French firm Gouach is pitching an Infinite Battery with replaceable cells
arstechnica.com64 points by pabs3 3 days ago
64 points by pabs3 3 days ago
A cryptography angle in the article. Would this be illegal in the US under DMCA?
One of the biggest compatibility challenges, Vallette said, was finding a way to work with Bosch's mid-drive motors. The communications between a Bosch motor and battery are encrypted; after "a serious effort," Gouach's app and battery should work with them, Vallette said.
It really depends. The DMCA does have limited exemptions for reverse engineering for interoperability. The EFF has a good overview: https://www.eff.org/issues/coders/reverse-engineering-faq (search for DMCA). My personal takeaway is that this question cannot be definitely answered outside of court.
...uhh, yeah, certainly seems like a buried lede. What precisely can I do with Gouach's app and a Bosch mid-drive?
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?
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.
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.
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 many cycles does the ebike battery go through in 200k+ miles? An EV car does ~300 miles/cycle. So 200k miles = 667 cycles.
i get about 90km of range from a 500Wt Bosch battery. Thats running at full power the whole time.
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.
This is such a terrible idea because the packs have to be factory balanced before assembly, and everyday Joe doesn’t have the equipment (or probably the understanding) to do this part properly.
If the packs are not perfectly balanced, the batteries just short into each other and explode, and BMS can’t do anything because there isn’t any per-cell switch (cost).
It’s not just a matter of balancing voltage either, the cell profiles (voltage vs SOC) have to be the same otherwise you end up with 1 cell doing all the work. Simply put, when you mix and match cells of different brands, models, or even ages, they don’t integrate evenly. This results in a few or even just 1 cell doing a majority of the work during both charge and discharge, maybe 10x higher than its safety rating, guaranteed fire…
Also end-user is expected to do the math and input the battery’s total current rating into the motor controller? Yeah, nah, a hundred kids will think it’s cool to set this too high and set themselves and people around them on fire.
The Toyota Prius community already has a better solution for this - You can buy remanufactured batteries, then send your used battery back to get a credit. ChrisFix on YouTube has a swap guide for DIYers - it's mostly taking all the interior panels out of the back of the car.
Cells in parallel will stay balanced and act as one big cell even if they're different capacities although they do need to be the same voltage first, but in series they need to be matched in capacity.
Slight mismatches in capacity can be OK in series too, as long as you have a BMS watching the cell voltages to make sure none get too low when discharging and none get too high when charging. The risk is that the lower capacity cells get too low or too high while the overall pack voltage seems fine, causing dendrites to form inside those cells, leading to a short and a scary fire. It really comes down to how well the BMS is designed / programmed and how much you want to trust it.
Most people aren't aware of how dangerous it is to try to "revive" a cell that got too low so this technology definitely comes with significant risks for user error.
Sounds like a challenge: start monitoring individual temperatures, long term recording of performance down to the cell, recommend a mAh value of cell in a particular location, dynamic ohm chips in series with batteries to control differential discharging.
I am not enough of an expert to know if all this could work, but its got to be better than replacing an entire pack at a time to be worth trying
This is a great idea. Would be wild if they could support switching on the fly between 32 and 48v for a range/speed option. That gets complicated though.
Most e-bike providers will buy their switching logic based on the voltage in use, a driver for 48V would be substantially more expensive than one for 32V. There is also the whole charger setup to consider so yes, that gets complicated.
Doesn't need to. Power is power.
This guy is right, the premise of switching doesn’t make sense, power is power.
I only remember when I built my own batteries, I would get more range at lower volts because at about 40+km/hr you end up pushing wind and range goes way down. So yeah, technically power is power, but it's fun to go 50km/hr if you don't have far to go.
There probably aren't many EVs that can't regulate voltage across motor poles between 0 to +battery pack(or -1/2 to +1/2 pack) voltage...
Changing the voltage doesn’t change the amount of power being used, the only thing that would change is the ampacity (which only impacts conductor size, in this case).
480 watts == 10 amps @ 48V == 15 amps @ 32V
An electrically commutated motor (brushless DC) in an e-bike will almost certainly have a speed controllee, if you want more range you simply have to go slower ;)
Yeah but the wind kills range much more so at the higher speed 48v gives you and you tend to never run at half throttle.
Reconfiguring a battery pack with the same number of cells doesn't change the power contained in the pack. However lowering the voltage will lower your top speed (if not already artificially limited by the controller) and raising the ampacity of the pack may allow you to get more torque from the motor if you haven't saturated the motor and you change the controller settings to pull more amps from the battery.
Let's hope the inane DMCA laws don't get them for decrypting the Bosch battery-motor communication.
If HN had profile pictures, mine would be a Clippy.
I like the idea of Batteries as a Service, and I could see it working in some US cities for scooters.
Many consumers just don't want to worry about battery health. Reportedly, battery degradation anxiety is driving down used EV prices in the US.
It would be cool to see a fully open source ebike. Sort of like a framework (the hardware company) of ebikes.
it's a cool idea for small setups, but very expensive per kwh.
if you want the same kind of style diy-er box-for-batteries I suggest the Trampa offerings. Similar focus on safety and novice level DIYer capability but much larger capacities and arrangements.
I wonder if this will allow flying with an ebike battery in disassembled form. The regulations allow up to 100Wh per battery, and an unlimited number of batteries, so transporting the individual cells should be okay, at least in theory.
Lugging an entire suitcase full of 1 kWh worth of batteries might not technically be against regulations, but I imagine you'd be signing yourself up for a long series of headaches at the security checkpoint anyway. To be honest, if I knew that security wouldn't stop me because "it's not technically against regulations", that's exactly what I would do if I wanted to bring down a plane.
Right, that's basically the problem, if one wants to travel by air with an ebike without hassle, there's no real option to do so.
There's the Ligo 10X (https://ebikes.ca/product-info/grin-products/ligo10x-battery...) which makes 99Wh battery packs that can be connected together, but otherwise it just seems like rules lawyering.
There really needs to be standardization of battery packs for ebikes instead of proprietary ones, so that one could rent a battery at their destination.
At that point why not just rent the whole bike and not need to bring the large object onto the plane?
Because ones bike is a carefully selected item perfectly fitted to ones body shape and preferences, whereas the battery is simply a line replaceable unit.
That's such an edge case though.... what about my fine tuned piano? Or my aquarium? At some point personal luxuries don't have to be accommodated for
Even as an avid cyclist who fully understands geometry and the personal connection one may have to one's bike, I agree with you.
Privileged enough to fly somewhere specifically to ride bicycles? C'mon, I think you can find a good enough bike to rent when you get there.
I would honestly not want to fly on a plane with this or anyone else's ebike batteries. To dangerous.
You don't even want to be in an elevator with them. There are some absolutely horrific videos of how quickly this can get out of hand.
An ebike is very weight sensitive. How much extra weight does this innovation lead to?
I would rather have the whole battery be replacable. And when you want to replace, you trade-in your old one for a discount on the new one.
> An ebike is very weight sensitive.
E-bikes tend to be quite heavy, and many of them have designs that are very much not optimized for weight.
> I would rather have the whole battery be replacable.
They are. And the replacements are single-source and are very expensive.
To a degree yes, however I have an ebike and the bosch battery with a it has a 500W battery which is about equiv (if my math is right) to a 28 Ah ryobi drill battery. Those don't exist btw, but if i wanted one and bought 7 4Ah batteries to get the same effect they would cost more than the single ebike battery.
As a single item they are pretty well priced for the power they offer.
Pedal powered bikes are very weight sensitive. The average e-bike (at least one that would use a fat battery pack like the on pictured in the article), are less weight sensitive.
The RadKick 7 (which RadPower calls a "lightweight bike" weighs 55 lbs.
Racing bikes like the $10K Trek Domaine Carbon weighs less than 30 lbs, but has a much slimmer (and lower capacity) battery pack than what Gouach seems to be targeting.
This page says the Domane+ (the one with battery assist) weighs closer to 40lb:https://www.trekbikes.com/ca/en_CA/domane-plus-faq/
I don't like their product naming -- they use the same name for different product lines.
The Domane I was talking about is the SLR carbon series, it ranges from 28.3 lbs for the SLR6 ($9K) to 26.1 lbs for the SLR 9 ($17K)
The Domane+ ALR is the Aluminum framed series and is heavier, but their specs page says it's 31.73 lbs for the ALR 5 (ML frame size).
https://www.trekbikes.com/ca/en_CA/bikes/electric-bikes/elec...
https://www.trekbikes.com/ca/en_CA/bikes/road-bikes/performa...
Very little I'd bet and location of the weight is far more critical to overall utility. Hopefully this is well thought out.
Balancing will be a nightmare I guess, or just dont do it. Nice idea for the advanced user but I would not let my parents fiddle around with lose 18650 cells for the sake of their house burning down.
I see a niche application but personally hope they get it to market and make it compatible with Shimano. My double sized battery is a frankenbattery: pcb from original with custom printed case fitting onto the original attachment device using the batteries from two original batteries. Measured and balanced of course. Safety is "meh" I guess because DIY. I'd like to replace it with something more properly designed.
I did my masters thesis on how to balance batteries with very little information on each individual battery a-priori! Unfortunately I didn’t get to do experimental stuff because it was the middle of Covid, I only had simulation data. You can do some interesting things, though I wonder how many issues we missed/avoided by working only in simulation.
Edit: here’s the publication if you’re curious: https://www.sciencedirect.com/science/article/pii/S240589632...
Edit-edit: wow I got two citations!!! Never thought anyone would read my paper, that’s amazing.
I think it is a pretty god idea. It may remove quite a bit of battery waste.
I wonder how much they will have to protect against recklessness of the e-bike owners? For example, against the end user sourcing substandard cells, and combining them in inadvisable ways.
I don't have a good profile of e-bike owner behavior about maintaining their own equipment, but what I can say is fewer than 1/5 of e-bikes will stop on red at a 3-way intersection near me (when cars are stopped in the parallel lane, and pedestrians are crossing).
We also see a lot of riding on sidewalks, at speed, to bypass red lights and traffic on a major street here.
That said, the e-bike riders are often wearing helmets as they plow through pedestrians, so maybe their recklessness only extends to the safety of others, and they'll be conscientious about not lighting a lithium battery fire between their own legs.