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Comment by yardie | Hacker News Reader

The battery cases are all custom but the batteries are the same 18650 you can buy on Amazon. My ebike has a custom case that fits in the lower frame. The actual case is held together with philips screws. And I could potentially increase range by swapping out higher capacity cells.

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Are you sure about that? Because the battery management systems are proprietary. I'm just starting to research this, so don't take my word, but I'm pretty sure they take steps to lock you in.

What exactly does a battery management system do and how is it incorporated into the battery pack itself?

You should ask user battery management system hacker jacquesm about that because I'm just starting to learn

https://news.ycombinator.com/item?id=29201673

It can be smart and ensure longer battery life by not overcharging weaker parts of the pack. You never have perfectly even drain even if you use just 2-3 batteries. It can be just a gimmick to ensure you use proper TM cells instead of generic ones, in same vein phone chargers are split into manufacturer's and the rest, regardless of quality/power.

Vendor lock-in has been done successfully in the past and brands like Apple don't get hurt by it. So why should e-bikes be different.

Because those are shitty business practices that only serve the profits of the corporation. My hope is that people arrive to be better, rather than pull the same old bullshit to protect profits

> people arrive to be better, rather than pull the same old bullshit to protect profits

Of course not, batteries for electric cars, bikes etc. will be locked down as hard as possible and new ones will cost 2/3 of the new car price - sometimes replacement will not be available even from manufacturer which in effect will send perfectly good car to the junkyard - you can see this playbook in action right now with old Nissan Leaf.

From a user perspective, it protects you from the battery (by protecting the battery), increases the performance and longevity, and informs you about the state of charge. It connects to the battery at the cell terminals and to temperature sensors. A charger is a separate thing from a BMS.

So can it detect if I replace the cells myself?

If you replace with the cells with the same type, it probably won't notice the difference.

I have no idea about commercial e-bike BMS specifically. But in general, some BMS can, while others won't but maybe should because replacing cells can reduce the safety of the product. It depends on a combination of the cells, BMS, charger, and load. You shouldn't mix old and new cells in the same pack.

Of course, but as an educated consumer who likes to repair their own things I would get all matched high quality cells and replace all at once. If their battery packs don't detect or prevent this somehow then it wouldn't really matter to me.

There's an awful lot of DRM talk in this thread so that was my concern. The cells theoretically are the only parts that need to be replaced sans physical damage

I don't know about DRM. Be careful when joining batteries in parallel. You might not get full performance without the factory procedure for mating the battery and BMS together. Datasheets aren't enough to fully match cells, so the reliability and safety might be less.

The BMS ultimately just electrically contacts commodity li-ion cells in all cases that I've seen. You could use proprietary cells in some fashion but that would greatly increase the cost to the manufacturer as well.

Amazon does not allow selling 18650 batteries, but yes, they are a commodity item.

You can buy them off amazon.

Even if they are not allowed?

You can buy many things that are not allowed for sale in many places that do not allow them, but I would not recommend it in this case because it's a market where sellers like to post "9,999 mAh" batteries that are just pulled from discarded laptop batteries and maybe re-wrapped with a fancy label.

ilumn.com and 18650batterystore.com are legit as far as I know.

https://www.compliancegate.com/amazon-lithium-batteries-requ...

> Amazon prohibits the sales of the following products containing lithium batteries:

> Electronic cigarettes > Cylindrical lithium-ion cell battery types: 14500, 16340, 18650, 20700, 21700, and 26650

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