The future is here, battery technology is moving on and we are not restricted to the lead acid or calcium disulphide leisure or vehicle batteries anymore, lithium ion batteries are currently being mass produced in sizes suitable for larger 4X4's.
Li have many advantages over traditional lead acid or calcium batteries, this is mainly the abuse they can take from charging, they deal significantly better than lead acid with abusive charging regimes, so are much better suited to hostile conditions such as connection to solar panels, or cheaper unregulated 12v supplies from cheap generators. Solar panels often supply voltages of up to 17v and cheap unregulated generator 12v outlets often supply 16v, Li can cope with this.
Discharge rates are their greatest benefit, traditional batteries are scrap at 50% discharge, Li can tolerate 80% discharge without any damage to the battery, great for people running constant current draw such as fridges or other items for long periods away from a charging source. One other benefit is their flexibility, the same battery can be used as a vehicle battery or leisure battery, so standardisation on one battery size for all applications.
With mass production now being undertaken the prices have halved in one year, and continue to drop, soon they will be within reach of most overland vehicle users.
Currently, i have two fitted to each of my boats engines to replace the lead acid batteries, the increased performance is amazing, cranking twin Caterpiller diesels of nearly 1000 HP each takes a lot of power, and these crank them so fast they are nearly at tickover speed just cranking, much higher than the lead acid batteries which struggle.