Battery Maintenance
It is important for both Lithium and AGM batteries to be regularly charged and not left flat, this can damage cells and reduce the lifespan of the battery.
If you have a solar panel, and the vehicle is kept outside then this will generally do an adequate job of keeping the battery topped up, however during the dark winter months it should be checked, to ensure that the levels have not dropped too low (i.e the van is completely flat) if so, the van should be plugged into the mains via the electric hook up, and or driven/left to idle to ensure they are charged.