I was thinking of something like this.. https://www.amazon.com/EXP1250-Terminals-Chamberlain-LiftMaster-Replacement/dp/B0010Z4MDK/ref=mp_s_a_1_1?dchild=1&keywords=12v+alarm+battery&qid=1585310237&sr=8-1

5 AH

Overkill. This one will do for you (12V@5Ah) - https://www.amazon.com/gp/product/B0010Z4MDK/ref=oh_aui_search_detailpage?ie=UTF8&psc=1

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You'll know you need to recharge when you see the vaporizer can't maintain temp