Hey guys. I'm kinda new to Li-Ion batteries, or at least new to actually tinkering with them. I bought this work light and being the person I am, the first thing I did was crack it open and have a look inside. I was surprised to find a general lack of circuitry, and a seemingly no-name battery. While I'm happy with the quality of the worklight, and the light output, I would like to get a bit extra runtime. I tested the light and it seems to get just a bit over 4 hours on full power, which is about right. Plugging these values into a calculator, 2100mAh, 500mA discharge (tested with multimeter) = 4.2 hours runtime. If I swap this battery for a Panasonic NCR18650, I should get between 6 and 7 hours runtime, which would be awesome. I've had a play around with the case and I can only really fit the one 18650 in it. But that's ok. So, some details which might help, along with photos. Both the wall and car charger output 4.2v. Wall charger 600mA, car charger can't be bothered to check. I'd also like an opinion as to whether the wall charger is decent quality or not (is it safe?). There is no apparent charging circuitry, apart from the PCB on the battery. I can't read all of the part number but I THINK it is an FS8205A. Someone will have to confirm. Note that I peeled the outer plastic off the battery before taking this photo. There were no identifying marks on the plastic. Sorry for all the pics! I just want to make sure I'm doing this mod right. I'm assuming all I need to do is transplant that PCB on the old cell to the new one, and I'm good to go? Or is there more to it? Cheers guys.