Duracell rechargeable batteries don't fit

I don't think rechargeable battery will work. The voltage is too low. But some people manged to get the correct brand and seems to manage to get away with it.

However, I had been luckier to to able to use the litium ion made by a Ken***. This has been working for 6 months now and no problem, on a single charge. It still has power but decided to recharge it just in case.

I had a thread created a few months ago on here and it seems Tado has deleted. Not sure why maybe I had specified the battery name. I had now hashed it out. The battery is essentially a lithium ion battery with higher voltage than AA battery, but it has an inbuilt voltage regulator that steps down to 1.5v, same as AA battery.