Question from mechanical guy

It probably won't work. The energy density of ultracaps is maybe

1/1000 that of a decent battery, and the cost per kwh is probably 1000x as much. Or something like that.

John

You can't *substitute* batteries with an ultracapacitor, it's intended to help batteries supply current 'surges'.

Graham

control.

help

OK, so how do those cheap little model airplanes sold at Harbor Freight and hobby stores do their dance? I charge a capacitor, then push the switch, the propeller turns and the airplane flies with a very light capacitor and small resistor as the circuit. This seems like a simple battery substitution thing and weighs much less. What am I not seeing?

Lets say I want 1,000 Watts for twenty minutes max, and I want the power/control system to weigh less than one pound. Can this be done with batteries? Also, I want to recharge the system in a minute so I can launch again with a different 'mission'.

Wayne

No. There is no way to store that much electricity in so little space.

You are asking for about 300 watt-hours (Wh) in about 0.5 kilogram, or an energy density of 600 Wh/kg.

The energy density of Maxwell ultracapacitors is about 3 Wh/kg.

The best Li-ion batteries made by NASA come much closer to your requirements, at about 100 Wh/kg.

Probably little sub-AA? rechargable (NiCd?) batteries. That's how the micro RC cars work, based on what was inside the one the dog chewed up. Maybe you think that looks like a capacitor.

I seriously doubt it. If such a high performance energy storage method existed it would be used for electric cars, mobility scooters and so on.

I think you're in very expensive territory, if it's possible at all. Maybe some kind of microturbine generator and liquid fuel.

Best regards, Spehro Pefhany

--
"it\'s the network..."                          "The Journey is the reward"
speff@interlog.com             Info for manufacturers: http://www.trexon.com
Embedded software/hardware/analog  Info for designers:  http://www.speff.com

battery

to

and

the

small

thing

Interesting, I wonder what the energy/weight of an elastic band is?

A one pound elastic band would take some winding !

Colin =^.^=

The Romans used equivalent natural products in some of their weapons.

Graham

It wouldn't take a 1-1/3 HP motor 20 minutes to wind it.

Best regards, Spehro Pefhany

--
"it\'s the network..."                          "The Journey is the reward"
speff@interlog.com             Info for manufacturers: http://www.trexon.com
Embedded software/hardware/analog  Info for designers:  http://www.speff.com

intended

Freight

switch,

with

I gues not.

When I was a kid I had this balsa wood plane that had a larger than the normal elastic band, but had to wind it by hand, took ages to wind but only a few minutes to unwind! I put bigger and bigger ones on till eventualy the elastic band just pulled the back and front together but generally available elastic bands are pretty weak.

If advances in elastic band materials could match advances in other materials like carbon fibre, aramid or polymers I wonder what then. I gues it boils down to the energy storage of excess electrons versus inter atomic forces.

I Like the idea of that solar powered airplane.

Colin =^.^=

As a matter of fact, I've got a couple of those, sitting up on a shelf; I'd practically forgotten about them - they were about two bucks a set at the dime store. 1 set = little tiny car, charging station (that takes two AAs), and controller, which is a hand-held transmitter with four buttons: "Forward", "Reverse", "Right turn", and "Left turn". And the little sucker is _fast_. Also needs something like a gym floor to run on (it's got about 1/16" ground clearance ;-) ). But I can see putting whatever little battery and motor they have into a little balsa wood airplane to run a plastic propellor (remember those gliders, that didn't use any power _at all_? Then the rubber-band ones?)

Cheers! Rich

What ever happened to the rubber-band air conditioner?

John

Thank you... Will put on my learning cap now.

battery

launch

battery

launch

I received a note from Maxwell saying the best bet is to use their supercapacitors to extend the life of a standard battery pack by using the stored power in the capacitor as a leveling means and use the extra power when the drain is high on the batteries, like when the device is going uphill. Makes sense to me. And thanks again for your insight.