Wont this stress both of your batteries?
In a parallel circuit each component shares equal intensity.
If you alternator is meant to put out 13.8-14.2 volts when running --lets just average it to 14 volts-- then that means your battery receives a 14 volt charge.
If you place two batteries in parallel this means each battery is only getting a 7 volt charge! True they are only each putting out 7 volts apiece but doesnt the battery have a 'optimal' recharge happiness rating? In other words is a lower charge on each battery damaging the cells in some way?
Or does it act kind of like a trickle charger.
Not knocking yourset-up - I love it in fact! I love anyone who does anything DIFFERENT with their cars - just curious!