I was looking at the new EU Battery Regulation (EU 2023/1542) coming in Feb 2027. Under Article 11, portable tools will basically have to move to user-replaceable batteries without destroying the casing.

Look at the most frequency use mini 4V Tools like electric screwdrivers, hot glue guns and mini rotary tools, they all sealed in batteries.

It seems US doesn't have anything like that yet , I honestly think this is the right direction to go.

Swappable packs solve three problems in my book. First, you don't have to stop what you're doing and wait for a charge, just slap in a fresh battery and keep working. Second, with a built-in battery, if the charging port breaks or the cells eventually die, the whole tool becomes e-waste even if the motor is still perfectly fine. A removable pack avoids that entirely. Third, just like the 20V platform, you'd only need maybe two or three 4V packs total, because you're rarely using several 4V tools at the same time. Plus you don't have to pay for a new battery every single time you buy a new tool.

The only trade-offs are a slightly chunkier handle and having to buy that first battery pack upfront when you get your first tool.

Do you think a unified 4V swappable pack makes sense, or is 4V just too small to bother？

I posted this on r/tools yesterday, some DIY experts strongly recommend designing the tools to allow direct replacement of the 18650 cell itself, rather than making a proprietary pack. But is it really practical to have 18650 cells in power tools swapped out like AA/AAA alkaline batteries? I know that people with the right skills can easily replace a cell with a soldering iron and a spot welder, but what about the majority of users who don't have that equipment or those skills?

I was looking at the new EU Battery Regulation (EU 2023/1542) coming in Feb 2027. Under Article 11, portable tools will basically have to move to user-replaceable batteries without destroying the casing. Look at the most frequency use mini 4V Tools like electric screwdrivers, hot glue guns and mini rotary tools, they all sealed in batteries.

It seems US doesn't have anything like that yet , I honestly think this is the right direction to go.

Swappable packs solve three problems in my book. First, you don't have to stop what you're doing and wait for a charge, just slap in a fresh battery and keep working. Second, with a built-in battery, if the charging port breaks or the cells eventually die, the whole tool becomes e-waste even if the motor is still perfectly fine. A removable pack avoids that entirely. Third, just like the 20V platform, you'd only need maybe two or three 4V packs total, because you're rarely using several 4V tools at the same time. Plus you don't have to pay for a new battery every single time you buy a new tool.

The only trade-offs are a slightly chunkier handle and having to buy that first battery pack upfront when you get your first tool.

Do you think a unified 4V swappable pack makes sense, or is 4V just too small to bother？

After replacing the battery in this old Dremel Stylus, it's back to life! Why did Dremel discontinue this unique pistol-grip rotary tool? Was it a bad design?

I'm an independent product designer / engineer. I do a lot of prototyping and teardowns, and I use a lot of small 4V tools – electric screwdrivers, hot glue guns, rotary tools, that kind of stuff. and I kept running into the same battery headaches. Most of these 4V tools use built-in 18650 cells. Either it dies halfway through a job and you're stuck waiting for a charge, or the battery just gives up completely and turns a perfectly functional tool into e-waste.

I tried the RYOBI USB LITHIUM screwdriver. The removable pack design is awesome, but the actual torque? Honestly, it's weaker than a TK4 screwdriver from over a decade ago. Not kidding. So I thought, alright, I'll design my own 4V pack. Use a 21700 cell – lower internal resistance, 4000mAh, 5C rating. More runtime, better discharge, more torque. Made sense on paper. I designed it, 3D printed a prototype to test… and man, it was just awkward and chunky.

That's when I finally realized my entire approach was wrong from the start. When you already have a swappable battery pack system, the extra runtime you get from a 21700 over an 18650 barely matters. Pack dies? Just pop in a fresh one and keep going. But with a 21700 pack, every single second you're holding the tool, you're carrying roughly 50% more weight and about 20% more bulk. The grip feel was genuinely bad.

So I threw six months of work in the trash, went back to 18650, and redesigned the pack structure and BMS from scratch. I've posted some 21700 vs 18650 comparison tests before. https://www.reddit.com/r/Tools/comments/1sfrc0a/18650_vs_21700_for_4v_tools_is_the_extra_capacity/

Just putting my failed development journey out there in case it saves someone else the same headache.