Archive for the ‘battery’ Category

…eBay winner…

…So, I’m the proud new winner of a used eBay FT-897! I know, I’m excited too. I already can’t wait to get it. Should be here within a week or so.

And, what next? Hmmm… antenna. I’m thinking a really simple really portable string-up wire dipole antenna. Not necessarilly all band, but at least 20m and maybe 40m. Something that can be thrown up over the trees and operated on low power (for battery life).

Then, portability. Transport container. Something hard-cased like aluminum, or soft cased? Something hand-carry, or shoulder/back carry?

Of course, I’ll need another programming cable (I think) and programming software (definitely).

What about solar charging? Portable panels are getting pretty cheap nowadays.

Hmmm… and the habit addiction hobby expands…

…ordered antenna and batteries…

Well, I finally figured out what to do about an antenna and battery pack to make my mobile FT-7800R a portable. For the antenna, I am going with an Arrow Antenna OSJ 146/440 Aluminum three piece J-Pole.

Yep, three piece. Normally, the antenna is sold with a 57.5in long element. For an extra $10, they will make it a two piece. For another $10, they will make it a 3 piece. Not too bad a deal. There are lots of good reviews on this antenna. For my setup, I’ll clamp it to a 1.5in PVC section that ends at an angled 3 way connector. Three small legs will keep it stable.

I also ordered a RigRunner 4005 from West Mountain Radio, complete with power cable and Anderson PowerPole connectors. This will be permanently hooked to the battery in my wife’s Jeep Liberty. When I want to setup the radio for operation (say camping at Peacock Flats), I can plug in the radio, set the antenna up on the roof of the Jeep, and use the radio from a small table near the Jeep.

When I’m ready to take the radio on my bike, it will pack nicely in the trunk bag with plenty of room for bananas and extra water. For battery power, I’ve ordered the parts to build my own 14.4VDC NiMH battery pack. I’ll be using 12 of the 4/3A 4000mAh cells (slightly larger than an A cell) NiMH batteries connected in series. The batteries will be glued together and held with shrink wrap. The power wires will terminate in Anderson PowerPole connectors, as will the charger. I considered a lot of other options before deciding to go with building my own NiMH pack. This was definitely not the cheaper option, but I get exactly what I want. And, if it doesn’t last long enough, I can buy another 12 batteries, use the leftover wire and shrink wrap, and build a second 14.4V pack to connect in parallel, doubling the capacity. And the total weight of two 14.4VDC battery packs? 3.3 lbs! Not bad for an 8000 mAh capacity battery.

Now the hard part… waiting for everything to get here… shipping to Hawaii sucks!…

…official word…

Well, I got the official word from Yaesu tech support. The FT-7800R draws up to 2A of current while transmitting at 5W. So, my understanding of the power/current/voltage relationship is somehow flawed. Also, the voltage range of operation is 11.7 to 15.8 VDC.

So, a 12VDC SLA battery would need a capacity of over 8Ah to give 1-2 hrs of transmit time from a topped off charge down to 11.7V.

Hmmm… however, a NiMH battery has a much flatter battery discharge curve. In fact, it looks to be the flattest. This means that it would hang out closer to it’s nominal voltage for longer, then steeply drop off at the end. For radio use, if you set up two identical radios for a battery test, one hooked to a 12V SLA, and one hooked to a 12V NiMH, the NiMH battery would give more radio use, since it wouldn’t drop below the 11.7V point until the very end, where it would just fall off to whatever the discharged voltage is for the battery, usually between 9 and 10 Volts.

This means that I could use a smaller Ah NiMH battery and get the same battery life.

Another thought is that to keep the voltage above 11.7, I could set up a battery pack with a nominal voltage higher than 12V. For example, there are 7.2VDC NiMH battery packs sold for RC cars. These typically have up to a 3.3Ah capacity. Two of those in series would give me a 14.4VDC 3.3Ah battery.

Edit: I was distracted by battery browsing and found a couple 14.4VDC battery packs. One claims a 3.6Ah capacity. It is a replacement battery for iRobot Roomba vacuums. I have one of those vacuums. In fact, I have an extra battery for one. Hmmm… I’ll need to get a special screwdriver, since the screw heads are a triangle shape, and I don’t have a special bit.

I’ve put the old battery in my Roomba and am seeing if it will charge. If it does, then I already have a battery and charger. When I want to charge it, I just toss it into the Roomba.

Of course, none of this may work. We’ll have to see. First, I need to check and see if the battery is any good. Then I have to finish my chemistry homework. Then I have to catch up on some pages and posts. Then I have to work on cleaning the garage this weekend. Then I have a bike ride on Sunday… the list never really ends, does it? 🙂