4 ms·
Batteries are heavier when fully charged. Takeoff weight matters. It's not much heavier, but it might be enough to affect things at this scale. edit: remember
by mkr-hn 5y ago
Batteries are heavier when fully charged. Takeoff weight matters. It's not much heavier, but it might be enough to affect things at this scale.
edit: remember the context. This is about an abstract optimization to find the minimum viable aircraft.
- rrss 5y agowhat kind of batteries are meaningfully heavier when charged? are you just talking about like E/c^2?
- jermaustin1 5y agoA water/gravity battery comes to mind. Definitely not the answer you are looking for, but an answer none the less.
- enchiridion 5y agoDepends on your definitions. Is the water pumped considered part of the battery before it’s elevated?
- jermaustin1 5y agoThe pumping of the water would be "charging" the barrel of water, I guess.
- einpoklum 5y agoI'm sure this will work great for powering an aircraft, too. You could just let it all hang from an anchor at the highest point in the battery :-P
- luma 5y agoGas tanks :D
- spijdar 5y agoI can't tell if this is satire or not, but taken in good faith, how? A fully charged battery would necessarily have more mass than a fully depleted battery, but the difference should be so tiny as to be immeasurable. Or am I wrong? We're essentially talking about the sum weight of a bunch of electrons, which are extremely light. There's no other exchange of matter going on when charging/discharging a battery, just the creation/destruction of chemical bonds, and associated movement of electrons.
- deleted 5y ago[deleted]
- btilly 5y agoA battery doesn't have a static charge. When it discharges, electrons move from one side to the other, then back through the batter, and you modify which atoms have which elections. But it continues to have no static charge. However it has less potential energy. And therefore you change mass by the mass associated with that potential energy.
- luma 5y agoI can't tell if you're being serious. You are technically correct, but also incredibly wrong in suggesting that the increased weight would be substantial enough to impact anything measurable. Depending on the size and capacity of the cell, you might see a difference due to general relativity on the order of nanograms. see: https://physics.stackexchange.com/questions/34421/does-the-mass-of-a-battery-change-when-charged-discharged https://physics.stackexchange.com/questions/34421/does-the-m...
- p1mrx 5y agoA nanogram saved is a nanogram earned.