Free 7 Day Trial RV GPS App RV Trip Planner Campground Reviews RV Maintenance Free 7 Day Trial ×
RV Trip Planning Discussions

Go Back   iRV2 Forums > RV SYSTEMS AND TECHNOLOGIES FORUMS > Going Green
Click Here to Login
Join iRV2 Today

Mission Statement: Supporting thoughtful exchange of knowledge, values and experience among RV enthusiasts.
Reply
  This discussion is proudly sponsored by:
Please support our sponsors and let them know you heard about their products on iRV2
 
Thread Tools Search this Thread Display Modes
 
Old 09-21-2021, 01:27 PM   #1
Senior Member
 
Join Date: Sep 2020
Location: Boise, ID
Posts: 515
Wire question

My 5er has an existing Zamp solar setup, using a 45watt panel, a PWM controller, and 8 AWG wires from roof to batteries.

I want to replace the tiny Zamp panel with three strings of two 100-watt panels, and put an MPPT controller near the batteries.

I think the existing 8 AWG wire is adequate, but would like input from this community before I start this project.

The way I figure it, the 100-watt panel strings will produce a maximum of 5.5 amps at 36 volts, so putting three strings in parallel will give me about 16.5 amps at 36 volts. I am not sure what the total one-way length from the combiner box to the batteries is, but it could be as much as 20 feet.

I think the existing wire can handle the amerge, with a voltage drop on the order of 2%. This should be suitable.

Am I calculating this correctly?

Thanks for any thoughts.
__________________
2018 F350 Limited
2021 Outdoors RV 24KRS
2021 Arctic Fox 27-5L
JHinman is online now   Reply With Quote
Join the #1 RV Forum Today - It's Totally Free!

iRV2.com RV Community - Are you about to start a new improvement on your RV or need some help with some maintenance? Do you need advice on what products to buy? Or maybe you can give others some advice? No matter where you fit in you'll find that iRV2 is a great community to join. Best of all it's totally FREE!

You are currently viewing our boards as a guest so you have limited access to our community. Please take the time to register and you will gain a lot of great new features including; the ability to participate in discussions, network with other RV owners, see fewer ads, upload photographs, create an RV blog, send private messages and so much, much more!

Old 09-21-2021, 02:13 PM   #2
Senior Member
 
Join Date: Sep 2017
Location: Northern California
Posts: 821
Your are golden.

The #8 is good for well over twice the current you will put on it.

Voltage drop between the panels and the solar controller is not a problem in that the solar controller will compensate for it.

Voltage drop between the panels and the solar controller is only an issue re power loss. I.e., some of your generated wattage will be lost in heat in the wire. That may be a few watts, but if you have #8 wire, you've done about all one would want to do to reduce those losses.

It's good to see a manufacturer provide decent conductor up to the roof.

An idle question ..... are you using 100W panels because they fit the available roof space? 200W panels are currently the sweet spot for dollars per Watt and might be a good alternative if they will fit the roof. I'm in the process of changing out my 100W panels (up to 7 years old) and doing a bit of re-arranging to get 200W panels up there. This was made possible in part because the latest crop of 200W panels are a bit more efficient and in the case of the ones I got, are 6" shorter than ones available a year or two ago (length was my constraint).
__________________
2020 GMC Denali 2500HD Crew 4X4 Gas 6.6L Rockwood 8280WS (30' 5th)
Solar plus LiFePO4 with mini split A/c & 12V fridge
hclarkx is offline   Reply With Quote
Old 09-21-2021, 03:36 PM   #3
Senior Member
 
Join Date: Apr 2010
Posts: 659
A 50 amp service cord typically has 8 gauge wire..... I'll bet you can't put enough solar panels on the roof to overload 8 gauge wire.
bucks2 is offline   Reply With Quote
Old 09-21-2021, 05:31 PM   #4
Senior Member
 
Join Date: Sep 2020
Location: Boise, ID
Posts: 515
Quote:
Originally Posted by hclarkx View Post

An idle question ..... are you using 100W panels because they fit the available roof space?
Thanks for the feedback on the wire. I thought I was good, but lack confidence in my understanding of electricity.

The rationale for the 100-watt panels is getting higher voltage by putting panels in series, yet having pairs in parallel spread out to increase the chances that at least one pair will be in the sun and active.

I had three 170-watt panels spread out on a 27-ft TT, connected in parallel, and that seemed to work. (I did not get much experience with the set-up, as I used it once before finding a rig I liked better.)

My understanding is that MPPT controllers are more efficient when used with higher voltage arrays.

Renogy has some 100-watt panels for $100 right now. That looks pretty attractive.
__________________
2018 F350 Limited
2021 Outdoors RV 24KRS
2021 Arctic Fox 27-5L
JHinman is online now   Reply With Quote
Old 09-21-2021, 11:01 PM   #5
Senior Member
 
Join Date: Sep 2017
Location: Northern California
Posts: 821
Quote:
Originally Posted by JHinman View Post
Thanks for the feedback on the wire. I thought I was good, but lack confidence in my understanding of electricity.

The rationale for the 100-watt panels is getting higher voltage by putting panels in series, yet having pairs in parallel spread out to increase the chances that at least one pair will be in the sun and active.

I had three 170-watt panels spread out on a 27-ft TT, connected in parallel, and that seemed to work. (I did not get much experience with the set-up, as I used it once before finding a rig I liked better.)

My understanding is that MPPT controllers are more efficient when used with higher voltage arrays.

Renogy has some 100-watt panels for $100 right now. That looks pretty attractive.
Got it. Good plan. You are correct on the benefits of higher voltage AND parallel paths. And $100 for 100W Renogy panels is a good deal. My son and I got latest 200W name brand panels for $150 each though we bought 20 panels and did cash and carry. I was thinking four 200W panels, two parallel branches of two panels, would also give you two parallel branches and a bit more Wattage if they will fit and the price is right. That would be about 20 amps instead of 15, but you have the wire for it. The fact that I'm upgrading from 100W Renogy panels to 200W panels spurred my thoughts on going 200 out of the box.
__________________
2020 GMC Denali 2500HD Crew 4X4 Gas 6.6L Rockwood 8280WS (30' 5th)
Solar plus LiFePO4 with mini split A/c & 12V fridge
hclarkx is offline   Reply With Quote
Old 09-22-2021, 01:51 PM   #6
Senior Member
 
glennwest's Avatar
 
Join Date: Mar 2009
Posts: 1,569
Quote:
Originally Posted by bucks2 View Post
A 50 amp service cord typically has 8 gauge wire..... I'll bet you can't put enough solar panels on the roof to overload 8 gauge wire.
Depends on how it is wired.Higher voltage requires less wire gauge.
__________________
2003 Teton Grand Freedom. 2006 Freightliner Century 120 with Detroit 14L and Ultrashift.2016 Smartcar carry on deck. Full time going from job to job. Building and maintaining plants across the USA. Sold 2006 Mobile Suites 32TK3
glennwest is offline   Reply With Quote
Old 09-22-2021, 02:35 PM   #7
Senior Member
 
Winemaker2's Avatar
 
Join Date: Nov 2006
Location: Western NY
Posts: 4,417
Quote:
Originally Posted by glennwest View Post
Depends on how it is wired.Higher voltage requires less wire gauge.
Not true.
Ampacity charts dont list or worry about V.
8 ga good for 40 to 55 A depending on insulation... doesn't matter at what V

If you are talking wattage thats another story and A a reverse relationship w V. Double V and A is halved for same wattage.

Sent from my SM-T387V using iRV2 - RV Forum mobile app
__________________
Don & Marge
'13 Newmar Ventana 3433 - '14 CR-V TOAD
'03 Winnebago Adventurer 31Y - SOLD
Winemaker2 is online now   Reply With Quote
Old 09-24-2021, 05:36 AM   #8
Senior Member
 
paul65k's Avatar


 
Alpine Owners Club
Join Date: Nov 2015
Location: Lake Havasu City, AZ
Posts: 2,206
Quote:
Originally Posted by Winemaker2 View Post
Not true.
Ampacity charts dont list or worry about V.
8 ga good for 40 to 55 A depending on insulation... doesn't matter at what V

If you are talking wattage thats another story and A a reverse relationship w V. Double V and A is halved for same wattage.

Sent from my SM-T387V using iRV2 - RV Forum mobile app
All true of course.....I think the issue is line loss and not wire capacity. The lower the voltage the higher the resistance and typically the reason for higher gauge wiring for Solar panels running at 12V (17ish actually). This comes up very often in these discussions and the reason to use more than just an ampacity chart when making wire choices for low voltage wiring
__________________
Paul & Jean
2001 Alpine 36FDDS (74291)-1600W Solar, 13,440Wh (525Ah @24V) LiFePO4
2019 Jeep Grand Cherokee Trailhawk (Hemi)
2006 Alpenlite 32RL - Sold
paul65k is online now   Reply With Quote
Old 09-24-2021, 05:46 AM   #9
Senior Member
 
Marine359's Avatar
 
Join Date: May 2021
Location: Asheville, NC
Posts: 370
You really don’t have much voltage drop over long solar cables. I use 30ft 10 gauge wire from my portable panel to a mppt controller mounted close to battery. I’ve measured to confirm spec 22v Voc at the panel, and measure 21.5v at the end of the 30ft cable. If you’re unsure, just use a multimeter to test if your panel is putting out factory spec, and test again at the end of your cable.
__________________
Jim. 2021 Canyon Denali 4x4 3.6L, Husky C-Line
2021b Micro Mini 2108DS, 170AH LiFePo4, Xantrex XC2000, 110w Solar Suitcase, Champion 2500w df
Marine359 is offline   Reply With Quote
Reply



Currently Active Users Viewing This Thread: 1 (0 members and 1 guests)
 
Thread Tools Search this Thread
Search this Thread:

Advanced Search
Display Modes

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are Off
Pingbacks are Off
Refbacks are Off


Similar Threads
Thread Thread Starter Forum Replies Last Post
A yellow wire and a green wire, what are they for? CountryFit Country Coach Owners Forum 14 07-04-2014 09:01 PM
2 Wire to 3 Wire Help ImagineIF Toads and Motorhome Related Towing 6 02-15-2012 02:52 PM
Wire color vss wire kenenders Newmar Owner's Forum 2 05-16-2009 09:43 AM
Which Wire? Brake Light Wire Off Switch mickey53usa Freightliner Motorhome Chassis Forum 2 04-14-2009 03:05 PM
6 wire motorhome, 4 wire toad?? smlranger Toads and Motorhome Related Towing 3 02-27-2005 06:03 AM

» Featured Campgrounds

Reviews provided by


All times are GMT -6. The time now is 05:36 PM.


Powered by vBulletin® Version 3.8.8 Beta 1
Copyright ©2000 - 2021, vBulletin Solutions, Inc.