Within hours of receipt, only 1 beacon now works

Hi Guys, within hours of having these beacons I have patiently waited for, I am now down to just 1. Probably battery issues as I emailed the other day, but still, thats pretty bloody poor. Is it okay to replace batteries ? I don't want to tear them open, are there instructions to do so safely ?

Please check your inbox, I've just replied to your message.