How to achieve longest uptime without charge and SIM

Yea, sorry for the wierd thread name, but currently, I owne a S3 who is working as an local remote control. The crazy part is that it works for 1 or max 2 days and I need to put him to charge. I use it like once or twice a day, for like 5 minutes, so I am not sure ehat is sucking the life out of it...

There is no need for a SIM card, so is there a way to kill that part or disable it somehow, cause I believe that this is a battery drainer too.

Thanks in advance for your help!

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