[Owen S Quirion]

Joe, I am guessing that the Lithium battery is not an Automotive battery right? Here is the problem with Lithium batteries as Automotive batteries, there is a property known as "C" rate when talking about the ability of any battery to either accept or receive a charge. Lead acid batteries have a pretty quick discharge rate and they also can be charged pretty quickly as a result. On the other side of the equation, the Lithium Ion batteries deliver their power over a longer time period and also take longer to charge. I think your problem would most likely be with the Lead acid battery attempting to dump it's charge into the Lithium Ion battery at a rate too fast for it's acceptance causing perhaps a Nova Flambe'. Translation: Orange flames instead of green ones.