Liberty Coach has been using them for awhile. I was just at a Prevost Stuff show in Tampa and there was a company there called Volta that was selling Lithium batteries, generators, inverters, and DC/DC converters. They had samples of each and they looked very polished. The have taken electric car technology (300 vdc) and scaled it down to 48 vdc. The batteries are 48 vdc and the generator charges the batteries at 48 volts. This reduces i squared r drops and improves efficiency. The DC/DC converter is used to power 12 volt stuff used in the RV.
Their web site (
volta) says it was started by a fellow out of Johnson Controls. AGM's were originally proven in Military aircraft and then migrated down to us. Lithium has been used in military and electric cars/buses and will migrate down to us. The density and efficiency will drive that.