Tag Archives: batteries

Lipo Woes

I was hoping to dust off my Blade CX2 this afternoon and get some flying in. It’s been many months since I’ve flown, and that’s really a shame.

So I take my two 800 mA 2S packs out of the liposack in the garage, and they’re both pretty swollen. One of them is still at nearly full charge (about 3.5 volts per cell), the other has one cell at 0V and one at 2.5V. Looks like no flying today… and best of all, now I get to figure out how to dispose of these things.

This really seems like something that should be on Wikipedia, or at least Snopes. The lazywebs give me all sorts of conflicting information: some people claim you should discharge the cells with a resistor or light bulb then throw them in the trash, some people say you absolutely must not discharge damaged cells, and to put them in salt water instead.. but then it seems that the salt water is more of an urban legend, and really just turns out to be a rather ineffective way to discharge the cells. The salt water won’t get into the cells themselves unless you puncture the casing (which seems like a really bad idea) and it just eats away the battery’s terminals, making them impossible to discharge properly.

For now I’m following the approach that makes the most sense to me: put the cells outdoors in a fire-resistant bag, and discharge them to zero with a 100 ohm resistor across each cell. Supposedly they’ll be inert at zero volts, and I can take them to the recycling center or throw them in a dumpster or something.

Is there an obvious resource on Lipo disposal that Google is just failing to find? This really seems like a great example of the internet at its least helpful- dozens of “authoritative” answers out there, all different.

Anyway, I guess my CX2 is still out of commission for a little while. I just ordered some replacement batteries, and that seemed like as good an excuse as any to also buy a Blade mSR. One of my coworkers has been raving about his, and it seems like a good second heli to learn 🙂

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“Luggable” power pack

Paul and I are leaving on a cross-country train trip next week, for Jen and Shawn’s wedding in Colorado. I’m sure the view will be great, and I’m bringing a handful of books- but Paul and I are geeks and we need our electro-doodads. If only we had a way to run our Nintendo DS and PSP for the ~30 hours that the trip will take…

I sifted through my stockpile of junk, and came up with this:

It’s kind of like a mega-size Minty Boost, or a heftier version of the Kensington power pack. The Minty Boost weighs in at about 6 Watt-hours, depending on the AA cells you use. The Kensington pack is rated at 7 Watt-hours, with a Lithium Ion battery. This brick occupies the middle-ground between the Minty Boost and a car jump-start battery, weighing in at 84 Watt-hours. It should run and charge a Nintendo DS for at least 30 hours.

It’s built almost entirely from junk that I had lying around the house: (Your house may vary.)

  • 12 Volt 7 AH Lead-calcium battery
  • Aluminum box, in my stockpile of project enclosures
  • Receptacle end from a cigarette lighter extension cable
  • DC-DC converter from an old Nokia phone charger (for a phone I no longer use). Swapped a resistor with a trimmer pot for 5V output.
  • USB sockets from a dead 4-port hub
  • Heavy duty wires and quick-disconnect plugs from a dead UPS
  • Odds and ends: Switch, mounting hardware, fuse holder, wire nuts, foam weather-stripping, JB-Weld epoxy, heat shrink tubing, LED, resistors

Parts I had to buy at the local Fry’s:

  • 10 Amp fuse (Pack of five for a few dollars)
  • 12V 1 Amp lead-acid battery charger ($20)
  • Cigarette lighter plug for the charger ($2)

Now here’s hoping that nobody thinks it’s a “hoax device”…

P.S. I’m still working on the Robot Odyssey DS port and in fact there are some interesting bits of UI working now- but I haven’t quite reached another blog-worthy milestone yet.