So I just performed this repair. [br]
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On amazon they now have HS70 batteries. Some of them are wired correctly. Others tell you to swap the RED and BLACK cables on the connector.
https://www.amazon.com/s?k=HS70+battery&crid=2BDNGCRE73V3Q&sprefix=hs70+battery%2Caps%2C143&ref=nb_sb_noss_1
You pull off the cups on the RIGHT side of the headset. Remove the small screws, then GENTLY, lift the speaker off the board, and leave to the side, there is VERY thin copper cables to the right speaker. You then unscrew the PCB that the battery connects to. Take care NOT to bend the pins when removing the battery connector from the PCB and the battery. Then gently remove the battery, it is glued in. Do not puncture the battery. In my case the battery was pregnart/swollen. [br]
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Then install your new battery, connect the battery cable again, carefully not to bend pins. Then install the PCB. Take care to make sure the wires/cables are in the same orientation and not tangled/routed incorrectly. Take a picture before you remove cables. Your new battery wire might be a bit short, so you may need to flip the battery so you can keep everything tidy. Re mount the pcb with its two screws. At this point I would try charging/turning on your headset before you fully close it up. If it boots from the battery, it may only last a minute or two. Then finish attaching the speaker, attach the cup, then charge for awhile.