yeah, basically need a battery maintenance charger these days... can't spend long working with the battery connected... I guess that's why a lot of places disconnect the battery instead of leaving it connected...
You've built the engine but not the rest of the driveline after the clutch?... it's going to be difficult to keep those CV's in their housings and the tailshaft will probably be toast at anything above 300rwkw... never mind your driveshafts but that's a pretty conservative estimation.