Using inverter and generator together?

[awiegel]

The A/C unit requires something like 3.5 kW to run right, but does not actually draw that much all the time. The little Honda 2000 generator can not start it, but could almost keep up once it is running

An inverter can be used which will run the A/C, but the draw will empty the batteries quickly. I want to use the batteries and inverter to run the A/C and at the same time use the generator to charge the batteries to the best of its ability.

The question is what kind of inverter and charger to use? It appears to me that the combo units can only invert or charge, but not both at the same time, right?

Anybody done this before?

Thanks, Andrew

[dkottum]

I would think the inverter and generator outputs would not be in phase with each other so it could not work.

Also trying to run the generator to charge the batteries to power the inverter at the same time as running the generator to power the air conditioner, could only be worse than running the generator to power the air conditioner by itself, because of power losses at the inverter and the associated wiring.

There is nothing to gain. You need a larger generator.

[J. Morgan]

I am working on something like you are proposing... But not exactly...

I should have an answer as to if this will work sometime next week.... and a longer term test over the summer...

[dkottum]

But most buy a second "Companion" Honda 2000 to help the other one.

[J. Morgan]

To answer your question more directly, I think you could use a large battery charger run by the generator to charge your batteries while the batteries run the air conditioner, but battery chargers can be hard on a battery if left.on high charge for extended periods of time without a balanced load. (like if the a/c didn't come on for a long time).

Even charging at 50 amps will only deliver 600 watts of run at a given time, and even if the a/c were to only 1/2 time, effectively you only have 1,200 watts to consume before you lose ground on your battery charge, not counting the efficiency losses of the inverter and the efficiency losses of charging a battery.

It might be a little risky. I wouldn't sleep well with this setup, nor would I leave it unattended, overcharged batteries can on occasion catch fire.

[Ag&Au]

This reminds me of a perpetual motion machine I once saw at a carnival when I was I kid. It looked great until you got out a pencil and paper and did the math. (we didn't have calculators then).


As far as I know, the only reasonable solution for running the A/C in a modern Airstream for any length of time without shore power, is two Honda 2000W generators with their cabling kit, or any single generator of sufficient wattage rating.


Welcome to Airforums,


Ken

[Bill M.]

I think the concept is to have the batteries make up the additional power need to start the AC and to have the generator recharge the batteries when the AC is not drawing the full load from the generator? So it is not perpetual motion, but instead power management and storage. Sorta like a hybrid car.
There are generators that have built in capacitors that supply some starting power. I suspect it is not as easy as just hooking up a big inverter to the AC and running a charger with the generator. I do not think I have seen an inverter that will start a AC. Both the cost and power losses would seem prohibitive that way. Phasing would seem to be a big problem if the inverter and AC were rigged in parallel. But they do get the 2 genies phased somehow so maybe it is possible.
If I want to run my AC boondocking I will just add the second Honda. $1000, works fine, no problems, plus additional power while the AC is running. I can see the desire to only carry one generator with a short trailer and possibly small TV. Or sell the Honda and buy a bigger generator. Maybe mount it on the trailer tongue. Of course the cheapest solution is to use campsites with power during hot weather. We are finding more forest service sites with electric than ever. So I have not added the additional generator for the AC.
You might spend some time looking at the generator and inverter sales sites to see if there is anything out there addressing this issue.

[overlander63]

By the time you accumulate enough peripheral "stuff" to make this work, you will either have enough 120 volt items to charge the batteries to run the inverter to operate the air conditioner you will need a 50 amp circuit, or you will have enough cash invested you might as well just go buy a second generator. So, to make it work, you would need enough electrically operating items that you would need a bigger generator to do it, in which case you could simply get the generator and forget the complex, Rube Goldberg solution.

[Shaggy1970]

Honda and Yamaha both have nice generators, from my research you need either 2x2000watt gens tied together or upgrade to a single 3000 watt model, both options set you back around 2200.00. I have been looking for a long time and decided to buy the champion 3100 watt inverter/generator. It's specs are identical to the honda 3000 handi, had it delivered on Tuesday and only cost me 659.00 from overstock. I love it, it's quite, has 1 30 amp plug 2x15 amp and a dc battery plug. It's the best option for the money and you could charge your batteries directly while running them at the same time but your drawing too much and not restoring enough so over time you batteries will be dead.

[jkcru]

I saw an inverter charger that could assist the generator at either Anchor Marine or West marine, not inexpensive, in excess of $1K

[Silver Hawk]

Keep in mind that inverters are at best only 90% efficient. The cheep ones are way less I'm told.

[Shaggy1970]

The efficiency rating are posted and the Champion is right inline with Honda 3000 Handi at 95%. I wish I could post link of videos but the forum does not allow me yet since I am a newbie and not a trusted member. There is a youtube video of a review that is 12 minutes long and shows the champion and made me make up my mind, also at supergen website there is a sound proof tent that you can buy for it that will drop the DB by 8 so making it the quietest generator out there. I am going to build my own sound proof box for those days I have a person camped right next to me.

[awiegel]

Wow.
Thank you to everyone who responded so quickly and with so much thoughtful information.

You are right that my considerations are driven primarily by weight and the expectation that the A/C will in fact be seldom used. I already have the Honda 2000 and 220 Ah of AGM batteries. I will want a good inverter anyway for silent running below 1 kW consumption in the evening or morning when generator noise would be inconsiderate to others. So the real cost appears to be the dedicated charger to run off the generator. A good quality charger will mind its manners and not fry the batteries, but I am concerned about the inherent inneficiency of the system.

Andrew

[idroba]

Sync of generators is an interesting topic. Conventional small generators (not the inverter type) are virtually impossible to sync but the inverter ones sync readily and automatically. When you look inside a Honda inverter generator you will see that the parallel connection wires are simply two wires directly connected to the 120 volt outlet. They do not go into the inverter someplace special, they just go to the outlet. So, when two Honda's are connected together, with the parallel connection, all the synchronization is done by the inverters talking to each other through the power output.

Others have noted this automatic sync function of the inverters and there is one You Tube Video where a guy hooked up his sine wave inverter to a battery, and then to his Honda, and the inverter in the Honda adjusted itself to follow the battery inverter. So, he was able to get more power from the two together and then start an AC unit.

It all seems impossible, but the inverters in the generators apparently can be completely happy with any other sine wave power system, running in parallel. I would love to try it with my Honda inverter generator, but don't have the guts to do it. But again it has been done by others. I had a link to the You Tube video but have lost it, but I am sure that those of you who are good at You Tube searching can locate the video I saw.

I believe, but do not know for sure, that you can even sync (parallel) different brands of generators which have parallel ports, such as Honda's and Yamaha's. It seems to be a well kept secret, but if it doesn't work the smoke may be pretty expensive. I wish I had some old beater inverter generators to try it out.

No guts, no glory, right?

[Shaggy1970]

The Moderators have been gracious enough to life my restriction on posting link to videos and such. You guys looking at external power should check out this video. I don't work for Champion or anything but I went back and forth for a long time with regards which one to buy and decided on this one! I love it and if your in the market watch this video.

https://www.youtube.com/watch?v=t0OD1d65EGE

[awiegel]

Originally Posted by idroba

"Others have noted this automatic sync function of the inverters and there is one You Tube Video where a guy hooked up his sine wave inverter to a battery, and then to his Honda, and the inverter in the Honda adjusted itself to follow the battery inverter. So, he was able to get more power from the two together and then start an AC unit."

Thank you idroba. I have a friend who is a Silicon Valley power supply specialist. He may know some more about this. If true, it is exactly the answer I am looking for. I think I will search a bit on You Tube as well,

Andrew

[perryg114]

I would think the best solution would be to have an inverter type generator combined with a big internal battery. The problem with this is that it would be as heavy as 2 generators or one big one. There is no free lunch.

Perry

[awiegel]

Found the you tube video:

https://www.youtube.com/watch?v=t0Q0TSwKBNI

Andrew

[awiegel]

You can find the You Tube Video by putting this isn the search bar:

"Paralell Honda generators with any inverter pure sine wave testing"


Andrew

[awiegel]

Although the You Tube video shows TimCat100 manages to get his Honda EU2000 to synchronize and supply power in parallel with his Xantrax inverter, other forums are casting a lot of doubt on the stability of this setup. It seems you can easily sychronize two or even three Hondas, but trying to sync them to inverters may not work reliably.

I am back to looking for a good stand alone charger to run off the Honda.

Andrew