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Help needed for rv setup

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ian brooks

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Nov 2, 2019
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Am a little confused on which way to go with the array set up on my motorhome roof.Have purchased not yet installed,4 x100w,12v renogy panels with two more to come.Have yet to purchase the charge controller but have two lithium 90ah batteries and have taken the plunge and ordered the calb cells with a bms to give me another 100ah.Also have a samlex 3000w inverter
After reading Wills book on pros & cons of putting them in series or parallel am wondering if I could get any input on this as I am leaning towards buying the victron mppt smart 150/45 controller .Am I better off pairing up the panels to treat them as one to give me 3 x 24v then connecting each pair in parallel,or hooking them all up in series.I know I would have to buy a step down transformer also to get 12v to the batteries. Curious if the being in partial shade & losing power on all the panels needs to be a big consideration. Am in California & will be off shore power as much as I can be.Like the idea of lower amperage going to the controller.
Thanks in advance for any thoughts on this.
Great forum by the way .
 
What are you mounting the panels to? The idea of different light exposure only really becomes a problem when your panels are separated enough that they receive different amounts of light. If they’re all on a single assembly, like a van build, it’s more of an academic problem than a real world one.
 
good evening; here is my 2 cents; your charge controller output should be able to go directly to the 12v bank. no step down transformer required. for the series / parallel question I will tell you what I am doing on my 5th wheel. 3 x 330w panels. for my rig there is no way to avoid some sort of shading on at least one panel at any parking direction. so; I'm going with each panel in parallel so the shading on one won't effect the others output. you just need to make sure the wiring can handle the current. the typical reasons for putting panels in series is to increase your voltage in the wire, lowering the current you are carrying and to save on the size of wiring required. all this at the expense of possible shading taking your output to (nearly) zero during those shade times. so it's really a trade off. I would look at what possibilities you have for mounting your panels first. that might lead you to an answer on the parallel / series question. it's also very possible to try different configurations once you got them up there. don't be afraid to experiment.
 
Braddo said:
What are you mounting the panels to? The idea of different light exposure only really becomes a problem when your panels are separated enough that they receive different amounts of light. If they’re all on a single assembly, like a van build, it’s more of an academic problem than a real world one.
Click to expand...
I'll be putting them on my motorhome roof, I will weld up aluminum frames with legs to minimize holes and once all 6 are up there they will be pretty close to one another ,will have two rows of three end to end,its 24ft total.Thanks for the reply.
 
Last edited:
backwash said:
good evening; here is my 2 cents; your charge controller output should be able to go directly to the 12v bank. no step down transformer required. for the series / parallel question I will tell you what I am doing on my 5th wheel. 3 x 330w panels. for my rig there is no way to avoid some sort of shading on at least one panel at any parking direction. so; I'm going with each panel in parallel so the shading on one won't effect the others output. you just need to make sure the wiring can handle the current. the typical reasons for putting panels in series is to increase your voltage in the wire, lowering the current you are carrying and to save on the size of wiring required. all this at the expense of possible shading taking your output to (nearly) zero during those shade times. so it's really a trade off. I would look at what possibilities you have for mounting your panels first. that might lead you to an answer on the parallel / series question. it's also very possible to try different configurations once you got them up there. don't be afraid to experiment.
Click to expand...
 
Evening to you Backswash. I will be welding up some aluminum frames to mount the panels too,to minimize holes in the roof & also enable me to remove a panel without unscrewing from the roof.With my configuration of vents on the roof will be mounting them in pairs so maybe that will lend itself to me having 3 parallel pairs.Your right though ,I can change things around if need be and will wire this appropriately .Am happy I don't have to buy another component.Thanks for the reply.
 
I would do 2s 3p once you or 3s2p once you have them all together this will keep amps down and minimize shading issues. 24 ft in a campground or anywhere boondocking does leave the possibilities for shading on some portions at some time. But no matter what I would do at least 2s first this will allow charging under lower light conditions.
 
ian brooks said:
I'll be putting them on my motorhome roof, I will weld up aluminum frames with legs to minimize holes
Click to expand...
It sounds like it’s not a likely problem, then. As for your welded frame and drilling holes. I have my panels sitting on 4” aluminum feet at the corners, and glued to my van roof with Sikaflex 11FC construction adhesive. Let it cure for 24 hours and it’s not shifting, and no drilling/heavy frame.
 
Braddo said:
It sounds like it’s not a likely problem, then. As for your welded frame and drilling holes. I have my panels sitting on 4” aluminum feet at the corners, and glued to my van roof with Sikaflex 11FC construction adhesive. Let it cure for 24 hours and it’s not shifting, and no drilling/heavy frame.
Click to expand...
I could save myself a lot of work going that route.I'm old school ,but I guess its time to trust these adhesives out these days .I'll give it a try , clean & scuff up the aluminum roof to get a good key.I know Will talks about using the outdoor double sided tape.not sure i'm ready to trust that 100% but think I can get on board with the silkaflex.
Thanks for the input.
 
May I suggest using the Renogy DCC50S 12V 50A DC-DC On-Board Battery Charger with MPPT as your controller. If you have a class A RV the big advantage of the DCC50S is it will switch the alternator from charging your starting batteries to your house batteries.
Will has done a review on this controller.
 
you mentioned being able to remove one or two panels: One design decision I made was to go with 2 100/50 victron smart controllers with an existing 3x330 watt panels for a total of 990w. each controller can handle a total of 2 panel outputs. (either series or parallel). this leaves me two great future growth options. a) I can add a 4th panel in the future for 1.3kw with out changing the solar charge controllers. and b) since we're frequently in the shade in the pacific northwest. I can remove one or two panels during the summer making them mobile on the ground and connect them to one dedicated charge controller. leaving the other two panels up top and still able to charge via the other charge controller. this will give me the best options while boondocking in the trees. Power demand in the summer will be minimal so just one 330w panel should be enough once I place it in a sunny spot. while during the winter (and out in the desert) I will want to keep batteries charged up on cloudy days and to keep the furnace going at night. it's a little bit extra to get 2 charge controllers but will be worth it in the long run.
 
backwash said:
you mentioned being able to remove one or two panels: One design decision I made was to go with 2 100/50 victron smart controllers with an existing 3x330 watt panels for a total of 990w. each controller can handle a total of 2 panel outputs. (either series or parallel). this leaves me two great future growth options. a) I can add a 4th panel in the future for 1.3kw with out changing the solar charge controllers. and b) since we're frequently in the shade in the pacific northwest. I can remove one or two panels during the summer making them mobile on the ground and connect them to one dedicated charge controller. leaving the other two panels up top and still able to charge via the other charge controller. this will give me the best options while boondocking in the trees. Power demand in the summer will be minimal so just one 330w panel should be enough once I place it in a sunny spot. while during the winter (and out in the desert) I will want to keep batteries charged up on cloudy days and to keep the furnace going at night. it's a little bit extra to get 2 charge controllers but will be worth it in the long run.
Click to expand...
I like that idea as I wanted to have a mobile panel anyway.If i make some sort of quick release mechanism for on or two of the panels closest to the ladder then after using them on the ground I put them back & no storage problem.I can find a cheapo charge controller that I can designate for the mobile panels.
AES said:
May I suggest using the Renogy DCC50S 12V 50A DC-DC On-Board Battery Charger with MPPT as your controller. If you have a class A RV the big advantage of the DCC50S is it will switch the alternator from charging your starting batteries to your house batteries.
Will has done a review on this controller.
Click to expand...
Have looked at that,but that would mean linking up the 6 panels in parallel as it has a 24v max input.My rig is a 24ftclass c .Seriously looked at buying that,but am leaning towards the 150/45 controller.
 
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