What size power inverter?

R

Richard Grasa

New member
Since I'm starting to put together a new mobile rig, which will be an S10 pickup for now, I need to figure out what size power inverter to use. I only need to run my shop vac and my DA with it regularly. Maybe some other small stuff like a heat gun. I don't want to use a generator if I don't have to, at least not until I get a van or something where I can lock everything up more securely. In the past when I was mobile, I would just use the customer's power but would like to set my own power up this time around. If I need to, I could still do that but if I can be self sufficient I would rather do that.



What size would be good to run the vac and DA one at a time, and what would be a good size to run them at the same time?



I'm up to speed on doing the wiring, upgrading to a bigger alternator if needed, or maybe even add another battery if needed.
 
What are the power ratings of the equipment you want to use? Look at what they draw amperage-wise, then you can do the calculation for how many watts you'll need from an inverter.
 
C. Charles Hahn said:
What are the power ratings of the equipment you want to use? Look at what they draw amperage-wise, then you can do the calculation for how many watts you'll need from an inverter.
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Charlie, can you point me to where I can find how to do the calculation to figure out how many watts I need? I googled it but couldn't find anything.
 
I'd grab a Kill-O-Watt meter, its handy for other stuff as well, but it will tell you exactly how many watts your equipment is using as most of the time its a lot less than what the peak load on the label is. They run about $20.
 
Electrical Formula



E = Voltage I = Amps W = Watts PF = Power Factor e = Efficiency (75 – 80%) HP = Horsepower (torque output)



• Kilowatts = I x E) / 1000



• Horsepower = I x E x e / 746



• When Kilowatts is known = kW x 1000 / e



• Amps when HP is Known = HP x 746 / E x e



• Amps when W is known = W / V



Electrical Outlets



The output from electrical systems is measured by voltage; (Watts / Volts = Amps) which equal the amount of current drawn, wiring and supply cables are sized according to their rated current draw. A typical domestic breaker (single phase 110 volt) is rated at 15A (amps) and should only be loaded to a maximum of 80% (15A =12 amps, 20A = 15A) Add the amperage drawn by each consecutively connected unit to ensure you do not exceed the 80% maximum.

 
My Rigid 5hp vac draws 9.2 amps. I have a 2000 watt harbor frieght power inverter that runs it like a champ...
 
Garry Dean said:
My Rigid 5hp vac draws 9.2 amps. I have a 2000 watt harbor frieght power inverter that runs it like a champ...
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So you got that sorted out finally? I don't think I ever heard what the solutions after we talked about it before...
 
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