Wheelhaus
Veteran
Location: Denver
| Thanks for the tip Wrath, here's my input on A123's...
1: I agree with Ron, the Z30A-800/clones would also work great, but they aren't quite as efficient as the Neus. They will however, run cooler in hot weather.
2: I haven't balanced my 10s packs in over a year and they're still cranking after 250+ cycles (estimated). I will occasionally check the individual cell voltages with a multimeter (by making a tiny hole in the heat shrink with a 1.5mm hand drill). My packs are a 5x2 brick so this is easy to do.
3: I think 3v average is still quite a bit high. I'd expect 2.8v average. They are 3.15v nominal, but will sag to 2.5v under load.
4: I average 6 minutes with a flybarless setup using 550mm blades, so with a flybar I'd be getting closer to 5 minutes. A 5s 3700mah lipo (at 3.7v average using 80% capacity) has 54.76 watts/hour. A 10s 2300mah A123 (at 2.8v average using 90% capacity) has 57.96 watts/hour. Your flights may be shorter of you decide to use longer blades, it will take more watts tp swing longer sticks and the added weight will ahve an effect. Your flights may be shorter by .5-1 min I'd guess... Its hard to say.
5: I charge mine at 3-3.5 amps (1.3-1.5C). They can handle higher C charge rates, but it shortens cell life. From the car battery, I'm a little paranoid about getting stranded so I let it idle while I charge. Keep in mind that the car battery will put out ~12v. If the A123 pack is at 36v, that's a multiplier of 3x. YOU may be charging a 36v battery at 3c (7 amps) but its pulling 3x that much from the car battery. 36v x 7a = 252 watts (most chargers can't even handle that)... 252w / 12v = 21 amps from the car battery. That's quite a load! The newer Astro Li-Ion charger works great for A123 batteries (not so much for lipos anymore since its a CC/Pulse charger). If it has different software than the 109, it should charge 10s just fine (mine has some issues with low voltage detection choosing a too-low cell count and "finishing" early, very annoying). Recently I have only been using my TME Xtrema because its such a damn good charger.
6: The 5x2 brick will fit the swift just fine thanks to its large undercarriage. I'm using a 5x2 brick and though its not the best for CG, it does work fine. Its a heavy pack so you'll need a couple heavy duty velcro straps to keep it secure. If you want to reconfigure the pack, you'll need a few special supplies to resolder or build tubes, etc. The cells are aluminum and aren't very tolerant of heat so they need to be soldered very quickly and carefully with aluminum flux. If you're using the stock 5x2 config, the tabs are not aluminum and you can solder on your own plug leads using standard soldering equipment. I get my heatshrink from www.batteryspace.com and use the 5" wide (measured flat) shiny PVC stuff.
Other observations:
After a couple hundred cycles its hard to tell, but sometimes I wonder if the cells are getting a little tired. I'm getting about 20-30 seconds less flight time and the power seems a little faded. Any battery would have a noticable performance difference after a year and several hundred cycles so this doesn't durprise me.
..........
Dave
TT e620 SE and Mini Titan |
