What can a 70amp alternator support?

[theabunai 3]

sorry my bad to end all confusion best easiest way is this

I did it the other way thinking you need to add 20% to get what ever EXTRA the amp needs to produce to make 3000....

3000 divided by .8 = 3750

We do it cause the amp is 80% efficient that means to make 3000 watts we it needs to make 3750 watts.... If it were 100% effieicent it would take 3000 watts to make 3000 watts... if it were 50% efficient it would take 4500 watts to make 3000 watts...

then 3750 divided by 13.8 = 271 amp draw at full tilt