Solar/Trailer and Battery Wiring

[ACJ]

I recently purchased a 2022 Flagstaff T21TBHW (A Frame) camper. I would like to add solar of some sort so I have been doing a lot of reading and trying to better educated myself on solar. In doing so I also looked at the wiring on the trailer to better understand how it is wired and this prompted some questions. My initial thought is that I would start with a 200 watt portable panel (often times the campgrounds are wooded) and possibly add an additional 200 watt rooftop panel in the future if needed.
The trailer is wired for Solar on the side (SAE front connection) and also Wired for solar (MC4 roof connections). I’ve drawn up a wiring diagram that is on the trailer. Now for the questions….

#1: Assuming I would put panels on the roof and also have a portable panel is there any concern having 2 controllers as depicted? My research says no but I would have thought the wiring would be separated but as you can see it comes together at the pigtail.

#2: The solar on the side says it is wired for up to 20 amps and the Wired for solar says up to 30 amps. The 200 watt Renogy panels I was looking at say 10.35 amps each. If both are used that would seem to suggest up to 50 amps however at what point do you need to consider the wire size and fuse size? Would it be everything after the pigtail (wire nut) to the battery? It seems you would also want to increase the fuse size to something larger than 20 amp?

Appreciate any insight/feedback. Thanks.

[TitanMike]

If you have two separate solar systems with their own controllers then as long as each are connected to the batteries either direct as in an installed controller, or through the "solar on the side" for the portables there should be no problems.

A typical 200 watt solar arrays will produce around 10 amps each and if in parallel, as they would be when both connected to the batteries, the total amperage would be ~20 amp. That would be during absolute peak output which only occurs during the middle of the year, with clear skies, with Sun directly overhead, and panels perfectly aligned to the Sun.

In reality, the flat mounted rooftop panels will never see that perfection and thus total output through the wiring to the batteries through the "20 amp rated wires", will be more like 15 amp max.

This assumes that both panel sets are each wired in parallel and using a PWM controller. If both panel sets are wired in series the voltages will double but current will be more like 5 amps total. This would then most likely be feeding an MPPT controller and the output current (based on my personal experience) is close to trippled, depending on all the earlier mentioned factors. In this case, the total current feeding the batteries could approach 30 amp which might be too much if the pre-wire is only 12Awg. If 10 awg, this is the usual size for 30 amp feeds.

I don't see any issues as the pre-wire for the panels will only see a max of 10 amp to the controller and from controller to batteries (if a PWM controller).

The portable solar panel will be similar so the total won't even exceed 12awg wire capacity. In closing, 400 watts of potential solar output at 13.8 volts (charging) is only 29 amps. Not sure where the 50 amps came from?????

[ACJ]

Originally Posted by TitanMike

If you have two separate solar systems with their own controllers then as long as each are connected to the batteries either direct as in an installed controller, or through the "solar on the side" for the portables there should be no problems.

A typical 200 watt solar arrays will produce around 10 amps each and if in parallel, as they would be when both connected to the batteries, the total amperage would be ~20 amp. That would be during absolute peak output which only occurs during the middle of the year, with clear skies, with Sun directly overhead, and panels perfectly aligned to the Sun.

In reality, the flat mounted rooftop panels will never see that perfection and thus total output through the wiring to the batteries through the "20 amp rated wires", will be more like 15 amp max.

This assumes that both panel sets are each wired in parallel and using a PWM controller. If both panel sets are wired in series the voltages will double but current will be more like 5 amps total. This would then most likely be feeding an MPPT controller and the output current (based on my personal experience) is close to trippled, depending on all the earlier mentioned factors. In this case, the total current feeding the batteries could approach 30 amp which might be too much if the pre-wire is only 12Awg. If 10 awg, this is the usual size for 30 amp feeds.

I don't see any issues as the pre-wire for the panels will only see a max of 10 amp to the controller and from controller to batteries (if a PWM controller).

The portable solar panel will be similar so the total won't even exceed 12awg wire capacity. In closing, 400 watts of potential solar output at 13.8 volts (charging) is only 29 amps. Not sure where the 50 amps came from?????

Thanks. The 50 amp came form the fact that the solar on the side says it is wired for up to 20 amps and the wired for solar says it is wired for 30 amp. Assuming I would use both to the max potential (more than 2-200 watt panels) 20 amp going through solar on the side and 30 amp through the wired for solar that would give you up to 50 amp. It does not seem like this would be possible though due to the wire gauge and the 20 amp fuse limitation? I don't plan on doing this but just trying to better understand why both run to the pigtail and then only a 20 amp fuse to the battery.

My concern even with the 2 seperate 200 watt setups is that (assuming perfect conditions) is you would have 10 amps coming from the rooftop and 10 amps coming from the portable for a total of 20 amps. The 10 amps would be seperate through each system it seems until it reaches the pigtail in the diagram. At that point it seems you would have a total of 20 amps running through the 20 amp fuse and 10 AWG wire to the battery? Based on your comment about 10 gauge being ok for 30 amps the wire seems fine but it seems like you would want a fuse larger than 20 amps? Also the fuse holder says a max of 20 amp fuse but with 10 gauge wire could you put in a 25/30 amp fuse?

To your point about 400 watts of potential solar output at 13.8 volts (charging) is only 29 amps. Wouldn't the 20 amp fuse be to small then? You also mention the 2 panels produce 20 amps but then also say 29 amps, care to elaborate that is a bit confusing.

On this point "I don't see any issues as the pre-wire for the panels will only see a max of 10 amp to the controller and from controller to batteries (if a PWM controller)." would things change if using an MPPT controller?

[TitanMike]

Originally Posted by ACJ

Thanks. The 50 amp came form the fact that the solar on the side says it is wired for up to 20 amps and the wired for solar says it is wired for 30 amp. Assuming I would use both to the max potential (more than 2-200 watt panels) 20 amp going through solar on the side and 30 amp through the wired for solar that would give you up to 50 amp. It does not seem like this would be possible though due to the wire gauge and the 20 amp fuse limitation? I don't plan on doing this but just trying to better understand why both run to the pigtail and then only a 20 amp fuse to the battery.

My concern even with the 2 seperate 200 watt setups is that (assuming perfect conditions) is you would have 10 amps coming from the rooftop and 10 amps coming from the portable for a total of 20 amps. The 10 amps would be seperate through each system it seems until it reaches the pigtail in the diagram. At that point it seems you would have a total of 20 amps running through the 20 amp fuse and 10 AWG wire to the battery? Based on your comment about 10 gauge being ok for 30 amps the wire seems fine but it seems like you would want a fuse larger than 20 amps? Also the fuse holder says a max of 20 amp fuse but with 10 gauge wire could you put in a 25/30 amp fuse?

To your point about 400 watts of potential solar output at 13.8 volts (charging) is only 29 amps. Wouldn't the 20 amp fuse be to small then? You also mention the 2 panels produce 20 amps but then also say 29 amps, care to elaborate that is a bit confusing.

On this point "I don't see any issues as the pre-wire for the panels will only see a max of 10 amp to the controller and from controller to batteries (if a PWM controller)." would things change if using an MPPT controller?

Didn't mean to confuse and admit i did wander a bit.

I need to back up a bit. Current from the panels will be limited to 10 amps for each pair of 100 watt panels. This is at a voltage around 20 volts.

If in series the panel output will increase to around 40 volts at 5 amp total.

Each array will produce, with mppt controlers, 200 watts. The PWM controllers will waste power and coupled with the flat mounted panel efficiency a full 400 watts will nevervbe realized.

For simplicity you may consider splitting the feed from both solar sources and connect each controller directly to the batteries.

That will eliminate thevconfusion in both our minds[emoji16]

[ACJ]

Originally Posted by TitanMike

Didn't mean to confuse and admit i did wander a bit.

I need to back up a bit. Current from the panels will be limited to 10 amps for each pair of 100 watt panels. This is at a voltage around 20 volts.

If in series the panel output will increase to around 40 volts at 5 amp total.

Each array will produce, with mppt controlers, 200 watts. The PWM controllers will waste power and coupled with the flat mounted panel efficiency a full 400 watts will nevervbe realized.

For simplicity you may consider splitting the feed from both solar sources and connect each controller directly to the batteries.

That will eliminate thevconfusion in both our minds[emoji16]

Thanks, Mike. I assume your Mike, haha. I've read a lot of posts about solar with your input and was hoping to get hear from you since you seem to be very knowledgeable. To be honest I'm still a bit confused.

I'm obviously new to all of this and doing as much reading as I can to try to understand. If I need to split the feeds and redo some wiring I can do that but at the same time I'm trying to understand why it was wired this way to begin with and if the way it is wired will work or not. I am somewhat handy but I have other hobbies I'd rather spend my time on then doing a bunch of wiring.

I understand that each 200watt panel will produce about 10 amps. Where I'm still confused is when the 10 amps from the roof solar and 10 amps from the portable solar come together at the pigtail. Would you not have a total of 20 amps moving through the wires at this point? That 20 amps would then have to run through the 20 amp fuse, no?

I've read a bit on series vs. parallel but not sure I'm ready for that topic yet. Based on what I read Parallel seems like the best option due to having to deal with shade.

[ACJ]

TitanMike, after doing a bit more research I think I am going to take your advice and seperate the SAE solar on the side connection to go directly to the battery.

My plan is to get 2 -100 watt panels as they fit better in my storage space and wire them in series, run them through the SAE but upgrade the SAE connector from 12 Gauge to 10 Gauge, then run into the camper to an MPPT controller. See below diagram. Any issues with this setup?

Also have a few questions;

- If I understand correctly wiring in series will allow a smaller wire gauge to be used running from the panels to the controller. What gauge would work? I plan to make a cord 50' in length so I can move the panels into the sun.

- I would like to go with a Victron MPPT controller to pair with the BMV-712. I was looking at the MPPT 75/15. Would this controller be sufficient with this setup?

- I believe there should be fuses somewhere in this setup but am not 100% sure where and what size?

- Am I doing the calculation right to say this setup will be 35.2 volts and 5.68 amps at optimal conditions. I am getting this based on the Renogy specs for each panel being Maximum operating voltage 17.6 and maximum operating current 5.68 amps.
Renogy Panel is this one (https://www.renogy.com/100-watt-ecli...-o-controller/)

[W5CRE]

Originally Posted by ACJ

TitanMike, after doing a bit more research I think I am going to take your advice and seperate the SAE solar on the side connection to go directly to the battery.

My plan is to get 2 -100 watt panels as they fit better in my storage space and wire them in series, run them through the SAE but upgrade the SAE connector from 12 Gauge to 10 Gauge, then run into the camper to an MPPT controller. See below diagram. Any issues with this setup?

Also have a few questions;

- If I understand correctly wiring in series will allow a smaller wire gauge to be used running from the panels to the controller. What gauge would work? I plan to make a cord 50' in length so I can move the panels into the sun.

- I would like to go with a Victron MPPT controller to pair with the BMV-712. I was looking at the MPPT 75/15. Would this controller be sufficient with this setup?

- I believe there should be fuses somewhere in this setup but am not 100% sure where and what size?

- Am I doing the calculation right to say this setup will be 35.2 volts and 5.68 amps at optimal conditions. I am getting this based on the Renogy specs for each panel being Maximum operating voltage 17.6 and maximum operating current 5.68 amps.
Renogy Panel is this one (https://www.renogy.com/100-watt-ecli...-o-controller/)

I'd put a fuse in there.

[PhilFromMaine]

Originally Posted by ACJ

TitanMike, after doing a bit more research I think I am going to take your advice and seperate the SAE solar on the side connection to go directly to the battery.

My plan is to get 2 -100 watt panels as they fit better in my storage space and wire them in series, run them through the SAE but upgrade the SAE connector from 12 Gauge to 10 Gauge, then run into the camper to an MPPT controller. See below diagram. Any issues with this setup?

Also have a few questions;

- If I understand correctly wiring in series will allow a smaller wire gauge to be used running from the panels to the controller. What gauge would work? I plan to make a cord 50' in length so I can move the panels into the sun.

- I would like to go with a Victron MPPT controller to pair with the BMV-712. I was looking at the MPPT 75/15. Would this controller be sufficient with this setup?

- I believe there should be fuses somewhere in this setup but am not 100% sure where and what size?

- Am I doing the calculation right to say this setup will be 35.2 volts and 5.68 amps at optimal conditions. I am getting this based on the Renogy specs for each panel being Maximum operating voltage 17.6 and maximum operating current 5.68 amps.
Renogy Panel is this one (https://www.renogy.com/100-watt-ecli...-o-controller/)

If you are wiring the panels in series, you will only be producing around 5-6 amps in total and about 40 plus or minus volts. 10 gauge wire will handle up to 30 amps so your system looks good. As noted, it is a good idea to put a fuse between the controller and the battery. Fusing typically has a rating of 1.25 of the wire capacity.

(Edit: there agree some pretty good beginners WEB sites such as Will Prowse's that will really simplify the process for you with diagrams.https://www.mobile-solarpower.com/