Got a like new Fieldpiece SRL8 from a pawn shop. I only need this for HFC leaks right now.

Listing claimed it was brand new and it did look brand new, zero scratches or scuffs or signs of wear on anything, rubber looked and felt brand new. Was missing the wall charger and RRE2 needle probe but has the wand probe, carrying case, and an extra sensor. They shop owner played it off as a low battery and because it didn't have a wall charger. Unfortunately, every time I hold the power button the "LOW-BATT" indicator is blinking. I left it charging in the car for over an hour and it was still doing the same thing on power on, showing the full display meter lit up for a second and then going to the LOW-BATT indicator blinking. Haven't even gotten the Fluke out to check the battery output yet cause it's still charging.

What should I be looking for if it's defective before I order a new battery and get a wall charger?