One correction to the above: The discharge efficiency of 85% that's widely cited is wrong, it's the same as other lithium chemistries. However, because it has high cycle endurance and low internal resistance, you can cycle it at extremely high current (10C continuous charging! That's a 6 minute full charge) where the efficiency is below 90%, while other chemistries are measured at low current.
The only true drawback it has is that the energy density is poor. You have only 70% of the voltage of LFP per cell, so it's going to be heavier.
Anyways, I just hooked it up to the car and turned on all the electrical loads, which I measured to be 54A with my crappy ammeter. Ran it for just about 20 minutes and...the battery is almost dead?
Here's the weird thing...when I disconnected the battery from the car, it sat at 11.20V, and now it's up to 11.30V and slowly climbing. This may be balance current. However, these are supposed to be doubled up 20Ah cells in parallel, so 18Ah should not be draining any cell anywhere near empty. Maybe the cells themselves are "recovering" from being loaded up, but AFAIK they're not supposed to do that.
I suppose I shouldn't have expected much given GTK sells 10 20Ah cells for 220 bucks, while Yinlong 40Ah cylindrical cells are 2x that price lol. I guess we'll see if the voltage miraculously recovers to 12V. If it really is only 20Ah capacity, then this battery is kind of junk because it weighs almost as much as a 20Ah lead acid -_-