Solar panel wiring

[Ronanmd1]

Hey guys. Quick question. I have an 85 W solar panel on the roof of my camper. I would like to add an additional hundred watt panel. What gauge wire do you think I need to connect the two and run them to my controller? The controller is a 30 amp controller so should have no problems with the additional panel. Will 10 gauge wire suffice? Thanks

 

[LookyLou]

Some people would say go to 10 gauge, but the wiring used by FWC is 12 gauge. I recently removed my 90W rigid panel and replaced it with two 100W flexible panels using 12 gauge to stay consistent. Haven't seen any issues.

Just a note, I have twice the wattage and half the weight now.

Should have added my are connected in parallel. If I add a solar plug for a portable solar panel, it will also be connected in parallel.

 

[MarkBC]

Ronanmd1, are you asking about connecting the two panels in parallel, so, the combined amps is the issue?
Or will they be in series -- if you have an MPPT controller?

 

[Ronanmd1]

MarkBC - I guess so...I am not very familiar with solar set ups. My truck has the one 85W panel up top. I have an extra solar plug in the back for a portable panel. I am looking to add more solar to the system for the times when I am camping in one spot for a few days at at time. I currently have a 30 amp controller. It is an Enerwatt EWC-30 model (PWM, not MPPT) module.

I called a shop to install an additional 100W panel on the roof, but they are recommending a minimum of 10 gauge wire from the roof and connecting the two panels in parallel. I am not sure how much voltage drop I may end up with if I decide to leave the 12 gauge wire and avoid the cost/effort of rewiring to the 10 gauge through roof and camper.

Don't mind doing it if needed, but hate the idea of rewiring if not needed. Lookylou - sounds like you haven't noticed any big issues, so maybe I will just start with that and go from there...

 

[LookyLou]

MarkBC - I guess so...I am not very familiar with solar set ups. My truck has the one 85W panel up top. I have an extra solar plug in the back for a portable panel. I am looking to add more solar to the system for the times when I am camping in one spot for a few days at at time. I currently have a 30 amp controller. It is an Enerwatt EWC-30 model (PWM, not MPPT) module.
I called a shop to install an additional 100W panel on the roof, but they are recommending a minimum of 10 gauge wire from the roof and connecting the two panels in parallel. I am not sure how much voltage drop I may end up with if I decide to leave the 12 gauge wire and avoid the cost/effort of rewiring to the 10 gauge through roof and camper.

Don't mind doing it if needed, but hate the idea of rewiring if not needed. Lookylou - sounds like you haven't noticed any big issues, so maybe I will just start with that and go from there...

Personally I think rewiring is adding additional cost that's not needed. You'll have 185 W on the roof with the ability to add a portable for those days the panels on the roof are shaded or you're just sitting for several days. With 200 W on my roof the batteries are topped off going into the night even with morning overcast until noon. The difference in voltage drop for the short wire runs in our campers is negligible between 10 and 12 gauge wire.

 

[takingatrip1]

The standard black /red connector, is that the same as is commonly used on trailers or does it look the same but is actually different slightly in dimension? I have a portable panel that needs a different connection ( currently has a power pole connector from the factory)

 

[LookyLou]

The standard black /red connector, is that the same as is commonly used on trailers or does it look the same but is actually different slightly in dimension? I have a portable panel that needs a different connection ( currently has a power pole connector from the factory)

Got my SAE solar connectors ( male & female) from FWC. They are standard red + and black -.

 

[ntsqd]

I'm at 10 ga. and I'd have gone with 8 if there had been a reasonable way to do so. The voltage drop is considerable when you look at the difference in battery voltage between fully charged and 50% discharged. Can't look at the percentage relative to ~12 VDC, have to look at the percentage relative to the differential.

Remember that it's the total circuit length, so power and ground wire lengths added together. In my case that came to nearly 25 feet.

That said, I've been told that PWM controllers can't make use of the additional voltage gained from less voltage drop.

 

[LookyLou]

That said, I've been told that PWM controllers can't make use of the additional voltage gained from less voltage drop.

This is nits & nats. 200W on 12 gauge wire is plenty for most of us. Now if you're adding inverters, TV's, air conditioners, microwaves, DVD players, then maybe you should try to squeeze out everything you can. Also any system with 400 W are less in parallel, a PWM controller is totally sufficient.

 

[ntsqd]

According to my Anchor Marine catalog's chart 200W @ 12 VDC over a 25' run requires 8 gauge for a 3% voltage drop. Re-run at 17 volts, but with the same other conditions calls for a little more than 10 gauge (11.8A vs. the chart's 10A).

Suggest finding and reading Handy Bob's solar blog. I'm not saying that his situation fits most of ours, but his observations and logic explaining them is worth taking into consideration.

 

[LookyLou]

According to my Anchor Marine catalog's chart 200W @ 12 VDC over a 25' run requires 8 gauge for a 3% voltage drop. Re-run at 17 volts, but with the same other conditions calls for a little more than 10 gauge (11.8A vs. the chart's 10A).

Suggest finding and reading Handy Bob's solar blog. I'm not saying that his situation fits most of ours, but his observations and logic explaining them is worth taking into consideration.

I've read Handy Bob's stuff and most of the stuff here. All I'm saying from real world experience is it's not worth rewiring a camper from the 12 gauge wire FWC uses to a larger gauge. If I'm starting from scratch then sure run 8 or 10 gauge wire. Bottom line is 200W with a 20 or 30 amp PWM controller and 12 gauge wire will run any camper FWC makes loaded with all the options they provide.

 

[ntsqd]

We

All I'm saying from real world experience is it's not worth rewiring a camper from the 12 gauge wire FWC uses to a larger gauge. If I'm starting from scratch then sure run 8 or 10 gauge wire. Bottom line is 200W with a 20 or 30 amp PWM controller and 12 gauge wire will run any camper FWC makes loaded with all the options they provide.

We'll have to agree to disagree. 12 ga is the largest practical wire, in terms of availability, for the connectors the FWC uses (10 ga versions are out there but are not easy to find in a quality part). Not the ideal gauge for their installs.

 

[Ronanmd1]

Guys - Thank you for all the feedback and opinions. Based on my searches on the forum and the responses to this post, it does't look like I am alone in my uncertainty. If I was building from scratch, I would definitely use the 10 gauge for my set up. However, In the end, practicality will take priority (at least to start). I will plan to run the system with the existing 12 gauge wire. Since, I am also installing a Trimetric monitor, I should be able to get some accurate info to help guide future decisions. If it looks like the voltage drop needs to be readdressed, then I will plan to upgrade the wiring during the long cold months up here in the north.

Cheers,

Jason