did not say by cutting your output power in half you will draw half the amount of current ! BUT....by cutting your power in half you will save on current drain. The person on the receive end of the transmission will hardly know the difference in signal strength.
I've been doing that for many years.
If one wants to make sure they are getting the full 100 watts out of the FT891, then get the booster from MFJ that will take 11 volts and boost it up to the full 13.8 volts. What did you gain by doing so?
You now have your 100 watts output but watch how fast your battery will die?
Put two hams side by side in a park both operating FT891's. One ham is running his radio at 50 watts out and the other at 100 watts by using the MFJ booster. Guess which ham is going to pack up and go home first?
Barry

I have one of those boosters and as you say it doesn't help that much. I don't contest so my use time is pretty low. I have experimented and they station at the other end can hear a difference but not the difference between copy/ no copy, unless maybe if I was not quite copyable. So I do run it as my batteries aren't in danger of being run down by my radio usage. Since my radio in the van is for fun and emergency I like to have it. But I fully agree that in a contest situation longer run time by running less watts is the way to go.

[LYFAN]

In any solar setup, if you use an MPPT charge controller instead of a PWM controller (or even direct wiring) the MPPT controller should give you about 15% more effective power to the battery. Not cheap, but always 15% more.