# Forums

## (off topic), 1 kg battery can power model S at a theoretical 140kW to 70kW (starting atalmost 200 horsepower!) for 138 days

Off topic but just for fun, I was reading about polonium-210, here:

One kilogram of pure 210po will produce 140kW and has a half life of 138 days! So, theoretically, assuming 100% energy efficiency, and no weight of the associated parts, a 1 kg "battery" will produce a TON of power. Assuming just for 138 days, and 140kW, and ignoring the decay after 138 days, that must be a ton of kWH of energy produced, 463680kWh. :)

Would solve range anxiety! Anyways I'm sure I probably got the math all wrong, plus I don't know much about how all this works, just stumbled on that wiki page.

Timo | March 23, 2012

There is a small problem with radiation and price with that....

NASA next Mars explorer robot will have radioisotope battery as main power source. Much better than solar panels used in Spirit and Opportunity: way more power at any conditions, including night time.

http://en.wikipedia.org/wiki/Curiosity_rover

BYT | March 23, 2012

How about the use of Super Capacitors in with battery technology? An Electric Hybrid system?

jbunn | March 23, 2012

Brian H | March 24, 2012

It's not a battery, per se. It's more of a thermoelectric generator, using decay heating. As for "better" than solar, the downside is the definite limit on lifespan. The Mars Rovers have run for years on solar, even as the panels are dusted, abraded, and otherwise abused. Much lower power levels, but fair's fair!

Timo | March 26, 2012

Those panels are really low power ones, though at Mars Sun radiation is not very strong no matter what kind of solar panels they are.

It has been small miracle that they still work. That radioisotope battery (that's one of the names it is called) will last longer than those solar panels without human intervention, and that new rover will be able to explore far more than those two earlier models because it doesn't need to stop at night and twilight hours (Mars has almost identical rotational period to Earth: 24.62 hours).

Brian H | March 26, 2012

@Timo;
The main benefits of the nuke battery are power output and consistency, of course. If I was being clever when designing the rover, though, I'd have included a second generator using much longer half-life nucleotides, with correspondingly lower output, and at some "crossover point", had the machine ditch most of the high-draw equipment and left just basic functionality and mobility to exploit the lower power source.

As demonstrated by Spirit and Opportunity, long-duration output is valuable in its own right, and engineers "at home" are often able to squeeze unanticipated levels and types of info out of the data.

Not sure what you mean by "That radioisotope battery ... will last longer than those solar panels without human intervention" It clearly will not last 8 years. And what 'human intervention' are you speaking of?

Nick Kordich | March 26, 2012

@Brian H - Re: human intervention - Timo may be thinking of Elon's recent comments about the cost for a trip to Mars being brought down to \$500,000, which would provide an Opportunity to dust off Spirit's solar panels:

http://www.bbc.co.uk/news/health-17439490

:)

Timo | March 26, 2012

It is designed to last minimum of 14 years, probably a lot longer than that. Curiosity one uses plutonium-238 dioxide which has half-life of 87.7 years, not Polonium that decays much faster.

That "687 Earth days" is for entire rover, not for its power source. Both Spirit and Opportunity should have been dead long long ago: their estimated mission duration was only 90 days, but Opportunity is still working at least partially and Spirit did work many times longer than it should, so maybe Curiosity rover works too (BTW. both Spirit and Opportunity also have small Radioisotope "battery" (or batteries) but it is only used for heating vital components - a must because Mars night temperatures might drop to minus 150C).

"Human intervention" for repairing and cleaning dust- and sand-blasted solar panels.

Curiosity is also a lot larger than both of those earlier mission successes: those did weight only 174kg while it weights 900kg (here at Earth). For rover of that size solar panels would not be sufficient power source. Same problem with cars here: get big enough mass car in off-road conditions and solar just isn't enough.

Timo | March 26, 2012

@Nick, that too :-)

I wish I had money to go visit Mars. Someone once uttered to me that "there will not be anyone wanting to go there" and my response was "are you kidding??". Turns out that he wasn't. I disagreed obviously. I bet there are millions of people willing to go ASAP to Mars and beyond.

Brian H | March 27, 2012

Apologies, for some reason I had 14 months in my head as the half-life. The NASA battery specs page didn't give the power output. I don't suppose there's any way to modulate the breakdown heat, so control could only be over how much is converted to electricity, and how much is used. I wonder if there's a buffer battery/capacitor system for peak load situations.

Brian H | March 27, 2012

@Timo;
you should have suggested a small wording change to your acquaintance: "there will not be anyone like me willing to go there." Heh.

mohanraj777 | October 17, 2015

hi, this is very late to comment, but all those plutonium things are costly compare to the Thermoelectric Generator(is a semiconductor device that transforms the heat difference between its two layers into electricity)
https://en.wikipedia.org/wiki/Thermoelectric generator

using solar roof causing weight problem,

problem to solution is thermoelectric generator,
tesla motors have to think abt this type of thermoelectric generator for future car,

sbeggs | October 17, 2015