I have purchased second hand Outback FX2024 inverter (24VDC in, 120VAC 2000W out). The unit was built in 2003.

It seem it is working normally, output voltage is 120VAC and provides power easily to run two small Window AC units. Even startup currents are not an issue, unlike my earlier 1500W Nova Electric inverter that sometimes did turn off due to overload at compressor startup. The only issue I have discovered with this Outback unit is the disappointing efficiency: around 87% with ~1100W load. The datasheet claim around 92% at ~1500W load. My unit is a far cry from this... My old (cheap, but true sine wave inverter) Nova Electric inverter was pretty much the same if not better than this "high quality" Outback inverter...

I looked Outback forums but didn't find any posts that anyone had discovered the same, or if someone did measure the efficiency of this inverter. I do not have an account with Outback, so I try here first...

So... Anyone has any expecience with this Outback model? Is this normal or is my inverter somehow broken? It get fairly warm after few hours of usage, so that I can barely hold my finger on the unit without getting burned. (So it is around 50C... my room ambient is a bit warm around 84F.) I can only imagine how hot it would be if I had the full 2000W load on it...

Here is the 3000 watt / 48V unit

http://www.gosolarcalifornia.org/equipm ... 203648.pdf

The 24 volt unit will be lower efficiency's as the currents and step up voltage required are higher. You would have to have some pretty accurate measuring equipment to measure efficiency correctly, not only for the currents by have to deal with power factor correction on both the AC and DC sides. I'd guess 90% would be what I would expect based on the above link for a 24V unit and yes, the FX, no-vented units run very hot, the listed power can almost never be maintained for extended periods of operation

Thanks for the link to the 48V version test results. I find it surprising that the efficiency is best at lowest input voltage... I would have thought opposite assuming there is a boost stage in the input to pump up the voltage to the DC/AC inverter stage. (The higher losses at higher input voltage suggest that the switchng losses and/or AC losses in magnetic components dominate?)

I have used Kill-A-Watt as my output power analyser that does report true power. For input power I just used the MX-60 charge controller displayed power and checked that the current going into or out of the battery is about zero. I used the same methology when testing the Nova inverter... Certainly this is not 100% accurate but at least I can compare the Outback and Nova to each others fairly well.

So I guess it really is that the Outback inverter is not really that good as the spec sheet made me believe. If nothing else I did gain more peak power that is needed for starting motor loads...

The OB is a good inverter, but I personally feel the specs are optimistic ... The losses are expected for its class of design IE, high battery voltage = higher parasitic losses. I have a GTFX3048, got it in 2004, been thru two sets of boards for it, but its still running and is the backup for the home office, the XW-6048, handles all other house loads as need be.

It is now quite a dated design, from what I know, it was designed in the 2001 time-frame and there are now more choices for true sine-wave in this power class such as the magnum inverters that offer split phase and better performance.

If one wants more that 3kw, nothing can touch the Xantrex XW line, simply the best in class in performance ( 95% peak efficiency ) and features ( split-phase , grid-tie support and generator support to name a few ) all built in.

OK... Finally I got to test this with a little bit more accurate method, since I got my clamp on current meter back.

Using a Kill-A-Watt as my output power analyser and DVM for input voltage measurement and clamp on current meter for DC current measurement I got now around 91...91.5% between 1000-1500W output power when Outback had been running a while and was pretty warm. This sounds about right, and I think the claimed 92% can be reached if the Outback was cooler.

I feel better now... at least I know there is nothing wrong with my unit.