A diesel truck with extra batteries is GREAT for the car-inverter “generator”.
It’s not ideal, but it sure will do in a pinch and on a budget. I did some research and your typical car alternator will only put out 750 Watts (3/4 kilowatt), but that’s plenty for running a modern freezer or refrigerator.
And you don’t have to have them constantly running.
The cheapest “power” for your freezer is to wrap it in blankets and run it for an hour every 12 hours or so. Also, keep your freezer full, even if you take up space with water jugs.
Here’s a trick to “alarm” you if your freezer has gone off for longer than it takes to thaw (even if it comes back on and re-freezes everything).
Fill a standard 1pt water bottle half full and freeze it upright. Then turn it upside down in your freezer.
If you question whether your freezer has thawed and refrozen, check the bottle. If the ice is now in the neck and conformed to the shape, the water has melted all the way and has refrozen. Even if it has “slid” but still retains the shape of the bottom, your stuff is safe because the temperature never got above freezing.
All true with one caution:
All freezers/fridges are heat exchangers, so when you wrap it in blankets, be sure to NOT cover the heat exchanger coils or restrict airflow to them. they are usually on the back or the bottom. IF you do NOT do this, your freezer will run and run and actually HEAT UP your food.