I did it — another ScanWatch has been brought back to life by me. Unlike the previous one I repaired, these two watches came from different second-hand sellers. For the first one, I already knew before buying it that only the battery was dead, because the seller showed the icon that appears when charging fails due to a bad battery. But for this one, I knew nothing. I could only gamble that the battery was the only problem.

Now I’ll talk about what’s different about this battery, and why I don’t recommend using the larger-sized 302020 battery.

1. The batteries are different.
For the first ScanWatch, I used a 301420 battery labeled “90 mAh.” For this one, I used a 302020 battery also labeled “90 mAh.” Yes, I know — the two batteries are different sizes but claim to have the same capacity. So clearly, one of them is lying. (These are just ordinary lithium batteries from Taobao, not those advanced high-density silicon-carbon batteries used in modern phones, where different sizes can still have equal capacity due to higher energy density. That’s why I believe one of these 90 mAh labels is false.)
Anyway, I still expect the 302020 battery to last longer than the 301420. I’ll do a real battery life test later.

2. This watch is different from the previous one in another way.
Its back cover is slightly bulged. (At first, I tried to open it from the back, but it clearly wouldn’t come off. After failing to open it, I glued it back with B7000. The problem was that the black waterproof gasket was a bit deformed, so the back cover couldn’t fit perfectly.)
This bulge causes several issues:

Waterproof performance becomes even worse. The front glass has already been removed and reinstalled once, so that alone reduces water resistance.

Because the back cover is bulging slightly, I was able to fit the 302020 battery. If your watch doesn’t have this bulge, there’s a good chance the 302020 won’t fit.

Since the cover bulges, the charging contacts now require taller solder joints on the motherboard to make proper contact. And both positive and negative points must be soldered to exactly the same height, which is tricky.


3. I removed a metal plate on the motherboard.
Removing it also helped create enough space for the 302020 battery.


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In conclusion, I do not recommend using the 302020 battery. I still suggest using the 301420 battery, unless your back cover is already bulging, you’ve removed the metal plate on the motherboard, and you intentionally want to take the risk of using a bigger battery. Feel free to try it, but it’s still risky.

This post is not a tutorial — just my experience. I hope it helps you.🫡


some experience