I have a 100ah lithium battery box that I keep charged at home but take in the car when going on holidays or sometimes for longer day trips. I initially bought it to power a small travel fridge but I also have 12v lights that can run off of it and can use it for charging phones etc. I want to add solar charging so it could be used as a power source even if I had no mains for a while. 

I’m sure it could also use it to generate a spark big enough to start a fire if needed. 😂