No difference, until / unless the battery offgasses, a cell ruptures, etc.

It's a bit of a design challenge for electric aircraft. Not insurmountable, but most large aircraft have lower maximum landing weights than takeoff weights. Landing is far harder on the structure, or can be anyway. So not burning off or being able to dump fuel means landing gear may need to be far more stout. We're still quite a ways away from really large electric only airliners though.

 

Funny! A consideration when looking at payload rating though. Comparing apples to oranges the ICE vehicle needs to deduct 180 lbs plus from rating for fuel load when comparing to EV payload and GVWR

 

Charging/discharging just moves electrons from anode to cathode and vice versa. No mass is added. An analogy might be an elevator. You use power to lift it up and gravity takes it down but you don't add weight to it when you lift it.

 

It does change…pretty sure anyway. E=MCsquared. If you change E, energy, you change M, mass.

 

Yes! Except energy doesn’t have mass, it can be converted to mass and vice-versa is what that equation says. Little known factoid only if you read the original paper (like I did 😅) which is that is an approximation to a quadratic equation.

However the electron argument isn’t quite right either, because that assumes there’s only a valance (‘shell’) electron transfer back and forth. I’d have to think about what happens but I doubt it’s a perfect balacing like that (a capacitor approximation). Likely it’s loaded with electrons from the grid, or at least there’s some imbalance.

Here’s some trippy physics trivia to ponder; did you know your watch (and time) runs slower on a plane flight? It’s measurable.

 

A few micrograms more weight when fully charged as per E=mc^2
The volume of a lithium battery fluctuates with its state of charge. During the charging process, lithium ions intercalate into the electrode materials, causing the battery to expand or swell. Conversely, de-intercalation during discharge leads to a reduction in volume.

 

A few micrograms more weight when fully charged as per E=mc^2

Except energy doesn't have mass but just can be converted by that equation - energy (potential energy in this case) doesn't interact with space-time.

The volume of a lithium battery fluctuates with its state of charge. During the charging process, lithium ions intercalate into the electrode materials, causing the battery to expand or swell. Conversely, de-intercalation during discharge leads to a reduction in volume.

Interesting thanks. So volume changes but still not mass, this is just swelling. Also thermally it'll probably swell as well, since the battery goes through temp variations. Now we know why those pouches are so loosely packed.

However apparently not the case for prismatic like the new LMR? Or at least much less, that packaging doesn't look conducive to it.

Something I heard about the difficulty with solid state or semi-solid state is the breakdown of the micro structure of the material, possibly in part due to this? GM is working with some startups with novel nano materials which keep the structure together better.

 

You all did not disappoint, great comments!

 

"Contrary to common belief, there is a minute weight difference between fully charged and depleted batteries. This difference, however, is so small that it's imperceptible in everyday use. The slight weight change occurs due to the movement of lithium ions between the cathode and anode during charging and discharging. "

Does Lithium Battery Capacity Relate to Weight?

Discover the intricate relationship between lithium battery capacity and weight. Learn how these factors interplay and impact your devices' performance.

www.ufinebattery.com

 

Nice article. Note that the weight difference is in nanograms...presumably for a single cell but still won't add up to anything significant on a battery the size of the SEV's.

 

The reason batteries are so heavy is that we carry both sides. If we discharge into the ground (like how ICE discharges to the atmosphere), then our battery would weigh half as much and lose weight as we drive… right? 😂

 

The reason batteries are so heavy is that we carry both sides. If we discharge into the ground (like how ICE discharges to the atmosphere), then our battery would weigh half as much and lose weight as we drive… right? 😂

Ozempic for batteries LOL

 

I lie to myself that when I drink too much beer that most of it comes out the other side so I can't be gaining "that much" weight... Then I start to struggle with that jean button...LOL

...(like how ICE discharges to the atmosphere), then our battery would weigh half as much and lose weight as we drive… right? 😂

Oh! And I discharge into the air too! I'm going to tell my wife not to worry about it honey...I'm just trying to lose some weight!

 

I'd say total vehicle/passenger weight would be less after charging since after paying for the charge your wallet would weigh less. But that is insignificant compared to wallet weight loss after purchasing the truck, or purchasing the larger battery.

 

Those links are talking about rest mass (intrinsic mass) not relativistic mass which is what the equation refers to. A rock at the top of a hill has potential energy; ignoring the field changes does it weigh more? Does it lighten up as it rolls down? I don’t think so. Another way to think of it is that weight (what is measured by a heavier battery) does not increase with a higher energy state. Mass is not weight, but intrinsic mass does have weight which is the confusion. So those links have it wrong I believe, it’s a common misunderstanding to equate mass with weight, they’re not the same.

But this discussion is getting on, citing links isn’t going to help as there’s a lot of confusion on the topic.

/disclaimer: I could be wrong, anybody here or on the internet could be wrong, it’s just a friendly discussion …

 

I need more info to answer your question. Are you using premium electrons or regular electrons to charge the battery?

 

This has been hella fun and informative. Still, from a practical perspective, the SEV isn't going to weigh more charged than depleted. I can sleep easy...