so I've had the MVP for almost 7 months now but lately its been acting up I don't think it fully charges anymore. when I first got it a full charge would last 3-4 days running at 4.5-5 volts with a standard drip atty. now I plug it in over night but the light never shuts off like it did, and I end up having to charge again mid day. is there something wrong with it or has it gone bad already?