when the batteries died in my HC-2, I disregarded the warning on the ring site that the world would end if I opened the HC-2. I replaced the batteries with the top of the line Energizer AA rechargeable batteries. IIRC the rating of the batteries is 2600 mAhr.
the only tricky part was to get the metal standoffs (that support the display) to stay put, place the screen in place, then put the halves of the HC-2 back together.
it worked fine upon reassembly.