Dear Sir/Madam Thank you for contacting FOBO, Please refer to the below video link for how to replace battery for FOBO Bike 2 sensors : https://www.youtube.com/watch?v=hjshOt_ZW-Q Unfortunately we regularly see new batteries that are dead in packets or discharge quickly as soon as used. We usually use and recommend Energisers/GP/Maxell brands in the market to clients as our experience is these last the longest and have nearly always proven to be reliable from new. Should you have any issue arise, you may revert to us for further assistance. Best Regards Amir Bayati Customer Experience | Salutica Allied Solutions Sdn. Bhd. (a subsidiary of Salutica Berhad) 3 Jalan Zarib 6, Kawasan Perindustrian Zarib, 31500 Lahat, Ipoh, Perak, Malaysia M +6016 787 3175 | my-fobo.salutica.com.my