Archive for June 2004

About LiPolys

With nothing better to do on the plane, I charged, discharged and charged the LiPoly battery to see how much capacity it really had. I got some strange results:The battery is a Thunderpower 2100, with a manufacturing stamp on the label of 6-4-04

  • 6-28-04: I set the Triton charger to charge at 2.1 AH, 11.1 volts. It ran for 69 minutes. Final charge was 12.56 volts, 1.796 AH put into the battery
  • 6-29-04: I set the Triton to discharge at 2.1 AH down to 9 volts. After 56 min, the Triton stopped at 10.5 volts, having discharged 1.635 AH.
  • 6-29-04: I set the Triton to charge at 1 AH. It started charging at 10.69 volts and finished at 12.56 volts, having put 1.654 AH into the battery after 110 minutes.

So, what’s up with the Triton only drawing down to 10.5 volts? And why did it only pull about 1.7 AH instead of 2.1 AH? I called Sal at NESail and he had a lot to say.

First, he warned me very sternly (!) that I shouldn’t ever ever ever discharge a LiPoly on a charger. There’s no need to and it could damage the battery by drawing the battery down too much. Discharging in a charger is bad because, if a LiPoly is brought down too flat, it’s capacity will be permanently significantly diminished; a charger discharges the battery too slowly to hit the obvious 3 volt/cell wall. If you are flying, the high drain on the pack lets the drain work correctly. In addition, a good speed control will tell you when it’s time to come in for a charge. You shouldn’t drain the battery more than 75% or they’ll go bad on you. That’s 1.575 AH on a 2.1 AH battery.

It sounds like the Triton company is aware of this 75% rule. That’s why they the charger only draws down to 10.5v on a 3 cell 11.1 v pack. The Triton charger seems to have a user interface problem. On the discharge cycle, the options it gives are “3v”, “6v”, and “9v”. The obvious implication is that it will draw the cell down to the specified amount but it doesn’t. It draws the pack down to what is considered “safe” flat… on the “9v” setting, it draws to 10.5v. Instead, it should give options like the following: “1 cell”, “2 cell”, “3 cell”. Or “3.7v”, “7.4v”, “11.1v”. Or “3.5v”, “7v”, “10.5v” because that’s what it draws down to.

Burning Man Art

I’ve been talking about lighting the Projeti for Burning Man in my regular journal. I found a bunch of sources for wire. Well, I found the source I’m going to use: http://www.coolneon.com. This from the Coolneon gallery:

Bad Speed Controller

Sean at Castle Creations talked me through 2 diagnostics:
– Set the Soft Start option to “fast start”.
– Resolder the connections to the motor

Neither helped so he’s sending me another speed controller. It’ll be here in a couple days. I’ll be in Vermont for the 4th so no flying ’til after I get back. :-(   And I don’t want to bring the Zagi. The Zagi is tired. It needs to rest.

Spam Stopper Idea

Run potential spams through a grammar checker…. like MS Word’s grammar checker. That will surely differentiate the gibberish spammers insert into their emails from legitimate emails that use real sentences. It might be computationally expensive but not THAT expensive…

Rail Guns are Cool

Cool snippet of the day:

Rail guns require a pulse power system to convert prime electrical power to the instantaneous current pulse necessary for electromechanical launch. The most advanced pulsed power systems use rotating alternating current machines, called pulsed alternators, to supply electromagnetic current pulses to the rails

“I’d like a phased plasma rifle in the forty watt range”

Escape velocity from earth is about 11 km/sec. This doc says 2.5 km/sec is being done right now experimentally and could be in the field, firing on targets 250 miles away. 6 km/sec is doable, not enough to break orbit but still pretty darn cool. To power one of these rail guns and fire it at 6 rounds/minute, you need something like 40-80 megawatts. Just the dissipated kinetic energy of the impact of one of these mach 7 projectiles is enough to….. it’s enough; no explosives needed.

Good and Bad Things with the Projeti

It’s together. :-) Last night, I reved it up to full power, pointing the nose up toward the ceiling. I could feel it pushing up against my hand. If I had let go, it would have shot straight through the ceiling. Well, not really… it would have hit the ceiling and then shattered into maybe five or ten pieces… but you get the idea; vertical performance :-)And now the bad news: I was getting ready for my outing today and the prop wouldn’t turn. When I gave it throttle, the prop would do this unhappy buzzing thing. The prop doesn’t turn, it just vibrates! Waah! But today was the day! Wahhh!

I called NESail at 5pm and Carolyn said I’ll get a call back by the end of their work day… which is at 6pm…  in 5 minutes. :-( I don’t think I’m going to get that call. :-(

Maybe I changed an important setting on the ESC when I tried to program it. It’s a Phoenix 25 brushless ESC. It took me a while to figure out an important aspect of programming: go slow. If you try to program it too fast, it drops out of programming mode unexpectedly. I’ll go try to program it AGAIN…

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NESail called me back at about 6:05 6 :-) The guy at NESail, Sal talked me though some diagnostics but couldn’t help. He thought it was most likely a busted ESC, though such problems are rare. He motioned me toward Castle Creations. He says that if it’s busted, I could exchange it though either NESail or Castle Creations. Of course I’m unhappy that I’m having trouble with it but NESail has been pretty sand-up-ish. I left a message at Castle Creations after hours. Hopefully they’ll call me back shortly!