Inverter losses and keeping it real

I know this is a subject that is full of ideas and some rather “warm discussions”  So, I’m going to say right up front I am not an expert, in fact far from it.  I question everything and then have to try it for myself before I’m made a believer.  Therefore, as I am building the electrical system in the vome it’s time to play.  There are pictures and measurements, thoughts and discoveries, but no math.  I’ve lived many years using only a minimal amount of algebra so I’m not going to impress anybody now.

Amid the installation clutter is a 2000watt low cost inverter from Harbor Freight and a smaller "plug-in" 150watt inverter.
Amid the installation clutter is a 2000 watt low cost inverter from Harbor Freight and a smaller “plug-in” 150 watt inverter.  The fan is my “load”

So here’s the setup I have this 2000 watt inverter that I used for a couple of power tools and I wondered just how efficient is it?   Here’s a closeup of the meter with the inverter simply hooked up and not even on.

The larger inverter is consuming 7 milliamps just being hooked up. Not even on.
The larger inverter is consuming 7 milliamps just being hooked up. Not even on.
Running the little fan at high speed took 6 amps
Running the little fan at high speed took 6 1/2 amps
The small plugin used 2 milliamps when turned on and none when turned off.
The small plugin used 2 milliamps when turned on and none when turned off.
The plugin running the same fan using half as much power.
The plugin running the same fan using half as much power.

So what did I learn today???

I’ll be putting the big inverter for tools on a “master cutoff switch” to disconnect it from the batteries when not needed.  AND the little plug strip will be used for small loads like laptop chargers, fans and perhaps my CPAP machine.

Now please before the critics, experts and naysayers jump me I will state that a higher quality (cost) inverter is probably more efficient.  But, part of my ramblings here is to play with the things that many of us already have and come up with the best use of what we got.

NOW FOR THE REAL SURPRISE ! ! !

If you will remember I flipped a small refrigerator on it’s back to make it a chest type unit.  (Flip the `fridge).

I have ran it today for 4 hours, achieved temperatures of 30 degs, on a 1000 watt ($69) inverter while charging the batteries with a folding 13 watt solar panel.

30 degrees with the thermostat set at mid scale.
30 degrees with the thermostat set at mid scale.
Folding panel from Harbour Freight
Folding panel from Harbour Freight
The buss voltage dropped to 12.2 when the compressor was running but returned to 12.5 when it stopped.
The buss voltage dropped to 12.28 when the compressor was running but returned to 12.5 when it stopped.

I know this is marginal operation. The point here is that a 100 watt panel could have kept this up with no strain.  The lowest the buss voltage dropped to was 12.28 and the highest it returned to was 12.7 volts.  Meaning my batteries went from nearly dead back up to about half charged.  Not to shabby when you consider the batteries were only about half charged when I started all this.

Again the lessons taken from this…

  1. You sacrifice power and therefore capacity or running time for your batteries when you jump from 12 volts in the battery to 120 volts from ANY inverter.  SO, try and use DC powered devices as much as possible.  Cigarette socket chargers for your cell phones, flashlights and even laptops.
  2. Larger inverters require more power just to operate.  Calculate your needs and buy an inverter to cover them, but don’t go overboard.  Remember, my refrigerator experiment ran on a 1000 watt inverter.
  3. We can get by on less if we take the time to think about our usage and plan accordingly.

With all this power at your fingertips…

“Get out, Be safe, and Go adventure”

2 thoughts on “Inverter losses and keeping it real”

    1. Glad it helped Ed. The experimenting helped me plan my layout a little better. Both of the inverters will be connected through solenoids with remote switches so I can disconnect then when not needed.

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