27/90 as soon as you switch on the alternator the field windings take max current on a 60amp that is about 3.5aps. So the alternator is trying to produce max output as it spins on start up the load, because the starter is pulling down the voltage the regulator still pushes 3.5amp in the field winding so the alternator output is 60 amps or a one horse power load on the starter motor. 720watts/hp so best to turn off the alternator on start up.