Few basic lights & acc. - Deep Cell Battery vs Jumper Pack?

[Air Doug]

I have a cautionary story on lithium battery packs. I bought a 19 Ah one with the idea of running our ARB compressor-style fridge for a few hours. The fridge draws about 3 amps when running and normally it runs off of the trailer AWG and car alternator. But when parked without the trailer I wanted to be able to keep the fridge running in the car. The lithium jump pack has jumper cable, USB, and power plug outputs and automatically sets to 5V or 12V.

Well, it runs the fridge okay for a few hours then shuts off while still 72% charged. The voltage at the plug was 10.7 at that point, which is below the fridge cutoff at 11.1V. Recharging the pack, it reached 12V by 85% charge.

I am not too sure what is going on but I think this particular Li formulation has a lower voltage than what I was expecting from, say, a LiFePO4 battery. It is still fine to charge phones and jump vehicles but I will find another solution for the fridge.