WALL•E has been working for several hundred years and one of the keys to this is his ability to use parts of broken robots to replace his own broken parts.

Now this won't work with the electrical batteries we know today - they all have limited shelf life and in 10+ years even the best battery wears out. I can't imagine a contemporary battery lasting for hundred years.

Is there any data on what battery WALL•E uses that has such outstanding lifetime?

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    I doubt any answer to this question would be anything beyond pure speculation. I'd VTC but I'm just a lil fish here. – Ender Feb 4 '13 at 8:17
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    why does the magic technology work? because MAGIC sparkles and rainbows everywhere – sarge_smith Feb 4 '13 at 10:02
  • @sarge_smith: Yeap, but magic is typically found in LOTR-like movies and WALL-E is closer to a Terminator-like movie where magic has some problems. – sharptooth Feb 4 '13 at 10:04
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    @sharptooth nope, wall-e is definitely sci-fantasy, not rooted in facts. It's softer than yogurt. check this: tvtropes.org/pmwiki/pmwiki.php/Main/… and see why question like this are effectively unanswerable. – sarge_smith Feb 4 '13 at 10:18
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    @Chris S: That'd be nice, but then he wouldn't use solar panels and we wouldn't have that "rush to Earth" drama near the end of the movie. – sharptooth Feb 4 '13 at 14:35

Modern rechargeable batteries have impressive lifespans often being able to be recharged thousands of times before wearing out. Assuming the curve of modern improvement of technology we can expect Wall-E to be the beneficiary of a technology capable of being recharged tens of thousands of times, improving both the efficiency and the capacity to be recharged.

Seeing that Wall-E was able to absorb a complete daily charge from a few hours of sitting in the sun, either his solar conversion rate is quite extraordinary or the batteries he uses are able to maintain and gather a charge quite quickly in comparison to modern batteries.

Wall-E catching his morning charge

Wall-E catching his morning charge.

But even if the batteries were only as good as batteries today, Wall-E would have certainly had:

  • Spare batteries from his own initial deployment. If the assumption that a battery would eventually run down after say ten years, Wall-E would have only needed 70 to have lasted 700 years.

  • If in fact, spare batteries were the expected norm for all such compactor robots, then as they began to die off, their spare batteries would also become available to Wall-E.

  • Since these robots had to have been coordinating their work, he would likely be able to find stockpiles from the other robots who died far earlier during his 700 year tenure.

  • It is possible that normal batteries would eventually decay over time even if they were of a superior quality. Perhaps, instead Wall-E was left with the materials to create batteries, as needed, preventing both the reaction to create power or the draining of an already existing battery source.

  • Just-in-time niche manufacturing would resolve this problem as Wall-E would only create batteries when they were needed out of materials presorted and pre-prepared. Lego-type batteries would be a great way to keep battery materials able to be activated without leaving them draining over time.

  • It is possible Wall-E could also run using direct solar power during the day, making it possible for him to work at a reduced power level until new batteries could be secured, recharged or produced. He was not working under any particular time constraints, so it could be he was forced to do his own manufacture.

  • As noted below by, Donald McLean alternative energy supplies such as fuel cell technology could also have played a factor, allowing him to resupply as long as a source of hydrogen and oxygen was available.

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    Well, with modern rechargeable batteries this wouldn't work - they age and eventually die even of a shelf. – sharptooth Feb 4 '13 at 8:58
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    Then they have to be better than our modern batteries, or perhaps they were able to be constructed only when needed out of available materials ensuring they were created only as needed. It isn't that hard to do if the materials are available. Just-in-time niche manufacturing would resolve this problem as Wall-E would only create batteries when they were needed out of materials presorted and pre-prepared. Lego-type batteries would be a great way to keep battery materials able to be activated without leaving them draining over time. – Thaddeus Howze Feb 4 '13 at 9:23
  • Great idea. Could you please add this into your answer? – sharptooth Feb 4 '13 at 9:31
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    One thing no one has mentioned (that I've noticed), but that should be obvious -- he either has something akin to capacitors or a backup battery, allowing his primary to be hot-swappable. Not much of a stretch; even now we are starting to see that more often. Possibly, however, he just swaps batteries with his solar panel out; it might let him run for a period without a battery. – K-H-W Feb 4 '13 at 17:57
  • I don't recall Wall*E ever building anything. EVE does. – Schwern Feb 12 '15 at 18:21

Considering the length of time he is active, my theory would be that he uses a fuel cell. As the Wikipedia article states:

Fuel cells are different from batteries in that they require a constant source of fuel and oxygen to run, but they can produce electricity continually for as long as these inputs are supplied.

The "recharging" would consist of using the solar energy separate water into hydrogen and oxygen. While not necessarily efficient, it would nevertheless provide Wall-E with an almost infinitely renewable supply of energy.

  • Where would he store the hydrogen? – bitmask Feb 4 '13 at 17:18
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    Storage of hydrogen is an important area of research amongst fuel cell proponents. My guess is that they'll have a good answer by the time we're ready to build Wall-E. It wouldn't be any larger than a battery in any case. – Donald.McLean Feb 4 '13 at 20:09
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    @bitmask On the shelf – Izkata Feb 5 '13 at 3:51
  • Just use a methane fuel cell. Methane storage is solved. – Joshua Mar 18 '16 at 3:26

The technology in Wall*E is so bonkers I would happily say it's because of magic advances in battery technology. But that's not satisfying, and not even internally consistent, so let's polish this turd and make it work!

Wall*E is fantasy, an analogy for the unsustainability of modern society. Wall*E, as a hero in the story, is supposed to represent frugality. He recycles. He's solar powered. He's making tiny contributions to cleaning up the mess that turn into huge results. The analogy doesn't hold up when you realize he's just shoving the problem around, then again, he was designed by the people who made the problem in the first place.

You've spotted a major problem with the science of the film, it takes place 700 years after the Earth was abandoned, and the disposable technology Wall*E relies upon will naturally degrade. Plastic will break down in sunlight and become brittle (no spork). The tape in his precious VHS of "Hello, Dolly!" would have crumbled. And, yes, most batteries would be running at a small fraction of their original capability even if they've been just sitting around.

Wall*E's batteries are the least of the scientific problems with Wall*E. Consider The Axiom. Having survived for 700 years in space in leisure, the Axiom would appear to be the epitome of sustainability. Why didn't they use that sort of amazing recycling technology on Earth? (Remember, any tech they had on the Axiom they had on Earth.) The Axiom dumps their trash into space, how do they sustain that for 700 years? The Axiom is an analogy for humanity having knowing how to save the Earth, but finding it easier/cheaper to trash somewhere else, just like we do now. Great analogy, bad science.

The world of 2100 (when the Axiom was launched) appears to have made some huge advances in AI, space flight and (ironically) recycling. The Axiom has hyperdrive, robots smart enough to keep everything running for 700 years with minimum human intervention, and has sustained a large human population. With all those robots running around, it's fair to say they've got good batteries. The energy density of batteries has been getting better at a rapid pace for decades now. What about their lifespan?

The primary way current batteries die is by the charging cycle. After four years and 1000 cycles, my laptop battery is down to 60% it's design capacity. With special equipment this can be reversed, but only so much, and certain types of batteries respond better than others (do not believe what you read on the Internet about battery reconditioning at home).

But batteries also degrade on the shelf. The shelf life of a rechargeable battery is measured in time and temperature. Different types of batteries have different optimal storage requirements, but the time scale is a few years and Wall*E takes place 700 years after the Earth was abandoned. Could Buy N Large have built a battery to last 700 years? Absolutely! But would they?

Buy N Large has created a disposable society. Why build a battery that lasts 700 years when you can just throw it out and make a new one?! And who wants last year's battery when next year's batteries will be better?! This is obvious for their consumer products, but the robots are different.

Like many predatory corporations, Buy N Large is happy to sell you a non-sustainable lifestyle so you'll keep buying. Cheap in the short-term, expensive in the long. But Buy N Large itself would be ruthlessly efficient taking short term loses to ensure long term profits. The durable, sustainable, smart, self-repairing robots of Wall*E are an investment in the future of low cost labor. Might Buy N Large develop long shelf life batteries for these robots? It's plausible if they thought it would save money in the long run. Would they last 700 years? Probably not... but the law of averages says some of them will, and there's a lot of dead robots to average it all out.

The fact that so much infrastructure is still standing (buildings, ships, highways...) after 700 years is a testament to how well things could be constructed in 2100. The lack of life on Earth to pull everything apart would help preserve things, but there is still the corrosive effect of water and effect of ice expanding in cracks.

Other possibilities include...

  • The rate of capacity loss is not linear and diminishes as the battery gets older. Wall*E could have originally been designed to go for weeks without charging. Now he can barely manage a day on what he can scavenge. He could even be using batteries from larger robots with larger capacities (but the same output).

  • We know the humans abandoned the cleanup effort after just a few years, but the robots kept at it. We see Wall*E as the last robot, but that's only in his particular area. There could be other robots still functioning. There could be an automated parts factory somewhere. Even if Wall*E is the last functioning robot, he doesn't have to have been that way for 700 years, that could have happened the day before the movie started.

  • Axiom and sustainability? Did you forget how WALL-E was trying to rescue the plant and was dumped into outer space? That happened when larger robots were dumping garbage into the outer space. People cluttered Earth and then they were cruising space and still dumping garbage. I'm sure the script was intentionally done this way. – sharptooth Feb 13 '15 at 6:09
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    @sharptooth I totally agree the lesson they intended the viewer to take away from the Axiom was that Humanity had learned nothing. Yet somehow humanity survived on the Axiom for 700 years in leisure with no sign of shortages, you'd need some very impressive recycling to do that. The Axiom is both the pinnacle of sustainability, and a ridiculous waste. Like many dystopian tales, it doesn't hold up to examination, and it's not supposed to. It's not about building a world, it's about reflecting of our own. – Schwern Feb 13 '15 at 17:38

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