Most likely a dumb question, but ? Could you set up a large battery bank and good inverter/charger and a small genset (honda 2k) and power an ac ?

I understand that running the ac draws less amps than when it actually starts and cycles, so if your battery bank/inverter can handle the starting/cycleing load couldnt the small genset keep the batteries charged enough for continous and/or extended service ?

Of course I dont know anything about this, but to me, it seems that if the generator can keep up with the running of the ac and the inverter/battery banks would handle the start draw/ cycle draw this would alieviate alot of extra wasted fuel powering a big genset.
 
Ok shoot some holes in my theory :)

Ken

what size, and how many A/C's do you have?

I have one 15K A/C and am carrying 2 honda 2K's with the parallel cable. I doubt an inverter would handle to startup current of the A/C compressor.

I got the two generators from Mayberry's +parallel cable for under 2 thousand bucks. They also included a quart of oil and 1 set of battery charging cable for free.

I have two ac's one 15k and a 13.5k , I understand that the ac draws 25amps at startup, not sure of what it takes to run it. One Honda 2k only puts out 20amps I believe, the parallel kicks it up to 30amps / 28amps continously enough to run one ac , which is fine.

But I believe you can get enough power out of a good battery bank and inverter to actually power an ac, but would one Honda 2k be enough to replenish most of the amp draw of the battery bank ? But again, I have no clue ?

We did decide after reading this forum for ,forever, most everyone would have forgone the $$ and weight /space requirements of installing a large genset . 

We also bought the two Honda 2k's and a parallel cable , since my 5'ver did not come "Gen Prepped", we figured that would be the best route, also I feel strongly about getting a nice inverter/battery setup like H&L have.

Suppose your AC only requires 12 amp hours to run. Then to use it for 8 hours it could draw as much as 120 amps with cycling and constant use for AC only. Thats a pretty strong draw for an battery bank.

Our motor home has 6 6 volts in a parallel, series setup adding up to 660 reserve hours. Does the battery bank last for 8 hours? Yes at a minimum draw. Does it recharge quickly? No.

The battery volts will drop rather quickly under load; from 12.6 (nominal full charge under load) to 11.5 (about 80%) in a few hours of use. Hooked up to 50 amps, it took more than 7 hours to restore the battery bank from 11.0 volts to full charge.

While charging the DC amps can read as high as 100 amps charging. At the FMCA rally running the genset 5-6 hours a day with AC running, did not bring the level back to full charge. I suspect the same conditions that make you want the AC also slow the charging/inverter system somewhat. Seems like the Interstate battery guy said something about 70 degrees as normal for amp hour readings. Heat and humidity is never a good situation.

We have a 7500 watt gen set (about .6 gallons diesel per hour), 2000 watt converter and 6 NEW house batteries.

As Robert Heinlein used to say TANSTAAFL. I suspect that includes inverters and generators also. Remember the math works under "ideal" circumstances. Practical circumstances will vary and usually downward.

That being said, we will go to Quartzite in January and boondock for at least a week or until the tanks fill.

Your mileage will vary,
Mike

Technically a large invertor combined with a genset can work to get past the start up.  However they must be linked to assure they are in phase and they must be compatible in waveform to be efficient.  I am assuming you are going to use the AC generated by the generator directly to the air conditioner.  Using the generator to charge the batteries and the invertor to power the air conditioner is a lose, lose, lose situation with an efficiency loss at the generator, and efficiency loss at the charger/converter, an efficiency loss due to heating the over used batteries, and finally an efficiency loss at the inverter.  I believe Yamaha and Onan both make a package that will allow you to overcome the start up current on air conditioners which is only a few seconds each time it cycles on.  Some use a synchronised pair of Honda 2000's when AC is needed.

Not so simple is it.  We just go to hook ups when it is too hot and stay in the mountains mostly in the summer.  Our Honda 1000 runs about an hour a month for ironing the quilting work.  Solar provides the rest of our needs.

I would recommend a large generator, an enhanced package, or a synchronized pair but I don't recommend the pain, weight, expensive, and inefficiency of the invertor route to get air conditioning.

Of course that is only my opinion.

Larry

As Larry said, use the genset for the air when you need it and the inverter when you don't need AC. No AC required? then use the genset to charge the batteries.

Watch the inverter charge rate the next time you recharge the batteries. Mine jumps to 100 amp draw when bulk charging and 30-50 at the next level. The draw is 10-20 for float charging.

Mike

k&c:
This is an idea near and dear to my heart as I prefer being an "unplugged" kind of guy. As you have read - technically very do-able, but practically not worth it to cobble the pieces together today. Yes, some high end class A MHs will invert the front AC unit while driving and power it with a 300+amp upgraded alternator. The issue with your lower amp genset idea (something I would love to be able to do in my rig) as has been said above is to synch everyting including the charger. It is just a matter of technology and an "integrated" solution is finally almost available - though currently on a slightly larger scale than you desire. The brand new not even really released Onan Hybrid Quiet Diesel system does just what you are suggesting (using an underpowered genset and an inverter to handle the peaks). I would bet that a smaller solution a. la. using a single 1,000 or 2,000 watt generator to power bigger loads solution might be coming out soon. I see a demand for such a solution as a dual 1k or 2k genset setup, though excellent, is a little overkill during the lower amp run times.


-- Edited by RVDude at 09:25, 2007-08-21

Now see thats what I am talking about ! I wonder if that controller could be modified or duplicated for my project ?  

Seems to me all it really does is delegate the correct location for the power needs and utilizes the transfer switch,inverter,batteries,and generator. Hope someone comes up with a "generic transfer switch / control head" for RV'ers soon. I also see the need for this type of setup. Lets call Xantrex ????

At least I know its not impossible !

Ken

K&C: That Victron setup is certainly on target - pricey as you said. However, given the price of a Xantrex or equiv. invert/charger this system is somewhat comparable and provides that extra oomph for high load starters like ACs and letting us use baby genets that are cheaper.
 
Leave it to our marine friends to really push the technology that needs to make its way into our land yachts!

Great find.