Thanks for the guide. Soldered in eneloop AAAs. Solder seemed to adhere ok to the terminals on the battery. The terminals heated up a bit but didn't seem to do any damage to the cell. (Although I wasn't trying to heat the connector like in a proper solder job, really just heating the solder enough to drip it on the terminal, then heating it again once on the terminal to stick the slightly mangled tab into it. The soldered batteries were a little bigger than the originals but the end of the battery holder bent enough to get them in(used a bit of good electrical tape to hold them in since the tabs were now spread a bit too for the smaller circuit board to clip in and hold them properly) and the holder snapped back into the shaver body fine. Got a flashing orange light even though the batteries were mostly charged, so popped the shaver on the charger and it charged for 15 mins or so and then went full green. Shaver works fine and seems stronger than new now. Will update if any changes or problems…….