there is a device called alternator charger
https://www.theverge.com/24248887/ecoflow-alternator-charger-review-boondock-power – EcoFlow’s Alternator Charger helps keep all your tools and toys charged when driving away from civilization.
https://intelligentcontrols.io/blogs/technical-articles/how-to-charge-batteries-off-your-engine-and-stock-alternator – How to Charge Batteries Off Your Engine and Stock Alternator