question about inverters

[laser3kw]

if you were going to put an inverter on a dedicated circuit how would you size the inverter? Like you are going to use it on a lighting circuit that's 15 amp (120v) max. Would you size the inverter at 1800 watt or up-size the inverter to 2000 watt or 2500 watt? My thoughts center around is it better / more efficient for an inverter to run near capacity or half capacity? And of course the higher capacity the inverter, the it cost.

 

[Steve from Socal]

Inverters have a draw when idle, in many uses multiple inverters sized for the load are used instead of a single large inverter. Most inverters in that size range have a surge rating to deal with inrush current. That all suggest you optimize the inverter to the load. The efficiency of the better inverters are in the 90~95% range, the loss in conversion is minimal, some inverters are as low as the high 70's% so the actual value is a factor. The poor efficiency ones are generally cheap modified sine wave.

In my truck I have a 1200 and 300 pure sine wave to run a microwave/hot plate and the 300 for a fridge. I also have a 1500 modified that is there just incase. For lighting loads with LED I would look for native voltage.

Steve

 

[u2slow]

How much battery and alternator are you pairing with it? Reason is, something like a 1500W heat gun, blow dryer, etc will chew through a group 31 deep cycle battery in a few mins. Another concern is if you plan to run a motor - say a small 120V compressor - an inverter can't normally provide the inrush current to get it started. Pure sine wave is more important for motors.

Overall as cheap as inverters have become, I would go with something in the 1000-2000W range.

 

[laser3kw]

lights only - already LED. Light usage 4~5 hours, 3- 120v LED 40 watt equivalent. Run off battery - size and quantity to be determined. Battery(s) to be recharged by solar / AC (backup).

 

[Steve from Socal]

That is the entire load? Even with poor power conversion of the lights they may be 20 watts? That is 60~70 watts or just about 5 amps 12 VDC. The switching power supply in the bulbs may be short lived with a modified sine wave inverter but at that low a value finding a true sine wave inverter is going to be a hunt.

I get the idea you want to stay with these bulbs for a reason. That said, on a demand like that a few native 12 volt bulbs would cut out a couple of failure points.

Steve

 

[couch67]

+1 on sticking with 12 volts. Get yourself a few packs of these or similar, and do away with the inverter. The losses in the inverter will be more energy than what the bulbs are consuming.

 

[u2slow]

IMHO, a modern power brick that can handle 100-250v input won't suffer with a ****-sine-wave inverter dishing out a choppy 120v.

I agree though, native 5-12V DC power is smarter for powering LEDs.

 

[Steve from Socal]

IMHO, a modern power brick that can handle 100-250v input won't suffer with a ****-sine-wave inverter dishing out a choppy 120v.

I agree though, native 5-12V DC power is smarter for powering LEDs.

That may be true for devices that have batteries and only charge through the brick. As an example my truck fridge is inverter driven, using a modified wave inverter the input stage is getting dirty power. The fridge will run but the electronics get a real workout, AKA short life span. The other thing with cheap modified sine wave inverters are they have a low conversion factor or electric efficiency. A cheap 1500 watt inverter may be 70% efficient or use 2100+ watts of DC power to get that 1500 watts of AC.

For charging a phone/computer or other battery powered device the cheap inverters work, for any load that is power sensitive a modified wave inverter will cause stress at the least and not work or damage the appliance. Even your 120 VAC bulbs have a switching power supply that will get hotter/die sooner on a cheap inverter. Anything that is not a pure resistive load is going to see more stress/heat by nature of the wave form supplied.

 

[theoldwizard1]

lights only - already LED. Light usage 4~5 hours, 3- 120v LED 40 watt equivalent.

If that is all you plan on running, you could probably get by with a 500W continuous inverter. Buy one that is pure sine wave.

If all you plan on using it for, find 12VDC lights. Much more energy efficient.