For your situation, a portable battery charger with at least 10 amps and 12 volts that works for deep-cycle marine batteries would be ideal.
NOCO Genius10 Smart Charger: This charger can handle 12V deep-cycle batteries and has a 10-amp capacity. It’s portable and can charge multiple types of batteries, including marine. The NOCO Genius line is known for being robust and easy to use, even in outdoor conditions.
Schumacher SC1281 6/12V Fully Automatic Battery Charger and Engine Starter: This charger delivers 10 amps for battery maintenance and works well for deep-cycle marine batteries. It’s portable and offers additional engine-starting assistance if needed.
Battery Tender Plus 12V 1.25A: Though it only delivers 1.25 amps, it’s lightweight, compact, and ideal for slower charging while you wait for a more permanent solution. It is compatible with deep-cycle batteries, but it might take longer to charge. snow rider
Portable Solar Charger: If you have no access to power and expect to be stranded for a while, consider a solar panel charger like the Renogy 100W Solar Panel Kit, paired with a charge controller. These are more suited for off-grid situations like a motorhome.
