On the LiFePO4 batteries you need to read the fine print because most are advertised as being a drop in replacement. They are lighter and have far more capacity than a equally sized lead acid battery. But most lead acid battery chargers do not charge at a high enough voltage to completely charge the battery.

I have a Dakota Lithium starting battery in my truck. It is a drop in replacement for an automotive group 24 battery. It weighs 27 pounds and has 135 Amp hours. So it is much lighter and has significantly more energy than the lead acid battery it replaced. The problem with this is that the alternator in my truck is controlled by the ecu which only allows for the voltage to peak at 13.8 volts or so. To completely charge the battery to 100% it requires 14.4 volts. So I wired in an Anderson power pole into the grill and I use that to plug in a lithium battery charger or a solar panel that uses a charge controller on the lithium setting to get a full charge into the battery.