Inverter question

[4Roamer]

I know different products have different efficiencies but let's pretend they are made by the same company and with the same parts. Do inverters scale the power they consume based on what output is needed or is it just lost as excess heat? Example: if I am using something that consumes 50 wats, will the draw on the battery be the same if I am using a 100w inverter as it would be on a 300w inverter?

I have both inverters now and on my last trip, I used the 300w for something that I used to use the 100w for. It seemed like the battery use was significantly higher with the 300w.

 

[luthj]

All inverters are voltage supply devices. With no load, they consume little power (typically less than 40W, up to 60W for larger units). When a load is applied the output power is the same as the input power times the efficiency rating. So with a 1000W load, the input power will be about 1,200W for a 80% efficiency unit. Obviously this varies some, and inverts tend to be more efficient above 50% of their rated continuous load.

More advanced inverters have a search mode. In this mode they pulse 120V to the output every second or so. If there is no load detected, they go to sleep for a second, then pulse again. This takes the stand-by power down quite a bit.

 

[dwh]

I know different products have different efficiencies but let's pretend they are made by the same company and with the same parts. Do inverters scale the power they consume based on what output is needed

Yes.

or is it just lost as excess heat?

No.

Example: if I am using something that consumes 50 wats, will the draw on the battery be the same if I am using a 100w inverter as it would be on a 300w inverter?

The same...plus a few extra watts for the bigger circuitry in the bigger unit.

I have both inverters now and on my last trip, I used the 300w for something that I used to use the 100w for. It seemed like the battery use was significantly higher with the 300w.

Seemed like? That's a poor substitute for measurements. Maybe it seemed that way because you were sort of expecting it would be that way...or maybe a big diff in the efficiency of the two units.

Only one way to be sure.

 

[john61ct]

If energy efficiency is a high priority

e.g. living off-grid and trying to get by mostly on solar

Running a 200W AC load off a 2000W inverter is wasteful. As is leaving an inverter running with no load.

Small inverters can be found sized just right for a given appliance, very cheaply, and rig them to turn on and off with the load device, rather than ever leaving an inverter just sitting there on standby all the time.

The **best** place to start is by selecting your load devices with energy efficiency in mind in the first place.

Avoid generating heat using electricity.

Sacrifice some of the modern conveniences many upper-income USians take for granted.

And **do without** inverters as much as possible, look to get the job done with propane or native DC power as much as possible.

 

[4Roamer]

Seemed like? That's a poor substitute for measurements. Maybe it seemed that way because you were sort of expecting it would be that way...or maybe a big diff in the efficiency of the two units.

Only one way to be sure.

I didn't have any testing gear with me and I don't have much at home either but, I'll run it again under more controlled conditions. I'll get a meter and see what it says.

I appreciate the fast feedback and it falls in line with what I thought about it, however, my pool of knowledge on the subject sure isn't very deep.

4

 

[workerdrone]

I'm with @Verkstad, easy enough to carry a couplethree inverters depending on power needs.

When battery bank was full and the solar was pumping away, I'd turn on the big one, hook up a power strip, and charge laptops, phones, cameras, etc

When I only needed a bit of 120, just turn on a 100w inverter instead of a 2000.

 

[john61ct]

Charging / powering laptops & other gadgets with batteries is most efficient staying with DC directly.

If only using "free surplus" solar may not matter much, but those burning midnight oil, just work out DC-DC conversion - not difficult, just volts amps polarity and pin size.

 

[4Roamer]

Thanks to everyone for the help. Used a Doc Wattson meter and did some testing. The draw was the same from both inverters. I ran (played with) several tests to obtain measurements. My conclusion was that the battery was not fully charged when I started using the 300w inverter. This was due to the SAE solar connectors and the cables I was using. The Overland Solar panels have an Anderson plug and I had an Anderson to SAE adapter. I did not notice this had the polarity reversed at the battery. To resolve this moving forward, I switched all the SAE connectors to Anderson plugs. Poof, no more polarity problems and the battery charges fine.

4

 

[dwh]

Cheers.

 

[Bear in NM]

4,

Glad that worked out. Anderson junky here, and I would add that you should probably never trust those little plus and minus symbols, nor the color of wire when hooking things. I volt meter everything. I have MC4's on top of my van, and when adding in parallel pigtails it also can get confusing.

The first glass panel I purchased prewired from "THE" local solar shop had the plugs and wiring reversed. Being new to big panels, it took a bit of researching to make the determination. I just thought a residential panel was somehow wired differently to accommodate massive parallel and series adaptors. I added a second panel to my system, and brought in the first panel so they could set me up for parallel pigtailing. I told them to be sure and check all polarity. They did, said "oops" and fixed things. I now have an MC4 crimper and do the work myself. That mc4 to Anderson reverse polarity "special" adapter I had made......cut the ends off and filed the experience into my volt meter always folder.

Craig