That is either a colossal amount of Solar or a very high installation cost. They are fairly straight forward to fit yourself and you could install a 250 W panel including controller and cabling for around £360.0It would cost me at least a £1000 to convert to Solar and, in my mind, that's an awful lot of nights EHU hookups to RELIABLE electric at an extra £5 per night.
For the self sufficiency you are/were looking for I think you are short of storage capacity so need to double the lithium, I guess we are reasonably heavy users of 240v and with limited solar due to weather conditions 200ah would only see us a couple of days, OK if you want to move every couple of days, we are currently -221ah in our batteries but luckily this is not even 50% so we are still OK, re your cables I would say they are undersized as far as efficiency is concerned we have 6mm from each panel and then 16mm from the controller and can get well over 30A from 520 watts.I assure you my system is not ‘clobbered up’ or ‘poxy’.
I should have known someone would leap on the warm wire comment. Wires do get warm with current flowing continuously. A short open clipped 6mm CSA run is enough for an absolute peak of 25-27A from the panels, go look at the IEE tables, as I did.
I’m not sure why you would describe the Renogy 25/50 integrated B2B/MPPT as ‘poxy’. I have found it generally well
designed, robust and reliable, flexible too as you can manually make it charge at 25Afrom alternator + x amps from the solar array or the full 50A just from the alternator just by isolating the solar array. it’s been in use continuously for nearly a year and I have only found one slight issue. I learned that it needs good ventilation and to be mounted direct to a metal surface to aid its own thermal management. MPPT charge controllers are big because they contain power transformers (like an invertor), and these have an inherant conversion inefficiency, the loss to heat is about 5-10% I’d guess, the literature (idealised numbers) only suggests a little more, a 96% peak efficiency. A cheap bang bang PWM charger doesn’t have these losses - that’s why they are so much smaller. Lest again being accused of long winded, for anyone still awake and interested I leave it to Brains or Grommet to explain why despite having a conversion loss an MPPT charger is overall more efficient than a PWM at capturing sunlight….
Maybe Raul can explain..? or maybe not, as it’s all just ‘poxy’
The slight issue is that when working hard, handling the full 50A either combined or just alternator it overheats due to the above power conversion losses and it then self regulates, which is actually a very useful self protection design feature, however it does mean you can be down to 35A after an hour in hot weather if it isn’t fitted properly. I remounted direct to metal to provide more of a heat sink and it improved.
Thanks to all those who have read and commented. Grommet was correct maybe the title was a bit off, though it still seems many have understood the core point that roof solar might not be always be the optimum solution for everyone with rapidly evolving B2B technology and the ability of lithiums to very rapidly recharge. It’s a different world to lead acid, where chemistry is ideally suited to the slow charge of solar.
Of course a panel or two on the roof, given the low cost and especially if you fit yourself with a cheap PWM remains a bit of a no brainer, why wouldn’t you avail yourself of something that’s free…
Also if you are used to being a low energy user, you probably don’t need anything else.
My intent was to build a system that was completely self sufficient, never needing hook up, but capable of powering anything. The mrs wanted to be able to use fridge, hairdryer, microwave, coffee machine etc, I wanted full home cinema and hi fi and with high power amp and subwoofer. I promised I’d build a system with no compromise, permanent 240V, and we could be high energy users.
The post was about what I learned as regards having all that solar on the roof from a year of all season ‘field trials’. For the reasons outlined it just doesn’t work as well as hoped. I expected to have to run the engine in winter, not a problem when you are moving a lot, but to avoid being cooked alive in full continental sun and with 35C in the shade we had to take cover and plug in EHU while stationary in summer and I’d absolutely hoped to avoid that. We are not on holiday and needed to be able to stay cool enough to work, to think.
The lesson I learned, as some have rightly homed in on is that to maximise solar capture (and stay under the tree, and never need to run engine or hook up) we really need a remote array that can always be pointed at the sun. If you’ve read Andy Weir’s fantastic book ‘The Martian’ or seen the movie, it would be something like that
might be better to start a new thread, then people wont resort to 'but you said this on post number 97' or 'thats exactly what i said on post number 128' .....????
i have banged the same thoughts around in my head for a while now, mainly looking at one of those mini projectors and a firestick to get the picture etc and using the on board speakers if i knew how to.
If a wire is getting warm you are losing energy. Wires should be specced not to get warm in my opinion.
Sadly I feel we are not talking about the same or even similar "high power" home cinema equipment I'd hoped you were referring to.
They are not. You won’t ever have 30A in your cables from your 520W of panels due to their operating voltage. Under sun OCV will be 20V plus and 12V panels are typically at ~ 19-20V producing peak power, so you will have an absolute maximum of 520/20 or 26A - and this would be only on the equator at the two equinoxes in full sun. If you don’t visit Africa it will be a max of 25A under full sun at 1pm on June 22 in western Europe unless you can tilt the panels. From the MPPT controller, where voltage is stepped down and current is stepped up yes you will have over 30A.
Dave, If you’d looked inside the van you’d have seen we have all this…. I originally set up projector and screen then reverted to 32” TV as it’s big enough for the van. Bea didn’t like it so I went down to 24” and I can just set up the projector and screen for special movie occasions. We use fire stick and steam via a 160G ‘Free’ French SIM, €14 a month
It is well insulated, well, apart from the giant front window, though we have a silver screen.
Sorry I didn’t explain properly, the 30+A is from the controller at battery voltage and on 16mmsq, the panel cables are all independent to just before the controller where they combine and the cross section increases before entering the controller.They are not. You won’t ever have 30A in your cables from your 520W of panels due to their operating voltage. Under sun OCV will be 20V plus and 12V panels are typically at ~ 19-20V producing peak power, so you will have an absolute maximum of 520/20 or 26A - and this would be only on the equator at the two equinoxes in full sun. If you don’t visit Africa it will be a max of 25A under full sun at 1pm on June 22 in western Europe unless you can tilt the panels. From the MPPT controller, where voltage is stepped down and current is stepped up yes you will have over 30A.
This is why the leads from my B2B/MPPT, which are carrying up to 50A are 16mm.
Use a current clamp to measure if you remain unconvinced
In an ideal world, maybe. But in the real world stuff is specified to be ‘good enough’. There is nothing unusual in a current carrying conductor heating up a little under load, they do not have zero resistance.
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Why is it the forums fault that you come on talking rubbish then get uptight when someone else doesn't agree with you or tries to help.
I go in the van flick the switch and the light goes on, stick kettle on and it boils that’s me happy 
It says read it. Understand what’s been said. Get an opinion, based on someone’s genuine experience, then see what others have to say, based on their own. I’ve already said the title is too much, but I can’t change it. The conclusion was I should have a remote array, and the point is that when mounted on the roof, solar can be compromised in a hot country.
No, for a solar panel system ANY detectable heat means you are losing too much energy in my opinion.
different scenario. You cannot compare apples to oranges.
You don’t seem to understand cable loss. Any conductor har a fixed resistance, and the more you try to push trough, the higher the losses in heat, at the expense of voltage, ohm’s law. Given your example, 50A at 12 volt with 2m of 16mm2 will have a almost equal loss compared to a 25mm2 at 3m distance for the same power, loss 2.4%. You don’t design for the wire ampacity, but for the total distance losses. At 48v you keep losses under 3%, at 24v under 2% and at 12v under1% or close.They are not. You won’t ever have 30A in your cables from your 520W of panels due to their operating voltage. Under sun OCV will be 20V plus and 12V panels are typically at ~ 19-20V producing peak power, so you will have an absolute maximum of 520/20 or 26A - and this would be only on the equator at the two equinoxes in full sun. If you don’t visit Africa it will be a max of 25A under full sun at 1pm on June 22 in western Europe unless you can tilt the panels. From the MPPT controller, where voltage is stepped down and current is stepped up yes you will have over 30A.
This is why the leads from my B2B/MPPT, which are carrying up to 50A are 16mm.
Use a current clamp to measure if you remain unconvinced
Is that 2x90amp batteries of Lithium or Lead Acid?
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