My Garmin 590 GPS battery had lost most of it's capacity (due to fake "off" state) - to the point where it would run for 10 mins when off the bike, then shut down. I like to remove my GPS and sit in the shade and plan trip routes in the trip planner... so time for a new battery. I knew the OEM batteries would be a rip-off - but was surprised to find them at 1000% mark-up by Garmin and TT. I know LiPo's as i use them in my drones i make (Lithium Polymer) and looked around for an identical battery that would do the same job at "market price" - found a candidate HERE which is also 1s 3.7v cell of 2000mah capacity and similar size for $5 Aussie price. After installing it and riding for a few weeks i can report its working well. These $5 LiPos come with a small PCB charger-circuit which i removed (de-soldered) then i soldered back the Garmin charge-circuit & plug (from my old Garmin LiPo) and taped it up for the test rides. it needs soldering skills to do this hack. But overall works identically to the original one, fits perfectly.