Smallest generator?

[Chance]

With small APU/generator, power for house inverter is supplied by APU, not batteries.

Batteries are essentially wired in parallel. It's no different than a car's starting battery where the vehicle's alternator supplies power for lights, heater blower, computer, etc... while vehicle is driving down the road. Assuming battery is already charged, the current the alternator keeps making goes directly to end users and not in-and-out of battery.

So wouldn't juice from APU/generator flow directly to house inverter? If there is excess, it can charge battery. If there isn't enough, then deficit would temporarily have to come from batteries. I don't see it that different than vehicle's starting battery. But I could be missing something.

[boywonder]

Originally Posted by Chance

With small APU/generator, power for house inverter is supplied by APU, not batteries.

Chance: What you've stated above is true.....as long as the APU power output equals or exceeds the wattage off the inverter & load.

In your earlier post, you mentioned:

Originally Posted by Chance

As reference, I'm personally thinking in terms of approximately 60 Amps at 12 Volts minimum (roughly 720 watts) in combination with 2000 watt inverter. For me that small a generator/APU could run typical loads and recharge batteries, and could even run my small air conditioner or 500 to 750 watt heater overnight on occasions.

This is the case where you would be cycling your house batteries a bit more if you have a 2000W inverter running a heavy load like an AC unit and your generator is outputting say 750W......you'll be pulling juice out of the batteries......potentially as much as 1250W in this case.

[Chance]

Originally Posted by boywonder

.....cut.......

This is the case where you would be cycling your house batteries a bit more if you have a 2000W inverter running a heavy load like an AC unit and your generator is outputting say 750W......you'll be pulling juice out of the batteries......potentially as much as 1250W in this case.

As far as I can tell, in the newer integrated systems like the ones Cummins/Onan is marketing for RVs and semi trucks, the idea is indeed to oversize the inverter so it can handle high surge loads, and/or intermittent loads that are higher than a typical generator can handle. But only for short periods while supplemented by the batteries.

The data I used as example above is based on my air conditioner being only 5000 BTU/hr. It normally only draws about 600 watts when cooling, and at night that's much less than 100% of time. Hence a generator with 800 watt output like the little Generac or 900 watt Honda can supply enough power on average, but can't supply the 23 Amps to start the compressor.

So my perspective is that the inverter should be oversized so it can handle AC inrush current and also occasional multiple loads that would be beyond the capacity of a typical generator. It's just about running the numbers to reflect intended use.

What I want to avoid is a large generator for many reasons. Weight, size, noise, fuel consumption, etc.... A large inverter with small APU and a couple of batteries "should" work better for me. But it may not for others depending on their needs.

[Chance]

For what it's worth, I know a smaller generator matched better to load is not always better. Example based on specs:

The 800 watt Generac at 50% (400 watts) runs 3.5 hours on 0.5 gallons, or 7 hours per gallon.

The 2000/1600 watt Honda at 25% (400 watts) runs 9.6 hours on 0.95 gallons, or 10 hours per gallon.