Hello everyone, the instructions state that the battery has a service life of approx. 4 years and should be replaced with an original "Panasonic BK-22HF3G1, Ni-MH/2200 mAh/3.6 V". Unfortunately, I can't find this battery anywhere (not even on Bosch itself). Does anyone have any idea where I can get such a battery after a few years if I can't find it now? I would hate to have to replace the siren again. Thank you very much.