Solar Power
For this build we decided that we wanted to be completely independent from external power sources. That meant that we needed to have a way of getting power without running the engine (in case we wanted to stay in the same place for a long period of time) and also to make sure we weren't draining the battery when using appliances and light.
Sizing
Sizing is tricky because you don't want to always worry about power but you also don't want to spend too much since solar panels are currently averaging a Euro/Watt. We decided to go with 2x100W (84W actual) solar panels, wired in parallel into an MTTP charge controller so as to charge at 12V. From the tests we get on a normal day around 10A of charging current which is around 120W, I'm sure that we can get better than that by angling the panels but for our purpose, 75% efficiency is good enough. If we consider a good 8h of sunlight we can charge 960Wh per day which is way more than we can use since our hobs, fridge and heater run off gas. The panels basically supply the phone, camera, laptop chargers, sound systems and lighting.
Installation
It took me a while to figure out installation because most builds you can find on the internet involve camper vans that have steel roofs. Our camper is the L3H3 version of the Renault Master MkII which means it has an increase roof height and that is brought by a glass fiber add-on. Glass fiber is tricky to work with because it doesn't like localised loads. The second fun addition was that since the ceiling had already been installed we couldn't easily use fasteners with a plate on each side to distribute the load on a larger area. What I opted for was rivets. It's not a great fastener as you can't remove them and reset if you mess up, but it has the advantage that you don't need to access to both sides. Each panel was fitted with 4xL brackets, bolted into the panel and riveted in 2 places into the fiberglass roof. The panels are installed at the back of the roof mostly for space constraints and because the back of the roof has a couple of stringers running across which seem to stiffen it.
Sizing
Sizing is tricky because you don't want to always worry about power but you also don't want to spend too much since solar panels are currently averaging a Euro/Watt. We decided to go with 2x100W (84W actual) solar panels, wired in parallel into an MTTP charge controller so as to charge at 12V. From the tests we get on a normal day around 10A of charging current which is around 120W, I'm sure that we can get better than that by angling the panels but for our purpose, 75% efficiency is good enough. If we consider a good 8h of sunlight we can charge 960Wh per day which is way more than we can use since our hobs, fridge and heater run off gas. The panels basically supply the phone, camera, laptop chargers, sound systems and lighting.
OffGrid Tech 100W panel (foot for scale)
Installation
It took me a while to figure out installation because most builds you can find on the internet involve camper vans that have steel roofs. Our camper is the L3H3 version of the Renault Master MkII which means it has an increase roof height and that is brought by a glass fiber add-on. Glass fiber is tricky to work with because it doesn't like localised loads. The second fun addition was that since the ceiling had already been installed we couldn't easily use fasteners with a plate on each side to distribute the load on a larger area. What I opted for was rivets. It's not a great fastener as you can't remove them and reset if you mess up, but it has the advantage that you don't need to access to both sides. Each panel was fitted with 4xL brackets, bolted into the panel and riveted in 2 places into the fiberglass roof. The panels are installed at the back of the roof mostly for space constraints and because the back of the roof has a couple of stringers running across which seem to stiffen it.
One down, one more to go
The cable penetration was a bit worrisome too because of both waterproofing and cable routing. we measured carefully to get the cable to penetrate into a cupboard (and of course we missed by a good 4 cm so the cable is inside the cabin...). We did the junction of the solar panels inside a Legrand terminal box with good ol' dominos and it works well enough.
For waterproofing we went maybe a bit overkill but you can't be careful enough. We used a Tar based SIKA waterproofing material called SIKA multiseal, one layer between the bracket and the roof, a layer of silicon between the tape and the bracket and then one layer of sika tape on the whole assembly to complete the seal. So far we've been through a couple of rain storms and it seems to be waterproof.
There is elegance in simplicity
For waterproofing we went maybe a bit overkill but you can't be careful enough. We used a Tar based SIKA waterproofing material called SIKA multiseal, one layer between the bracket and the roof, a layer of silicon between the tape and the bracket and then one layer of sika tape on the whole assembly to complete the seal. So far we've been through a couple of rain storms and it seems to be waterproof.
Final assembly
Wiring
You can't plug stuff directly into a solar panel output, in order to harvest energy from the sun, you need to have a battery/charge accumulator and a controller to ensure you don't overcharge and to regulate your voltage. There are two types of regulators CMPs and MTTPs, the MTTPs are usually more efficient in their harvest (and also sensibly more expensive) For this build I went with the best price/quality ratio a STECA PR charge module that can do both 12V & 24V. The interface is so easy even a child could use it, you basically have 3 ports, Solar In, Battery in/out, Load out. All we had to do was plug it in, no configuration needed. super happy surprise.
Happy face means you didn't screw up the wiring.
The load is connected to an inverter and a couple of 12V loads (water pump & extract fan), the inverter does the rest of the load control (1kW inverter). I have added small resettable fuses 3A but realistically I'm pretty sure that if there's a short the inverter will take care of the protection, in any case, better safe than sorry.
Final words
Done, installed in the shade, to conserve the sun.
I was dreading the installation because it involved drilling into the roof and I was afraid the glass fiber would not survive and also because it involved silicone and I hate that thing. In the end thanks to the helpful hands of my dad we were done in 1 day, all wiring and drilling and thinking. the installation so far has been through rain storms and 1,500km of highways at 110km/h. I still look in my rear view mirror every now and then to make sure the guy behind me has not received a solar panel across the face but I think it's pretty good. Ideally I would have liked to have it even lower profile to avoid air going under while on the highway (even embedded into the roof) and wired a separate battery so as to not put our mobility into the game. The inverter is doing well even though the lights flicker a bit when our laptop charger is on but that's a minor inconvenience. To improve on the setup I would get a bigger battery and a bigger inverter, I think 2 solar panels is enough for our usage.
Guillaume.
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