Decided not to go with the Bird system it is too complicated (KISS). In 2006 Winnebago started installing this unit. They already have a system to charge the house batteries from the chassis alternator so a bidirectional system is not necessary. and if this is good enough for them then it should work for us.Installed Ultra Trik L Start 5 Amp Starter charger to keep the chassis batteries in good shape.Total cost from rvupgrades.com $37.90. Everything looked great after installation.