[Closed] "Massless" Batteries

Is how you maintain/fix the cells not a sizeable elephant in the room here?

so instead of being inside a frame, the battery could be a bolt in section of the downtube with no other reinforcement needed.

The whole downtube of a regular frame probably only weighs about 200g - you're not really offsetting an awful lot of a 2-3kg battery.

The whole downtube of a regular frame probably only weighs about 200g – you’re not really offsetting an awful lot of a 2-3kg battery.

I hear you, but isn’t it more how you can remove weight from an ebike frame, because the battery is now a load-bearing member...?

It’s not as easy or as straight forward as it sounds. We looked into this for aircraft and the mechanical capacity of batteries for carrying static loads is pretty bad, but as soon as you start to consider fatigue, thermal cycling, battery expansion during charge and the necessity to inspect, repair and teplace them, it’s a no go for any of the current lithium (ion, polymer, sulphur, hydrogen) batteries. Maybe, once they get to solid state with decent energy density and longevity, it might be worth revisiting, but now, for anything that’s currently optimised for stiffness to weight, not a chance.

Is how you maintain/fix the cells not a sizeable elephant in the room here?

The Van Moof bikes have their electronics and batteries integrated into the frame, but are apparently 'removable for servicing'. Great concept, I'm just not a fan of the 'one size fits all' model. I'd like to see at least a few different sizes. Perhaps having such a structurally integral system, limits this though.

https://www.vanmoof.com/en-GB/s3?color=dark

it might be worth revisiting, but now, for anything that’s currently optimised for stiffness to weight, not a chance

Yes, I just don't see how you would integrate it into a car chassis in a way that would save much weight, be durable, pass crash tests, and allow for maintenance or replacement of the battery. As I understand it, Tesla put the battery under the floor because it's a big chunk of weight and you want a low center of gravity. You might be able to integrate it into the floor structure, but you'd only save a few kilograms of sheetmetal. You would not want to use it for the pillars or roof because you'd be putting a huge amount of weight up high, plus it would likely be torn open in a serious accident and catch fire. Same with having it in the front or rear crumple zones-those are designed to deform in a crash, so you would not want the battery there. So, basically, the only place I can see putting a structural battery is in the floor, and that just isn't going to save much weight while causing lots of other problems.

The Van Moof bikes have their electronics and batteries integrated into the frame

That's different to what's being discussed here. VanMoof just slide into the frame and look all neat and tidy, massless would make the battery cell itself part of the frame