# Mini Cargo emissions?

## From : ahoudini

Q: the mathematical conversion from mechanical horsepower to electricity is 746 watts = 1 horsepower that 746 watts could be any combination of 1 volt at 746 amps to 746 volts at 1 amp. so if your alternator is a 60 amp alt at 14 volts the alternator needs to put out between 13.5 and 14 volts to charge a lead acid battery you need at least 60 amps x 14 volts == 840 watts / 746 == 1.12 horsepower if you add in the energy lost to friction slippage heat etc. then you are closer to 2 horse power to drive the average alternator. a dual alternator set up will give your 1700 watts at idle. the military went to 24 volt systems as an efficiency measure higher rotor coil energy creates a stronger magnetic field for the fields to be cut by so the alternator can put out more electricity from a smaller package. typical military alternators are 28 volt units at 60 amps which are not that much bigger than the 12 volt 60 amp unit yet put out twice the power. in heavy aircraft the alternators are 28 volt 300 or 400 amp 400 hz ac units. these units are just over 15 inches in diameter weigh in at about 30 lbs yet put out 8400 or 11000 watts. the 400 hz when rectified to dc user smaller rectification units and makes cleaner dc power than the common 60 hz ac of our house hold electricity when rectified to dc. with two of these units with field coil selector switch alternators are not self excited so you need an external battery to drive the rotor coils you can use one or two of the units as you need. what you need is a 2 to 1 step down transformer and a rectifier to provide the dc power for the 12 volt really 13.5 volt lead acid batteries. then the dc power has to be inverted back to 60 hz ac power and then back through a 9.5 to one step up transformer to get the 120 volt 60 hz ac power to drive common house hold or commercial gear. be aware that 12 volt dc can start the excitation of the rotor but you need away to keep the 24 volts for the rotor excitation this occurs once the alternator starts running and the rotor gets its energy from the voltage regulator from bleeding back to the battery. so the bottom line is this whole thing is not as simple as it looks. it would be much simpler if the auto industry went from 12 volt systems to 24 volt system much like it did in the 50s when it went from 6 volt systems to 12 volt systems. the independent miki kanazawa wrote 20 kw is the same as 26.82 horsepower mathematical conversion. so giving yourself 25% for losses itd take roughly 33.5 hp to drive this type of load. the smallblock chevy in my 1975 g20 van makes 38.4 hp at 1000 rpm. stock except for carb intake cam and headers. lets pretend this is typical output for an engine that would be running a 20 kw generator. to keep the engine from stalling you would need to generate the torque necessary to run the generator as well as overcome frictional and other losses in the engine. in a typical smallblock chevy this is about 7 hp at 1000 rpm and about 21 hp at 2000 rpm. 20 kw should be comfortably generated with the engine idling at 2000 rpm. of course youd have to figure out how to connect generating hardware to the engine! i think a transmission with a pto shaft would be ideal and easily adapted. ie. most older manually shifted truck trans. .