Ordered the exact same batteries as harakhty to france. Cheap shipping.
I've never soldered in my whole life before so I was a bit nervous.
I had some trouble getting the old soldering tabs off so I cut them off first then used the kind of razor blade you use to clean ceramic stove tops with to get the last pieces off, then I sanded them a bit.
New batteries came with a plastic connector so I just pulled the cables out of it and kept red and black far away from each other
Put some solder mixed with flux directly on the circuit board metal pads and attached the cables red on the left, black on the right.
I had the batteries outside of the case while soldering, also I had to modify the case, bend off and sand down some plastic to make the batteries fit.
Taped like a paranoid man to avoid shorting and it worked like a charm
I know the stuff is obvious to some but for any other noobs like me out there I just wanted to share anything that might help.
I used harakhty's suggested file manager to copy over the power management files.
Will the battery lamp turn green or switch off when batteries are fully loaded?
I'm still a bit nervous the whole thing will explode
Thanks for all help!