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.
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This is what I got from internet, also 303450, but the connector is different, so it needs to use original connector.
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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.
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Clarence
KT-1255 is not my favorite. Too much compatible issue, it’s failed product.