Solar Panel selection

[Captain Rick]

I want to fix a solar panel to the roof of my 2016 Caravelle to complement the 120aH AGM leisure battery which is connected to a Ctek D250SE. Ctek say the max power can be 200watts with no more than 23VOC. I would like a permanent installation and thought that a 200watt semi-flexible panel stuck on the roof would work - minimal extra height and no extra wind noise. However a well regarded installer that I approached says he wouldn't, and I shouldn't fix a semi-flexible panel onto a ribbed surface, like the roof of my van. He suggested I look at a different solution as he didn't use rigid panels either (too bulky and prone to wind noise). I would appreciate any advice and experience that anybody has to help me move forward.

 

[Martin Gibson]

Hello @Captain Rick , i and many others on here have fitted semi-flexible panels to our ribbed roofs. Have a good read through the many threads on solar panel installation and everything you need to know is all there. If you decide that that is definitely the way you want to go,then there are plenty of people to give advice and help you on your way

 

[VanDamMan]

Hi @Captain Rick ....have a look at this link may be of help

[Guide] Mobile Solar Panels ? . . . - How I Did It -

Mobile Solar Panels ? . . . - How I Did It - There is loads of background to this . . . . . but for now here is a vid for you all. =] Just remember W = V*A and as a general rule a good 100W panel will give you up to 6A charge with good sun. 25w = 1.5A 50W = 3A 100w = 6A 200w = 12A 300w = 18A...

www.t6forum.com

 

[Captain Rick]

Hello @Captain Rick , i and many others on here have fitted semi-flexible panels to our ribbed roofs. Have a good read through the many threads on solar panel installation and everything you need to know is all there. If you decide that that is definitely the way you want to go,then there are plenty of people to give advice and help you on your wayView attachment 87618

 

[Captain Rick]

Gosh! That's a panel and a half. I'm very impressed and thanks for the lead

 

[Martin Gibson]

That's a 300w Photonics Universe panel @Captain Rick ,they do them in plenty of other sizes including the 200w you were thinking of

 

[Captain Rick]

Thanks. I'd looked at it but it has a OC voltage of 26.8 where the Ctek will only take up to 23VOC. I'd have to go down to a 150watts in their range to meet the parameters and given half a chance I'd rather not do that.

 

[Martin Gibson]

Yes i think @Deaky had a problem running a panel with a Ctek although i am not sure of the specs. I think most people that run large solar panels use a seperate Mppt controller like the Victron. The men best suited to advise you on anything electrical are probably @Dellmassive and Martyn @travelvolts that can also supply any of the kit that you need,hope this helps

 

[travelvolts]

Thanks. I'd looked at it but it has a OC voltage of 26.8 where the Ctek will only take up to 23VOC. I'd have to go down to a 150watts in their range to meet the parameters and given half a chance I'd rather not do that.

You are stuck with a panel of 150 or 170, otherwise you will need to use a seperate regulator. I don't know of any larger panels that have a VOC of anywhere near 23 volts.

 

[Captain Rick]

Thanks for that. For interest did you have the panel with the self adhesive backing or did you use an alternative adhesive and did you fill the valleys in the roof or just allow the panel to stick to the raised areas?

 

[Captain Rick]

You are stuck with a panel of 150 or 170, otherwise you will need to use a seperate regulator. I don't know of any larger panels that have a VOC of anywhere near 23 volts.

Its weird that Ctek say you can use a panel of up to 300watts but limited to 23VOC and those two things don't quite fit together, do they?

 

[travelvolts]

We normally just use the self adhesive ones and stick to the ribs. We then just fill in at the front to prevent crud from getting driven under the panel when driving. The adhesive is incredibly strong!

 

[travelvolts]

Its weird that Ctek say you can use a panel of up to 300watts but limited to 23VOC and those two things don't quite fit together, do they?

They don't, you're right. But, there is nothing to stop you from using 2 x 150 watt panels at 23 volts each connected in parallel. Other than physical space of course!

 

[Captain Rick]

Hmmm. That's a thought but its not as elegant as a single panel and I guess it would mean cabling at the side rather than at the rear. Must re-measure the roof of the Caravelle!

 

[VanDamMan]

The issue with all setups is working backwards..matching the panel to suit the controller....However as I found out after initially fitting the Ctek to charge my battery then later adding solar at a later date..your restricted on panel size....so in my case I’ve connected two 150w (300W) in parallel to keep within the limits of the Ctek
this setup wouldn’t be ideal for roof insulations.....but if you did start the whole battery/solar journey from scratch ..you‘d choose the biggest panel that suits your needs and work the system around that.....

 

[Martin Gibson]

Yes,as @VanDamMan says,i was in that situation,as i was starting it all from scratch. I chose the largest panel i could find at the time and built the rest of the system around that after advice from Martyn. I used an ablemail dc-dc charger and a seperate Victron mppt controller for the panel which i don't think are that expensive if i remember rightly. Might not work out much different in cost to use a large panel and a seperate controller as to use two smaller panels with what you already have which,as stated above,might not be the best solution for your roof

 

[Captain Rick]

I've just been having a conversation with @Deaky and like him I too was afraid of overloading my Ctek so I emailed their support line to ask them whether their 300max watts and 23VOC were advisory or never to be exceeded. They were clear that they were never to be exceeded. I'm happy with my existing setup consisting of under drivers seat 120aH AGM battery, 95aH AGM starter battery and Ctek. It all works quite well so I'm going to try to maintain it and keep within the Ctek parameters. I think an answer could be to use 2 x 125 watt SunWorks panels each of which are 22.3 VOC mounted side by side on the roof and wired in parallel (Each is 58 cm wide so a total width of 116 cm which will fit within the max roof width of 124 cms). I think this should work but I'm still looking at other alternatives as my suggestion is a jolly expensive way of doing it.
It's a 2016 Caravelle 4motion

 

[travelvolts]

You can get away with 23.6 volts. By the time you get from the panel to the Ctek it will have dropped to 23. I'm really annoyed with Ctek. They have been aware of this situation for some time but they missed an opportunity to up the spec on the solar input when they recently updated the unit for Lithium compatibility.
In case anybody is wondering, if you over drive the solar input you will destroy the charger, there's no coming back.

 

[VanDamMan]

I've just been having a conversation with @Deaky and like him I too was afraid of overloading my Ctek so I emailed their support line to ask them whether their 300max watts and 23VOC were advisory or never to be exceeded. They were clear that they were never to be exceeded. I'm happy with my existing setup consisting of under drivers seat 120aH AGM battery, 95aH AGM starter battery and Ctek. It all works quite well so I'm going to try to maintain it and keep within the Ctek parameters. I think an answer could be to use 2 x 125 watt SunWorks panels each of which are 22.3 VOC mounted side by side on the roof and wired in parallel (Each is 58 cm wide so a total width of 116 cm which will fit within the max roof width of 124 cms). I think this should work but I'm still looking at other alternatives as my suggestion is a jolly expensive way of doing it.
It's a 2016 Caravelle 4motion

If your only option is to roof mount this post is worthless....

My setup includes 2 x 150 @ roughly £130 ea ( ridged ) stored in the van but once on location setup outside...this only works if you’ve space to store in-transit

as example

 

[Captain Rick]

Oh, that's really interesting. Photonic Universe do a 130W narrow panel (50.5cm wide so 2 side by side would be 101cms) at a much more economical price than the SunWorkd 125s. Only thing is their OCV is 23.9volts. Is this just too much? (and in parallel does it still stay as 23.9VOC?)