I thought my battery was broken, but at least I found that’s a mistake, it’s bludtooth pairing issue.
For disassemble this keyboard, suggest to reference this video .
Even this is no screw desig, but it has a lot of glue between keyboard and case, so, please be very careful to disassemble it.
After disaseemble it, the battery part number is AHB303450PRT-02, it’s a common lithium battery spec, it can buy it from internet very easy. Just search 303450 3 wires parts.
This is what I got from internet, also 303450, but the connector is different, so it needs to use original connector.
and remeber when unplug the original connector from board, it needs to pull up, not pull back. I made a mistake here, it only can use hot melt (or hot glue?) to fix it on the case.
Clarence
KT-1255 is not my favorite. Too much compatible issue, it’s failed product.