Quick way to run 12-110 volt inverter in Scamp 13.

[John in Santa Cruz]

FWIW, my Escape had several spare fuse spaces, and I used like 4 of them to power a triple-marine style plate with a pair of 2A USB charging ports (fused at 10A), a cigar outlet (fused at 15A), and a dual powerpole, each powerpole fused at 30A. my portable 200W inverter has a powerpole on its 12V input (it originally had battery clips, I do have a pair of battery clips on a powerpole, so I can plug those into the inverter if needed).




(yes, they are upside down, I did that so the flaps would hang down instead of being in the way when open)

[Civilguy]

Inverter efficiency depends on inverter load.

https://www.e-education.psu.edu/eme812/node/738

Figure 11.8. Typical generic inverter efficiency curve. Below 10-15% of power output, efficiency is quite low. At high output power, the efficiency is steadily high with some small variations.

[John in Santa Cruz]

Originally Posted by Civilguy

Inverter efficiency depends on inverter load.

https://www.e-education.psu.edu/eme812/node/738

indeed,,, my portable inverter claims to be 300 watts, I'd never put over a 200 watt load on it, and prefer to keep it around 100 watts.

using a 1500 watt or whatever inverter (Escape installs these with a transfer switch as a factory option) to run low wattage stuff like laptop chargers is really inefficient.

[gordon2]

Originally Posted by John in Santa Cruz

FWIW, my Escape had several spare fuse spaces, and I used like 4 of them to power a triple-marine style plate with a pair of 2A USB charging ports (fused at 10A), a cigar outlet (fused at 15A), and a dual powerpole, each powerpole fused at 30A. ..]

A textbook example on how to do it right.

[zack sc]

Thanks John. That looks beautiful.

[zack sc]

Originally Posted by Civilguy

Inverter efficiency depends on inverter load.

https://www.e-education.psu.edu/eme812/node/738

Thanks Civil guy. It looks like I do have an efficiency problem. My 300 watt inverter is too big to be efficient for this low power application (4 watt). I wonder if a 65 watt Duracell inverter (DRIN5cla) would be significantly more efficient? (It is not pure sine wave though.) Does anyone know of a very very small 12v to 110v inverter they could suggest?

[Civilguy]

I believe that small motors such as your air filter is using have relatively high mass and are not particularly sensitive to overheating on square-wave power.

I suspect that pure sine wave inverters get over-marketed. They talk about protecting our "delicate electronics" when there is generally a power brick transformer between the inverter and the electronics.

Maybe others will chime in here.

[John in Santa Cruz]

Originally Posted by Civilguy

I believe that small motors such as I believe your air filter is using have relatively high mass and are not particularly sensitive to overheating on square-wave power.

I suspect that pure sine wave inverters get over-marketed. They talk about protecting our "delicate electronics" when there is generally a power brick transformer between the inverter and the electronics.

Maybe others will chime in here.

the switching power supplies in use for most all digital electronics are completely oblivious to square vs sine power input. switchers start off with a full wave bridge rectifier to turn the AC into DC, then they run a high frequency oscillator on that DC so they can use a small toroidal transformer to kick down the voltage and kick up the current.

where you want true sine is for analog stuff like old school audio gear.

[zack sc]

So maybe it would be worth it for me to just get the smallest wattage inverter I can find in order to hopefully have better efficiency and less power draw on my 12 volt battery?

[Civilguy]

Originally Posted by zack sc

So maybe it would be worth it for me to just get the smallest wattage inverter I can find in order to hopefully have better efficiency and less power draw on my 12 volt battery?

Looking at various curves online, it looks like it would generally be best to have an inverter operate somewhere around 20% to 80% or so of the rated power.

[zack sc]

20 to 80% would be nice, but the smallest inverter I have found is 65 watt. So a 4 watt air purifier is still below 10%. but maybe the current draw at 12 volts would be less (with the 65 watt inverter) than with a 300 Watt inverter?

[zack sc]

https://www.cdw.com/product/duracell...att/5632730#PO

This 65 watt inverter is one possibility, but really a 20 watt inverter would be better and might help me get down to a 0.5 amp draw at 12v so that running the air purifier continuously is a reasonable option. I am thinking the no-load current draw of the inverter is a key spec for this sort of thing. Does anyone know of any very small inverters?

[Civilguy]

Inefficiency is basically power which is used on the input side but isn't delivered on the output side. Power that is not delivered as work or output power is expelled, generally as heat.

So, the same percentage of an inverter with a lower power rating would be better from the standpoint of efficient operation. However, this presumes that the smaller inverter has a similar efficiency curve, which it may or it may not have. If it has half the rated power but double the inefficiency, you have gained nothing.

I'm not crystal clear on your circumstances or what device you are trying to power. It sounds like you are trying to clean up the air while maximizing your battery life.

We ran a box fan continuously for several days here with a MERV 13 filter on the suction side when the local AQI was very high, and it was definitely helpful. The filter was visibly quite dirty after running about 42 hours.

The same principal applies if you run a 12 VDC car fan and pass the air through a some sort of high-efficiency particle filter. You can use anything for the filter which is compatible with the fan. You could set up a small cardboard box with a fan pulling air from one side and a small HEPA filter from a vacuum cleaner on the other side of the box; any arrangement that allows the fan to draw air through the filter.

https://www.amazon.com/s?k=12+volt+c...f=nb_sb_noss_2

Our arrangement was to simply set a 20x20 furnace filter against the back of a box fan and secure it with a bit of blue tape.

By the way, ionization air purifiers are probably not helpful if they don't have a collector plate. Basically, if you aren't collecting the particles on a filter or a plate, the device is probably not helpful.

I've attached a picture of a 10" x 10" MERV 12 filter. Something like this could work well with a small 12 volt fan.

[zack sc]

those are good ideas. much appreciated!

I am thinking that the general nature of inverters is to have a no-load current that tends to be larger for higher wattage inverters. The magnitude of the no-load current is probably the key thing in the efficiency curve at low power.
So this discussion has really helped me see one can really benefit by using an inverter that is sized just right for an application (not over-sized). (Before this I may have just thought: bigger is better, more versatile.) I am guessing that the 65 watt inverter has a lower no-load dc current than the 350 watt, though I don't really know for sure. I looked for that spec, but couldn't find it for the 65 watt inverter. I think for the 350 watt Belkin the no-load current is about 400 mA, which means about 50% of the battery power I am using will go to heat. I think the no load current is the key thing here; we are far to the left on the efficiency curve and so the peak efficiencies and other nuances of that curve may not be relevant. I would love to find an inverter with a smaller (e.g., 200 mA) no-load current. Any suggestions are greatly appreciated!

[John in Santa Cruz]

even if your efficiency was 50%, at 4 watts load, thats only 4 watts wasted, which on a 12V input is only 1/3rd of an amp. 100 watts at 50% would be much worse, wasting about 8 amps at 12VDC.

[zack sc]

Originally Posted by John in Santa Cruz

even if your efficiency was 50%, at 4 watts load, thats only 4 watts wasted, which on a 12V input is only 1/3rd of an amp. 100 watts at 50% would be much worse, wasting about 8 amps at 12VDC.

True. Thanks John.
This whole discussion has helped me to think about and understand inverter efficiency in a new, hopefully better, way.

[zack sc]

I did some measurements today using an ammeter inserted (in series) into the input of my inverter via Anderson connectors. I was a little disappointed, though not shocked, to measure 1.0 amp current draw on the input(12v) side of my inverter with my air purifier actually using only 5.2 Watts. So that means that about 55% of the energy from my 12v battery is going to heat and just 45% to actually running the small air purifier.
Directly related to that: the Bestek 300 watt inverter has a no-load input current of 550 mA. So that was disappointing; I was hoping for a no-load current of around 200 to 400 mA.
It looks like the total current draw at low power is essentially the sum the the no-load current plus whatever the device is using. So I feel like that no-load current is a key spec and one that controls efficiency at low power.
I would love to find an inverter with a no-load current of like 200 mA or less. I have heard that such things used to exist.

[John in Santa Cruz]

this air purifier... does it just use a fan? or is there an ion generator or something too ?

[zack sc]

Originally Posted by John in Santa Cruz

this air purifier... does it just use a fan? or is there an ion generator or something too ?

I think just a fan.
https://smile.amazon.com/gp/product/...0?ie=UTF8&th=1

[zack sc]

is is a TaoTronics TT-AP001