If you want to prepare for a power outage the cheap way, buy the same starter battery as in your car. Then buy two battery clamps and something like this: https://www.amazon.com/Updated-3-Socket-Cigarette-Splitter-Charging/dp/B07G8Y94PJ/ref=psdc_15729631_t1_B07CM7PJQB Cut of the plug, connect the clamps. Now you can load your phone, plug in a car charger for your laptop, even power a router. And anything else that runs on 12V. You can use it to start your car if the battery in the car has a problem. Swap it from timr to time with your cars battery to keep both working.
@rudolf Fairly easy and not too expensive to hook up a solar panel and solar charger to keep the battery charged, if you have somewhere to mount it outside. And safety first - typical car batteries can provide enough current to burn up wires and equipment in seconds if you miswire it.