Battery depletes quickly from full charge even when not in EV Mode

It switches automatically from EV to HV at around 62 MPH. So if you're going 70, it's using gas because it's more efficient.

 

even in hv, it will use a portion of the ev battery. after it reaches that parameter, it will hold it there using the engine to charge the battery, unless you switch to ev.
when i leave my house in hv mode with a full charge, let's call it 12 miles, it will use about 4 miles of the battery, then hold it at 8.

 

(Actually, the switch to HV is at 65 in my experience, not 62.)
But here's why the battery depletes anyway: It's still a hybrid when the ICE runs in HV mode. So, the car will use what it "believes" (via its Hybrid Synergy computer) is the least environmentally-harmful means to produce motive power, meaning a combo of running the ICE only fast enough to keep the MG from overspinning at high vehicle speed, and using the traction battery's power through the MG for the rest of the motive force.

 

The battery also needs room for more charging when regeneration braking, or regeneration going down hills. So it has to bleed off a couple of miles of battery so that it has some room for that type of regeneration charge.

So it's normal!
Enjoy your car.

 

My experience is that the car indicates 65 MPH when it switches to HV, but actual speed (GPS indicated) is 62. The speedo in my car is about 2.5 MPH faster than actual around 65 MPH.