What happens when Green Lantern's ring runs out of 'juice'?
When Hal first reveals to his friend Tom that he is a superhero i.e. The Green Lantern, he is pushed by Tom to show how it works.
Hal puts on the ring and tries to turn into Green Lantern but is unable to do so because apparently, the ring is out of power and thus proceeds to re-charge it with the Lantern.
Now, what happens if Green Lantern's ring looses its power/charge/juice when he is mid-flight or in-action? Though this didn't happen in the movie but it sounds like a perfectly plausible scenario.
P.S. I don't have any background from the comics universe which might be useful in answering the question.
Best Answer
This answer is from the comics, as they don't show it in the movie. In the comics, classic Green Lantern had to recharge the ring every 24 hours. This (and a weakness to yellow objects) was his kryptonite; that crucial weakness that prevents him from being an invincible god. So, it would be common for fights to go longer than Hal expected, resulting in him running out of charge mid-fight. Then Hal is just a regular guy (but the uniform would stay, even though it's generated by the ring...), and had to use his wits and environment to defeat his foe.
Modern Green Lantern (since roughly the year 2000), instead has the ring be more like an electronic gadget. He charges the ring, and the more he uses it, the faster it drains, until it runs out of power. When he charges it off the lantern, it returns it to maximum charge.
Note that the rings are capable of providing their charge level upon request. So during long battles, you'll see Green Lanterns checking their rings' charge. The modern rings also result in situations where a stranded Lantern will set things up so they're in a low-power-usage state. For example, if they're in space and unable to reach their lantern in time to recharge, they can have the ring put themselves into hibernation, provide a life support bubble, and just drift toward their destination while sending an occasional distress signal. This then helps the Lantern survive until they can be rescued and get back to a lantern to charge their ring.
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What happens if a Green Lantern ring breaks?
Rings are a potent tool, but they are not indestructible. When they are destroyed, the Lantern using them ceases to be able to use them (and frequently dies - not because the ring is destroyed, but because they're facing a foe that will kill them). The rings contain immense emotional light power, stored within them.Do Green Lantern rings need to be recharged?
All power rings need periodic recharging. The process is not instantaneous so many Green Lanterns recite an oath while the ring charges. The oath is not required to charge the ring, but is recited to reaffirm the person's commitment to the Green Lantern Corps, and to measure the time it takes the ring to charge.How long does Green Lantern ring last?
Originally (even with the non-GL Corps Alan Scott stories) a Green Lantern had to charge their Ring every 24 hours. That, and a weakness to yellow objects, prevented the Corps Ring Slinger from being invincible.How do lantern rings recharge?
Power rings are usually recharged by a Green Lantern's personal battery, which looks like an old fashioned lantern made of dark green metal. The user typically points the ring towards the lantern and usually gives the Green Lantern oath (below) while recharging the ring.Green Lantern: Why It Didn't Work
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Answer 2
Back when the rings needed to be charged every 24 hours, the rings had an emergency power reserve specifically to protect the bearer from mortal harm when their ring's regular charge ran out. (See Green Lantern v2 #46 (1966).)
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