Solar panel install - correct wire size

[Van Diesel VW]

I'm looking to install 200w solar, two 100w panels in series. My thinking in 2.5mm2 panel to MPPT and then 4mm2 MPPT to battery, is this right.

Also looking for a supplier for the curly cable, 2 core 2.5mm2, any contact suggestions.

 

[sdes]

It looks as if the Victron Energy SmartSolar MPPT Charge Controller 75/15 is not really recommended for anything over 220W input fro the PV panels on a 12V system. So unless you uprate your selection of solar controller, that would probably limit your ability to add a second 170W panel.

Victron Energy SmartSolar MPPT Charge Controller 100/15

Victron Smart Solar 100/15 MPPT Charge Controller with Bluetooth built-in. For 12V & 24V systems in motorhomes, caravans, campervans & boats.

www.12voltplanet.co.uk

I think if sticking with Victron (very good choice IMHO, long guarantees and excellent product support) You'd need to opt for the 100 | 30 to cope with 2 x 170W pannels on a sunny day and still have some headroom.

The general rule is to allow the high voltage cables (PV panels to the Solar controller) to be longer, and try to keep the low voltage (nominal 12V in this case) short if possible as they will be bigger X section for the same wattage / power.

(I've just wired up a domestic sytem on a house in Frace last week where we used 6mm2 to run a 2,5kw "string"of 5 panels in series to a Victron MPPT, where the cable then "jumps" to being 35mm2 between tthe MPPT and the 24V battery, if it had been a 12V system, we would have gone to 70mm2 cables.)

I don't see your link to the solar panel, it gives a 404 not found, but if its max output voltage is more than 50V, then the next bit of advice won't work, you may already know, but if possible, put the panels in series - to give a higher voltage - following the same logic as above.
The Victron MPPT numbering system uses two numbers to define the controller's capacity: the first number is the maximum PV open-circuit voltage, and the second is the maximum charge current. For example, an MPPT 100/30 can handle a maximum PV open-circuit voltage of
100V and a maximum charge current of 30A.

Some peoples' calculations above are based on putting the panels in parallel, fine you could, but you will need thicker cables to the MPPT, in series and I think that 2.5mm would be fine to cope with 340W.

One last consideration for you, I have a Renology 170W panel on my 2007 Cali, it is great for keeping things running while camping, but what it didn't do initially was charge the main battery as well as the leisure batteries. Not many solar controllers are capable of a "twin output" that is required for that, you may not need that, but having a van that sometimes "sits" for long periods, as mine did in the pandemic, I realised having something to keep the imobiliser, tracker and other "always on" circuits ticking over when the van isn't in use is quite useful.

SolarCamper Solutions do seel them....like this one

Shop Solar Kits for VW California and Mercedes Marco Polo Vans

DIY easy to install Solar panel kits for VW California / Transporter and Mercedes Marco Polo camper vans. Zero drilling or gluing.

www.solarcampersolutions.com

Victron also make a couple, but they don't have the nice bluetooth interfice to see stuff on your smartphone

BlueSolar PWM Charge Controller (DUO) LCD&USB | Victron Energy

BlueSolar PWM-LCD&USB Liquid Crystal Display Two 5 Volt USB outputs Lighting control function, fully programmable Three stage battery charging (bulk, absorption, float), fully programmableLoad output with low voltage and manual disconnect (programmable)Load output protected against over load and...

www.victronenergy.com

Hope that helps. Good luck!

Stephen

 

[bigmac77]

I have the Victron 75/15 MPPT on a small 12v solar setup I have in my shed. I have three 150w panels connected in series and it works absolutely perfectly.

 

[sdes]

I have the Victron 75/15 MPPT on a small 12v solar setup I have in my shed. I have three 150w panels connected in series and it works absolutely perfectly.

That would be the case - I believe the Victron controlers are capable of being "over panelled" without harm (so capable of being connected up to significantly more potential wattage than is actually being "harvested" to the batteries on a sunny day) - probably a good idea for grey UK skies out of season.

Assuming for a moment a lossless controller AxV=W that gives 12 x 15 =180 180W as the max output from the Victron MPPT to your shed batteries, the other (450-180) so say about 320W is beeing "spilled" on a sunny day.

If RedWhiteMonkey wants to make full use of the 2x170W panels on a sunny day, I still think a slightly higher spec MPPT controler would be needed.....of course there is also the considertion of the max recommended charge current for the batteries LiFePO4 chemistry used in most modern domestic installs can accept can accept much higher / faster charge rates (typically 2 to 3 x faster) than older Lead Acid / AGM type batteries most of us have in our Californias. (and can be very deep cycled without harm)

I just wish I could afford a nice FogStarDrift leisure battery (or two) too, even with Black Friday pricing they are quite exotically expensive, but they do come with their own APP and bluetooth interface - what more could you want!

Lithium Leisure Battery | Fogstar UK

Looking for the best Lithium Leisure Batteries? You’ve found them. Fogstar Drift is the UK’s leading range of lithium leisure batteries.

www.fogstar.co.uk

Dream on, my Cali needs a £600 subframe for the MOT first!

 

[bigmac77]

That would be the case - I believe the Victron controlers are capable of being "over panelled" without harm (so capable of being connected up to significantly more potential wattage than is actually being "harvested" to the batteries on a sunny day) - probably a good idea for grey UK skies out of season.

Assuming for a moment a lossless controller AxV=W that gives 12 x 15 =180 180W as the max output from the Victron MPPT to your shed batteries, the other (450-180) so say about 320W is beeing "spilled" on a sunny day.

If RedWhiteMonkey wants to make full use of the 2x170W panels on a sunny day, I still think a slightly higher spec MPPT controler would be needed.....of course there is also the considertion of the max recommended charge current for the batteries LiFePO4 chemistry used in most modern domestic installs can accept can accept much higher / faster charge rates (typically 2 to 3 x faster) than older Lead Acid / AGM type batteries most of us have in our Californias. (and can be very deep cycled without harm)

I just wish I could afford a nice FogStarDrift leisure battery (or two) too, even with Black Friday pricing they are quite exotically expensive, but they do come with their own APP and bluetooth interface - what more could you want!

Lithium Leisure Battery | Fogstar UK

Looking for the best Lithium Leisure Batteries? You’ve found them. Fogstar Drift is the UK’s leading range of lithium leisure batteries.

www.fogstar.co.uk

Dream on, my Cali needs a £600 subframe for the MOT first!

I’m using it to keep a battery charged for a few things including a diesel heater in my shed. I’ve over-paneled it a bit because I’m trying to maximise charge on overcast winter days. On a sunny day I could easily manage with one panel but add clouds and even three panels won’t get the battery to float. I’ve also got the panels nearly vertical which you obviously can’t do on a van roof. I suppose it comes down to when you use the Cali.

 

[Blanco]

You can make curly cable by wrapping the cable around a tube to form a coil and heating it up boiling water. Once cooled the cable retains it shape. I tried it first using single core solar 2.5mm to prove to myself it would work, then with twin core 2.5 mm. You do need an large pan though. I found when she was out one day that Mrs B's fish kettle worked a treat

The 2.5mm twin core solar came from LowEnergySupermarket in the UK, but I'm sure is available in Europe.

The problem I came across with "standard" twin core curly cable is finding a suitable waterproof connector capable of accomodating solar cables from the panels and the smaller individual cores in the curly cable. EDIT: Both 2.5mm cable, but different external diameters. Making a solar curly cable meant all the cables were the same external diameter and I could use MC4 connectors.

 

[RedWhiteMonkey]

Very clever solution. The curly cable was the hardest part to independently source, I found one on eBay but I think it was a one off.

 

[Paul White]

Good morning,

I’m looking for some help with the planning of my proposed solar panel install on a 2022 T6.1 Beach. I think I’ve read through just about every solar thread on this forum, there is some very useful advice and ideas. The one main question that remains in my head is what gauge wire I should use.

I have looked at Solar Camper Solutions offerings and seen quite a lot of helpful posts from Roger. If I were based in the UK I would probably order from him, but I’m an Englishman living in Germany which makes that more complicated. Whilst Roger delivers to Germany my previous experiences with UK and German customs (thanks Brexit) puts me off importing. I am in discussions with my wife about this and it is still potentially an option.

I want to put one panel on the van roof. We only need it to extend the off grid running of a Dometic CFX 35 compressor fridge. I am pretty sure one panel will meet our requirements but I will build in scope for adding a second panel anyway. I am confident enough to make a cable and do the install. At the moment I am tending towards fabricating my own aluminium frame to attach into the roof rails, although there are several good looking mounting solutions available here in Germany if I decide to pay for them.

I am looking at using a 130W panel (https://greenakku.de/Solarmodule/Fl...ibles-Solarmodul-doppel-ETFE-130Wp::4248.html) connected to a Victron 75/15 MPPT to give the option fit a second panel later. I estimate that the wire run from the panel to the MPPT is no more than 5 metres and from the MPPT to battery is no more than 4 more metres.

Doing all the calculations and looking at sites that calculate wire gauge I think 2.5mm2 diameter wire is safe. I would prefer 4mm2 diameter wire for more safety and more efficiency (although this is probably neglible) but that makes the curly cable roof connector difficult. This curly cable is the only bit I am having difficulty sourcing. I have found 2.5mm2 and 4.0mm2 versions for sale on a Swiss website but the price and delivery costs are outrageous, so I would make one. Sourcing a 2.5mm2 curly cable seems possible for a reasonable price. Sourcing a 4mm2 one is more difficult, I have found them on the likes of Alibaba but I’m a bit cautious with those.

The question therefore is whether 2.5mm2 diameter cable is safe for a 130W solar setup or safe for a potential 260W solar setup? I think it is but would appreciate other people’s thoughts and knowledge on this.

Thanks in advance.

I lived in Germany, near Oldenburg. I purchased a 120 W Tri- fold solar panel with controller from a supplier of Camper Vans and Caravens. Check on the internet, far easier than fitting a panel and wiring to your van.
Basically extend the three panels to where the sun is shining and that’s it. I connected positive and negative wires to the auxiliary battery, everything that is required was supplied with the panels, it neatly folds up after use, is not heavy and proved to be of great use.

 

[RedWhiteMonkey]

I lived in Germany, near Oldenburg. I purchased a 120 W Tri- fold solar panel with controller from a supplier of Camper Vans and Caravens. Check on the internet, far easier than fitting a panel and wiring to your van.
Basically extend the three panels to where the sun is shining and that’s it. I connected positive and negative wires to the auxiliary battery, everything that is required was supplied with the panels, it neatly folds up after use, is not heavy and proved to be of great use.

Thanks, but my post is from two and half years ago. I have long since fitted solar panel and I'm perfectly happy with the results.

 

[bigmac77]

You can make curly cable by wrapping the cable around a tube to form a coil and heating it up boiling water. Once cooled the cable retains it shape. I tried it first using single core solar 2.5mm to prove to myself it would work, then with twin core 2.5 mm. You do need an large pan though. I found when she was out one day that Mrs B's fish kettle worked a treat

The 2.5mm twin core solar came from LowEnergySupermarket in the UK, but I'm sure is available in Europe.

The problem I came across with "standard" twin core curly cable is finding a suitable waterproof connector capable of accomodating solar cables from the panels and the smaller individual cores in the curly cable. EDIT: Both 2.5mm cable, but different external diameters. Making a solar curly cable meant all the cables were the same external diameter and I could use MC4 connectors.

View attachment 142655

I’m trying this with my Starlink cable. If it works I’ll be very happy

 

[Blanco]

Curly cables available from https://curlycablecompany.com/
If asked they'll make you one with a long enough tail to reach to wherever the solar controller is going to be.