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spencerin
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# Posted: 28 Jan 2024 13:46 - Edited by: spencerin
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I'm curious about the idea of buying an RV and connecting a solar system to it as its sole source of power.
I know how to wire a typical solar system (panel to CC to battery to inverter), but do most RVs run everything off 12V DC? I know you can plug RVs into shore or generator power, so there's obviously some 120V AC capability there, too.
Do I simply wire panel to CC to RV battery? Are there typical 120V AC outlets in RVs? What if I wanted to plug in a 120V AC appliance or tool?
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FishHog
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# Posted: 28 Jan 2024 14:27
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Most rvs have separate house batteries. They are tied to the vehicle battery with a dc to dc charger to allow charging while driving.
From there there is usually shore power connection and solar if you want. House systems can be of many voltage setups but 12v is basic. Inverter for 120 volt requirements
AC while off grid is very hard. Typical ac units only run when connected to shore power. Needs an awfully big battery bank to be an off grid option
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Brettny
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# Posted: 28 Jan 2024 15:26
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To supply a trailer with power when with out useing the AC you would really need to completely cover the roof in pannels and get way bigger batteries.
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gcrank1
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# Posted: 28 Jan 2024 15:26
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The RVs Ive messed about with have some 120vac outlets for when hooked up to shore power but the lights and fan, etc are run on 12vdc.
The cord and RV plug for shore split the 120vac into the RV 'converter box' (rather than inverter) and the outlets, it converts the 120vac to 12v so when on shore you arent depleting the battery for the 12v stuff.
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spencerin
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# Posted: 28 Jan 2024 16:45 - Edited by: spencerin
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In this scenario, panel and battery capacity theoretically would be unlimited. The RV would be dropped off and left on vacant land where there is always ample sunlight. Panels and batteries would be placed on the ground.
So, is it really as simple as adding batteries to the RV's own battery to beef up the bank, and adding however many panels and a charge controller needed to power the RV's own appliances?
What I'm not clear about is that some RV appliances run on 120V. They're obviously usually powered by shore power or a generator. But, if your only source of power is solar, how exactly do you tie the battery bank into the existing 120V wiring in the RV so you can use those appliances?
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gcrank1
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# Posted: 28 Jan 2024 18:42 - Edited by: gcrank1
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Keep in mind that the 'storage', the bat-bank is only that; how it get charged, even from multiple sources, are your options. You can have multiple charge sources hooked up to the b-bank at the same time.
After the b-bank is where you want to get particular.
Do you just want the b-bank to be the as equiped or expanded? Be aware that ime the wiring from the oem b-bank is too wimpy, you will want to at least look at it.
It all goes to the converter box (mine was at the rear, b-bank in front with puny, poorly done wires), as does the 120vac from the RV inlet wall plug, then the circuits are divied out from there.
So, upgrade the b-bank wires if needed, add MRBF fusing at each battery + terminal (100ah battery use a 100-125a fuse). Remember you fuse to the wire size, not the device.
If more than 2 batteries the parallel wiring of them Is Very Particular!
There are often some Big draws on the RV 12vdc, the lights if changed to led arent bad, maybe the same with the ventilating fans, but the furnace is a b-bank killer. Whenever the furnace is even turned (not running, just in standby) on the unit is making a phantom draw. I learned to turn the furnace off at the control board for the non-heating season!
Some converters may actually back-charge the b-bank whenever hooked up to shore power. You do NOT want to be drawing off your b-bank, feeding the converter and trying to charge your b-bank at the same time! There may be other stuff depending upon how fancy the thing is. You will want to sort out what is in the unit that is heavy draw 12v running off the converter so that will only run when feed by the gen on the RV inlet plug.
You may want to separate wiring so the b-bank only feeds directly some of the 12v low draw stuff (like some lights) and if inverting the b-bank to 120vac to feed only some of the outlets directly.
The rest leave as is so when you run the gen into the RV inlet it works as intended.
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spencerin
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# Posted: 28 Jan 2024 20:55
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There has to be some sort of by-pass of the converter box to allow 120V from the generator or shore power to continue to power the appliances that require 120V.
My understanding is that the converter box changes the incoming 120V to 12V. I can't imagine it's converting 100% of the incoming 120V to 12V, only to then invert some of that 12V back to 120V to power those appliances.
Or maybe it is? That's what I don't know. Knowing how that all works would help me figure out how to tie a solar system in to be able to use the RV's full electrical system, both 12V and 120V.....
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ICC
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# Posted: 28 Jan 2024 21:17
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Quoting: spencerin is it really as simple as adding batteries to the RV's own battery
Yes & No.
Most RV's are going to be fitted with 12 volt house (or coach) batteries. Lead-acid or lithium.
If it has lead-acid they are likely the Marine-RV, "so-called" deepcycle type. Those are not the best for longest useful life. (Golf Cart lead acid are better. ) Adding batteries to an existing battery system is usually not the best idea either, especially if we are talking a used unit. Even if new the batteries to be added would ideally be the same make & model and have the same date of manufacture.
If this is a newer RV it may very well come with a lithium battery or two. That makes adding capacity more possible, with the caveat of adding similar batteries... similar capacity, the same type of chemistry so they can share the charging system.
Quoting: spencerin if your only source of power is solar, how exactly do you tie the battery bank into the existing 120V wiring in the RV so you can use those appliances?
You need an appropriate-sized inverter and an automatic transfer switch. That way the system will be able to automatically switch between shore or generator input and the inverter. The 120 VAC outlets would seamlessly switch from one to the other.
Most RV's do not come with an inverter that operates off the coach/house battery, because the battery system is likely unable to power the larger AC devices. Most RV's I have seen only have 120 VAC
plugged into shore or generator.
Quoting: spencerin My understanding is that the converter box changes the incoming 120V to 12V. I can't imagine it's converting 100% of the incoming 120V to 12V, only to then invert some of that 12V back to 120V to power those appliances.
Correct.
Are we talking used or new RV? The converter on older RV's (or new) that came with lead-acid batteries are not likely to be usable with lithium batteries. So if that is the case you would need to replace the converter for lithium batteries.
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spencerin
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# Posted: 28 Jan 2024 21:51 - Edited by: spencerin
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The idea would be to buy a used (around 5 years old or newer) RV and drop if off somewhere where there is nothing but solar available.
I did think about wiring the end of an RV plug-in for a generator to the end of a 3-prong extension cord, plug one end into the inverter and the other into the RV generator plug-in receptacle. Wah-lah.
I'm sure there are better ways to do this, but this is all new to me. If there's a better way to go about this, let me know.....
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gcrank1
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# Posted: 28 Jan 2024 22:06 - Edited by: gcrank1
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My converter faceplate had the fuses for the 12vdc circuits and c-breakers for the ac side.
All the wires went into the back from the battery and the shore power. I expect the 12vdc battery leads and the converted to 12vdc went to the fuseblock then back out to the 'devices'. Somewhere there the converter 'charger' tied in, and if not the new-gen lith friendly parameters (and even with lead-acid) they are hard on batteries.
I preferred to use my smart charger that I took along.
If you invert b-bank 12v to 120vac to feed into the RV plug all that 120v will pass through alright but the stuff to the 12v side will be returned to (converted) back 12vdc; not efficient at all!
Now with enough overpaneling and b-bank you could maybe do ok. Id prefer to do some re-wiring to get the best of both worlds; ie, 12vdc and 120vac.
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spencerin
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# Posted: 28 Jan 2024 22:17 - Edited by: spencerin
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crank, good point about the re-conversion.
This is where I get stuck, though. Where/how do I tap into the 120V system if not though the shore/generator receptacle?
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Nobadays
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# Posted: 28 Jan 2024 23:06 - Edited by: Nobadays
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Our rv (Pleasure-Way van) has a built in generator plus we have a shore power plug. So there is a built in transfer switch already for the converter. I intend to beef up my solar, mainly adding an inverter capable of running the microwave, etc.
My plan is to install a 30amp receptacle (in the compartment where the 30amp cord resisides) wired to the inverter so I can plug the shore power cord into it.... when not on shore power. This should then provide power to the converter and 120v to the receptacles in the van, as if it were plugged into shore power. (BTW, we rarely use the microwave, or much 120v power really. )
This might have even suggested above but I wasn't clear reading the posts... hope this helps.
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gcrank1
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# Posted: 28 Jan 2024 23:51
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If you dont have any 12vdc hooked up to the converter your gen input on the RV cord will be distributed through the circuits of the converter as normal.
You could also have the inverted to 120vac from the b-bank tied in there with an auto transfer (some inverters will do that) so that whenever you start the gen it fairly seamlessly switches from the inverter to the gen (no back-feed issues) and all the 120vac just keeps working.
With the 12vdc using the fuseblock but no wires connected to the converter side you could run all the 12v off the b-bank, have a fuse panel and basically anything 12v will be in your stand-alone solar/bat system.
This is pretty much how I had one of my cabin systems set up and it worked well enough. The low draw 12v stuff was the most used and when we wanted to run the microwave, etc. Id start the gen.
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Nobadays
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# Posted: 29 Jan 2024 00:34
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I know with my RV I can be plugged into shore power and if I start the generator there is some sort of transfer switch on the 120vac/12vdc converter that will cut the shore power feed and transfer the load to the generator.
I'm hoping, and pretty sure, that the samevwould be true if my inverter is feeding thev120v side and the generator is started. I do need to confirm this with those who know the Pleasure-Way electrical better than I.
I'm thinking this could be a solution for spencerin.
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gcrank1
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# Posted: 29 Jan 2024 08:25 - Edited by: gcrank1
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Yes, it should 'work' to an extent. Remember what I said about the efficiency; your inverter will take 12vdc and make it 120vac which you will feed into the RV converter (via the easy plug) where it will convert some of the now 120vac back to 12vdc.
This may be ok for your elec use profile. But if most of the time, after using some 120 for meal making, etc. you are running the lights, fan(s), etc. and maybe having the furnace idling your 12vdc draw-down is going to be heavier than you expect.
Add to that the potential of an RV 120/12v absorption fridge that may be running on 12 (are those an automatic switch over?) and that the converter units are notoriously power hogs......
As to the transfer switch, if automatic will it Always work?; ie, will the triggering occur from the shore/now gen to the bat-bank inverter and back again if/when you need more beans and fire up the gen?
I know that my changing the plugs from one to the other (or throwing a manual t-switch) will, but Im nervous about 'automatic' stuff.
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Nobadays
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# Posted: 29 Jan 2024 09:27
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Quoting: gcrank1 Im nervous about 'automatic' stuff.
Me too! I was thinking last night that it would be easy to put an easily accessible switch between the inverter and the new 30amp receptacle... and a little note above the generator switch that says, "turn off inverter before turning on the generator." This switch could actually be off 90% of the time which would solve the other issues as well. It is only the morning coffee grind and very rarely the microwave that use 120vac.
We run two house batteries, FLA/65ah so realistically we have 65ah of power to use. With the planed upgrades we will install two agm/85ah batteries. Presently we have rarely ever had enough power for lights, charging devices and running a small 400w inverter for the coffee grinder. We have a portable, 75w solar panel with a cheap Chinese pwm scc. This panel has its own stand built in, 20' of 10awg cable and is moved as needed to keep it producing to its maximum. Has worked great for boondocking.
Sorry spenserin... hope this somehow helps you as well!
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Brettny
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# Posted: 29 Jan 2024 09:52
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Alot really depends on the trailer so with no information it's really hard to help.
Some have inverters and some dont thus only getting 120v power when shore power is connected.
A trailer in a woodsy environment..the real question is how do you plan on keeping the rodents out?
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gcrank1
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# Posted: 29 Jan 2024 10:35
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We also need to be sure about what we call (and think) about the diff devices.
The typical RV has a Converter, it takes the incoming 'shore' power 120vac and connects it to whatever needs 120 in the unit, as well as 'converts' some to 12vdc those those things.
An Inverter takes 12vdc (or 24, 48) and 'inverts' it into 120vac. Be use to only get a Pure Sine Wave Inverter!
Two entirely different functions.
Some of the new(er) RVs that have solar capability wired in probably have an inverter, maybe a combi converter/interter and charger. I prefer stand-alone devices to choose from or replace.
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razmichael
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# Posted: 29 Jan 2024 11:18
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way back (2010) when I started with a popup, I did some simple rewiring internally and kept a small solar setup at the lake (with 2 trojan deep cycles). I fitted in a Xantrex 1800 Inverter/charger, wired in a HD toggle switch to bypass the built in converter and used a marine 4 way switch to turn on/off the regular trailer 12V and the feed to the inverter (or both). This all allowed me run the system in multiple ways (retaining the converter function if I needed - never did). The generator in line was rerouted to the inverter and I ran HD connector out the wall for the batteries. Although much more extensive, this system was eventually moved to the cabin, including the inverter and is still the core (and, yes, this is a modified Sine Wave inverter that has served me just fine for the limited AC use I still use - would I do it differently today - likely). Although don't recall how accurate the diagrams were, here is a link to what I used to plan the setup Popup Wiring
The system was easy to use (arrive, plug the batteries in and turn the big red switch to DC (or DC and Inverter). Obviously any newer RV will likely be wired differently than than this old popup.
Regarding being nervous about Automatic Stuff", I'm much more nervous about relying on a label that says "turn xxx off before using yyy" - especially if bad things can happen.
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travellerw
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# Posted: 29 Jan 2024 12:46 - Edited by: travellerw
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I will post a quick explanation on how my RV is wired. Its a 5th wheel with ground based panels when at my cabin property. The panels can be unplugged so the RV can still be towable (and I didn't have to drill into the roof).
4 X 6V GC batteries in the front belly.
1 Renogy MPPT controller hooked to panels and batts.
1 12V off brand inverter (Mastercraft brand). Hooked to buss bar
10 AWG wire running from inverter to cutover switch next to RV electrical panel.
Cutover switch has shore power on side A, inverter on side B. The output goes to the RVs 120V electrical panel.
So basically, when the switch is over on Side B all the electrical outlets are energized from the inverter. If you switch over to Side A, then you can plug the shore power in to energize those outlets from a regular plug or generator. With this configuration, there is no way to have both live (or to accidentally have the shore power connection live from the inverter, which would be a shock hazard).
We pretty much leave the switch on Side B since the RV is at our cabin %95 of the time. Actually, we rarely even turn on the inverter as the essentials (lights, pump) operate on 12V.
Before I put in the switch, we used to just run the shore power cord up through and access panel and "plug in" to the inverter. I didn't like how that looked, so I made a more permanent installation.
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ICC
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# Posted: 29 Jan 2024 14:57
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Quoting: razmichael Regarding being nervous about Automatic Stuff", I'm much more nervous about relying on a label that says "turn xxx off before using yyy" - especially if bad things can happen.
I am in complete agreement with that statement. IMO and experience, labels and signs stating rules tend to become a part of the background clutter. A moment's brain fade and something bad could happen very quickly. Probaly nothing that will cause physical harm to you, but it may damage equipment.
An automatic transfer switch is a fairly simple and dependable relay switch. It switches both the hot and the neutral simultaneously. There are two wires (hoy & neutral) on the incoming side A and another two on the incoming side B. In the middle is a hot/neutral pair that carries the power out.
If power is coming in the A side both wires are completely disconnected from that source before side B closes. The break & make occurs quite fast and in my decades of RV use, I have never had one of these fail. I never lost any sleep over worrying about it.
The talk of using switches to manually switch things makes me a little nervous as if done incorrectly there are reasons to possibly worry.
Commercially made transfer switches switch both the neutral and the hot, not just the hot. One reason is that when there are two sources, let's say a generator and shore power, the 60 Hz cycle of each will not be in the same phase, or up-down wavy sine pattern. If the neutral is hard wired from the two sides and only the hot wire is switched there could be some piece of equipment that gets jolted and is damaged.
If there is a generator in the system there is also the issue of the neutral-ground bond. There should only be one such bond in any system. Some generators use a floating neutral (UN-bonded), while others may not. Some inverters have a floating neutral, some do not. MOST often if a generator or inverter has a built in plug in power outlet is will have a floating neutral.
This can get complicated as there is no absolute "this is the way it is done" in general terms. NEC has very specific rules about how things are done, but with the variety of equipment manufacturers and so many DIY'ers who may get things wrong I guarantee nothing when referenced in general terms.
It is simpler with an RV that has NO generator and NO inverter. The shore power is bonded (according to code) Therefore there should be no neutral-ground bonds in the RV if shore power may be used. If there is generator-only or inverter-only power a ground-neutral bonding plug may be needed to allow some electronics to work.
Anyone with an RV should own a couple of testers in order to determine whether or not the shore power they are plugging into is safe. Over the decades I have camped I have encountered shore power wiring with incorrect wiring that was dangerous.
Here is a youtube that may help explain some issues
https://www.youtube.com/watch?v=p37z_G9CLRo
And another link about Neutral-Ground bonded and un-bonded use with generators. This does pply to inverters as well.
https://www.electronicshub.org/bonded-neutral-vs-floating-neutral/
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travellerw
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# Posted: 29 Jan 2024 15:06
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Ahh... One thing I forgot to mention. In my setup you must turn off the breaker to the battery charger when energized by the inverter. Otherwise, the inverter (powered from the batteries) energizes the battery charger and tries to charge the batteries (from the batteries). Recipe for a dead battery bank pretty quickly.
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spencerin
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# Posted: 30 Jan 2024 15:51 - Edited by: spencerin
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travellerw, did you have to add the switch/breaker to the battery charger, or did it come with it pre-installed?
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Nobadays
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# Posted: 30 Jan 2024 21:55
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Quoting: ICC If power is coming in the A side both wires are completely disconnected from that source before side B closes. The break & make occurs quite fast and in my decades of RV use, I have never had one of these fail. I never lost any sleep over worrying about it.
If I'm understanding you right.... if I were to wire a receptacle directly to my inverter then plug my shore power cord into this. In your experience the built in ATS would not allow power to back feed my inverter if I were to start the onboard generator. You don't feel a separate switch is necessary.
I do know that there is no adverse affect if you are plugged into shore power and start the generator.
Thanks!
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travellerw
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# Posted: 30 Jan 2024 22:38
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Quoting: spencerin travellerw, did you have to add the switch/breaker to the battery charger, or did it come with it pre-installed?
Our trailer came with a breaker in the panel for the battery charger.
Quoting: Nobadays If I'm understanding you right.... if I were to wire a receptacle directly to my inverter then plug my shore power cord into this. In your experience the built in ATS would not allow power to back feed my inverter if I were to start the onboard generator. You don't feel a separate switch is necessary. I do know that there is no adverse affect if you are plugged into shore power and start the generator. Thanks!
Our unit has no onboard generator. So if we run a generator its a portable unit and we just plug the shore power lead into that (treating it like shore power).
If you have an ATS and do as described, then yes, you would not backfeed as you are essentially treating the inverter as shore power. The ATS would switch the inverter out of circuit (as long as you ATS has generator power preferred, many are setup the other way). HOWEVER, you would have the same issue we do where the inverter feeds the battery charger in a viscous loop killing your battery quickly. You would have to remember to turn the battery charger on and off for the different scenarios.
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gcrank1
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# Posted: 30 Jan 2024 23:09 - Edited by: gcrank1
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For the RV if it won't need to be used as an RV Id be inclined to disconnect the wires from the back of the converter box and rewire; ie, KISS.
I have in the wings an inverter with internal ATS.
My plan is to use the shore power side to be the gen input and the inverter the other.
I envision running most of the time off the inverter (for our typical lower draw loads) and fire up the gen only for big stuff, and having the ATS do the transfer to gen and when it is shut off transfer back to inverter.
Note that no loads other than perhaps an led light to two would be on during transfer.
So, will this work like I think?
Btw, Id be thinking of doing the same thing if I had an RV rather than an off-grid cabin.
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offgrididaho
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# Posted: 31 Jan 2024 10:45 - Edited by: offgrididaho
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Keep it simple. Your solar setup is as normal, panels to charge controller to batteries.
For AC, wire a proper inverter-charger in line with the AC inlet. So "shore" power (whether grid or generator) comes into the RV and directly into the inverter-charger. From there inverter charger feeds charging energy to the batteries and also feeds any AC demands downstream of it (microwave, coffee machine etc). When there is no shore power, inverter-charger draws power off the batteries, converts it and uses it to energize the 120 outlets in the RV.
With good size battery bank you can run plenty of intermittent 120v equipment off an inverter-charger. In our cabin (granted, 8 golf cart batteries and 1800w of solar) with 5,000watt Victron inverter-charger we have no issues running intermittent microwave (don't nuke something for 45 minutes!) or coffee machine (multiple cloudy days in a row we brew coffee in the drip maker like normal then pour into a thermos, sunny days we just let the drip maker run). A bigger inverter charger will pull some serious watts when charging (some are adjustable, some aren't) so be sure to size your generator accordingly.
This IMO is cleanest most flexible setup as you get quick bursts of AC power without needing generator / shore power, the inverter-charger will energize all the outlets in the RV (not just a single inverter sitting on a counter somewhere), you get quality 3 stage charger for your batteries (a lot of older RVs have more rudimentary chargers which don't handle newer battery chemistries well), no finicky switches or manual "oh yeah always do that step first" it's pretty much automatic.
To be clear, this is probably NOT the cheapest route (or lightest weight, a 3000 watt inverter charger is quite heavy and physically relatively large), but why not do it right first?
-- Bass
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Brettny
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# Posted: 31 Jan 2024 11:32
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My inverter also has a transfer switch and it's something I didnt think I would ever use..until I figured out how to properly use it for offgrid. I run my generators power to my battery charger and the 120v inlet on the inverter. This way when my generator is on all the 120v loads are on the generator and the batteries are getting charged. When the generator is off the inverter automatically switches to pull power from the batteries. It's very seamless and with a wireless remote start generator it's very easy to use and convenient. The only other way I could see making it better would be to have a inverter that has a outlet for a generator remote start.
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redwolfguild
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# Posted: 2 Feb 2024 13:00 - Edited by: redwolfguild
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OP - There is a lot of good advice here but then there is a lot of bad advice depending on what you end up buying. Every RV / Trailer comes wired differently, with different inverters or Inverter/ Charger, or Inverter/Charger with Gen backup.
There is one way to solve this problem for a 1 size fits all. You need to wire a 30 to 50-amp box at the site of the trailer. Run your wire (sized to amperage distance) to your Battery / Inverter/ Charger shack. Have your ground-mount solar system run to your shack.
In your shack decide how many amps/watts you want to run to the rv. Size your inverter to that. Then size your Battery bank to the inverter and then build your solar aray that can handle the charging of said battery bank. C rates apply so 500 amps of Flooded batteries requires different number of panels than 500 ams of Lithium.
After you build all this then you put your trailer in front. of the 30 or 50 amp plug box and plug it in with your shore power cord that comes with the RV. The built-in converter that is specific to that RV will run the rest.
Once you start changing things inside the coach and rewiring, you will be introduced to all the electrical gremlins and you will loose your mind. Keep it simple.
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gcrank1
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# Posted: 2 Feb 2024 14:08
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If the unit in the RV takes 120vac and makes it 12vdc it is a Converter.
An Inverter takes a lower dc voltage (usually 12v on RVs and inverts it to 120ac.
It will get awfully confusing if the incorrect terms are used  
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