One thing that hasn't been discussed is lack of use of batteries. A battery that is left uncharged for too long will need replacement. If the cells are left at a very low voltage for too long they fail and will need replacing or at best have reduced capacity. On top of that you have the Bosch batteries as previously mentioned will self-brick if the charge is too low as the BMS will disable the battery from use when it becomes unpowered. At that point you have a short window of time where you can scrap the battery and salvage some of the cells before they too will die if left uncharged to for too long. I've seen a few forum postings where people used their ebikes only occasionally maybe spring/summer's only and the battery pack had failed because of lack of charging thru autumn and winter. If you forget to charge the battery at all after using it and then store the bike I guess the self-bricking can come even sooner.
The whole point of proprietary ebikes is having consumers as cash cows who can be exploited. High replacement part and repair costs mean many such ebikes can be uneconomic to repair. If your motor is beyond economic repair then you have a bike to be scrapped and a battery of no use. If the frame fatigues and fails, again the replacement proprietary frame could cost a £1000 or more if available. If the battery fails for an older ebike you have to make the decision whether to pay out for a very expensive replacement when the ebike may be getting old and the motor isn't working perfectly, that battery may cost 3x as much as a standard battery of the same capacity. Despite their high pricing many such ebikes have the shortest life. A bit like expensive German executive cars which get scrapped early compared to other cars because of excessive costs for spare parts and labour rates and being much more complicated than other similar products/cars with more complicated engines, transmissions and electronics. Also typically much more likely to have options fitted which can cause issues.
https://web.archive.org/web/20210430103 ... nufacturer
However just like those German executive cars they have better performance and perhaps a better user experience while they work however I really don't like the throwaway culture of such products, I feel products should be as easy and economic to repair as possible.
It's important to understand many ebike kits use components that are easy to repair or replace cheaply and allow easy customisation. If you buy a ebike kit and the hub motor has an issue perhaps 5 years into ownership its likely new parts are available and depending on the fault could cost just a few pence to a few tens of pounds. If you are using a bike converted into an ebike you always have the option to remove the original ebike kit and fit a new kit. An ebike kit is a bit like building a hifi system where you need speakers and an amplifier plus a few sources including a CD player and turntable perhaps. It's an open standard and you can mix and match but you have to follow certain rules like the ohms of the speakers must be compatible and sources need to use output standards the amplifier accepts. On an ebike you have the controls, the display, a controller, battery and the motor. In the case of a mid-drive motor the motor and controller are likely combined. The controller may use any battery of the right voltage and the motor and controller need to be matched for power. The controller also needs a display that electronically matches it for communication standards if its a sophisticated display but more simple displays work with more controllers and on many controllers you don't need a display anyway it could be just a basic controls with a simple battery charge indicator. It's a cheap way to buy an ebike not just initial purchase but long term costs.
I recently read on one of the forums someone who had an old lead acid battery early ebike, the batteries were end of life and the person replaced it with a modern li-on battery pack using the latest cells. It was only 24V and not only was the battery pack small compared to the original batteries (2) it actually massively extended the range as overall capacity was increased significantly. So not only was this old ebike continuing to be used but in fact it had been massively improved and updated to newer technology. The battery pack was not expensive either as only 24V so not a huge amount of batteries in series or parallel. 6 batteries in series possibly with 3 or 4 cells in parallel so only 18 or 24 cells in total I think. If the cells were around 3500mAh that gives maybe a 24V 14Ah battery with only 24 cells. Not sure what the original lead acid batteries were but their capacity would have diminished a lot I'm sure even if originally quite reasonable. I just think its great that such an ebike can be kept on the road.