JBL Charge 2+ battery replacement troubles

Switch red exterior wire with black exterior wire, and red interior wire with black interior wire. It worked well for me when replacing battery.

make sure wire colors match the previous battery

same thing happened to me. You can either disconnect or just snip and solder the wires as others have said. If you don't want to do that, there are actually two revisions of the Charge 2+. The first revision shares a battery with the charge2 as the ifixit part suggests (part #: GSP1029102). The 2nd version has the polarities of the battery reversed and has part number GSP1029102R (note the R at the end). Other vendors have this battery with the correct polarities for the 2nd revision charge 2+ if you aren't comfortable reversing the wires.