Hi - I'm thinking about installation a simple 12 v system in my van, that would be independent of the van battery i.e. a stand alone lithium battery under the driver's seat supplying power to two USB sockets, two switchable lights and a maybe an LED display showing voltage (battery charge) with a fuse box type protection. Has anyone done this and has a schematic showing the set up please? I want to avoid solar panels and split charging as I'm happy to just recharge the battery as and when needed and just want a simple system to provide device charging and a reading light or two. Thanks