Couple of questions about alternator.How to figure amperage from wattage.Is this corr

[spnkysprky 10+ year member]

Ok,I have a couple of questions.Ok,Im a High voltage Electrician and In my line of work one way to find amperage (when giving at least 2 factors of the equation)is dividing the Total wattage by the volts...So I assume its the same in DC voltage....Then given these factors in my vehicle.I have a total of 1500watts im using(maybe less,Im doing worst scenario).Dividing that with 14.4Volts gives me a total of 104.2AMPS.

Is this the correct way to figure the amperage?I was guessing I could use a 160amp alt???yes or no

If so.....then will my factory (Dodge truck)136amp alternator be enough (I have the basic truck with no extras)to Supply my needs So long as I upgrade the big 3(wire size,Deep cycle battery maybe caps)....are there other factors I should be aware of?

I was thinking not all electrical systems would be exactly 14.4 volts...closer to 13.8 or less so I was thinking to use 12.6 volts instead.My 1 amp is 63% efficient total 995watts RMS and I will add another at 500rms approximate same efficiency.

Im putting it here in this section for better response.

This is their Take...look at MDC

http://answers.yahoo.com/question/index;_ylt=AsINmeX5NFQ.wUhUVTUF2fzsy6IX;_ylv=3?qid=20080110211714AAdr8Cv

Click to read more...

 

[squeak9798 5,000+ posts]

I don't see any major misstatements made by MDC in that link. Like he said, you have to take the amplifier's efficiency into account....and his formulas are correct (basic ohms law).

Only thing I would add would be to suggest you first hook the equipment up with your current electrical system and see how it fairs. If you aren't getting any significant voltage drop then save your money and don't bother upgrading. How much current your system is actually going to use in practice is going to depend on how you use the equipment and how you setup the equipment.

The calculations will give you "maximum" current draw, not necessarily practical current draw. You will not inherently need to upgrade the electrical system......but you won't know until you get everything up & running. You may need to upgrade some parts or all of the electrical system, you may need to upgrade nothing due to your usage habits and settings.

If you do have significant voltage drop, come back and let us know specifics on the situation and we can guide you on what upgrades will be the most cost and performance effective.

 

[spnkysprky 10+ year member]

I don't see any major misstatements made by MDC in that link. Like he said, you have to take the amplifier's efficiency into account....and his formulas are correct (basic ohms law).
Only thing I would add would be to suggest you first hook the equipment up with your current electrical system and see how it fairs. If you aren't getting any significant voltage drop then save your money and don't bother upgrading. How much current your system is actually going to use in practice is going to depend on how you use the equipment and how you setup the equipment.

The calculations will give you "maximum" current draw, not necessarily practical current draw. You will not inherently need to upgrade the electrical system......but you won't know until you get everything up & running. You may need to upgrade some parts or all of the electrical system, you may need to upgrade nothing due to your usage habits and settings.

If you do have significant voltage drop, come back and let us know specifics on the situation and we can guide you on what upgrades will be the most cost and performance effective.

Thank you for your answer.Ill do just that.