Electric Power and the Tesla car

What's your interest in supercaps, Wayne? I don't think they are very useful in robotics or motor control, etc. The supercaps I've used are fine for storing a big charge you take out slowly, like battery back up on RAM memory when you loose main power. But so is a battery - only a lot better in capacity and density, etc. So a supercap in a robot application where there is already a battery is like a redundant piece of equipment that will add weight, complexity, and not improve performance. Have you heard something else about them I haven't?

As I understand it, a lot of power can be available in an instant from a supercap and in a lighter weight 'containiner' for use when you need that extra jolt of power like climbing over a hump and can be quickly recharged from the onboard batteries for another jolt when needed. Am I wrong?

Wayne

You're right..

-- Joe Legris

Huh. I went to the Maxwell sight, and that seems to be what they are promoting for the BoostCaps or Ultracapacitor technologies.

When they first came out, I opened one of the small 1/2" ones, and what outside looked like an electrolytic cap I found inside looked like two stacked silver oxide coin cells. My conclusion at the time was they weren't really much different than a rechargeable battery in nature.

But those had high ESR (Equivalent Series Resistance) and would slowly take up a charge and slowly return it at close to a constant voltage, seeming even more like a battery.

So I don't know much about these new Boost Caps, other than what I'm reading now. Still seems like overhead in a robot to me. At least one with any kind service period.

See the articles too:

-- Joe Legris

In my mind's eye I see the supercaps as that extra boost when you need to get out of a hole. Especially if the motor will accept the extra boost such as a well balanced servo with a good PID controller.

Wayne

"Wayne Lundberg"

Of course it will depend on the type of motor and traction system you use, but if we thing about R/C cars, the batteries have a very high discharge rate, and the wheels will start spinning much sooner than any current limit (for both battery and/or motor) are reached.

I was reading about supercaps and they are very nice, but if you are thinking about R/C sized robots, it's really hard to get convinced of its utility, since the power to fill the caps will come from the battery pack anyway.

Cheers

Padu

Must look into this because Maxwell seem to be promising a lot. But I have yet to see the proof I have been asking for anyway from them.

Wayne