who said anything about lithium? that looks like a flooded lead acid chart, not an AGM chart, and I bet most fridges are on AGM batteries.
for example that chart has 100%- 12.7 V, 75%- 12.4 V, 50%- 12.2 v, 25%- 12.00 V, 0%- 11.9V
AGM battery is 100%- 12.8 or higher V, 75%- 12.6 V, 50%- 12.3 V...