Advice on my system

[dirt diggler]

Ok straight into the begging for answers
I am in the process of converting an ambulance to RV, it already has a full 12V managment system with smart charge alt, battery isolator and more electrical gadgets than i can shake a stick at, these will be pared down to suit my needs as i progress, i have shore power hookup and an onboard battery charger but no inverter, i may or may not fit an inverter i don't really need one although the wiring and controls are there for it (removed before i purchased the vehicle), i have a generator if needed and my mains sockets are fed from the shore hookup or the missing inverter, i should state here i'm a mechanic of 30+ years so i know my way around a 12V system just fine BUT i allso recognise that a little knowledge is a dangerous thing hense joining here
I have spent a while searching the archives but couldn't find an exact answer i'm confident in using

My system as it stands is 4 X 100W renogy pannels (specs below), now due to roof size issues i can fit either 4 or 6 pannels to the roof (2 or 3 either side running length ways), i realise than due to living in the higher N latitude (between 51 and 57 deg) i would gain power by tilting my pannels but due to the width restriction on my roof if i tilted both sides to over 50deg the sothern pannels (or front most pannels) would shade the northenmost (rear) set (hope that makes sense ? i'll be parking facing east for sake of argument with the right side of the RV facing south), my thoughts are to tilt the northermost (rear) set leaving the southern set flat, would this cause the same issues as shading 2 of the pannels ? my thinking is there would be an unequal amount of power from the 2 sets?
So onto the actuall question, the age old dilema, (dun dun daaaaa), serial or parallel (yes i bet you knew that was coming) or do i connect 2s 2p ? or 3s 2p if i can fit another 2 X 100W in the system ?
I don't as yet have a controller (that's the next question for a recomentdation), my battery bank at the moment is 4X100Ah AGM batterys, i could fit more but they would have to be fitted on the other side of the van, not a big issue and one that will be decided after i use the RV and finalise my loads.
I should add that just to confuse matters (for me) both sets will be hinged inwards so i can park either facing east or west and tilt the rearmost set to gain extra power (ignor this part for the sake of this post i just like to add it all for compleatness and to save on your time), I think i've coverd it all but ask away as i'm sure there's more info that would help in answering these question.
Thanks for taking the time to read my meandering drivvel

PANNEL SPECS

Maximum Power: 100W	Maximum System Voltage: 600V DC (UL)
Optimum Operating Voltage (Vmp): 18.9V	Open-Circuit Voltage (Voc): 22.5V
Optimum Operating Current (Imp): 5.29A	Short-Circuit Current (Isc): 5.75A

 

[Craig]

I would do 2s 2p that gives you the best chance to maximize power when the sun is on all of it but still lets you get some power when the shading occurs. If its not hard I would set it up and test it for a few days in each scenario

 

[FilterGuy]

If you can afford it, do two separate charge controllers. That would maximize your production.

 

[dirt diggler]

Cheers guys, these are both thoughts i've had and it's good to know i wasn't way off in my thought process
I've been playing with a model, not on a PC but using card and glue using 1 inch to the foot i have a table top modle of my roof and i deffo can't go 3 pannels per side but using a gap inbetween the roof vents i can get a 5th in there which makes the set up even more confusing DOH.
Cheers again for the input, i'm off to glue 2 straws to some card i just coloured in and play ( i meen pannel tilt simulations) with a "fake" sun, i glued a battery powerd light to the wall 51 Deg off the horizontal on my table top LOL

 

[dirt diggler]

Ok been doing some research (dangerous !) i've been thinking of using a Renogy DCC50S instead of the battery isolator i currently have BUT this meens liming myself to parallel on the pannels due to its low input voltage for the solar, though that would end my series or parallel conundrum, i may have to go this route as i have a smart alt and my thinking is with just a Bat isolator if the Rv batterys are low and the alt ups it's voltage to charge them i might overcharge my vehical batterys, my head hurts
sod it i'm going to glue some cardboard models

 

[dirt diggler]

Been thinking again ! must stop this thinking lark, it's costing me money !
Rather than fit my pannels to a frame i want stiffen them by inserting alluminum box tubing inside the frame C section (running side to side or top to bottom) and bolting it in, would there be any plusses from using a heatsink paist to also use the box section to act as a heat sink to cool the pannels as well ? i dont really want to add a frame under the pannels to stiffen them as it will raise them even higher than the 40mm unistrut i'm going to use as a base for the inner hinges and outer mount/lock mech, or as a base if i use linear actuators to raise the pannels without having to clamber onto the roof?
Half assed card mock up LOL





Yellow blobs are my extractor fans and the leany over square thingamy is my actuall roof vent, straws are makedo unistrut/hinges

 

[tictag]

So onto the actuall question, the age old dilema, (dun dun daaaaa), serial or parallel (yes i bet you knew that was coming) or do i connect 2s 2p ? or 3s 2p if i can fit another 2 X 100W in the system ?

Generally speaking, with an MPPT controller, higher voltage (i.e. series panel connections) are more efficient but series connections are really bad under partial shading conditions. I agree 2S2P will be a good compromise. If adding a 5th panel, you'll need two controllers for two arrays: Array 1 = 3S1P, Array 2 = 2S1P. I mean that's fine ... I have three controllers for exactly the same reason: (1) 2S1P - left hand side, (2) 3S3P - roof, (3) 2S1P - right hand side. Obviously the side arrays will always have different solar irradiance than the roof array (note: I don't both tilting the panels, they're flexible anyway, so difficult to achieve in practice.)

i've been thinking of using a Renogy DCC50S instead of the battery isolator i currently have

Your call on what SCC you buy, obviously, but one point about the DCC50S, it has no means of data connectivity i.e. whilst it does have an RS485 data port, there are no products currently on the market to connect to it (apparently Renogy are 'working on one'). It is not compatible with either of their bluetooth or mobile devices. But having an Alternator DC-DC converter and MPPT SCC in one device is appealing. Have no idea as to the efficiency/quality of the device.

would there be any plusses from using a heatsink paist to also use the box section to act as a heat sink to cool the pannels as well ?

I'm guessing that whatever you thermal paste the panels to will be at the same ambient temperature as the panels i.e. no heat transfer. Unless you're thinking about some kind of active cooling solution, I'd keep things simple and just leave an air gap.

Other considerations:

• I know that you're keen to create an articulating roof panel system to ensure correct sun alignment, but have you stepped back for a moment and considered this? I mean, you're obviously going to get improved output by optimising array orientation, but how much additional output? More than a couple of ground-mounted, removable suitcase-style panels? How much will your articulation system cost? What are the risks of the panels detaching whilst on the road? I love the idea, but I would encourage you to stop and think whether this is the most pragmatic solution.

Edit: corrected multiple typos because apparently I can't spell worth a shit.

 

[fisherus]

I think you should try elevating the panels on the south side of your rig after setting the north side panels until you almost start to shade the north panels. Because you are laying your panels in landscape direction, minor shade will minimally affect their power production and the south side will still be lower. A pure sine wave inverter and an mppt charger will be your best bet to boost loss of panel power production. 24v system is better than 12v in your case and wire north panels together in series and south side in series and parallel with a combiner box to your charge controller.
I sincerely hope you have a very secure way to mount your panels. I have a friend who thought he had an ingenious idea to mount his panels and elevate them once he had setup but didn't think about a 45mph crosswind. If you have room to add panels in pairs I would mount them flat and make up the loss with more panels. You can parallel each series up to the maximum amount of amperage configuration of your panels and charge controller.

 

[dirt diggler]

Generally speaking, with an MPPT controller, higher voltage (i.e. series panel connections) are more efficient but series connections are really bad under partial shading conditions. I agree 2S2P will be a good compromise. If adding a 5th panel, you'll need two controllers for two arrays: Array 1 = 3S1P, Array 2 = 2S1P. I mean that's fine ... I have three controllers for exactly the same reason: (1) 2S1P - left hand side, (2) 3S3P - roof, (3) 2S1P - right hand side. Obviously the side arrays will always have different solar irradiance than the roof array (note: I don't both tilting the panels, they're flexible anyway, so difficult to achieve in practice.)

Your call on what SCC you buy, obviously, but one point about the DCC50S, it has no means of data connectivity i.e. whilst it does have an RS485 data port, there are no products currently on the market to connect to it (apparently Renogy are 'working on one'). It is not compatible with either of their bluetooth or mobile devices. But having an Alternator DC-DC converter and MPPT SCC in one device is appealing. Have no idea as to the efficiency/quality of the device.

I'm guessing that whatever you thermal paste the panels to will be at the same ambient temperature as the panels i.e. no heat transfer. Unless you're thinking about some kind of active cooling solution, I'd keep things simple and just leave an air gap.

Other considerations:

• I know that you're keen to create an articulating roof panel system to ensure correct sun alignment, but have you stepped back for a moment and considered this? I mean, you're obviously going to get improved output by optimising array orientation, but how much additional output? More than a couple of ground-mounted, removable suitcase-style panels? How much will your articulation system cost? What are the risks of the panels detaching whilst on the road? I love the idea, but I would encourage you to stop and think whether this is the most pragmatic solution.

Edit: corrected multiple typos because apparently I can't spell worth a shit.

Appreciate the reply chap as to the tilting mech it will cost nothing, i have 3 garages full of ally offcuts, box sections, extruded section, linear actuators hinges ect ect (i'm a scrapper who basicly hoards everydamthing LOL) the only cost is my time (free) and the pannels which is a cost either way.
The 2nd part as to how much extra? well that's the million dollar question i spose got to be better and living in the UK at higher latitude i knda recon i have to do it to make 400W work for my given location.
I did concider a floor deployment rack but in the UK space is allways a problem and camp sites are space limited, i could basicly have an awning out and chairs OR have a floor array not both and when boondocking i'm allways at risk of being moved on as it's frowned apon/illeagal everywhere so speed of set up/buggering off was a concideration as well as for strength the hinges will be stronger than the pannel frames, the locking mech will be the weakest point, at the mo i'm looking into lever latch toggle clamps for the non hinged end of the frame with the added securaty of the linear actuator holding it down, i have quite a few flight cases and am looking at the butterfly latches from them which also lock with a key the leading edge will have a spoiler to deflect wind pressure at speed, i got that idea from my ambulance that has a spoiler in front of the roof vents so they can be open on the move.

I really do appreciate the input, it's great to bounce ideas and possable issues off other people and get differing points of veiw, as i saida little knowledge is a dangerous thing, 35 years as a mechanic has tought me that, seeing the bodges people bring in for me to fix after they fail drives that home daily !

 

[dirt diggler]

I think you should try elevating the panels on the south side of your rig after setting the north side panels until you almost start to shade the north panels. Because you are laying your panels in landscape direction, minor shade will minimally affect their power production and the south side will still be lower. A pure sine wave inverter and an mppt charger will be your best bet to boost loss of panel power production. 24v system is better than 12v in your case and wire north panels together in series and south side in series and parallel with a combiner box to your charge controller.
I sincerely hope you have a very secure way to mount your panels. I have a friend who thought he had an ingenious idea to mount his panels and elevate them once he had setup but didn't think about a 45mph crosswind. If you have room to add panels in pairs I would mount them flat and make up the loss with more panels. You can parallel each series up to the maximum amount of amperage configuration of your panels and charge controller.

The sail effect in wind is the reason i chose to tilt the pannels sideways instead of lengthwise giving a lower profile, in the UK we get a lot of wind to go with the clouds and rain ! i spend most of my wild camping time up in the mountains in wales and scotland gold panning so it was allways a concern but one i hope to mittigate with help from here and some thought
The hinges are of the style below, from a building site safe store box but longer with 4 holes each wing, i have 10 of them, had them years, you know how it is "they will come in handy some day" when i realised i needed them at last it took me a year to find the Bstds ! they will be bolted to the (reinforced) solar pannel frame and to unistrut bolted through the roof and the box section frame of my ambulance body (i have 4 X 3M lengths to use as a base to build off of).
I have little intention of using an invertor TBH, everything i have is 12V including a sony TV/DVD (again collected in the scrap), PS classic (5V) ect ect, i have an array of cordless drills ect that are 12V, i simply removed the batterys and added a lead to plug into the vans 12v supply, been using them for years for call outs where i need a drill that wont go flat every 30 mins, i work on canal boats a fair bit with 60s/70s petrol engines (instead of just being old i'm now old AND a specialist apparently) lol so i am out on site a fair bit, sometimes a few miles from shore power and not all boats have mains power especialy the older ones i work on nowdays and i never saw the point of charging 12V batterys, to convert it to 240V then back to whatever battery voltage i have, you loose at every conversion and i don't have the solar to spare being in the UK to waist of all those conversions of voltage.
I can't add more pannels, my roof area only stretches to 5 at most, hense the tilting to get a bit more "oomf", it's really the series/parralel issue i need help with, i'm open to using 2 charge controllers if i have too, the reason i intend to hinge both sides from the inside and not just the one side is it gives me the option of parking in 2 directions instead of being locked into just the one and due to my latitude hinging both from one side will shade the rear set, lowering the front pair negates the reason for tilting in the first place (IMHO) and gets me to where i am with the twin inner hinge idea (ish) minus the 2 way option but that is just an opinion and open to changing with help from those more in the know.
IE you lot
(in the UK this is known as arse kissing) lol

Hinge style

 

[fisherus]

If you were to go with a 24V system, which I feel would be more efficient in your situation, you can use a drop down 24v/12v converter (very inexpensive) to run your 12v items without any problems. Good luck and like my grandfather once told me:"Sonny Boy, don't ever miss a perfect opportunity to shut up!"
So I will!

 

[dirt diggler]

LOL appreciate the humor mate my style indeed.
I have conciderd that in the past and i have not as yet ruled it out so again thanks for the input, now i have to make a card model of a 24 to 12 convertor, where's me glue

 

[fisherus]

Ah, about that arse you previously mentioned, reach back and give it a tug!