Trish's FT-817 QRP Page
Portable and Emergency Power Considerations for the FT-817
Being a discussion of the FT-817's power consumption and requirements for portable and emergency power use let's start out by quoting the FT-817ND's specifications as listed in the manual for reference. For the sake of all of my discussions please assume the unit requires a negative ground and the stock MH-31 microphone is used. Also a W4RT SSB filter is installed. Yaesu Quoted Power Requirements Receive Current: 450mA My Observations Running from an external 12v 5000mah lead acid battery
on 3.97Mhz LSB with back light and LED's disabled. Running from an external 12v 5000mah lead acid battery
on 52.525Mhz FM with back light and LED's disabled. Powered Down Now with all that said its pretty plain to see that the 817 requires a fairly substantial amount of current for a QRP rig, especially when compared to some of the typical home brew QRP rigs or Elecraft's K2 but one should keep in mind that this is a commercially designed rig that is microprocessor controlled and covers from 160m thru 70cm (more or less) in all modes where a homebrew CW only radio can get by drawing significantly less current with out all the extra bells and whistles.. Internal Batteries The most basic way to improve your internal battery capacity is to use the supplied "AA" battery holder with 2300mAh to 2700mAh AA cell NiMH batteries that are currently available (Jun '06). If you wish to charge these cells with the radios' internal charger you will need to disconnect the battery trays green wire. (Warning, do not attempt to charge non-rechargeable batteries in the tray. With the green wire disconnected the radio will try to charge any cell installed in the tray if you turn the charge timer on.) The problem with using the internal charger to charge any battery is that it only supplies a few milliamps of current. The supplied NiMH 9.6v 1400mAh pack requires 8 hours to charge, a 2300mAh pack requires two 8 hour cycles for a total of 16 hours. Here's the problem with the internal charger, 16 hours of charge time for 3 to 4 hours of runtime, a terrible tradeoff in my opinion... The other option to charge when using the "AA" battery tray is to use one of the many 1-2 hour individual cell quick chargers that are available at most department and hardware stores. The down fall of this approach is that you end up frequently opening the battery cover (which is somewhat difficult to operate). Also you should be aware that wires and connectors for the battery tray are quite frail/delicate and could easily break or wear out with frequent swapping of the internal battery or cells. The other option for the internal battery is to buy an after market battery pack which is the option I chose after quite a lot of deliberation. Of the different after market packs available I decided on W4RT's "One-Plug Power" 9.6v 2300mAh NiMH battery pack for its' self resetting fuse, thermal and over current protection, external charging option, and the fact that it disconnects itself from the radio when the external quick charge jack is used. Now I am quite capable of making my own battery packs and have made several external ones for for use with my 817 but in the interest of saving time and the fact that W4RT's battery pack is very reasonably priced (as compared to ordering all of the parts and making my own) I found it couldn't be beat. In the beginning I have been running the W4RT battery pack through multiple charge/discharge cycles using my radios internal charger to condition the cells but ultimately the 16 hours it takes to charge the pack is just to impractical. Now W4RT does sell their "One Fast Charger" that connects to the packs external charging jack which will charge the pack in ~2 hours but the thing looks like a clumsy multiple piece hunk'o'junk (sorry W4RT, I like many of your products but this one just seems sub-standard) which would not lend itself easy to travel with, even more limiting is the price and the fact that it requires AC power to charge with. After doing some research I discovered Maxims' MAX712 charge control IC chip on Maxims' website at http://www.maxim-ic.com. Reviewing their white papers they even supply the perfect circuit/schematic to deploy it. The thing that makes this option the one for me is that I am addicted to solar energy and solar panels for all of my amateur radio work and I can design this circuit to run off of the 12-16VDC that my solar panels typically supply so I can not only continue to keep my hobby independent from the grid but can charge my batteries anywhere I might be as long I have a partly sunny day or the 13.8v supplied by most cars these days. When I've completed the design of my charger I will post it here for all to use free of charge, no pun intended ;-) External Power My 817 follows me around the house most of the time running off of one of my 12v, 5000mAh lead-acid batteries which I charge with ~10w of solar panels, by the time one is run down (about two days of monitoring with about 30 min talk time per day) the next has been recharged (even on cloudy days). Just for reference I am self employed and work from my home office. I also have a 40w solar panel array residing on my roof which is connected full time to my ham shack and base equipment. The 10w portable cell is enough to run the radio in receive mode but does not supply enough current for transmit but it does a nice job of trickle charging my 12v, 5000mAh lead-acid batteries. The 10w panel supplies about 560mA in full sun. The 40w array on my roof can supply ~3.3A and is more than enough to run my 817 in full 4.5w transmit mode (Note: I use a solar charge controller to limit the arrays voltage, without the controller the array can supply as much as 21VDC under low/no load conditions which would most likely fry my favorite radio.) I originally acquired the 12v, 5000mAh lead-acid batteries for extended use with our HT's on ARES/RACES events which last for days but are rather heavy and clunky in the hip pouches we use. |
