Hello Arnaldo,
Good day. Thank you for the question.
For a battery replacement, I suggest that you contact your regional Sales Manager or your direct distributor from whom you purchased the FM5300.
The battery specification is part number 7H550 3/5F6S, Ni-Mh battery pack 8.4V 550mAh,45x37x17mm
Also, please take note that this device is EOL (End-of-policy), therefore, getting the spare parts and batteries might be hard. Please refer here for all our EOL products - https://teltonika-gps.com/policies-certificates/eol-policy/
However, currently we have projects that can replace the FM5300 such as FMB640, FMC640 and FMM640.
Hope this information helps. Thank you for contacting us.
Kind regards.