PSW Inverter - No Load Current

[otrfun]

Our in-bed camper will only hold two batteries. Wanting to power the microwave, TV, satellite and laptops. Thinking a 2000w PSW inverter would be the right size. Noticed most 2000w inverters have no load current approaching 2 amps. A bit high. Don't want to be constantly turning the inverter off and on during the day to conserve. The Xantrex Prowatt 2000 is the only "2000w" PSW inverter I've found so far with less than 1 amp of no load current. Of course, in reality it's only 1800w continuous with only 3000w surge (typically surge is double the continuous) which may explain the lower no-load. Does the Prowatt 2000 have a good track record powering microwaves? Other 2000w PSW inverters with =< 1a of no load current I may have missed? Thanks.

[3_tons]

Whats a bit curious to me is why the apparant apprehension against the idea of installing a remote off-on switch?... Seems like I may be missing something...

[MrWizard]

no..
they come with the needed batteries and inverter
and a large fridge will cycle less because it is more 'energy efficient'

[prairie_camper]

After reading some of the recent posts, my next thought was how do the new RV’s (most?) now coming with residential fridges handle it. I guess with a residential fridge RV’s it’s from full service to full service. Not exactly the way I want to travel or camp!

[MrWizard]

on any standby draw is pretty inconsequential compared to running the fridge
which probably has a 100w 10amp 12vdc inverter draw and a 50% run cycle with that small a fridge
a larger 8 cuft fridge will use less total power (lower compressor run time cycle) because of larger evap coils and more insulation

[BFL13]

prairie camper wrote:

BFL13 wrote:
The Sunforce PSW 1000w they sold a while ago had two receptacles , but they way it worked was each was rated for 500w so you could not get 1000w plugging in one thing. Many/most other inverters let you get the whole rated amount from one receptacle.

On our sunforce 1000 watt inverter I can pull at least 800 watts on the single receptacle. Plugged in a coffee percolated to a kill a watt and brewed a pot of coffee.

But I want to do more boondock camping this summer, and we have a small 3.5 cu. ft.? Residential Freezer we take with us, hence the question of standby inverter draw.

Multiple inverters is not in my design!

Had a 120v fridge that size for a while to replace the broken original fridge in a TC we had. Total nightmare off grid, unless there was lots of solar. No gen, so no easy way to recharge the batts with a charger) Lost battery AH every day so it was a nail-biter whether we ran out of AH before going home.

It drew about 4 amps when on. Cycled on maybe 2/3 the time ISTR. I posted something about it back then, I try to find that.

Swore never again to have a 120v only fridge for off-grid. Eventually found a used smaller 3-way fridge that fit in the TC. What a blessing!

[2oldman]

prairie camper wrote:
I would like to know if the standby current (no load) is additive to the consumed current of a running appliance, I.e. a microwave?.

No, but the operational draw of the inverter itself will be.

I think it's prudent, and definitely makes for a more pleasurable camping experience to have enough battery and perhaps a bit of solar so you don't have to worry about tiny draws. That makes them trivial.

Then again, some folks would rather scrimp on water and propane. I prefer to get more.

[prairie_camper]

BFL13 wrote:
The Sunforce PSW 1000w they sold a while ago had two receptacles , but they way it worked was each was rated for 500w so you could not get 1000w plugging in one thing. Many/most other inverters let you get the whole rated amount from one receptacle.

On our sunforce 1000 watt inverter I can pull at least 800 watts on the single receptacle. Plugged in a coffee percolated to a kill a watt and brewed a pot of coffee.

But I want to do more boondock camping this summer, and we have a small 3.5 cu. ft.? Residential Freezer we take with us, hence the question of standby inverter draw.

Multiple inverters is not in my design!

[BFL13]

The Sunforce PSW 1000w they sold a while ago had two receptacles , but they way it worked was each was rated for 500w so you could not get 1000w plugging in one thing. Many/most other inverters let you get the whole rated amount from one receptacle.

I think this whole standby draw thing is bogus in most scenarios, since you can just turn the inverter off when not in use. If the standby draw is included in the draw when loaded, it can be trivial in comparison with the load itself's draw.

If a microwave draws 120 amps, what is another 1 or 2 amps? OTOH if your res fridge draws 4 amps, then another 1 or 2 amps could mean something. Scenario is everything.

Using a smaller wattage inverter for smaller loads won't help much, as it appears they have as much standby draw as a bigger inverter. The real culprits are inverter/chargers, which have way big standby draws, since they need 12v to operate all their fancy features.

Then there is the question of where on the efficiency curve your load is wrt the wattage range of that size inverter. If not near peak efficiency watts, you will "lose" perhaps as much as from any standby draw included. But info on their curves is not included.

[prairie_camper]

This post came at a very opportune time for me, I had the exact same question as the OP. Now I would like to know if the standby current (no load) is additive to the consumed current of a running appliance, I.e. a microwave?
Also that standby current could be prohibitive if the inverter is left on 24/7 for a camping weekend to power a small residential freezer or fridge!
I presently have a sunforce 1000 watt psw that has a no load draw of just slightly more than 2 amps measured with a trimetric. 2 - 6 volt Costco GC batteries. 300 watts roof mount solar plus 100 watts portable. Victron mppt 100/30 controller.
Now shopping for that next inverter.

[BFL13]

Ran a better organized efficiency test with the PMX-2000 using Kill-A-Watt for output watts and DC voltage at the inverter with DC amps from Trimetric. Load was the smaller microwave that is in the C, not the bigger one used in other test.

Output- 1195w
Input- 117 amps x 11.13 volts =1302w
Efficiency - 1195/1302 = 91.78%

On rated vs measured inverter efficiencies, AFAIK, inverters have an efficiency curve with peak efficiency less than at full load. So it depends where your load is on the curve what you will get when measuring.

[BFL13]

I meant the OP does not need such fat wire for his intended use. You can wire for the surge rating of the inverter (twice the watts) or for its rating or for the most you will ever use it for (what I do). Whatever you choose for wire gauge, you fuse for that wire's ampacity.
If somebody else ever tried to use the inverter for more than I ever do, it would blow that fuse.

[2manytoyz]

I use solar power in my home, so idle current is a factor. I've tested a number of my inverters, all the information has been posted on my webpage: http://2manytoyz.com/noload.html

The parasitic load measured only 0.32A



The waveform is cleaner than the grid power coming into my house.



Please note that any high current inverter load will require very fat 12VDC power cables between the inverter, and the battery bank.



Read the note below the chart:



This is a fantastic inverter! Mine has run 24/7/365 for almost 5 years, powering a portion of my home. I presently feed it with a 1000AH battery bank, with the fat cables shown. It runs everything I've tried, with only a couple of exceptions, a large air compressor, and a 1965 era radial arm saw. The startup current spike is too high. But appliances like a shop vac, microwave, window A/C unit, 1500W heat gun, etc., no problems at all.

And we recently purchased a motorhome that has the same model installed in a storage bay. It's the backup power for the residential fridge onboard for when the generator is off, and we are rolling.

[BFL13]

otrfun wrote:
BFL13, thanks for all the test data. Pretty impressive performance for a $214 inverter. Found a guy online who checked the no-load current on a Prowatt 2000 back in 2012. He read .32a. He mentioned the factory rating was <.80a, which is what it still is. Interesting how both your Powermax no-load reading and this guy's Prowatt no-load reading were both 40% of the factory no-load ratings: 1.5a/.6a (40%) and .80a/.32a (also 40%).

Took a closer look at some pics of the DC terminals on the PowerMax. Agree, the terminal bolts/nuts are located pretty close to the chassis. Not much room for larger terminal lugs.

You can make adapters. Short lengths of copper water pipe banged flat with hole in one end close to the end so it goes on the inverter and second hole at the other end to bolt your giant ring lugs needed on the very fat wire is one way.

You don't need such fat wire, but if that is what you have, it can be made to work.

Yes, it is a serious sort of inverter and is not a flimsy toy. There are other brands out there with various features of course.

[otrfun]

BFL13, thanks for all the test data. Pretty impressive performance for a $214 inverter. Found a guy online who checked the no-load current on a Prowatt 2000 back in 2012. He read .32a. He mentioned the factory rating was <.80a, which is what it still is. Interesting how both your Powermax no-load reading and this guy's Prowatt no-load reading were both 40% of the factory no-load ratings: 1.5a/.6a (40%) and .80a/.32a (also 40%).

Took a closer look at some pics of the DC terminals on the PowerMax. Agree, the terminal bolts/nuts are located pretty close to the chassis. Not much room for larger terminal lugs.