Conrad Electronic S555TH Notice D'emploi page 23

In general, it is possible to operate the outdoor sensor with
rechargeable batteries.
However, due to the lower voltage of rechargeable batteries
(rechargeable battery = 1.2V, battery = 1.5V) and the lower
capacity there is a shorter operating time and the radio range
might be reduced.
When the outdoor temperatures are lower, rechargeable
batteries are more sensitive than normal batteries.
Therefore, we recommend that you use high-quality alkaline
batteries in order to allow for long-lasting and reliable
operation.
The outdoor sensor requires two batteries of the type AA/
Mignon (e.g. Conrad item number 652502, to be ordered 2x).
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