The Ampeer ON-LINE!
March 2006
The Club Newsletter of the Electric Flyers Only, Inc
AMA Charter 2354
Walled Lake, MI, USA
Editor: Ken Myers

Fly the Future - Fly Electric!

     HOWEVER, there is more to this as shown in the second set of curves. While doing RUN 19 with my CBA I also connected a DATAQ data acquisition device to each of the three cells. The resulting chart (above) therefore displays the individual cell behavior during the same CBA discharge. Notice that curve 3 (cell 3) clearly drops to 3 volts ahead of curves (cells) 1 and 2, and that at CBA cutoff of 9 volts total, cell 3 is already a bit below 2.5 volts. Now imagine where this cell may have gone had I discharged the pack using the "2.5 V/cell" (or 7.5 volts for the pack) standard industry recommendation. Note that "2.5 volts per cell" is the oft-published minimum allowed voltage for Li-Po cells below which "bad things happen". I don't know from experience if this is true, but considering my investment loss to date I'm not anxious to test this. I just accept the 2.5 number as "gospel".
     Meanwhile, I also did some CBA testing for a friend who recently purchased some Falcon Batteries "Predator" 1550 3-cell packs. This appears to be a product that actually LASTS as I happily reported on last month. As usual, these also tested below label capacity (at a one hour rate). But otherwise they performed equally and very much like my original two and hopefully will also hold the promise of longevity as above. (Time will tell.) On this hope my friend and I collectively ordered even more of these for both of us - for what that's worth.

     Now I note with some pause the February 2006 issue of Model Aviation, page 10, item (5) under "Emergency Safety Alert: Lithium Battery Fires", this:
"Use charging systems that monitor, control, and balance the charge state of each cell in the pack. Unbalanced cells can lead to disaster . . ."

     This advisory sounds good to me, BUT now what to do with all those costly "normal" Li-Po packs and chargers we all bought? AND - of course - any new balancing product (chargers and batteries) will no doubt be specialized by vendor and the connectors between brands will not match, right?
     I've already decided that I DO NOT WANT a "captive" balancing charger, so I won't likely buy one from a battery vendor. Thus, I see here a golden opportunity for some third party balancing charger with adaptor (matching) cables for all future batteries. And I see here an opportunity for a future CBA that accesses individual cells, with matching adaptor cables of course. And I see here an opportunity for ESC makers to interface with individual Li-Po cells so as to retard throttle when the first cell goes low. BUT what I see most is the likelihood of batteries for our use built like those in some consumer products now (e.g. laptops) wherein the packs have built-in cell protection circuitry.
     The latter will likely be quite a while in coming, but the balancing stuff is already emerging. I'm not rushing to buy much given my described experiences with lousy pack life. Besides, I continue to eagerly await Li-Po's that are TRUTHFULLY described with pack capacity MEASURED AT MEANINGFUL (FUNCTIONAL) CURRENT LOADS combined with an assurance (guarantee) of substantial CYCLE LIFE, like some-hundreds of useful (not abusive) cycles. I'm VERY, VERY tired of "investment" loss.
     No more, please.

     I was very interested to read the recent article in the Ampeer questioning the longevity of Li-Polys. I was beginning to think it was me!!!
     I have a 2-cell 2100mAh Thunder Power Li-Poly that I started to use last spring. I have always recharged when I come back from the field at a rate of 0.6A with my Triton Charger. I now keep a log of the charge time, final voltage and mAh restored.
     My 2-cell pack always used to recharge to 8.4V, then 8.39 and now it has just dropped to 8.31V. My voltage cut-off is set to 6V.
     Prior to the drop to 8.31V I flew briefly on a cold but sunny day when it was 36F. The battery was fully charged before I went out, but it only flew for around 3 minutes before the ESC cut. I used to get close to 30 minutes! The notes that come with battery give a lower discharge temp of around 32F and it was warmer than that.
     Whether the batteries present condition is a cell balance issue I don't know, as this battery has no taps. I have a newer 3-cell from Thunder Power that does.
     I have had other Thunder Power batteries that have "gone bad" and could no longer be used.
     I'm now pretty much convinced that the only way forward is to buy the Li-Polys as single cells. Connect them in series to fly and then recharge them individually.
     Do you know who makes 2100 mAh single cells? (MaxAmps.com sells single 2100mAh cells. KM)
     In addition to my current 2-cell issue, early last year my TP 3-cell went bad and I sent it back. About three months later they sent me a replacement that included the balancer connections.
     I think I will either have to consider Li-Polys as good for one season only or re-look at Ni-Cads.

Robert

Dear Ken:

     I really appreciate your newsletter! Here's my most recent project... she's a ball to fly!

     Electric Long EZ from RaidenTech (It comes with a cheap 400 motor which quickly found its way into the box labeled, "I'm keeping this but know I'll never use it.")

Wingspan: 55"
E-Flite Park 480 outrunner motor
APC 9x7.5E Propeller
Phoenix 35 ESC/BEC
Thunder Power 3S/2100 Li-Po, yellow stripe (10-12C)
Hitec Electron 6 Receiver
3- HS-81 Servos
RTF Weight: 38 ounces
Full throttle: 22 amps

     It takes off from mowed grass, climbs strongly, cruises well at 2/3 throttle, will loop with a little dive help, will fly inverted, and has very gentle stall characteristics. With the power off it will glide very slowly and land gently. It could be powered with an AXI 2814/12 for a lot more zip if you want it, but you'd have to use the newer 20C series of Li-Po to handle the higher amp draw.

All the bestÉ Tom Kempf

Ken:

     Very interesting February Ampeer! You guys up north somehow find a way to work around the weather!
     You mentioned that small magnets from Radio Shack could be used to hold things together. I had bought a couple pair of those for my B-17. Seemed as if $2.00 for two wasn't so bad, but then I stumbled on an even better source. Our grandkids got one of those Magnetix kits for Christmas and are those ever a deal for small magnets! Got myself one of the smallest kits ($5.00 at Walmart) and got 24 magnets. Had to use the Dremel tool to split the plastic housings apart to get the magnets out, but what a deal!
     Speaking of the B-17, I finally decided on Li-Po batteries for the new AXI motor setup. It's really overkill, but the price was right. I'm using two MaxAmps 6300-3S3P packs, one on outboards and one on inboards. Had to saw off the bombardierŐs window to allow sliding the packs in from the front as they were too long to fit in the normal hatch. That's where I used the magnets, to hold the window/hatch on. Bench tests run full throttle for 9.5 minutes. Static current drain is 48A per pack, 24A per motor. This year it WILL fly, and power will NOT be the issue!
     Thanks for a wonderful newsletter, and congratulations on a great 10 years with it!

Bob

     Thanks Bob. Actually, the Ampeer has been published since February 1988. It was a paper only publication until 1996. The paper version reached almost 200 subscribers back then. Lots of folding, stapling and stamping! Glad those days are gone. Only about 40 paper subscribers today, but the Ampeer notification email is sent to almost 800 folks, and thanks to you all! :-) Ken

     Once again, the EFO met at Rick Sawicki's house, and again we thank him for his super hospitality!
     It was a night of wonderful plane talking. The attendance was very good, and everyone there had a lot of fun.
     Pres started out by sharing three more of his beautifully crafted rubber powered free flight models.

One of the German concepts that didn't make if off the drawing board.

     Richard Utkan had the new Cox P-40, which he said flies very well and even faster than he expected! He also had a very nice Steven's Aero DiddleBug, which he also enjoys flying. He said the kit went together well. It is covered with tissue.

     PMAC member, Hank Wildman attended the meeting. He had just come from the PMAC field and shared his Kyosho Corsair, GWS A-10, a C-47 with onboard video and a huge One Design. Hank has done a lot of work on all of the planes, upgrading the power systems, installing retractable landing gear and the like. Hank can be seen pointing out some of the features of the C-47 and Corsair. He noted that the C-47 is not one of the most pleasant planes to fly, while the One Design is EXCELLENT!

     Ken Myers shared his completed Electro Flying Fusion. There will be a review of this great kit in an upcoming Ampeer. Ken noted that this is a craftsman type kit. While it does have some very nicely cut and perfectly fitting laser-cut parts, there still is a lot of carving, sanding and shaping to do. He said that it was a real joy to build! He highly recommends it to anyone looking for a "40" size plane.

     After the extensive show and tell, we all adjourned to Rick's basement for some AirHog bipe flying! Ken, Rick and Richard each had their AirHogs. It was interesting trying to get all three in the air at the same time in the confined area. What a blast! Richard - check for a warp in your wings! Many folks took a turn at trying to see how many laps they could get around the support post! Just way to much fun. There is a short video of some of the action on the Web at: BasementKen.wmv
     We can thank Camille Goudeseune enough for providing us with our winter meeting entertainment!
     There is a site dedicated to these little, inexpensive fun machines at: www.aeroacemods.com. You can also purchase them there.
     What a great night!

     Nice review in the December issue. I'll try the VCR tape and see if it helps the porpoising.
     I bought one for my 5 year old. It's a great plane. I find it's me going out to fly it quite a lot. I can't seem to get enough of it. I can't find them for sale anywhere. I bought it last fall visiting some friends in New York City at Toys R Us. The single 10 second charge ones are garbage and cost about 10-15 bucks. So I said, how bad could it be? Bought the Aero Ace for around 30-35 bucks. Well worth the $.
     I've been experimenting with mine too, thinking about how much weight those stickers are adding and those little raised bumps from the mold must create a lot of drag maybe I'll try to sand them off or use a razor. I did have a little luck with the wheels I stole from my kid's matchbox car.

Thanks,
Robert