View Full Version : Inverters, Generators & Shore Power How Does It All Work

01-27-2013, 11:18 PM

And please remember I do not own a coach yet but that's changing in the very near future.

I have been doing a lot of research on this forum over the past few weeks but the use of how generators, shoreline power, and inverters work is a bit confusing for someone still learning about such prestigious motor homes. Can anyone give some insight as to how Power Management systems work? How does the refrigerator get power when there is no shore power, or when driving down the interstate? In a 45' motor coach do you need to run the generator driving down the interstate to keep the Motorhome warm/cool or is it a matter of choice and if so I'd like to know what you mostly do. How much diesel would a generator normally use?

Thanks in advance for your posts, all of the information you provide is very educational and helpful.

01-27-2013, 11:46 PM
I'll take a stab at helping you.

Most systems (water pump, heat, refrigerator, radio, lights, etc.) on board can be operated without shore power or the generator, because they run on either 12 volts D.C. and/or L.P. Most MHs have a small inverter to convert the 12 volt D.C. to 110 volts A.C. to run the television. Your microwave oven, air conditioner, washer/dryer run on 110 volt A.C. and require more current than can be obtained from the small inverter previously mentioned.

Many MHs have a bank of batteries and a large inverter that is capable of powering about anything on board, except the air-conditioning. However the batteries will need to be maintained and charged. If you run the energy hogs via the inverter you will deplete your batteries more rapidly.

The generator is capable of running the entire coach and is operable even when you are driving. It is also handy to charge the batteries when shore power is not available.

Driving in hot summer weather sometimes requires more air-conditioning than what can be delivered by the chassis system. In this case, many of us do crank up the generator and run the big air-conditioners as we drive.

Generator fuel consumption is minimal. I think about one gallon per hour.


01-28-2013, 01:35 AM
I'm confused on when/where/how the different systems take over depending on what you are doing (driving, hooked up to shore power, or boondocking).

In many cases, it's almost all done automatically by an energy management system. This will almost certainly be true in the case of luxury motorhomes. But it will depend on the year of your coach.

When do we use the generator to charge the batteries?

The batteries (specifically the house batteries) will need recharging when they've discharged to around 50% of their capacity. There will likely be some indicator in the coach telling you what the state of charge is. This might be a simple "battery voltage" meter.

Do we have to run the generator when hooked up to shore power?

Not normally. But, if you happen to be hooked up to shore power that doesn't provide enough power to run everything you want to run, you may need to run the generator. However, most campgrounds don't allow you to run the generator.

When should I turn the inverter off?

Some folks turn their inverter off when they're boondocking, but not actually running anything off the inverter (e.g. when they go to bed and don't need TV or any other appliances on). This saves a little drain on the batteries because, even with no appliances on, the inverter itself draws some current from the batteries. However, I leave our inverter on all the time.
When you're plugged into shore power or the generator is running, the inverter is essentially bypassed automatically. In this case it doesn't matter if the inverter is turned on or off.

How far should batteries be discharged before running generator?

Typical deep cycle batteries used as house batteries on motorhomes should not be regularly discharged more than 50%. However, that doesn't mean that you can't recharge them sooner, e.g. when they're discharged only 25%.

How do I know when the house batteries are discharged to 50%?

It depends to some extent on the kind of battery. A fully charged flooded wet cell battery will read 13.6V or more when fully charged and still connected to the charger. Turn the battery charger off and that fully charged battery might read as low as 12.6V. When 50% discharged, the battery voltage will read approximately 11.8V with the charger turned off.

How long does it take to recharge batteries when using the generator?
It really depends on the make and model of inverter, whether it has a built-in battery charger, the quantity and size of your house batteries, and how far discharged they are. If boondocking or dry camping (no hookups), plan on running the generator several hours a day to recharge the house batteries.

01-28-2013, 02:56 AM
Thank you very much for all of the replies, This information was very helpful. again thanks for all the info.