Cruisers Forum
 


Join CruisersForum Today

Reply
 
Thread Tools Rate Thread Display Modes
Old 25-03-2016, 16:45   #16
֍֎֍֎֍֎֍֎֍֎

Cruisers Forum Supporter

Join Date: Apr 2006
Posts: 13,055
Re: Installing a 50W solar panel - fuse and wire gauge question

Interesting. Just how much voltage drop IS there in a fuse?
__________________

__________________
hellosailor is offline   Reply With Quote
Old 25-03-2016, 17:17   #17
Registered User
 
deblen's Avatar

Join Date: Oct 2014
Location: Grand Manan,N.B.,Canada N44.40 W66.50
Boat: Mascot 28 pilothouse motorsailer 28ft
Posts: 1,403
Images: 1
Re: Installing a 50W solar panel - fuse and wire gauge question

Not as much as there in when he drives 40Amps thru 12Ga. Ill bet.

http://assets.bluesea.com/files/reso...on_chartlg.jpg
__________________

__________________
My personal experience & humble opinions-feel free to ignore both
deblen is offline   Reply With Quote
Old 25-03-2016, 18:29   #18
Marine service provider
 
newhaul's Avatar

Cruisers Forum Supporter

Join Date: Sep 2014
Location: puget sound washington
Boat: 1968 Islander bahama 24 hull 182, 1963 columbia 29 defender. hull # 60
Posts: 4,017
Re: Installing a 50W solar panel - fuse and wire gauge question

Quote:
Originally Posted by mitiempo View Post
Wrong

Place the fuse between the controller and the batteries - as close to the batteries as convenient.

The panels are self limiting but the batteries aren't.

Size fuse at 25 or 30 amps - less that 12 ga can handle.
My error I assumed it would go without saying that the batteries are supposed to be fused at the positive on the battery before any loads or charging systems to be abyc compliant.
__________________
Non illigitamus carborundum
newhaul is online now   Reply With Quote
Old 25-03-2016, 21:12   #19
Marine Service Provider

Join Date: Sep 2008
Location: Victoria B.C.
Boat: CS27
Posts: 1,743
Re: Installing a 50W solar panel - fuse and wire gauge question

Quote:
Originally Posted by deblen View Post
Not as much as there in when he drives 40Amps thru 12Ga. Ill bet.

http://assets.bluesea.com/files/reso...on_chartlg.jpg
That is not the issue as he will not come close to that. A larger fuse does have less voltage drop than a smaller one. Mainesail showed that in a post on Sailboat Owners a while back.

https://www.bluesea.com/resources/52...e_Sizing_Chart

The fuse is there for short circuit wire protection, not load.
__________________
mitiempo is offline   Reply With Quote
Old 26-03-2016, 06:18   #20
Moderator Emeritus
 
GordMay's Avatar

Join Date: Mar 2003
Location: Thunder Bay, Ontario - 48-29N x 89-20W
Boat: (Cruiser Living On Dirt)
Posts: 31,586
Images: 240
Re: Installing a 50W solar panel - fuse and wire gauge question

Quote:
Originally Posted by hellosailor View Post
Interesting. Just how much voltage drop IS there in a fuse?
Millivolts.
__________________
Gord May
"If you didn't have the time or money to do it right in the first place, when will you get the time/$ to fix it?"



GordMay is offline   Reply With Quote
Old 26-03-2016, 08:12   #21
Marine Service Provider

Join Date: Sep 2008
Location: Victoria B.C.
Boat: CS27
Posts: 1,743
Re: Installing a 50W solar panel - fuse and wire gauge question

In any charging system the ideal is to get the rated output to the batteries without any voltage drop. This is especially important when the charge source is lower output such as a small solar panel. Voltage is pressure and the lower it is the slower the charging. Many solar controllers have an output voltage that is too low and non-adjustable as it is. Everything you can do to minimize voltage drop is a plus.
__________________
mitiempo is offline   Reply With Quote
Old 26-03-2016, 08:52   #22
Registered User

Join Date: Feb 2013
Location: WY / Currently in Hayes VA on the Chesapeake
Boat: Ocean Alexander, Ocean 44
Posts: 922
Re: Installing a 50W solar panel - fuse and wire gauge question

I would like to hear from OceanPlanet and/or MaineSail about breakers vs fuse between battery and controller. My understanding is that it should be a fuse. How ever if I have a fuse on the battery post to protect to the positive distribution bus. If I connect solar panels to this bus (2ft of 4-0 cable to the battery) would a breaker be ok between the bus and controller or should the protection still be a fuse?

I like the idea of DP breakers between the panels and controller for disconnect for maintenance.
__________________
darylat8750 is offline   Reply With Quote
Old 29-03-2016, 09:27   #23
Registered User

Join Date: Aug 2014
Location: Groton, CT
Boat: Bristol 29.9
Posts: 236
Re: Installing a 50W solar panel - fuse and wire gauge question

Quote:
Originally Posted by Paul Elliott View Post
Regarding the wire, #12 will be fine for your 40-ft round-trip panel/controller connection. #12 is OK for the controller/battery run if the distance is short. This all assumes that you have a 12V system.

Here's how you figure it:

The maximum current from your panel is around 3A (50W / 17V = 2.94A)
#12 wire has a resistance of 1.588 milliOhms / ft, so 40 ft = 0.0635 Ohms
0.0635 Ohms x 3 Amps = 0.19V voltage drop in the wires, which is 1.11% of 17V

We generally figure that a 2% voltage drop is good enough. Less is better, but 2% is probably near the point of diminishing returns. I used 17V in my calculations, rather than 12V, since 17V is approximately the Maximum Power Point (MPPT) of your panel, and the Genasun controller will be loading the panel to this voltage.

The wiring between the controller and the battery will be carrying slightly more than the raw panel current (the controller boosts the current and drops the voltage), but it's going to be under 5A. If you have (for example) 10 ft round-trip of #12 wire between the controller and battery, that gives you a 0.0795V drop at 5A, which is an additional 0.66% at 12V. This gives you a total percentage voltage drop of 1.77%, which is still pretty good. You will have connector losses, but these should be manageable at these power levels.

There isn't a compelling reason to put a fuse between the panel and the controller, since the short-circuit current will be limited to the maximum panel output which is not much more than 3A. I have a breaker in my panel wiring, but this is more of a convenient disconnect point should I need to work on the charging system. If your panel were to be feeding the battery directly (not using a controller) then a fuse would be essential.

Your charger will probably never feed more than 5A into the batteries. 50W at 10V (a very dead battery) is 5A. You generally fuse to protect the wiring, and for #12 wires a 15A fuse should be fine.

As has been mentioned, if you plan to increase your solar panel capacity you might as well run heavier wires now.
Thank you, Paul! This is exactly what I was looking for. Hopefully we'll be wiring it up this weekend. Only 4 weekends to splash!
__________________

__________________
Our blog: http://www.adventuresontheclub.com
Cthoops is offline   Reply With Quote
Reply

Tags
solar

Thread Tools
Display Modes Rate This Thread
Rate This Thread:

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
Solar panel Installation and wire sizing from the solar panels to the mppt charger boatrips Electrical: Batteries, Generators & Solar 17 08-02-2015 19:25
Solar Panel Gauge Showing Charge at Night ? Dulcesuenos Electrical: Batteries, Generators & Solar 32 13-12-2011 09:01
Wire Sizing for Installing Solar Panels / Wind Generator Eddie Electrical: Batteries, Generators & Solar 17 30-03-2010 20:06
Solar Panel Fuse noelex 77 Electrical: Batteries, Generators & Solar 2 26-02-2010 15:17



Copyright 2002- Social Knowledge, LLC All Rights Reserved.

All times are GMT -7. The time now is 16:09.


Google+
Powered by vBulletin® Version 3.8.8 Beta 1
Copyright ©2000 - 2017, vBulletin Solutions, Inc.
Social Knowledge Networks
Powered by vBulletin® Version 3.8.8 Beta 1
Copyright ©2000 - 2017, vBulletin Solutions, Inc.

ShowCase vBulletin Plugins by Drive Thru Online, Inc.