Boondocking on solar, with a residential fridge

[99phantoms]

Take a 38-ft all-electric coach with residential refrigerator, and add 960 w of solar.
Can you boondock without having to run the generator?


The set-up would be -
- Whirlpool refrigerator - EnergyGuide rating is 618 kWh per year
- 8 AGM batteries - 880 Ah total capacity, 50% available at 12.5 v nominal
- Magnum MS series 2800w PSW inverter - 90% efficiency, & 25 w power consumption


Energy required to run just the refrigerator is 618 kWh/year -

618,000 Wh / (365 * 24h) = 70.5 w (uses power like a 70 w light bulb)

at 12.5 v dc, that’s 5.6 A dc average continuous draw (70.5 w / 12.5 v)

only 90% inverter efficiency increases the battery draw to 6.3 A dc (5.6 / 0.9)

The residential refrigerator in 24 hrs uses 151 Ah from the battery bank (6.3 A * 24 h)



100 w of solar adds ~ 30 Ah per ‘solar day’ to the battery bank (AM Solar)

With 960 w of solar, that’s 288 Ah added each day (30 Ah * 9.6)

Minus fridge use, the net battery gain each day is +137 Ah (288 - 151)

Operating the residental refrigerator requires 52% (~ 500 w) of total daily solar production (151 / 288)



Add the 25 w of inverter power consumption, & now it’s a 95 w bulb we’re burning

The refrigerator ‘system’ now uses 204 Ah every 24 hrs, or 71% (~ 680 w) of daily solar production (204 / 288)



So, is it really practical to carry a residential refrigerator when your goal is to boondock to the max without having to run the generator?

BTW, how good are those Norcold gas refrigerators?

[wildtoad]

I'm no expert, but from what I've read on various forums if you want an all electric motorhome then you should either find a power source or plan to run your generator often.

Many people will curse the Norcolds for not being cold enough, or not big enough, or some but few have had them catch on fire. I've had four motorhomes with Norcolds and they all worked flawlessly. My current unit has a Dometic and it works well also. We don't boondock but wanted the the flexibility to do so.

[tmw188]

Originally Posted by wildtoad

I'm no expert, but from what I've read on various forums if you want an all electric motorhome then you should either find a power source or plan to run your generator often.

Many people will curse the Norcolds for not being cold enough, or not big enough, or some but few have had them catch on fire. I've had four motorhomes with Norcolds and they all worked flawlessly. My current unit has a Dometic and it works well also. We don't boondock but wanted the the flexibility to do so.

X2 On that. If you boondock you usually want to find some shade if possible anyway, so being in the shade you wouldn't have enough solar replenishing your batteries. Your propane will keep the frig. cool while you are sitting in the shade. Also the day before we leave to head out the wife can go to the storage lot and turn on the refrigerator the morning before we bring the coach home and it is nice and cool when I pull into the driveway.


iPad using iRV2 - RV Forum

[computerguy]

99phantoms,
It seems to me the equation you are using is really complicated and doesn't give the answer you are needing. I am not a solar expert by any means. I have a Samsung refer and it uses a worst case scenario of 157 AH. But that does not all come from that batteries. While solar is active not all the energy goes into the batteries. Some can and will (excess generating capacity) be used by the system.
I would use an existing spreadsheet that others have created and are available on the internet.
Try jackanddanmeyer or technomadia.
I am curious what the more knowledgeable solar members will have to say though as I am designing the new system now for my rig (I had 480 w of solar on my '05 Monaco).

[tmw188]

Originally Posted by tmw188

X2 On that. If you boondock you usually want to find some shade if possible anyway, so being in the shade you wouldn't have enough solar replenishing your batteries. Your propane will keep the frig. cool while you are sitting in the shade. Also the day before we leave to head out the wife can go to the storage lot and turn on the refrigerator the morning before we bring the coach home and it is nice and cool when I pull into the driveway. iPad using iRV2 - RV Forum

I would say obviously the larger high end units demands are greater than mine and they usually don't have propane refrigerators.

[1bigmess]

The annual KWh usage is an estimate of "typical usage". Inside an RV doesn't strike me as "typical usage". In fact, is it even clearly explained what the "typical usage" of the appliance is?

It is not like leaving a 70 watt light bulb on for a year, that would be easy. It is like switching a much larger light bulb on and off many times over the course of a year, and the much larger light bulb has to be able to switch on and off all night. Change how you are thinking about the problem. It will take more wire to carry the amperage needed to start and run the fridge, and the batteries have to be able to supply the surge current to start the compressor. You need energy storage to run the fridge when the sun isn't out or solar collection hasn't been as good today as it was yesterday. You live in Memphis according to your member profile. Is the hot weather gonna make your fridge work harder than in a cooler climate? Will you be running the A/C in your coach, which will provide an electricity source for the fridge, too?

Your problem is much more involved than a very simple 70 watt light bulb.

[99phantoms]

Originally Posted by 1bigmess

Your problem is much more involved than a very simple 70 watt light bulb.

I know it is an oversimplification, but it helped me picture just how much energy one of these beasts actually uses, on the whole… sort of a ‘light bulb moment.'

Configuring this once-in-a-lifetime, largest-ever purchase for a purpose I've never seen... for an experience I can only try to imagine... has proven quite perplexing. Which is perzactly the reason I seek insight from those who have 'been there, and done that.'

I'm sure the EnergyGuide ratings were intended merely as a tool for comparison. As the forum sage has said - YMMV.

[C&SL]

99phantoms,

We are fulltime in an all-electric coach. From Sep 1 2015 to today we have boondocked 241 day, so yes it is easy to do with an all-electric coach with the right equipment. Our generator run time is 1.44 hr. / day.

[99phantoms]

Originally Posted by C&SL

99phantoms,

We are fulltime in an all-electric coach. From Sep 1 2015 to today we have boondocked 241 day, so yes it is easy to do with an all-electric coach with the right equipment. Our generator run time is 1.44 hr. / day.

Using the generator is inevitable if boon docking all-electric?

Got details?

[TheJuggler]

Originally Posted by 99phantoms

Using the generator is inevitable if boon docking all-electric?

Got details?

Ditto on the "got details?"... I'm also currently designing what will be the place Dixie the Wonder Dog and I live in until we're done living. I've been up and down about being able to use solar and lithium to give yourself a reasonable life "boondocking" and am curious to hear the specifics on anyone's experience.

[FaithBowls]

You really have to check and measure your own consumption to figure your power needs. Just figure you are going to invest in a solar system or generator. How much depends on what you actually use. Best not to guess and build the wrong system. Everyone's needs and power habits vary, so you need to calculate it yourself using real world numbers. Re: refrigerator, I have a samsung residential with propane hookup and I'm very happy with that set up. Haven't gone solar because cost is still high when considering wiring and batteries.

[99phantoms]

I've never owned an RV. What would be helpful is to know the specifics of YOUR system, and what you can do with it.

How are you configured?
> type of coach & refrigerator
> battery bank size & type of batts
> solar system - # of watts, series or parallel
> generator use, etc.

Then tell us how well YOUR set-up works for what you are trying to do?? What would you change or recommend to the nooob looking to do what you're doing?

Thanx

[TinMan Trvlr]

Our brief recent real world experience since having a solar supplier in Yuma mount 1280 watts of solar (8 X 160w), a Magnum controller, through 6-225 AH batteries, monitored by a Magnum BMK, has been very satisfactory. We only need to run our generator when we need A/C or need to run our washer and dryer. We run our double door residential refrigerator and our Dometic chest refrigerator/freezer in the basement as well as powering our TV's, satellite receivers and lights all day from the solar system. By the end of the day, the batteries are fully charged, despite the system having powered the coach all day. knowing what I know now, I would have found a way to add two more 160 watt panels for a total of 10.

Prior to mounting the solar panels we had to run our generator 6 hours per day to charge our batteries while using the same electrical demands. When parked in National or State Parks where there was a restriction on generator hours, we often had to move on so we didn't excessively drain our batteries, as every day was a loosing proposition. We also had to visit the coach every 2-3 weeks while the coach was in storage to run the generator for 6 hours or more to charge the batteries despite the "disconnect switch" above the entry steps being turned off.

Mount as much solar as will fit, and save your generator for the hot days when you need A/C. Solar is not only quieter, but you don't have to change its oil or buy fuel for it. Best wishes for success with your eventual choice.

[99phantoms]

Excellent discussion. Thanks.

Some questions -

The solar experience you just described is in the desert SW? (good, hi angle sun)

Have you used this system in the parks (with trees)?

You have 675 Ah of AGM batteries?

Panels are mounted 4 down each side? mounted flat to the roof, or elevated? do the panels tilt? parallel or series panel wiring?

Did you add a 2nd monitor or use the Magnum inverter control panel to monitor the solar controller & BMK?

With such good results, why would you add 2 more panels?

(excellent motivation)