Question Portable Generators (?)

Hello Matt - I'm no expert but I'm looking to do something similar so I thought I would share what I've learned.

I too have a portable generator that we have been using to power our home during grid outages for the past 10 years. In my case it is wired with an inlet in my garage which is wired to an interlocked backfeed breaker in my main panel. I too want to retain the generator for use during extended outages that coincide with diminished solar production so I can use it to charge the battery back up.

What I found is that with small portable generators the best idea is to use a Chargeverter. I purchased one along with my batteries and other equipment. The Chargeverter converts the "dirty" power from the generator into pure DC power to charge the batteries directly, saving the inverter from having to deal with the generator connection. I hope this helps!

- Matt M.

For optimal performance, it is recommended that the generator has less than 12% Total Harmonic Distortion (THD), is rated at least 1.5 times the total output of all inverters and provides a 240V output.

You can try to use a smaller generator with low amperage, but it is not guaranteed for it to work as it should. 

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I have a portable generator (20 amp; split phase) that was being used to power our home during grid outages for the past 8 years. It connected through a Reliant 6 circuit transfer switch. Last month I put in a 6000xp with 8 panels; changed the transfer switch to a 12 circuit 30 amp transfer switch (Nature's Gen). The solar array dropped my electric bill to $35/month and it gives me the power to switch any of the 12 circuits back to grid if needed. Then I installed an outside 20A receptacle to the generator input on the 6000XP. It works perfectly when I tested it. The XP sent generator power to the house and it also charged the batteries (Ruixu 48v).

I use a small 2000W 120VAC portable generator for exactly the scenario you have in mind - I use it to charge the battery bank and nothing else. In my case it runs through a Chargeverter and is connected to the battery bus. I limit the charging current to match the generator's capability using the settings in the Chargeverter. If you are going to try to use the generator input of the inverter or Gridboss, then as EG4 stated above you need to worry about sizing the generator to handle the loads that might be pulled through the system. I didn't want to invest in a larger generator just to handle this backup charging scenario, so the Chargeverter was a better investment to let me keep using my existing generator for the rare times it might be needed.