I just replaced batteries in two pairs of my glasses (got them new from eBay but they sat for too long so batteries wouldn't charge; probably would be the case with many of these glasses since they've been discontinued for a while now). To open the frame you need a tiny torx and phillips (torx is T4 and phillips PH000 or PH00 works, it seems PH00 fits better though; if you have one of these iFixIt kits then you have all you need to open the case). There is one torx holding a nose piece, and two more underneath. There are two phillips screws in the inner side of the frame and two more on each end in the hinge, you must fold the glasses to see them. You must have a plastic spudger or guitar pick to open the case. With all screws removed gently pull around hinge area inward to get it open, then work with a spudger inward towards the nose piece. I got a pair of batteries from a DigiKey link above because eBay ones seemed too shady and I was worried about it being a fire hazard. Anyway, DigiKey batteries did work fine, however they are too thick and I could barely get the cover back on. I were able to close it but it is definitely pushing a bit so there's a slight opening in the cover. It is not too apparent though. The wires are a bit thicker which makes them difficult to route. You have to route them because edge of the board is almost touching the housing and there's probably a millimeter or two of clearance from the battery PCB pads. The pads are very small with little spacing in between and lots of other components around them. PCB doesn't come out of the housing so you have to hold the soldering iron on a 45 degree angle or so (I have a professional temperature controller soldering station with a pencil iron, used a thin needle tip at 350 degrees; solder is lead free. You absolute must have a thin tip in order to be able to solder this, it's incredibly tiny). I did slightly burn the housing trying on my first pair while trying to get through the factory solder (hint: use flux or apply new solder over the factory solder joint to make it melt easily with little effort).
So yeah, you do have to solder in your new battery. You may be able to get a small inline connector and cut old battery wire and attach it to a connector or directly solder old battery wire to new battery wire. I actually wish I did that instead of soldering to original pads as it was a real pain in the butt and I could barely see them even with a magnifying glass lamp. You have to be really careful to not short the wires. I got them soldered properly but as I was trying to position the wire my first attempt resulted in a short but I caught it just in time as battery got really hot. I cleared the short with a plastic spudger and then used some electrical tape to insulate the contacts (physically bending wires in opposite direction helped a lot as well). I would recommend a different battery that is a bit thinner than that from DigiKey, however it did work and charges but with it being too thick you cannot make a perfect repair. So yeah, all in all both of my glasses are working and I'm fairly happy with results. I would be 100% happy if battery thickness was just as OEM. I couldn't find the exact OEM battery specs though. Maybe those eBay ones are the right size but I would never buy a battery from unknown source, just too risky in terms of fire safety.
I've attached some pics, sorry I didn't take one reassembled where you can see the case doesn't fully close (it is very minor though, just a small split at the top above the nosepiece since there are no screws in that area). I mean you do use these in the dark anyway, so I just didn't care to redo it for this minor issue. You can see a pic of original battery, DigiKey battery side by side with original and with battery removed. OEM battery markers are there but I couldn't find one just like that, wouldn't be surprised if it's some generic or customer battery that was made for Epson/Seiko.
Anyway, hope it helps guys! Good luck! I'm happy to answer any questions since I just repaired mine.
Last edited by expired56k; 06-26-2020 at 05:56 PM.