You're in the realm of replacing original parts with the new battery mod. Why not replace the Bosch motor controller with any available motor controller that lets you configure your throttle inputs however you want?
The insurance is OK with a home made battery? And there's no concern for public workers if some unidentified custom battery catches on fire for example?
The insurance is perfectly ok with a home made battery. And public workers will arrive on the scene when there is nothing but some charred trespa left of my build if it should ever catch fire. Which is why it's located where it is on my bike, because I lack confidence in my ability to build stuff ;)
Note how the theme of safety has been paramount during this build, during the use and even in case of a crash or other accident, this wasn't a 'oh let's build a pack' project done in 48 hours, you're looking at a couple of months of research and work.
As for Alibaba batteries: you get what you pay for, and I would never use a pack for a project like this with cells that I haven't tested myself, each and every one to a very high standard.
I'll take your word for it because I'm on the other side of the planet but it just seems incongruent and illogical that replacing a component with another compatible part, mass produced and used all over will get your bike confiscated and invalidated but a totally custom one off with no real world test, certification, or such is fine.
It just seems like bureacracy gone totally out of control. You take bicycles, possibly the pinnacle of appropriate technology, a set of tools can fit in a shoebox and nearly anyone can take apart and fix every last piece, and its super useful. Now incredibly there comes along additional components capable of augmenting and improving the bicycle. Add a multimeter and wirestrippers to your bike toolkit, attach a battery to your frame, replace a wheel or bottom bracket with a motor and any bike becomes an ebike, incredible. But then the law decides to ruin incredible by saying only select pre-approved models can be ridden. And making certain modifications is completely illegal, but dramatically internally modifying is allowed and even insurable.
I hope your pack is safe. Some aspects of the design seem inherently safe like using that many batteries in parallel for a 350 watt load, the peak usage will always be below the continuous rating of the cells. I'm no electrical safety professional but I have taken some workplace safety 101 online website multiple choice certification things and theres some issues i wonder about. Hopefully you've addressed and mitigated all of these concerns already, or plan to as you finalize the build, or get lucky, or are at least aware and prepared if a failure does occur. Here comes more internet stranger critique:I saw nothing about shock and vibration design, no drop tests, no mention of short circuit tests, no thermal measurements taken during a controlled charge/discharge, no mention of arc flash considerations during your assembly, first time use of a new tool that was uncontrollabe/inconsistent during assembly, possibly wasn't connected to a suitable electrical source, an ad-hoc decision to do 3x the number of welds w/no mention of ensuring that didn't overheat the cell.. And that's simple stuff any hobbyist is capable of, nothing compared to controlled third party testing that would be done to certify a commercial pack.
And how many man hours of development and testing do you think go into that commercial battery pack you can buy? Probably more than 2 months. And they're equipped with mutual nda's and proprietary data from manufacturers, vs youtube, online distributors, and some guts of a bosch bms. This was a first time pack build, manufacturers probably destructively tested more packs of each of their models than you have built, and at some point economies of scale and upfront investment give them access to superior manufacturing processes and materials. And because laws get applied equally to every person, consider this project built by another version of you, equally confident and less skilled or lucky, do they too get the official thumbs up to ride it in public?
In the USA if you wanted a 2 kwh pack you can buy them premade, although thats the largest they sell currently, and replace any ebikes battery with it, convert any bike into an ebike, or buy a third party assembled bike with it, or buy from a custom manufacturer that integrates the battery and motor into the frame itself. And needless to say you can put any motor or drive on it. But the idea of licensing, registering, and insuring a bicycle is an unheard of, and its especially word to have anyone inspect your bike or care what parts are on it. Entirely different worlds but it just feels like the European regulations introduce big limitations on the potential.
> I saw nothing about shock and vibration design, no drop tests, no mention of short circuit tests, no thermal measurements taken during a controlled charge/discharge, no mention of arc flash considerations during your assembly
So, this is why this project took a couple of months instead of a few days. I don't just slap stuff together.
The pack is 9 layers, has two inner layers of foam to cushion shocks, is shrink wrapped twice, uses high density ABS spacers instead of glue the way other people build their packs (at the expense of some space), has the wiring very carefully routed so that shorts are not just unlikely but pretty much impossible. The 'inconsistent' welds problem was solved by the overkill method: where a manufacturer would use two welds I used six, trial welds on bad cells proved that I could not tear the cells from the welds without major damage to the cell structure, in other words: those welds are pretty solid. I also measured their internal resistance across all cell groups, and monitored each group during a pretty stressful charge/discharge cycle to see what would happen to the interconnects. On the electrical front there is thermal monitoring, voltage and current monitoring, short circuit protection, overcharge and undercharge protection.
That pack is safe, short of getting crushed.
Also, and in case you're not a aware of it, I built a one-off windmill, 5 meters in diameter, rated for 2.5 KW, had a couple of Canadian winter storms attempt to take it down but it survived everything, built an overhead crane, a computer controlled plasma cutter and owned a fair sized machine shop. I'm not your average DIY person, and spent probably more time on safety on this particular design than I did on anything else.
I would trust this pack over a manufactured one, including the ones that Bosch puts out. I didn't do a drop test but that's mostly because this is a one-off and a after a drop test I would simply discard the pack, there is no way to do that non-destructively with a battery this heavy. That said, I'm very sure that the pack inside the foam core would be fine (it's dimensioned for that) but the housing would crack for sure.
As for why the bike is still legal: type approval is mostly related to the drive train, the maximum power the motor can put out, the degree to which it amplifies the pedal input power and various cut-outs, the batteries are not subject to the type approval, you can buy and fit aftermarket batteries for many bikes.
