We have a fifth wheel that has two 12v batteries and an Onan 5500 propane generator. We haven't tried boondocking yet so I'm trying to anticipate how it'll go.

Does anyone have any idea on how long fully charged batteries will last in between re-charges when running an average amount of lighting & pumps?

Any idea how long will I need to run the generator to re-charge two fully depleted batteries?

I know they're very general questions - I'm just trying to get a rough idea on generator usage.

Thanks.

DreamerBob, You have the same energy setup we had when we first began using our 5th wheel. You can expect the batteries to last all day with conservation. Such as only one or two lights on at night, very short showers, light toilet use, very little water use to wash dishes (use paper plates), some TV/Satellite and laptop use. We would usually get about 4 hours (32 inch older tv) of TV off the two batteries. We could go two to three days without running the generator to charge the batteries. But had to conserve and use a 12v TV and VCR. The next day you will need to run the generator for at least four hours, that's why a lot of RV'ers carry the little 1000 watt portable generators to use throughout the day and into the night to provide power and charge batteries. These folks will only use the Onan to power A/C, microwave or other large power draining appliance (blow dryer). So a typical boondocking day would go something like this: 1. Start the generator in the morning to take showers, make coffee/breakfast, use microwave, vacuum and watch the news on tv. 2. Turn off all appliances and lights and leave the generator running to charge batteries while you enjoy the rest of the morning. 3. At lunchtime with the generator still running, fix lunch. 4. Cleanup after lunch and then trun off the generator. Go have fun. 5. In the evening, turn on the generator and fix dinner. 6. Watch TV for a few hours before campground quiet time (10PM), let the generator run. 7. At 10PM, shut down the generator, continue to watch TV, conserve batteries by turning of unneeded lights. It all begins again the next day. Hopefully you'll have enough propane to power the generator this way for several days. It's doable..... The 1000 watt generators are quiet and supply enough power for lights, tv, computer and other small appliances. It's easy to carry an extra 5 or 10 gallons of gas to refuel them for long stays. They charge the batteries. When it comes time to use the microwave or blow dryer you kick on the Onan for a short time. Other alternative is to add some solar panels to charge the batteries without running the big generator. The key is conservation.

Bear, thanks for the very thorough answer - its what I hoped for.

Is the idea of getting a small gas generator to save on propane costs/usage since the Onan is so hungry? I've noticed that many people have small ones like you suggest but I thought since I have the Onan, I didn't think that I needed another one. Is it worth it to get a second one?

Thanks again.

If you find yourself boondocking alot then you can think about getting a smaller generator to help out, but many since you already have a big one just use it for now. It will take a lot of fuel savings to make up for the cost of the small generator. You also should look at the particular converter you have (unless you have a big inverter/charger) and see if it can charge your batteries back in less than four hours. Some converters have big chargers and three stage chargers, or these can be added for under $100. A replacement converter with a big three stage charger (60 to 90 amps) is under $300 and that is less than a Honda generator.

To tag on to Bill's comment, One boondocker used a heavy duty battery charger from Sears. He would hook it up to the batteries, run the generator and build up a charge quickly. This helped cut down on the time he had to run the generator. He had a boat that he towed behind the 5th wheel, so the battery charger came in handy to charge batteries for all his toys.

Bjoyce or The bear If I have a 2,000 watt pure sine inverter (Trace) I would not have to run my Honda 2,000 watt generator 4 hrs to charge my batteries because I have a built in 3 stage charger? How long would it take using the perameters in Bear's example?

Dr Gonzo: You would probably run the generator about 1-1/2 to 2 hours most days to get the batteries mostly charged and about once a week run it until the inverter says you are in float charge, which would probably be around 3 hours. What happens is as the batteries get closer and closer to being fully charged the charger goes into taper charge mode gradually decreasing the amps while keeping the voltage up (14+ volts) until the batteries are fully charged and then floats (about 13+ volts). The last hour or two takes a while, but you are not adding that much more charge to the batteries.   You don't need to top the batteries fully every day, about once a week will keep the batteries happy. That last bit of charge is something solar does really well, as long as you have sunlight.  A solar bank that would reduce your generator usage by an hour a day would run over $2000 (3 panels plus controller and wiring).
Just make sure your inverter is configured for the size of your battery bank in amp-hours and type of batteries (wet, AGM, gel, and some have setting for Trojan, Interstate, etc.). That way the charger knows when to stop and what volts and amps to use.   I  know my Prosine (Xantrex) inverter defaulted to 200 amp-hours of gel cells from the factory so I have to change it to 440 amp-hours of AGMs to charge my batteries right. 


-- Edited by bjoyce on Friday 9th of October 2009 06:38:45 AM

-- Edited by bjoyce on Friday 9th of October 2009 08:13:49 AM

You mentioned a heavy duty battery charger...I have just a regular charger I use for my deep cycle...would it charge faster if plugged into the gen??? I really don't want to run the gen more than a couple of hours a day if possible.

I wonder how good this solar kit is if it is cheaper than a small genset. Do your homework and make sure you get good panels, a quality controller and heavy wires to do it right.

Although we have the onboard generator, we sure enjoy the peace and quiet of boondocking in the woods. Last thing we want to hear is the droning of other people's generators either. So we have four 6 volt batteries (and room to expand with 2 more) With careful use of the power hungry items, we can go for a quite a few days without needing to recharge. Plus, we have some solar to top them off each day, and are now in the process of upgrading this month to four 100 watt solar panels. We don't use the power hungry furnace, and we turn off the inverter when not in direct use. We use a catalytic heater instead and mostly 12 volt or battery operated items. We even bought 12 volt adaptor cord for our Dell computer and our new Cradlepoint router also comes with optional 12 volt cord. Most of our time is spent outside till bedtime anyhow. Hardest part is when our grown kids visit, they leave lights on all over and run the pump a lot while washing hands, brushing teeth, or doing dishes. We have to keep reminding them we are off the grid and each bit they waste is something that we are gonna have to replenish when they leave! With the new 400 watts of solar install plus our battery bank, we can be a little freer with our power use and not have to run the generator much at all.