Yes, If no inverter and if you have a multi meter you can connect the to the battery.... put DC setting (mine says "9 DC") and it will show around 14.5 on quick charge (most likley battery is very low), around 13.8 normal charge.
12.8 or so with "no charging" the battery is full. (FYI = 12.1 is like 50% discharged).
Its best to check the charge of the battery itself (with a multi meter) after they have "rested" for about 30 minutes (that is After being plugged in or driving wait 30 minutes).
2017 Axis / 25.4: Big Foot Levelers, Aims 1200 Watt inverter, Ceramic Window Tint, Full River AGM 6V batteries, Front Hellwig Sway bar / Rear Track Arm, Safe T Plus Steering Stabilizer, PD 4655 converter, Hard Wired Surge Guard, WEboost + WiFi Ranger, LED Headlights/Driving lights, TPMS, Surge tank, Tornado flush, Viair Compressor