Residential fridge and boondocking

Look at the EPA sticker for the fridge, it should list kilowatt usage per day or per year. If it's per year, divide by 365 to get per day.

Taking the kw/day figure, divide by 12 to get the number of 12-volt amps the system will use in a day. Compare that figure to the amp-hour rating of the battery for the "dedicated system".

For example if the fridge is rated at 2 kw per day, 2000 / 12 is 166 amps per day (on a 12v system). Divide more to get amp-hours 166 / 24 = 7 amp-hours

Now lets say you have a modest battery system of 500 amp-hour total capacity. YOu can never use the total capacity, most folks use less than half, so 250 / 7 = 35 hours or a day and a half.

This is all rough math, there's a lot of variables that can change the numbers but for all intents, it's an accurate ball-park.

energy star for a 17 cu foot domestic

Real world experience - have the residential fridge, 2000W inverter, 4x6-volt batteries.

We spend time at the races dry camping. Run the generator a couple of hours each day and it keeps the battery fully charged. We have run the Fridge for 2 days without any charging of the batteries while we were dry camping. Planning on adding some solar in the next year or two to keep it topped off so we don't need to run the generator as much.

We have also tested running the fridge in the yard for up to 4 days and it was still running - but this didn't involve any lights, pump, or anything else but the inverter and fridge.

I asked a sales person that very question at the RV show in Louisville, KY this year. He said about 24 hours.

I would imagine that would vary by several hours depending on the outside temps, how often the fridge was opened and what was in it.

Add about 500 watts of solar to the roof and the problem goes away. Solar is cheap nowadays and is a small fraction of the purchase price. In bad weather or long term low amounts of sun the generator will look after things if you run it a couple of times per day for an hour. You will love the residential refrigerator.

Living in Florida, we had lots of storms and lightning, and thus lots of power outages. A residential refrigerator will last about 24 hours if you don't open the doors. Of course, that was in a a hot house (90 degrees or more) because there also was no A/C.

We also have a residential refrigerator in our camper. It easily goes 12 hours. I don't how much further, because we never went longer than that without power.

Hi,

Here is a simple flow chart.

Budget-->Energy Audit-->Battery bank size-->number of watts-->PWM or MPPT.

One rule of thumb is between 60 and 150 watts of panels per 100 amp-hours of storage. The smaller the battery bank the higher the wattage needed (per 100 amp-hours). Here is a link to the rather special spreadsheet which includes an energy audit, that N8GS has created to help size solar battery charging systems!

Solar Spread Sheet N8GS

For a nice explanation of solar, try this link:

Golden rules of solar

wkswenson wrote:
Planning on adding some solar in the next year or two to keep it topped off so we don't need to run the generator as much.

Realistically, using the refer, watching TV, water pump and lights, you probably get 24 hours out of a bank of four batteries. Typically, a couple of hours of generator usage in the morning, some at dinner time and you should be good.

I think solar is useful, but not the answer. Even though solar is getting cheaper, 500 watts of solar as mentioned, is about $700-$800 if you install it yourself. Then you need sunny days to make it work. $700.00 can buy a lot f generator fuel, or even a small Honda generator.

Hi,

Yup 700 buys a lot of fuel. In my case it would get me to Vancouver and 1/4 back. However, when the fuel is gone--you get to buy more. Whereas with the solar there is no cost.

If you think you can get 5% return on the 700.00 that would be $35 per year.

735 is about 230 gallons of fuel. If you are running a generator such as a Yamaha 3000 sIEB for 5 hours per day at 1/4 load, that is 230 days supply.

Of course, that doesn't allow anything for maintenance for the generator, nor anything on the cost price.

Yamaha suggests oil changes every 50 hours. If you DIY that's $2.50 every ten days. 20 x $2.50 = $50.00 per year. New air filter? How often and what price?

If the generator cost $2000 then at the same 5% it costs $100 per year in lost interest.

735 - 150 = $585.00 @ 3.25 per gallon that is only 180 days of use.

Please remember that is running the generator at only 1/4 of full speed.

Then you have the problem of exercising the genny. This can be quite inconvenient.

In comparison solar is virtually maintenance free.

In short, the more you use the RV the better deal solar becomes. Not to mention that battery life seems to be much better for RVs that have solar charging.

wkswenson wrote:

We have also tested running the fridge in the yard for up to 4 days and it was still running - but this didn't involve any lights, pump, or anything else but the inverter and fridge.

It probably also didn't include opening and closing the fridge on a regular basis. Keeping the fridge closed and running for 4 days and not opening the door is still a good test, but you need to factor in the normal use of opening the door...Just say'n

-paul

Flanz wrote:

wkswenson wrote:

We have also tested running the fridge in the yard for up to 4 days and it was still running - but this didn't involve any lights, pump, or anything else but the inverter and fridge.

It probably also didn't include opening and closing the fridge on a regular basis. Keeping the fridge closed and running for 4 days and not opening the door is still a good test, but you need to factor in the normal use of opening the door...Just say'n

-paul

Agreed - we didn't open and close it frequently, but had food in the fridge/freezer, the ice maker was running and we would visit the rig for a drink 3-4 times a day. So there was some opening and closing, but not normal usage for sure.