Typical car alternators are about 65% efficiency, generally due to being engineered to work well across a widely variable RPM range. Gensets are more typically 80% efficient. Only the very highest quality alternators and motors reach 90% and they're very expensive ($1500 compared to $100).Catigale wrote:1 HP is about 750 watts, so if you are pulling 25 amps at 12 VDC that would be 300 watts, about 1/2 a HP at 100% efficiency.
I think alternators run at about 90% efficiency IIRC??
But you are correct in that 40% seems really low.
