Comment by Animats
Comment by Animats 3 days ago
Is this a problem due to bad cell quality control? Car-sized lithium batteries are lasting 200,000+ miles. Why aren't e-bike batteries?
Comment by Animats 3 days ago
Is this a problem due to bad cell quality control? Car-sized lithium batteries are lasting 200,000+ miles. Why aren't e-bike batteries?
Yes, it's about weight.
Basically as long as it pass safety regulations, manufacturers will aim to make the lightest (and cheapest) parts. That's why they use plastic in low-end bikes and carbon/titanium in high-end ones.
You could put motorbike brakes on a bike, and a set of pads would last you a lifetime. But with so much weight there, the bike would feel unbalanced and hard to handle. So you'll need to put weight elsewhere to find balance. And soon enough, you'll have a bike weighting 50kg. Nobody would want to come near this monstrosity. People legitimately want a bike that they can power with their legs and handle easily when they are not riding.
Keep in mind that a single car tire is heavier than a whole road bike. It necessarily results in less atoms, and faster wearing.
First, plastic frames are almost unheard of. There's been a few models here and there, but it's so brittle and it needs so much overdesign to compensate that it doesn't make sense over simple steel. Second, you have it entirely backwards. The lighter materials cost more, not less, because they're more difficult to work with and it's more difficult to get the same strength out of the frame while using less material. As you correctly point out, fewer atoms -> weaker structure. So designers how to work out the geometry to counteract that effect.
> First, plastic frames are almost unheard of.
That's why I talked about "parts", not "frames".
Cheap pedals and cheap brake levers? Plastic.
> The lighter materials cost more, not less
Plastic is lighter and cheaper than steel and aluminium.
Carbon is lighter than steel and aluminium but much more expensive.
Totally agree with this. eBikes are already too heavy for my tastes.
Having the motor means people don't care about things like slow rolling tyres, heavy finishing kit or the weight of the transmission to handle the extra torque.
That in turn means you need heavier brakes to stop.
Luckily not every bike has to be the same and we can pick and choose as needed. I'd rather have a lighter bike and have to service it once a year (if that) but that's just me.
I think that you got it right, expectations for cylcing are different. Even avid cyclists could never hit the kilometres travelled by your average car user in a year. Being a lot more expensive as well cars need to last longer for the cost benefit math to make sense. If your car broke every in 10,000kms you'd be livid, out of action constantly. If your bike breaks down, you can probably fix it that afternoon if not on the spot. Worst case you can probably walk it the rest of the trip.
That's where the e-bike is crossing barriers a bit. People will ride them much further, and getting the e-drivetrain repaired can be a real time and money sink. So you want it to be reliable, more reliable than the rest of your bike even.
> Even avid cyclists could never hit the kilometres travelled by your average car user in a year.
According to different sources, the average kilometers travelled by motorists are under 25k km/year (including Europe & US).
You'd be surprised by how many amateur cyclists ride more than that each year.
What a strange way of counting 25 k km ;) shouldn't you say 25000km or 24Mm?
25000km/year is ultracycling territory for amateur cyclist. Yes some people do it, a lot definitely not and I don't think many of them have a full time job.
> You'd be surprised by how many amateur cyclists ride more than that each year.
You wouldn't.
As an 8k km/yr cyclist with a lot of cycling friends, I can tell you that 12.5k/yr is extremely high for an amateur. Sure, there are some, but a truly tiny proportion.
8k/year eats bikes, BTW. I used to wear out rims regularly before I switched to disks and chains/sprockets didn't even last a year (on a fixed gear bike).
Just for the sake of disclosure, and to provide one data point, I ride 8 miles per day, 5 days a week, year-round, on two bikes (summer and winter). That's about 2600 km/y. Maybe add a few hundred km for occasional weekend recreational rides, and getting around town.
Now that the edit window has passed, I realize that I have to add a correction or a caveat. I realized this when I added a drop of oil to my brakes. The car is "unreliable" too, but comes with expectations for periodic maintenance that replaces those parts. All fluids are unreliable. That might even deserve to be a law of engineering.
In fact, when I add up the time and money spent taking care of the periodic maintenance of my car, which involves driving it to the mechanic's, it's way more than what I would consider to be remotely acceptable for maintaining my bike.
I think that's a generalisation too far. :P
I don't care a hoot about my car, I wash it once a year whether it needs it or not.
It's the same for a commuting bike. My road bike on the other hand gets washed, tyres pumped, transmission cleaned and lubricated on every ride.
I think most club riders would be just the same.
It's not just vanity, dirty transmission is more tiring to pedal when you're trying to keep up with a group and when you're coming down hill at 50mph you want to know your brakes will work.
Tell my teenagers ;)
And look at the average railway station bike parking.
Bikes have it rough. They have crappy suspension, usually are used on roadways that are much worse than the ones that cars ride on, they have to regularly deal with impact and g-forces that you rarely see in cars outside of actual accidents and people drop them all the time. I've been working on bikes all my life and if there is a form of bike damage that I have not seen yet it would amaze me.
>I wash it once a year whether it needs it or not.
I admire that, I used to wash my truck once a year too, until I ran out of time.
> There must still be a limit to how much size and weight a rider is willing to tolerate.
This is true for bikes, and after decades of marketing and fearmongering, basically the inverse is true for cars.
I'm saying this as a european non car-owner who's never been to the US, but my impression of car brain from over here is that anything that approaches light-weight is seen as a "death trap" by a majority of US drivers, especially because the rest of car users drive cars that literally have the size of WWI tanks.
My favourite are utes (Australia) / trucks (US) with a hard cover over the tray are.
Glorified shopping cart.
Might as well buy a hatchback.
(Gouach co-founder here) Car-sized batteries last long because they have so much redundancy, that even when multiple cell fails, you barely notice it. It's very different in a smaller e-bike battery packing 40 or 80 cells.
Cells aside, cars have very good suspensions, and their batteries have been designed with very pricey component to eliminate shocks and vibrations.
On e-bikes, most batteries will have to sustain those, and we've seen a LOT of commercial batteries who were out of order for a simple $5 electronics component which was broken, and which couldn't be replaced because the battery was not made to be repaired (soldiering, glue, etc)
Battery cells are generally binned like many ICs and the best cells go to cars and other high margin, high performance, or safety critical goods. The lower quality ones go to more cost conscious markets like the ebikes, where problems in quality control can definitely show up, especially if the OEM isn’t careful in how they spec the deliverables QA on the battery manufacturer’s side.
How are ebikes not in the high margin category? The Bosch batteries sell for €1000/kWh at the pack level.
I think it's the BMS, Batteries in cars usually get used between 20/80% and have active cooling and heating while ebikes don't.
High margin means stuff like aerospace, defense, and biotech - although a more accurate phrasing might have been “high value add”
How many cycles does the ebike battery go through in 200k+ miles? An EV car does ~300 miles/cycle. So 200k miles = 667 cycles.
Cycles is not the only variable in play here:
- Depth of Discharge - how often you go from full to low battery? Going twice from 80->30 (which accounts to a single cycle) is much better than single 100->0 cycle
- Thermal management - what are cell temperatures when battery is being charged? Maybe it is charged in direct sunlight? This will kill battery pretty fast. At what temperatures are the cells when driving the ebike?
- Ebike/scooter probably being charged to 100% more often than necessary.
- Did you leave your battery at winter completely discharged or fully charged in your garage? Bad.
TLDR: Info I gathered about reading how to take care of Lithium NMC batteries which are so widespread.
Battery service life depends on many other factors besides just manufacturing quality: time, operating temperature, number of charge cycles, charging parameters, etc. On top of that, each cell design is optimized for some set of operating parameters: load, energy density, specific energy, price. It's all variables, so you'd have to narrow that question down quite a bit to even hope to have a reasonable answer.
I imagine it’s partly due to bad quality control and engineering. No active cooling, probably a not well optimized battery management system. The batteries probably have more shock from lack of suspension.
On the user side folks may not be keeping them optimally charged.
In my experience, virtually everything is less reliable on a conventional bike, than on a car. Many of the consumable parts last a couple thousand miles at most. This may be due to differing user expectations, or the fact that a bike is more sensitive to added weight. As a rider, it's not objectionable because everything is also more maintainable by a reasonably handy person. I'd rather fix the bike once in a while than ride a permanently heavy bike.
What I can't guess is how this translates into expectations for the components of an e-bike. There must still be a limit to how much size and weight a rider is willing to tolerate.
On the other hand, maybe a high quality battery would last a long time and not need service, but the market isn't ready to believe it.