Generator efficiency sweet spots

[Refinished]

I have a Samlex EVO that is designed for generator AC input to charge batteries. I also have a 3500 watt run of the mill gas generator and a 2200 watt inverter generator. One of the EVO features is to set a maximum current draw for AC inputs, including the generator input. If I needed to run one of these units to charge batteries, I am wondering what amp draw settings might make best use of my gas. I am guessing there is a sweet spot in the load placed on the generators that is most fuel efficient. I am also guessing that the sweet range might be different for conventional generators than it is for inverter generators. Anyone have any data on this?

 

[snoobler]

About 70% for a "regular" generator is a pretty reasonable efficiency target. Most publish a 50% load run time or fuel burn.

The inverter generators operating by varying their speed to optimize fuel burn for a given load, so they tend to be a bit more efficient, especially at lower power levels. They still struggle to be efficient at low power settings.

For the 3500W, shoot for a 2400-2500W load.

For the 2200W, 700-1400 is probably pretty good.

The other consideration is any charge limitations your batteries may have. FLA rarely like to be charged about 0.15C. AGM can often handle up to 0.20C and LFP can take 0.5C.

 

[RCinFLA]

Up to about 30% continous rated power there is higher % loss from mechanics. Flywheel air cooling push is significant and for 3600 rpm sync generator its the same whether no load or full load..

40% to 70% is good fuel efficiency. Should get 4.5 to 6 kWH per gallon of gas on that size generator. Above 80% alternator losses rise and its just hard on engine and alternator with greater temperature rise.

My Yamaha EF3000 inverter-gen gets 4.2 kWH/gal at 25% load and 6.5 kWH/gal at 85% load, non-ECO mode.

 

[Trukinbear]

Somewhere between 65-80% of rated power is usually the 'sweet spot' for best specific fuel consumption for most generators but it will take considerable tracking to find the exact spot. Usually, 70% is a good rule of thumb though I do run my 8HDKAK at 75% and my 3.2HDZAA at 90% but both are diesel.