A good portable power station and solar panel kit keeps your gear running for days while you are off the grid. You want something built to last a decade, so you only buy it once instead of replacing a cheap battery pack every season.
Shop the early spring outdoor recreation sales when retailers clear out older stock. Look for last year's model since the battery tech inside rarely changes enough to justify paying full price for the newest release.
The 0% intro window is a deadline, not free money. If you still have a balance left when those 18 months are up, deferred interest or standard rates will kick in and wipe out your savings.