A good mod. Well done!
If you disconnect the alternator - then:
Just be sure to keep that lead acid battery charged up as much as possible via a battery charger. Yes it has xx Amp Hours capacity but the further down you drain it and the more often you do that, the shorter the overall lifespan of the battery. California98Civic had one that died after about a half year of heavy discharge use. He just got a bigger one so he won't have to drain it down so far.
My thread on my EPES project:
http://ecomodder.com/forum/showthrea...highlight=EPES
I had a few additional challenges to deal with due to a 55 mile commute, each way. So my installation is a bit more complex...