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Old TVs were dangerous as hell to repair.

So we had a solution: TV repair men!

The issue isn't so much that consumers can't fix these things. The issue is that even skilled technicians can't.

Manufacturers are saying, rightfully, "Its too dangerous for consumers to repair"

But they are also saying, wrongfully, "Therefore only we can repair it!"

They are creating a false dichotomy so they can corner repairs.

Yes, it is clear they are arguing for their own book. But they do have a point: as currently shipped these packs are dangerous. But I would expand that to 'dangerous to use', and not just 'dangerous to repair'.

But they could make them less dangerous, they could also make them much less dangerous to repair. But with a pack costing roughly 1 euro / Wh they are stupendously overpriced and a major source of revenue. And most bikes have one or more pack replacements during their lifespan. So it's clear why they would want you to buy another, at the same time they are playing the safety card for disingenuous reasons.

A safe to repair pack would have cell modules that could be replaced individually and with sense wires that are bonded to the case in such a way that they can never end up crossed and squashed.

Leading causes of pack failures:

- breaking interconnects / bad welds

- water ingestion

- shorting out sense wires

- impact damage, or dropped pack

- electronics failure

The problem is that by making them repairable they open themselves up to legal liability.

A phone battery goes bad... it's a few ounces of solvent to burn. An ebike battery goes bad, and it's going to be near impossible for it not to take the structure with it. That's a massive liability.

You can buy replacement batteries on amazon for phones and powertools. You don't know where they come from, and I avoid them for this reason. I've seen batteries from reputable companies combust just sitting on a shelf. The idea that any company would sanction anyone to buy shady grey market and use them with their product puts them in the path of unavoidable financial ruin.

Pretty much all liability laws include various forms of "the manufacturer is not liable if the fault happened because the customer (or some repair shop) messed around with the item". It's already the kind of thing which people do frequently, arguably the lack of proper spare parts and documentation makes this more dangerous, not less.

Old TVs were easy and safe to repair after some minimal training. I learned to do it from a pro when I was 16. As long as you properly discharge the tube and the bigger caps, it's safe to work on.

Battery packs are much worse because they cannot be completely discharged before you work on them, i.e. you have to work on them "hot" while they're still storing energy. It takes more training, more tools, and a dedicated facility to do it safely.

And when they go they make your average TV failure look like a picnic. Though, to be fair, an old tube could do some pretty bad stuff if mechanically damaged.

And I guess the TV tube was also more likely to just kill the person working on it, not random people who live in your building. (Still not a great outcome, but better if the only person who dies is the only person who actively consented to the risks.) A lithium fire is gonna spread pretty quickly.

Quite. The hard part is to realize - up front, hopefully - that all of your normal firefighting instincts aren't going to work and have a good chance of making things worse.

Building or repairing a multi-cell battery pack with multiple cells is on par with doing a motor swap on an ICE car.

I created the ebike subreddit and have been part of the community for 10+ years. I've had a lead acid battery blow up in my face. I've fucked up and had to run out the front door and yeet a 18650 out on yard before it popped. Yeah, yeah yeah, maybe I'm unlucky or maybe I'm incompetent, but I wasn't a noob in either of these cases.

I believe in ebikes as a valid alternative to cars and a wonderful thing overall. It would be an ecological disaster if apartments started banning ebikes or the government started to heavily regulate them. And if we're not careful, that's where we might end up.

> It is super easy to mess up with these. Drop a pack, drop a sliver of wire or interconnect ribbon, misplace a tool and you have a thermal runaway on your hands which you will not be able to stop. Doing this in a facility that is not set up for it (say, your kitchen or living room, especially if it is in shared accommodation such as an apartment building) is super dangerous.

What's your point? Changing your own break pads or hydraulic fluid can very easily leave you with a runaway 2-ton vehicle on your hands which you will not be able to stop. This is also super dangerous for you and the people you share space on the road with. It's still neither illegal to do nor do car manufacturers refuse to sell you either pads, rotors or fluid.

And the same is true for home reloading rifle rounds, messing with rodent poison or common cleaning chemicals.

At some point you have to trust people. Slap some warning stickers onto things, rely on the news to really drive the point home after the first person burns down their kitchen.

> Changing your own break pads or hydraulic fluid can very easily leave you with a runaway 2-ton vehicle on your hands, which is also super dangerous for you and the people you share space on the road with.

Yes it is. But just handling brake pads or hydraulic fluid by itself does not have the potential to harm you and a lot of others, neither does working with them and presumably you know how to bleed your brakes and test them. Most people that have worked with and on brake systems are in agreement that this can be done safely. Most people that have worked on e-bike battery packs are in agreement that this is a risky affair at best. That pack mentioned above is a one-off. I would never sell it to anybody else. At the same time I would have absolutely no qualms about selling someone a car on which I've worked on the brakes. Brake systems can - and do - fail but modern cars have multiple cylinders, and have mechanical backup for failed vacuum assist. So it's not as if a failed brake immediately translates into people dying though it definitely does have that potential.

A fuckup with a 40 or 50 cell e-bike pack is pretty much guaranteed to cause a serious fire. You're essentially dealing with the DIY equivalent of a live grenade, it isn't going to go off with the same bang (fortunately) but when it goes it will keep on going until it runs out of stuff to burn.

> They also could stop price-gouging the consumers on the packs, which is one of the reasons people want to repair them to begin with.

This is a huge piece of it, stop ripping us off! This has been going on for decades -- from NiMH battery packs for power tools, to laptop batteries.

I assume a big difference in the danger aspect with the bike batteries is their size/capacity? Less to go wrong with a 2AH cordless drill battery, than a 20AH bike battery?

Cordless drills usually (but definitely not always) use LIFePO4 so should be a little bit safer. Here too: be careful of cheap stuff.

But a 50 cell 36V 625Wh e-bike battery is an entirely different beast and when it goes you're going to be very sorry if you are nearby. Individual cells that go are already very impressive, a large pack is going to very effectively spoil your day (if not your life).

What happens exactly when a 625 Wh battery pack "goes"? Does it explode? Does it burn fiercely for several minutes?

625 Wh is the energy equivalent of a few ounces of gasoline. That's certainly enough to do some damage, especially if it gets misted to an explosive air/fuel ratio, but not something that most people would be afraid to handle.

That's precisely what is so deceptive. Compared to a lead acid battery of equivalent capacity the dangers are far higher (though to be splashed with acid can ruin your life quite effectively as well).

What will happen - usually - is this: one cell will go bad, into thermal runaway. Maybe it had a bad interconnect which vibration fixed and now the rest of the cells in parallel will dump a few hundred amps into it or maybe the pack was subject to a fall, who knows. But let's assume that one cell only got damaged. This cell is in close proximity to the rest of the cells in the pack but typically they'll have between two and six closely spaced neighbors. Those in turn will start to go up after which there is a geometric expansion until the whole pack is gassing out and possibly already burning.

Elapsed time from first symptoms to violent explosion/fire is on the order of 10 to 20 seconds at best. And once it gets going your best chance of stopping it is to immerse the whole thing in a very large volume of water or to bury it in a large amount of sand. The vapors are not going to be pleasant to deal with, anything combustible that it can come into contact with will likely burn.

Some examples:

https://www.youtube.com/watch?v=vlQumRetMf0

https://www.youtube.com/watch?v=rKn8MLG9slA

So naively I'd think that fusing the cell interconnects so that "a few hundred amps" cannot pass would be a way to deal with that, but I guess if it were that simple it would be done.

This is done in some packs, but this introduces a new risk: now, once a fuse is blown the pack will be asymmetrical and that in turn will put more strain on the remaining cells in that particular block of parallel cells. So likely that is a stay of execution rather than a solution. Another problem is that cells can develop higher internal resistance than their brothers causing them to overheat. In general, pack construction is a very delicate interplay of mechanical stability, thermal stability and electrical properties. Get anything wrong and it translates into risk, and it isn't always obvious that you've done something wrong.

Even the big manufacturers mess up. That's a pretty good sign that this isn't an easy problem.

So I think I'm agreeing with you these large battery packs sound almost too dangerous to be sold as consumer products. Are there any other examples of consumer/household products that can fail so dangerously and that have not been recalled or banned?

There are things such as space heaters, heating pads, kitchen appliances, etc. that have been known to start fires, but at least if you're in the room with them you can probably react and extinguish them if you have water or a fire extinguisher handy.

I don't know anything that comes close to this. Just recently someone gifted one of my children a battery powered toy, I checked it and decided that I couldn't tell the difference between that toy and a purposeful attempt at arson...

The big thing that stands out for me is that the perception of the risks (impact / likelihood) is entirely unlike the real risk. For most other things those are much more in line. And that's why people get caught out.

Nobody thinks twice about leaving their e-bike charging in the kitchen overnight, or to take it into an elevator or in an extreme case even a bedroom (1 room studio, no storage space). Stairwells are another such spot. I charge mine outside under an overhang, and only do so when I know it isn't going to be anywhere near freezing.

> I'm all for DIY stuff, but this isn't one of those

After my own research, I absolutely agree. I was quite disappointed.

> They also could stop price-gouging the consumers on the packs, which is one of the reasons people want to repair them

Totally true. These prices are seen as an essential profit center when they're actually contributing to the problem. There are other ways to differentiate for a premium without worsening safety.

It's stupid to DIY this stuff unless you really know what you're doing and are willing to put in the proper effort, and there should be more warnings about this. However, companies are doing the opposite of reducing the motivation for it. I don't know if we need something as extreme as price controls, but in my view, if the industry isn't going to step up then they should be forced to somehow. There is way too much risk of massive property damage, maiming and/or death.

Do e-bike batteries generally need REPAIR or do they more likely just get less effective over time in a way that's not really fixable? Not arguing against repair here, just trying to understand the landscape. Is "fixing" them swapping out cells?

Yes and yes. E-bike batteries consist of 40 to 100 cells. Typically one cell fails prematurely and compromises a pod of 4 to 10 other cells that are connected in parallel with it. Replacing the whole pod is safe as long as it's done properly (removed and re-welded without damaging the enclosure or shorting anything out) with like cells that have identical manufacturer, specs, actual capacity and charge curves to each other and to the rest of the battery. Ideally they should be matched with cells from a donor battery of the same "vintage".

The vast majority of the time, the remaining 90% of the cells in the pack have a lot of life left. If multiple pods have failed simultaneously (which is very rare), that's a sign that they're all starting to go and all cells should be replaced - which may still make sense, as the enclosure and BMS are often half the cost and perfectly functional.

The problem is you really do need to match the cells by actual capacity and charge curve, and that requires specialized equipment. If you don't, a good BMS will shut down the pack, and a bad BMS will allow it to catch on fire. Given the financial incentives (many hundreds of dollars to replace a pack), people will try to fix a pack in hacky ways. This is why it's important to provide the right tools and training for local shops to develop economical ways to service batteries and to educate people about the hazards involved.

This is all good stuff. I'd like to add one small bit: most BMS are not capable of balancing packs that have become significantly unbalanced fast enough, and if they're really out of whack you may have a problem. A good BMS will allow this situation to exist but will de-rate the pack (you'll be charging to a lower overall voltage), a bad BMS will still allow the pack to reach the full working voltage but this will result in some pods to be under their maximum voltage while others will be over.

And that's a serious risk: a battery that is just fine at 4.2V may well go ballistic at 4.35 so even a small offset can cause real trouble. That's why those sense and balancing wires are all important. Keep in mind that they are not fused whenever you work on a battery and carry full voltage.

Could you go down a rabbit hole a bit on this part of your response? "[Manufacturers] could design their packs to be more reliable and easier to repair."

What is it, if you were a state or local government, that you would force on the industry?

Also, what happens to the remaining "good" cells when you recycle rather than repair a battery? Are they kept in tact?

You could build a pack out of modules, the logical unit is the 'pod', the block of cells that are set to operate in parallel, typically there are three electrical connections (all the joined + contacts, all the joined - contacts and a sense wire connected to the +) the + and - are usually passed on to the rest of the string except for the topmost + and the bottommost -. Those are brought out using wire. You could allow a pack to be split on the pod boundaries. That would allow for one relatively easy unit of repair. You'd have to know which pod to replace but that is something that you might be able to figure out using a DVM.

Another thing they could do is to allow for a complete reset of the BMS instead of bricking the BMS as is now done. This would also take care of capacity drift, which causes a lot of trouble with older packs where the reserve becomes an ever larger part of the total pack capacity and which can render a fully functional pack effectively useless.

I would not bother with the right-to-repair on this one but demand that for an e-bike to be certified that there would be a cost+ arrangement to deliver a refurbished battery to the end user, and that this should happen at least twice during the life of the bike. This because the batteries are by far the weakest spot in the chain, they fail at a rate much higher than motors or controllers. And the life of a bike should be defined as no less than 20 years.

Finally, when you recycle you could break up a pod into its constituent cells fairly easily, test them, discard the ones that are not passing a testing regime and then to match the cells and recreate new pods. But unless this is done at a very large scale it is probably more cost effective to just discharge the batteries, grind them up and to recycle them completely. That will give you brand new cells at some loss of material.

I hope this answer is what you had in mind.

Yes, absolutely, super interesting. Would it ALSO be a good idea to standardize battery specs? If so, which?

That's always hard, you don't want to give any manufacturer an edge but at the same time you also don't want to force everybody into buying a new bike. It may be possible to create an adapter that would accept modules for the new system. I'm imagining something like a stack of supersized 'D' cells. Packs would then combine these in the quantity needed to reach the required voltage. Doing that reliably and with very low contact resistance will be a major challenge.

The garden and powertools world has a working model for this:

https://www.powerforall-alliance.com/en/

With a lot of the major brands already subscribing to the concept that's a really nice move forward, and I'm looking forward to Bosch extending the concept to e-bikes, there really is no reason why they could not. It will make batteries more likely to be stolen though, so that is another angle that will need work.

> stop price-gouging the consumers on the packs

Are their margins even that high? It looks like a Bosch 400Wh pack is ~$650 which is not super far off the cost per joule of cordless tool battery packs.

Both are ridiculous. The cells themselves go for $4-$6 each, there are usually 40 in that Bosch pack so that's $160-$240 in cells at retail pricing.

That could merely suggest that cordless tool battery packs are also wildly overpriced.