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Mr. Scott 
Groupie 
Joined: 08 Jun 2017 Online Status: Offline Posts: 46 |
 Topic: 12 volt only solar setup?Posted: 23 Aug 2021 at 3:00pm |
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I'm a big electronics/solar newbie. My current solar set-up is a folding panel w/charge controller that clamps onto the battery--simple, effective, but not much energy, and I plan on going to 200--300 ah lion battery pack to run a fridge we'll be installing--in addition to furnace and lighting. So, I want to install 300 watts or so of panels and run all the 12 volt stuff. No need or desire for inverter stuff. Oh, I need to install a 12 volt station for charging phones. So, here's my perhaps stupid newbie question(s): Would it be possible to run the existing battery connections through a charge controller and then run the solar panels through their own charge controller, all feeding through busses, etc. and so to the lion battery pack? That way the alternator + shore power would use the existing wires but be "controlled" for charging lion batts? Seems to me you just need to control how the batts are charged, and the existing wiring should be good for all the 12 volt stuff, yes? Also, ideas on where/how to route wires from solar panels? I've got a 2013 R178. I'm a bit intimidated by the whole project, but I'm going to take it slow and make it happen. Just getting my feet wet and my brain introduced to all this stuff. Thanks so much for the collective wisdom here! Cheers, Scott
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Colt
Senior Member 
Joined: 16 Nov 2019 Online Status: Offline Posts: 383 |
Posted: 23 Aug 2021 at 5:09pm |
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It's not too hard. You only need to make one change to your 'pod.
You will need to change your "converter" (really just a battery charger and behind your power panel) to one designed for Li batteries. To run the refrigerator on 12V long term, you might need a bigger battery bank. Running your panels and their charge controller in parallel with the 'pod's converter is a valid design and keeps things simple. Find/calculate the power draw you will use over 24 hours. Multiply that by 2 or 3 for the number of days you expect to be cloudy with no solar generation. That will be in watt-hrs. Convert to amp hours using 13.5V for Li batts (don't pull LiPO4 below 13.1V) Add 20% so you don't over discharge the batts. That will be your battery bank size in A-hr. Size your panels to fully charge the batteries in 5 hours (a days worth of full sun) while still running your stuff, too. Again, use 13.5V. I have found on my home system that running the panel voltage above the battery voltage (24v on the panels and a 12v battery) yields a few extra minutes of charging at each end of the day. |
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John
'16 R-Pod 180 |
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offgrid
Senior Member
Joined: 23 Jul 2018 Online Status: Offline Posts: 5290 |
Posted: 23 Aug 2021 at 11:58pm |
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I'm assuming you will be changing over to a Danfoss/Secop compressor fridge and not trying to run the horribly inefficient (when run electrically) absorption fridge that comes in the rpods. As Colt suggests, you will not be able to run the original fridge on 200-300 amphours. That battery size range will probably be just fine with the Danfoss compressor fridge.
As for all the changes needed to convert to Li from lead acid, StephenH has a nice write up of the series of mods he did for that. You need to change the converter, solar charge controller, and, if you want to charge from your tow vehicle alternator, you will need a DC to DC converter for that. The only thing he did that I don't think is necessary is running a separate 12V supply connection to the trailer from the TV. You can't run through 2 charge controllers in series (or through a charge controller from the rpods converter) if that's what you're suggesting. But if you buy a new solar charge controller set up for Li batteries you probably won't need to use the old one, if your new solar modules are also nominally 12V ones. Solar modules of different power ratings can be connected in parallel as long as they have the same voltage rating. But, as I commented in another post this week the most cost effective way to get 300-400 watts is to buy a residential or industrial spec solar module. Thosd operate at higher voltages and would need an MPPT charge controller. So you should decide on what solar modules you're getting and how/where you will be mounting them first. Cable sizes shouldn't need to change for the current levels you are suggesting. As long as the DC/DC converter is limited to no more than 30A and you get an industrial/residential solar module you can run 10 gauge for those circuits. For the run from the charge controller to the battery I might go with 6 gauge because when the MPPT steps voltage down current goes up. If you get 12V modules and run them in parallel then I'd go with 6 gauge all the way. |
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1994 Chinook Concourse
1995 RV6A Experimental Aircraft 2015 Rpod 179 - sold |
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0ttr
Newbie 
Joined: 01 Aug 2016 Online Status: Offline Posts: 21 |
Posted: 25 Aug 2021 at 12:31am |
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I am doing something similar for a 2013 Rpod 177. I bought a SOK LiFePO4 12v 100Ah battery. Because it's Li, I mounted it inside the Rpod under the seat near the electrical panel. I found the 12v to the existing panel/converter and spliced in the battery. I removed the lead acid battery. In theory, I could patch the connections and add the external battery back in--it's reversable, but I don't intend to do that. What I did not do is replace the existing converter. Instead, in the splice I added a Victron BMV-712 smart battery monitor. There's instructions for setting it up on youtube and at battle born battery's website. This uses bluetooth to a phone app. This device monitors the battery and controls the charge. I hooked it all up and the converter started running its cooling fan, which made me nervous, but sure enough, the battery charged up, the converter shut down, nothing ever got hot, and it all runs perfectly. I have purchased a 200w solar panel. I do not yet have a charge controller for it yet, but when I get one, I'll mount everything and patch it in. The complicated part is that I'm going to run the cables down the space in the wall behind the toilet where my other control panels are mounted. I have decided to buy a small access panel to install in the wall near the floor so I can manage the cables as they will have to go into the floor and follow the existing "conduit" along the bottom of the trailer to the battery and BMV. The BMV unit has about 15 feet of cable to run the other direction. I don't need it mounted as I have the app, but it will look good next to the charge controller and other panels. I'm a bit nervous about drilling into the roof, but I have the cable mount and I know the right location so it shouldn't be too bad I hope.
Like you, it's not a priority to hook it all up to 120v. If I want to run my A/C or convection oven, I have a generator for that--there's not enough roof and space for all the power needed from solar. That said, there are quality pure sine-wave inverters that I could install in the space near the battery and just have an outlet. That's several hundred dollars at minimum for such an option however and it really won't run anything I'd want to run--it'd be just for the odd appliance, so it's not a priority for me. Also, they have their own fans so I'd have to vent the space to dissipate any heat. |
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Mr. Scott
Groupie
Joined: 08 Jun 2017 Online Status: Offline Posts: 46 |
Posted: 25 Aug 2021 at 8:37am |
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Wow, guys! Thanks so much for the feedback. That BMV Smart battery monitor sounds like the ticket! I'll look into it. I was thinking I'd mount the battery somewhere like you suggest, Ottr. I could put the LCD batt screen on the face of the cabinet below the seat there on the left side of the doorway facing out. And with the blue tooth App, I'd have easy access to status. So that monitor is the charge controller, basically, taking care that the 12v coming from whatever source in the RPod is doing its thing properly? I know not to put the solar panel charge controller in line with any other. That would be a separate system going strait to the batts. via a buss connector. Now, how are you going to locate the correct place in the roof to drill for the solar panel wires? That has me stumped. I was thinking I might have to run them on the outside through black covering mounted along the side of the trailer where it would blend in reasonably and then have it come up underneath basically in the front where it would be easy to drill a hole for that and rerouting the existing battery connectors, but if I can get them straight into the roof and down, that would be much preferred. PS: Any chance you could post a pic or two of what you've done? Oh, and where did you find the wires and how route them?
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StephenH
podders Helping podders - pHp
Joined: 29 Nov 2015 Location: Wake Forest, NC Online Status: Offline Posts: 6289 |
Posted: 25 Aug 2021 at 10:43am |
1. It allowed me to install a battery isolation solenoid so that the DC to DC charger would not be trying to drain the vehicle battery. It also isolates in reverse. The higher voltage LiFePO4 battery does not feed back through the connector and fool the alternator's controller into thinking the vehicle battery is charged. 2. It allowed me to run a heavier gauge wire since the wire size in the Frontier's 7-way connector was inadequate for the load the DC to DC charger would have been drawing. In addition, Renogy specified the gauge wire to be used and the fusing. The stock Frontier wiring did not meet that specification. 3. Since I was relocating the battery to the inside, and installing the DC to DC charger inside, I would have needed to run wiring regardless. I tried running the DC to DC charger from the 12V circuit from the vehicle. It ended up being a situation where it was like the battery was trying to charge itself. I found I needed to isolate the battery charge function from the regular RPod circuits for charging as opposed to load. Isolating the charging from the load side was the solution, thus my installation choices. Other than that, I think you did a fine write-up of the changes needed. The converter would definitely need to be changed, but in some of the newer ones, the converter is not a separate module. That would be a complication. I saw a NoBo that was built that way. It is likely that the solar charge controller has a way to reprogram it, likely via DIP switches, so that it will not need to be changed. Even the DC to DC charger needed to be set for the LiFePO4 profile.
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StephenH
Happy is the man that findeth wisdom,... ouR escaPOD mods Former RPod 179 Current Cherokee Grey Wolf 24 JS |
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offgrid
Senior Member
Joined: 23 Jul 2018 Online Status: Offline Posts: 5290 |
Posted: 28 Aug 2021 at 12:44am |
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For sure if you need to charge from the TV at more than 30A then you will need a higher ampacity connector. 30 is typically the max for a 7 way and the wiring to it from the TV battery is generally 10 gauge with a 30A breaker at the battery. For most folks, 30A is plenty and limits the load on the TV alternator.
As for the DC/DC converter trying to power itself, that shouldn't be an issue. As long as the 12V supply from the TV goes only to the DC/DC converter input, and nowhere else, you should be fine. The DC/DC converter output then connects normally to the trailer 12Vdc buss. |
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1994 Chinook Concourse
1995 RV6A Experimental Aircraft 2015 Rpod 179 - sold |
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StephenH
podders Helping podders - pHp
Joined: 29 Nov 2015 Location: Wake Forest, NC Online Status: Offline Posts: 6289 |
Posted: 28 Aug 2021 at 8:40am |
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Well, that was the problem. The 12V supply line from the TV did not go just to the DC to DC input. If that had been the case, it would have been much easier. I ended up disconnecting that wire from the little breaker underneath the front of the trailer so I could use just the circuit I installed and not feed back through the connector.
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StephenH
Happy is the man that findeth wisdom,... ouR escaPOD mods Former RPod 179 Current Cherokee Grey Wolf 24 JS |
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Mr. Scott
Groupie
Joined: 08 Jun 2017 Online Status: Offline Posts: 46 |
Posted: 28 Aug 2021 at 8:53am |
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So is there some sort of plug-and-play unit that I can get to replace the existing converter? Our RPod is a 2014, I think.
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offgrid
Senior Member
Joined: 23 Jul 2018 Online Status: Offline Posts: 5290 |
Posted: 28 Aug 2021 at 11:51am |
Something is not right. If you cut the 12V line from the TV immediately after it leaves he trailer side of the connector and splice in the DC DC converter at that point then there shouldn't be any backfeed into the TV 12v system. All the other +12v lines coming through the connector are dedicated to some lighting or braking function controlled and powered by the TV. The only one of those lines that should ever get connected into the trailer 12v system is the breakaway brake line, and that should only happen when the Bargeman connector has been pulled. o Sounds like maybe there is a wiring issue somewhere in the trailer. |
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1994 Chinook Concourse
1995 RV6A Experimental Aircraft 2015 Rpod 179 - sold |
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12 volt only solar setup?