Solar wiring size!

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Cbessler

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Jul 29, 2021
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Hey everyone! Just finished my solar install and wanted to ask a few questions and I guess double check my system against the experts. I have a 2014 fwc fleet. Looking to make sure everything here is appropriate and won't be a fire hazard etc with the pre-installed 12g wiring.

I added 350w of renogy flexible solar panels wired in series to the roof for lithium and the smaller wiring. I have a 206ah sok lithium battery I charge to 14.4v and a 100/30 victron mppt solar charge controller.

The panels come into the 12g sae roof connection mounted with 10g mc4 connectors and a sae adaptor for the reversed polarity issue fwc has. It then runs on the stock 12g wiring to the charge controller and 10g wiring from the storage cabinet through a predrilled hole into the battery. The 10g is roughly just a couple of feet. I spliced the wiring found from the pump cabinet area and just left the old wiring "dead" that runs into the battery compartment. Nothing fit there for the install so had to come up with something else.

I added a 40amp breaker (let me know if you guys think 30 amps is better here) and then another before the battery (again at 40 amps).

I have found a few forums on here regarding the amp rating and length of wire for the pre-installed 12g wiring. Does my system seem ok here? I don't want a fire hazard etc.

Here are some panel specs:

Maximum Power at STC: 175W
Module Efficiency: 17.3%
Optimum Operating Voltage (Vmp): 19.5V Open-Circuit Voltage (Voc): 23.9V
Optimum Operating Current (Imp): 8.89A Short-Circuit Current (Isc): 9.50 A
Operating Temperature: -40°F to 185°F (-40ºC to +85ºC)
Maximum Series Fuse Rating: 15A
 

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Here is the roof setup. I've cleaned up some other wiring haha
 

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If the specs you listed state 15 amp fuse max, wouldn't at 10 amp be more realistic? And 30 or 40 amp is out of the ballpark
 
So should I switch the breakers to more like 20 amps coming in and a 30 beneathe? I think that is per panel specs.
 
Are you sure you want your panels wired in series? I'm thinking parallel. Series will add up the voltage of all the panels, parallel adds up the amps.
 
I've read adding up the panels in series will allow for better volt creation for the lithium for charge efficiency percentage correct? I've also watched videos on in parallel charging and only one cell needed to kick the whole panel out. I chose in series because the higher volts for lithium. I did set it up so that I could change it over if I wanted to tho
 
This looks good, except the breaker size is too big. Series is what I would do. More volts is better, the MPPT will have more room to work with and create the AMPS camper Rich is talking about.
 
Totally and thanks vic for the info! Always appreciate you on these threads! I've come across a ton of stuff and wanted to make sure mine was good. Drop it to a 30 amp breaker then?
 
Cbessler said:
Totally and thanks vic for the info! Always appreciate you on these threads! I've come across a ton of stuff and wanted to make sure mine was good. Drop it to a 30 amp breaker then?
Click to expand...
The manufacturer says 15A max. Your panels are rated at less than 10A short circuit current, and in series that is not additive, so 10-15A would be right.

Unless you are fusing on the output side of the MPPT? That should be super close to the batteries, and a fuse would be overkill there.
 
Hey vic thanks for the info. I will update the first breaker prior to mppt to 15 amps. Is that where it should be? Between the panels and the mppt charger?

Ohhhh or should I fuse the actual panels on the roof?

Renogy 15A Male and Female Connector Waterproof in-Line Fuse Holder w/Fuse, Black https://www.amazon.com/dp/B00YG2BZM0/ref=cm_sw_r_apan_i_23WJDXXBDTK1KB3NKDM9?psc=1

Then maybe just keep the 2nd breaker after the mppt. The other breaker is mainly there as a way to service the system and looks like I built it too big. It's nice switching things off and on too. Yes it's really close to the batteries maybe 1.5 ft ish
 
I don't think a fuse is needed between the Victron controller and the panels. The Victron controller has a fuse as I recall. I think there should be a fuse between the Solar Controller and the Battery as well as between the battery and the rest of the system.

However, Renogy does recommend a fuse (reason not stated) between the panels and the solar controller.

They also give an example to help you appropriately size the fuse.

https://www.renogy.com/blog/how-to-fuse-your-solar-system/#:~:text=There%20are%20three%20different%20locations,the%20battery%20bank%20and%20inverter.

I hope this is helpful.

Craig



Edit: The Victron solar controller manuals recommend a disconnect switch between the panels and the controller and a fuse between the controller and the battery.

Note: The Victron controllers are not protected against reverse polarity so be careful when connecting the battery side.

https://www.victronenergy.com/upload/documents/Manual_BlueSolar_100-30__100-50/MPPT_solar_charger_manual-en.pdf
 
ckent323 said:
I don't think a fuse is needed between the Victron controller and the panels. The Victron controller has a fuse as I recall. I think there should be a fuse between the Solar Controller and the Battery as well as between the battery and the rest of the system.

However, Renogy does recommend a fuse (reason not stated) between the panels and the solar controller.

They also give an example to help you appropriately size the fuse.

https://www.renogy.com/blog/how-to-fuse-your-solar-system/#:~:text=There%20are%20three%20different%20locations,the%20battery%20bank%20and%20inverter.

I hope this is helpful.

Craig
Click to expand...
A circuit breaker between the panels and the mppt is a good idea so that you can de-energize your system. You want to be able to directly disconnect all power sources.
 
The breakers are handy for servicing. I’d keep the smaller breaker where it is, not on the roof! From an electrical perspective, on the roof would be ideal, but servicing would be more difficult and I have not seen a camper done that way yet.
 
I have my panels fused on the roof before they enter the camper due to the chance of the wires shorting behind the lift panel.
 
Using a circuit breaker to disconnect the panels may be reasonable a disconnect switch would serve the same purpose.

It is my understanding that a fuse is not needed to protect solar panels (see link). However, Renogy recommends it. No reason provided by Renogy so it is not clear to me if the fuse is intended to protect the panels or the Solar Controller or just the wiring (which is relatively inexpensive by comparison).

https://electronics.stackexchange.com/questions/18092/solar-panel-short-circuit#:~:text=No%20%2D%20you%20will%20not%20damage,short%20circuited%20into%20an%20ammeter.


P.S. I edited my original comment above relative to a disconnect between the controller and the battery.


Craig
 
Thanks astropuppy! I will be making a video on this as soon as I can. I can try to update this thread when it's finished. Looking to add the info for everyone as it's been a kind of specific install with lots of research involved

I followed titos recommendations here: https://youtu.be/uJIEXhnF8MU

And did lots of reading and searching from explorist.life. https://www.explorist.life/

This got me the most info, obviously had a few questions down the road but helps for the fwc camper guys do to the specific campers etc
 
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