It might be a smart idea to put a peak-holding clamp DC ammeter on the cable from the alternator to the battery to see how much current you are actually pulling from the alternator. You might find out that 40-50A is all you really need, along with a small 12V battery to smooth out the bumps along the way.
Re: Dc Dc converter best set up?
You should really test your system to see how much you need. Mine pulls under 15 A with everything on. Unlike your motor/controller, you can test anything about the 12V system while stationary.
Ok guys, humor me I think I'm nearly there,
Unfortunately I can't put an amp clamp on to test system yet, to many things hanging loose power steering plumbed in on the hydraulics but not wired in yet.
Also planning on using 12 v water heater element designed for Solar Power
not sourced yet.
But I think your saying even with the big amp draw components eg, power steering peaking at possibly 75amps the dc-dc converter at 55amps will cope most of the time with the battery taking care of the extra current when the heater or steering etc kick in, then at lower demand times dc-dc tops up battery
1 EV - 5,000 e-miles - http://www.evalbum.com/4000