Nighthawk M6 battery drain

Hi,
I bought mine to use remotely on battery. Each time I charge it to 100%, I use it for 2-3 hours, it drains to about 70-75% and I switch it off to use again the following night. When I go to use it the next day, it is completely drained to 0%. This has happened each time since I bought it about 3 weeks ago. I'm guessing this isn't normal?

Thanks,
Daniel