Adding portable solar panel March 05, 2021, 10:42:00 am I know that this subject has been discussed before, but I’ve never found exact clarification. I currently have two factory install solar panels on my 2006 midbath, and I Would like to sometimes use a portable solar panel to get out from under trees etc. I’m looking at the renergy portable panels. My question is, can I simply connect the clips directly to my positive and negative on the two house batteries, Or would I need to connect it somewhere before it gets to my Blue Sky charge controller?Anyone actually do this and is it really simple or does it require some specific skill or knowledge?
Re: Adding portable solar panel Reply #1 – March 05, 2021, 10:52:33 am Scroll down to the Q/A section (assuming you are looking at solar "suitcases"). "Renogy systems are designed to make direct battery connections."Renogy Folding Solar SuitcasesCharles 1 Likes
Re: Adding portable solar panel Reply #2 – March 05, 2021, 12:03:41 pm Quote from: Charles & Donna - March 05, 2021, 10:52:33 amScroll down to the Q/A section (assuming you are looking at solar "suitcases"). "Renogy systems are designed to make direct battery connections."Renogy Folding Solar SuitcasesCharles Thanks and I looked at this. I am thinking perhaps I didn't ask the question correctly. I guess that I am really asking if I can have two different but parallel charge systems directly connected to the batteries?
Re: Adding portable solar panel Reply #3 – March 05, 2021, 12:21:37 pm Quote from: Jackhiett - March 05, 2021, 12:03:41 pmI guess that I am really asking if I can have two different but parallel charge systems directly connected to the batteries?Yes, you can connect two different arrays and charge controllers to the same battery bank. The Array 1 and Array 2 voltages could be different. And you can connect more than two arrays and charge controllers - all in parallel. Note - This only applies if the added solar array has it's own controller.Also, you already have three different charging systems tied to the house battery bank in addition to the house solar system; when the engine is running, when you run the generator, or when you are connected to 120V and the converter is on.Charles 2 Likes
Re: Adding portable solar panel Reply #4 – March 05, 2021, 12:45:39 pm Quote from: Charles & Donna - March 05, 2021, 12:21:37 pmYes, you can connect two different arrays and charge controllers to the same battery bank. The Array 1 and Array 2 voltages could be different. And you can connect more than two arrays and charge controllers - all in parallel. Note - This only applies if the added solar array has it's own controller.Also, you already have three different charging systems tied to the house battery bank in addition to the house solar system when the engine is running, or when you run the generator, or you are connected to 120V and the converter is on.CharlesVery good explanation. I can’t think of any downside. Sounds like something I can use my stimulus check for. Now I need to pick out the perfect one that includes controller and get long enough cables, all at the best price. The Renegery site looked pretty good and I can get through Amazon I believe. Thanks
Re: Adding portable solar panel Reply #5 – March 05, 2021, 12:58:19 pm Greetings, I have been using the exact setup that you are proposing for the last 6 months and it has worked perfectly. I have the Renogy 200 watt Eclipse Solar Suitcase. As long as you use the included solar controller and set it to your type of batteries you should be fine. Just as an aside, I also use the panels to charge my Goal Zero(GZ) YETI 1000 on occasion and this also works fine as long as you disconnect the Renogy charge controller and just direct connect the panels to the generator. The GZ already has a controller to manage the input. I am pretty sure you will really appreciate the additional flexibility your setup provides for power generation. Matt 4 Likes
Re: Adding portable solar panel Reply #6 – March 05, 2021, 01:14:55 pm Me again I forgot to mention that you might consider purchasing (2) 25' power cables. 25' seems like plenty but I have found that 30-40% of the time that additional 25' has allowed a more optimum panel position for me and often reduces the amount of adjusting required over the course of a day. I just like having as much flexibility as possible(or maybe I am just lazy:) and these cables do not require much storage space. Matt
Re: Adding portable solar panel Reply #7 – March 05, 2021, 01:17:01 pm Now I’m thinking that I can’t believe I haven’t done this before. Thanks to you guys. 1 Likes
Re: Adding portable solar panel Reply #8 – March 05, 2021, 04:55:54 pm Quote from: Mattb - March 05, 2021, 01:14:55 pmMe again I forgot to mention that you might consider purchasing (2) 25' power cables. 25' seems like plenty but I have found that 30-40% of the time that additional 25' has allowed a more optimum panel position for me and often reduces the amount of adjusting required over the course of a day. I just like having as much flexibility as possible(or maybe I am just lazy:) and these cables do not require much storage space. MattDoes the extension cable go between panels and controller, or between controller and battery? Are they 10 gauge?
Re: Adding portable solar panel Reply #9 – March 05, 2021, 10:37:54 pm Yes, the cables connect from the the solar controller to the battery. I purchased 10 gauge cables. If you end up buying a Renogy 200 watt portable suitcase the solar controller comes connected to the back of one of the panels right in the suitcase. It is water and weatherproof. I do believe it is easy to remove if you prefer to surface mount it permanently somewhere on your coach. Matt
Re: Adding portable solar panel Reply #10 – March 05, 2021, 11:57:00 pm Most excellent and thank you. Perfect
Re: Adding portable solar panel Reply #11 – March 06, 2021, 07:12:44 pm A thread on and about my experience on this very issue .....cheap but very doableHomemade Portable Solar Panel Builtglen 2 Likes
Re: Adding portable solar panel Reply #12 – March 08, 2021, 02:55:44 pm One way to get your 25 or 50 ft distance is to buy 2 25ft outdoor extension cords (up to 10 ga. are readily available for reasonable prices) and cut off the male end of one of them, leaving a couple feet of cord on it. Attach the cut end of the long piece to your controller, and attach the short piece to whatever you will be using to connect to your battery (maybe large alligator clips if connecting directly to your battery). When all you need is 25 ft. just plug the two together, but when you need 50 ft. just put the other 25 ft. cord between them. Rich - Birch Bay, WA
Re: Adding portable solar panel Reply #13 – March 08, 2021, 04:42:22 pm One more idea, if you don't mind spending a little more and you want 10 ga., buy 2 30 AMP RV extension cords ($40 each on Amazon) (www.amazon.com/Conntek-14363-Extension-Black-25-Feet/dp/B00F17Q8BM/ref=sr_1_26?crid=1IGLNIBEIMZKP&dchild=1&keywords=10+gauge+extension&qid=1615238921&refinements=p_n_feature_keywords_two_browse-bin%3A7065062011%2Cp_36%3A1253529011&rnid=1243644011&s=lamps-light&sprefix=10+guage+%2Caps%2C271&sr=1-26) and do as I described in previous post. Advantage there is if you don't need it for the solar panels it is available if and when you need an extension for normal RV AC.Rich As an Amazon Associate Lazy Daze Owners' Group earns from qualifying purchases.
Re: Adding portable solar panel Reply #14 – March 08, 2021, 06:34:36 pm "buy 2 30 AMP RV extension cords..."If I understand what you're saying, that would mean using 30A RV plugs and sockets for your solar panel connections. In order to avoid exposed live terminals, you'd want to mount a 30 A Marinco or SmartPlug power inlet on the coach--similar to the existing shore-power inlet--and connect that to the solar controller's input side.Maybe I'm being over-cautious here, but that seems potentially hazardous. Of course, you as the original owner would never make the mistake of plugging your shore power cord into the solar power inlet (would you?)... but what about the next owner? Doing that would result in a catastrophic failure of the solar controller, and possibly a fire, given that it's expecting 18 VDC on those inputs, and all of a sudden it's seeing 120 VAC.It just doesn't seem like a good idea to use 120V 30A hardware for a low-voltage DC circuit. 3 Likes
Re: Adding portable solar panel Reply #15 – March 08, 2021, 07:26:16 pm Or something like thisAmazon.com: 10 Gauge 10AWG One Pair 30 Feet Red + 30 Feet Black Solar Panel...Comes in all sorts of lengths. glen 1 Likes As an Amazon Associate Lazy Daze Owners' Group earns from qualifying purchases.
Re: Adding portable solar panel Reply #16 – March 08, 2021, 08:33:09 pm Quote from: Andy Baird - March 08, 2021, 06:34:36 pmIt just doesn't seem like a good idea to use 120V 30A hardware for a low-voltage DC circuit.I'm in 100% agreement with Andy, mixing high voltage plugs with low voltage applications is a recipe for disaster.There are plenty of low voltage plugs to choose from that will not cause potential issues.Running extra-long extension cords for solar panels can lead to significant voltage drop and less effective charging unless the wire size is upgraded accordingly. Volage drop makes a big difference in charging circuits.Larry 1 Likes
Re: Adding portable solar panel Reply #17 – March 08, 2021, 11:33:24 pm There’s something we haven’t talked about with regard to portable panels, and it’s a big potential “gotcha.” A controller that's mounted on the panel (as in the case of many "suitcase" systems) is convenient, but it puts out a voltage suitable for charging your batteries--much lower than the voltage straight out of a solar panel. That means voltage drop—already a concern with long connecting cables—is even worse. I’ll go into detail in my next message, but let me summarize.Suppose you have a 200 W solar suitcase with built-in controller, connected to your batteries with a 35' 10-gauge extension cord. Your voltage drop is going to be 6.2%. That means instead of getting the 14 V they need, your batteries will be getting only 13.1 V. They won't ever charge properly at that voltage!Bottom line: if possible, avoid suitcase solar panels that have built-in controllers. (Many of these are cheap, inefficient PWM controllers, which is another strike against them.) And if you must buy one of these, make your connecting cable as short and as heavy gauge as possible. If you buy one of these controller-equipped suitcase systems and put it at the end of a twenty- or thirty-foot cable, don't be surprised if your batteries never get a full charge. 2 Likes
Re: Adding portable solar panel Reply #18 – March 08, 2021, 11:33:40 pm Important: the following assumes you have an MPPT (not PWM) charging controller that can handle more than 18 V, and that the controller is in your coach--not on the panels. See my last post for the reasons."There are plenty of low voltage plugs to choose from that will not cause potential issues."I use MC4 connectors, but trolling motor connectors are another possibility. I carry a 10' and a 25' extension cable (Ancor 10/2) for my portable solar panels. I use the 10' cable when I can, the 25' cable when necessary, and both together once in a blue moon.With long cables, voltage drop is a serious concern. Assuming #10 cables, the voltage drop for 200 watts of 18V panels wired in parallel would be as follows:10' - 1.4%25' - 3.4%35' - 4.8%As you can see, with a 35' extension cord you lose almost a volt, and with an 18V setup that's serious. That's why I connect my portable panels in series. They are 20 V panels, so instead of 18 V, I'm putting 40 V through the connecting cable. Thus my numbers for 200 watts of panels would look like this:10' - 0.6%25' - 1.5%35' - 2.1%That cuts my voltage drop to less than half, compared to running panels in parallel at 18 V. To achieve such small voltage drops at 18 V, you'd have to go from #10 to #6 cable. That's a lot more expensive, heavier and bulkier. (And you can't fit MC4s onto it.)In short, if you can put your portable panels in series, you'll cut your voltage drop in half. Given the long extension cords we've been talking about, that's a huge benefit. 3 Likes
Re: Adding portable solar panel Reply #19 – March 09, 2021, 12:21:18 am Quote from: Andy Baird - March 08, 2021, 11:33:40 pmImportant: the following assumes you have an MPPT (not PWM) charging controller that can handle more than 18 V, and that the controller is in your coach--not on the panels. See my last post for the reasons."There are plenty of low voltage plugs to choose from that will not cause potential issues."I use MC4 connectors, but trolling motor connectors are another possibility. I carry a 10' and a 25' extension cable (Ancor 10/2) for my portable solar panels. I use the 10' cable when I can, the 25' cable when necessary, and both together once in a blue moon.With long cables, voltage drop is a serious concern. Assuming #10 cables, the voltage drop for 200 watts of 18V panels wired in parallel would be as follows:10' - 1.4%25' - 3.4%35' - 4.8%As you can see, with a 35' extension cord you lose almost a volt, and with an 18V setup that's serious. That's why I connect my portable panels in series. They are 20 V panels, so instead of 18 V, I'm putting 40 V through the connecting cable. Thus my numbers for 200 watts of panels would look like this:10' - 0.6%25' - 1.5%35' - 2.1%That cuts my voltage drop to less than half, compared to running panels in parallel at 18 V. To achieve such small voltage drops at 18 V, you'd have to go from #10 to #6 cable. That's a lot more expensive, heavier and bulkier. (And you can't fit MC4s onto it.)In short, if you can put your portable panels in series, you'll cut your voltage drop in half. Given the long extension cords we've been talking about, that's a huge benefit.Here's a good explanation of the difference between MPPT vs PWM solar controllers: https://www.solar4rvs.com.au/buying/buyer-guides/choosing-the-right-solar-charge-controller-regulat/Chris 2 Likes
Re: Adding portable solar panel Reply #20 – March 10, 2021, 06:13:16 pm This may up being a long post, so be warned, but maybe it will shed a little more light on solar systems, both on top and portable. First let me say that I'm a pretty practical guy, so things like cost, weight and space are all important to me. So, with that in mind, going back to one or two of my previous posts on this subject, I suggested ways to use other useful cables to extend the distance between portable solar panels and the rig. I should have put in a disclaimer that if you didn't feel comfortable with the difference between 12 volt DC and 120 volt AC systems you should not try it at home. With that out of the way, I'd like to respond to Andy's posts. 1st, the second post. I agree, with all he had to say, and if portable systems of 200 watts or more with no roof mounted solar is all you have, I would say his method is should be your method of choice. I was one of the first on this forum to recommend putting panels in series, and actually ran tests on my panels, series vs parallel and reported my results back in 2005 or so. Most said I was nuts because of shade. Oh well, time and ideas change, but I still say, that for most folks who want to add to their factory mounted panels you can at least double their capacity without changing wiring by putting them in series. One important thing to think about, if you use Andy's method for portable panels, in my opinion, you MUST mount that MPPT controller as close as possible to the battery bank.Now Andy's 1st post. The way a PWM controller works is to turn the voltage from the panels on and off for varying pieces of time. As a result, the battery will always see the voltage the panel is putting out, minus the loss in the cable. Therefor what he said about a battery never seeing enough voltage to fully charge it may be true if it were a MPPT controller mounted on the panels but not a PWM. It might take a little longer, but it would take a really long cable to reduce 18 or so volts from the panels to less than 15 volts to not fully charge most batteries. Both types of controllers rely on sensing the battery voltage, and the difference in voltage between sensing and charging can make them both crazy with long distance which is why an MPPT controller should always be close to the battery....better for a PWM controller too, but not as important.So, lets go back to the original post. As I recall, our poster had 200 watts of solar on the roof and wanted info on adding portable solar when he was parked under the shade. In his situation, again remembering my practical nature, I would recommend a 100 or 200 watt suitcase with a waterproof PWM controller mounted on the panels. ( If it were me, I would order 2 100 watt panels , a waterproof PWM controller and build it myself...again, I'm practical and cheap). Talk about being cheap, if a person was willing to monitor the battery voltage, one might not need a controller at all. Just connect the panels (wouldn't recommend this for more than about 100 watts) thru a diode (to prevent discharging the battery) and monitor the battery voltage. As I recall, Trojan recommends 14.8 V as a daily charge and then disconnect it. Not a recommendation for most, but then again, something to think about.RichRich - Birch Bay, WA 3 Likes
Re: Adding portable solar panel Reply #21 – March 10, 2021, 06:36:29 pm Thanks to all who have contributed to this portable solar panel thread. This is what our members do best - provide valuable Lazy Daze and general RV technical information to those of us who are technology/mechanically challenged, which includes me.🙂Chris
Re: Adding portable solar panel Reply #22 – March 11, 2021, 12:22:03 pm One more thing that should be mentioned when talking about adding portable solar is fusing. It may be well understood, but it is extremely important to remember to fuse anything new that you attach to a battery as close to the battery as possible. For portable solar, it should be sized by considering both the safe current handling capacity of the cable used (probably 30 A for 10 ga. cable) or the maximum current expected from the panel(s) (probably 15 A for 200 Watts of solar panel) whichever is less. Hopefully that will always be the maximum solar panel current. In my opinion, fusing between panels and controller is rarely if ever necessary, but if it makes you feel better, put one in there too. 1 Likes
Re: Adding portable solar panel Reply #23 – March 11, 2021, 01:33:32 pm Thank you Rich for your succinct and straightforward explanation of how a PWN and MPPT controller would interact in the described portable set up. My experience over the last year with a 200 watt Renogy solar suitcase matches your description perfectly, i.e., the charge time increases somewhat when I add a second 25' power cable extension but can still achieve a full charge. Thanks again to you and everyone else who has contributed to this thread. Once again, I feel like I am more knowledgeable after reading everyone's thoughtful contributions.Matt
Re: Adding portable solar panel Reply #24 – March 11, 2021, 01:52:55 pm "what [Andy] said about a battery never seeing enough voltage to fully charge it may be true if it were a MPPT controller mounted on the panels but not a PWM. It might take a little longer, but it would take a really long cable to reduce 18 or so volts from the panels to less than 15 volts to not fully charge most batteries."That's a good point. Using my example (200 W of 18 V panels connected in parallel, with a 35' cable), with a PWM controller mounted on one panel you'd see 0.86 V drop in the cable, so you'd still have more than 17 V hitting the batteries. This setup would fully charge your batteries, contrary to what I said.If you wired those same two panels in series and used an MPPT controller mounted close to the batteries, you'd get significantly faster and more efficient charging... and I hate to throw away potential solar power. But a solar suitcase with a built-in PWM controller is a convenient, off-the-shelf solution, no denying that. If your needs are modest, that could be your best bet. 2 Likes
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