RV: DC Power Distribution

Solar, wind, hydro and other non-fossil sources of electricity.
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Kingfish   10 GW

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RV: DC Power Distribution

Post by Kingfish » Jul 13 2013 12:22pm

Lil’ conundrum problem for the graybeards. We have 5 acres in the forest far removed from The Grid and we create our own power via Generator and trickle via Solar. We have two RVs with permanent snow roofs that have solar on top, plus two out-buildings (utility & storage) with more solar.

The two RVs are about 200 feet apart. There are three distinct charging systems: The primary RV is tied into the local solar and the Utility building. The Secondary RV to its’ solar, and the Storage Shed is about 100 feet from the Primary RV and has its’ own solar. The layout is close to an obtuse triangle with the RVs at the long base, and shed slightly closer to the Primary RV.

I believe the batteries used are 12V Deep Cycle, with two in series to make 24V. We have four generators: Each RV has its’ own propane, plus two portables that run on gasoline (2kW and 7.5kW) that output both AC and DC.

I would like to unify these systems using 2-conductor that we can safely bury into the ground maybe a foot deep. We get about 3 feet of snow in the winter and runoff can be a bitch in the low areas, but the ground is pretty hard and I think a mobile trencher could get the job done fine in one day.

The question that I cannot workout is the wire gauge; I don’t know enough about RVs to figure out what is reasonable. I can tell you that we run the generator whenever we do laundry, or pump water into the holding tank (via the Utility Bldg), and I think the RV generator kicks on if we run the microwave AND the coffee pot – which I think is the highest load on the land.

I know that there’s not enough solar to keep the batteries charged; we have to run the generator for an hour minimum to keep the Primary RV up to snuff (traditionally done when we do laundry). The Storage Shed overproduces power, and the Secondary RV is only used when guests are there, so my thinking is to tie the systems together and share the load. Now we’re back to the size of wire for the cable.

We also have a little stream that runs through the property but the drop is not very much as is the flow. I’ve toyed with trying to create a lil’ hydro but I don’t think it’s worth the cost. Best drop we can get is 2 feet; I could get 3 or 4 upstream but my Mom would really have a hissy fit and probably take out a contract to erase my birthday if I messed with that purdy section filled with wildflowers. However that has always been a tantalizing source of 24/7 low-output power flowing at least 1 gal/s.

Image
Life is tough when you have to reach for a beer :D Sidebar related thread here.

Anyways, thanks for listening. Look forward to ideas.
Best, KF
* My 2WD Garden Wall
* Kinaye MotorSports
* Primary ride: 2WD Disc 9C 2806-equiv / Dual Lyen 12FET / 20S7P LiPo.
* Epics: Going to California: 2011 8)
* 50-mph, 101, 10k-Club. 12,527 miles-to-date, 7037 as 2WD.

It is by caffeine alone I set my mind in motion.
It is by the beans of Java that thoughts acquire speed.
The hands acquire shakes, the shakes become a warning.
It is by caffeine alone I set my mind in motion.

Kingfish   10 GW

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Re: RV: DC Power Distribution

Post by Kingfish » Jul 13 2013 12:45pm

ADDENDUM:
with what distance of wires can 12v battery be used?. Eye-opening. I can tell right away this can get very expensive.

This link was quite useful: Wire Loss Tables for Solar Electric Systems. Guess I need to figure out the minimum capacity and over-current protection.

~KF
* My 2WD Garden Wall
* Kinaye MotorSports
* Primary ride: 2WD Disc 9C 2806-equiv / Dual Lyen 12FET / 20S7P LiPo.
* Epics: Going to California: 2011 8)
* 50-mph, 101, 10k-Club. 12,527 miles-to-date, 7037 as 2WD.

It is by caffeine alone I set my mind in motion.
It is by the beans of Java that thoughts acquire speed.
The hands acquire shakes, the shakes become a warning.
It is by caffeine alone I set my mind in motion.

inh   1 mW

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Re: RV: DC Power Distribution

Post by inh » Jul 13 2013 11:51pm

At such a low voltage, you're amperage will be quite high if you are trying to move any decent amount of power. That's going to take some large cable to pull off if you try to do it at your DC voltages.

If possible, tieing everything together with 120v AC would be much cheaper for cable, but it doesn't sound like that's possible. I don't think it'd be cheap to up the voltage of your DC storage systems and then drop it back down to 12-24v with a DC-DC converter in each RV...

If you're just looking to use some of that solar on the shed and guest RV, figure out how many amps you would need to pull from those to your other RV and size your cable for that. You shouldn't need a large cable for that I don't think. Then just protect the cable with an appropriately sized breaker and you'll be good to go. The two RV systems should equalize and share some of the load nicely.

KMB   10 mW

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Re: RV: DC Power Distribution

Post by KMB » Aug 31 2013 6:29pm

Thinking here.... I've had RV's most of my adult life....tent trailers to 40' diesel pushers...they have all been 12v...passing throught invertors...and 120v through convertors. Most rv refridgerators etc. are 120v/12v/propane. Sure it's 24v??? Not trying to be a know it all ....just thinking..I know your smarter than I.
Kent

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edcastrovalley   1 kW

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Re: RV: DC Power Distribution

Post by edcastrovalley » Aug 31 2013 6:30pm

Here are some charts from my charge controller manual. They're for 12vdc but you double the lengths for 24vdc (see "Notes") and a couple sizes in there would reach 200 feet.
Wire Chart 1.jpg
Wire Chart 1.jpg (69.68 KiB) Viewed 1819 times
Wire Chart Solid.jpg
Wire Chart Solid.jpg (89.26 KiB) Viewed 1819 times
Notes.jpg
Notes.jpg (34.2 KiB) Viewed 1819 times

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Hwy89   1 kW

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Re: RV: DC Power Distribution

Post by Hwy89 » Jan 17 2014 11:07am

The ideal solution would be to consolidate all of the solar into one location as close as possible to the battery bank. get a quality charge controller and an inverter that will accept generator input when the battery bank gets low. You can then run 110V AC through #12 direct burial cable which will be much less expensive than the cable you would need to move DC that distance. The two RV's would still need their house batteries but would be kept charged through their converters.

Kingfish   10 GW

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Re: RV: DC Power Distribution

Post by Kingfish » Jan 19 2014 10:58am

Consolidate Solar: In concept – good, in practice – not as. There are tall trees, so we get our solar where we can. We also have a “mobile” array which is repositioned by younglings to optimum ad hoc… but I digress.

Ideal Solution: I don’t know why I didn’t think of this before – though it appears to me that the best solution is to create charging arrays in series, razing the voltage so that the negligent impedance is overcome. Relatively speaking, who cares what the charging voltage is so long as we sample the battery frequent enough to know when we’ve hit our target, and then regulate the top-off. Geez, this appears dead-simple now; just need a comparator circuit and a VR.

Energized, KF
* My 2WD Garden Wall
* Kinaye MotorSports
* Primary ride: 2WD Disc 9C 2806-equiv / Dual Lyen 12FET / 20S7P LiPo.
* Epics: Going to California: 2011 8)
* 50-mph, 101, 10k-Club. 12,527 miles-to-date, 7037 as 2WD.

It is by caffeine alone I set my mind in motion.
It is by the beans of Java that thoughts acquire speed.
The hands acquire shakes, the shakes become a warning.
It is by caffeine alone I set my mind in motion.

dnmun   100 GW

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Re: RV: DC Power Distribution

Post by dnmun » Jan 19 2014 11:21am

need to cut down those trees that get in the way of the sunlight. burn the wood for the heat in the winter or rip it for lumber if you can, then burn the slash.

then go solar, add a passive solar porch on the south side of the RVs and insulate it so you can go out and be in the sun in the winter. getting early morning light to the optic nerve is very important in maintaining the circadian rhythm and serotonin for mood enhancement and protection during the shorter winter days.

cut big thermopane windows into the side of the RV and park it for solar gain in the winter.

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wineboyrider   100 MW

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Re: RV: DC Power Distribution

Post by wineboyrider » Jan 19 2014 12:15pm

Run 36v or 48v dc and smaller gauge wires? :shock:
ES IS SAVED! THANK YOU JUSTIN.

Kingfish   10 GW

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Re: RV: DC Power Distribution

Post by Kingfish » Jan 19 2014 1:49pm

dnmun wrote:need to cut down those trees that get in the way of the sunlight. burn the wood for the heat in the winter or rip it for lumber if you can, then burn the slash.
:lol:

I just got back from HKG yesterday. The smog was really bad there; I have never seen a Blood-Orange-colored full moon before. They are planting trees like no tomorrow trying to reverse 3,000 years of past incompetence. If they keep at it -> burning coal, Solar will be of no help.

Grateful to be back home in a true rain forest, KF
* My 2WD Garden Wall
* Kinaye MotorSports
* Primary ride: 2WD Disc 9C 2806-equiv / Dual Lyen 12FET / 20S7P LiPo.
* Epics: Going to California: 2011 8)
* 50-mph, 101, 10k-Club. 12,527 miles-to-date, 7037 as 2WD.

It is by caffeine alone I set my mind in motion.
It is by the beans of Java that thoughts acquire speed.
The hands acquire shakes, the shakes become a warning.
It is by caffeine alone I set my mind in motion.

dnmun   100 GW

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Location: portland, or and loveland, co

Re: RV: DC Power Distribution

Post by dnmun » Jan 19 2014 3:11pm

they will not burn coal much longer as the economy improves and they convert more to burning natural gas. as soon as they can start shipping LNG from the shale gas into japan and singapore their price will drop by 30-40%. the CCP is making it a current goal to convert and electrify the fleets.

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