LiFePo voltage sagging

 12.95V resting it is only starting at 25%.  what are you charging them up to? A flooded deep cycle would be drooping a lot more at that low state of charge if it even works.  The one problem with LFP batteries is getting an accurage state of charge from voltage due to the small change from 70 to 30% and every cell will be slightly different so charts will be close. 20% soc won't huirt a LFP battery and expecial in the way your thinking..  the cycle life is based off a 100 to 0 to 100 charge cycle, by limiting the top or bottom end all we are doing is increasing the cycle life.  so the battery you have says if you go from 100% to 20% to 100% all the time you will get 6000 cycles so they ignore the standard industry standard of 100-0-100% so you can't compare to other batteries.  also they kinda don't tell the truth in their littiture with this statment trying to increase sales. 

 "battery is truly rated for 12.8V 120Ah (1536Wh)
since roughly 20% of the rated power stored in all Lithium Iron Phosphate batteries is unusable. We
strive to give you more for less - change the game."

a LiFePo4 has 100% of its capacity available at the rated cycle life.  at the end of the cycle life you simply have a battery that only is 80% of the original batteries capacity but it can be used for who knows how much longer. 

I don't mind that they recomend from 100% to 20% capacity that will increase your capacit and is how they get up to 6000 cycles, and protects then from warenty claims. SO I guess their statment could be true if you look at it like you can only use 80% of the capacity of you want to get 6000 cycles, but even 3500 to 4000 cycles at 100% is a long long lasting battery, I would be tempted to use it as a 120AH battery myself haha.  I see it uses celindrical cells so you can pound the charge a bit harder than prismatic as they disapeat the heat a tiny bit better, I would like to see you charge it up to 100% and try it after it sat resting for 30 minuits to get a true 13.6V resting volatage.  in the mean time I will continue to look for my volatage chart for LFP under load, I changed laptops a couple months ago so I'm still trying to find a bunch of stuff....  with that chart I will know what a normal drop is if they have a measurment for a 5amp load.