LiFePO4 Batteries 

LiFePO4 batteries are characterized by the high density of energy and low values of self-discharge, which is the reason why they are such a popular product among yacht, boats and photovoltaic communities. Their biggest advantages are as follows: lack of lazy battery effect; high capacity, long life span; readiness to work in extreme temperatures (-10° C to +40° C).

LiFePO4 batteries are devices that can handle yacht, boats or photovoltaic requirements. What we should know before buying the battery: -LiFePO4 battery have voltage of 12.V; -it cannot be connected in serial or parallel configuration, because of the BMS (Battery Management System) onboard; -to achieve the longest lifespan of the battery it should work within range of it's designated temperture.

The main difference between AGM and LiFePO4 batteries:
AGM - a group of gel batteries having AGM (Absorbent Glass Mat) that is called VRLA (Valve Regulated Lead). In comparison to traditional batteries, AGMs have up to 4 times the lifespan and higher number of cycles. All thanks to previously mentioned fiber glass.
LiFePO4 - a group of lithium-iron-phosphate batteries. Their construction is based on four cells connected in serial. Every one of them works with voltage of 3.2V which gives 12.8V in summary. One of the most imporant parts of this battery is it's BMS - Battery Management System.

Choosing battery with higher capacity shouldn't be of any issue. The capacity of the battery is expressed in amp-hours (Ah). The higher the capacity (e.g. 80Ah), the longer the time that battery can stay on during one cycle, which in turn let's us be more mobile and independent.