24v solar panel for 12v charging? - SailNet Community

   Search Sailnet:

 forums  store  


Quick Menu
Forums           
Articles          
Galleries        
Boat Reviews  
Classifieds     
Search SailNet 
Boat Search (new)

Shop the
SailNet Store
Anchor Locker
Boatbuilding & Repair
Charts
Clothing
Electrical
Electronics
Engine
Hatches and Portlights
Interior And Galley
Maintenance
Marine Electronics
Navigation
Other Items
Plumbing and Pumps
Rigging
Safety
Sailing Hardware
Trailer & Watersports
Clearance Items

Advertise Here






Go Back   SailNet Community > On Board > Gear & Maintenance > Electrical Systems
 Not a Member? 


Like Tree1Likes
  • 1 Post By btrayfors
Reply
 
LinkBack Thread Tools
  #1  
Old 12-30-2011
Bene505's Avatar
Glad I found Sailnet
 
Join Date: Jul 2008
Posts: 3,579
Thanks: 5
Thanked 39 Times in 38 Posts
Rep Power: 8
Bene505 will become famous soon enough Bene505 will become famous soon enough
24v solar panel for 12v charging?

I found a Kyocera solar panel at a good price. It's much bigger than our current solar panel and would be a great addition to the top of our davits.

The only problem is, it's 24 volts instead of 12. Is this a problem?

I already have a Xantrex C60 controller laying around that I think may be MPPT, but I wanted to hear from people who have done this.

Would you buy it, or wait until a good 12v panel comes along?

Regards,
Brad
__________________
.
.
Great minds discuss ideas;
Average minds discuss events;
Small minds discuss people.
.
The best minds discuss sailing.
.
Reply With Quote Share with Facebook
  #2  
Old 12-30-2011
mitiempo's Avatar
Senior Member
 
Join Date: Sep 2008
Location: Victoria B.C. Canada
Posts: 7,071
Thanks: 0
Thanked 68 Times in 59 Posts
Rep Power: 7
mitiempo will become famous soon enough mitiempo will become famous soon enough
It will work as long as its output is lower than the max voltage the controller can handle. If the controller is MPPT it will give you the most out of the panel, converting to a higher amperage at the required voltage (14.4) and if the controller is PWM it will waste the extra voltage.

It is no different than a multi panel array in series that produces say 48 volts going to a MPPT controller and being converted to the proper charging voltage.
It is well explained in any MPPT manual such as for the Outback controllers.
__________________
Brian
Living aboard in Victoria Harbour
Reply With Quote Share with Facebook
  #3  
Old 12-30-2011
Bene505's Avatar
Glad I found Sailnet
 
Join Date: Jul 2008
Posts: 3,579
Thanks: 5
Thanked 39 Times in 38 Posts
Rep Power: 8
Bene505 will become famous soon enough Bene505 will become famous soon enough
Thansk Brian,

I think it comes down to whether I want the extra piece of hardware.

It seems that big 12v panels are getting hard to find. Anyone know a good source?

Regards,
Brad
__________________
.
.
Great minds discuss ideas;
Average minds discuss events;
Small minds discuss people.
.
The best minds discuss sailing.
.
Reply With Quote Share with Facebook
  #4  
Old 12-30-2011
Senior Member
 
Join Date: Aug 2006
Location: Arlington, VA
Posts: 1,809
Thanks: 0
Thanked 4 Times in 4 Posts
Rep Power: 10
btrayfors will become famous soon enough btrayfors will become famous soon enough
Quote:
Originally Posted by Bene505 View Post
Thansk Brian,
I think it comes down to whether I want the extra piece of hardware.
....
What extra piece of hardware? You need a good controller even with "big 12V panels". These typically have an open-circuit voltage of 17-18VDC....more than enough to fry your batteries if you don't have a controller.

And, might as well spend a few extra bucks and get a good MPPT controller because, as Brian says, they'll give better performance.

I'd go with the "24V panel" and a MPPT controller which can handle the peak amperage and an open circuit voltage of 40VDC or higher (the panel is likely to have an OC voltage on the order of 35.4VDC). Better overall performance and better partial shade performance.

Bill
mitiempo likes this.

Last edited by btrayfors; 12-30-2011 at 01:43 PM.
Reply With Quote Share with Facebook
  #5  
Old 12-30-2011
Maine Sail's Avatar
Senior Member
 
Join Date: Jan 2003
Location: Maine Coast
Posts: 5,302
Thanks: 10
Thanked 119 Times in 87 Posts
Rep Power: 15
Maine Sail is just really nice Maine Sail is just really nice Maine Sail is just really nice Maine Sail is just really nice
Quote:
Originally Posted by Bene505 View Post
Thansk Brian,

I think it comes down to whether I want the extra piece of hardware.

It seems that big 12v panels are getting hard to find. Anyone know a good source?

Regards,
Brad
With a 24V panel on a 12V system you will certainly want an MPPT or you're giving up some output current. The Blue Sky 1524 & 1524iX (IIRC) will do 12 & 24V panels and automatically detects whether it is connected to a 12V or 24V system. They basically take excess voltage and turn it into usable current.

Evergreen was one of the few still producing a 12V panel (actually 22.5V +/-) in 150W and up sizes. Most in that size range are 24V.. If I remember the 200W panels were rated at about 22.5V and low 11's for amp output. With an MPPT you could see more than the 11A output.. If you search the net you still may find some of the Evergreen Panels. Last I saw they were as low as $1.60 watt...
__________________
______
-Maine Sail / CS-36T


To view links or images in signatures your post count must be 10 or greater. You currently have 0 posts.




© Images In Posts Property of Compass Marine Inc.



Last edited by Maine Sail; 12-30-2011 at 06:00 PM.
Reply With Quote Share with Facebook
  #6  
Old 01-01-2012
Barquito's Avatar
Barquito
 
Join Date: Dec 2007
Location: Madison, WI
Posts: 1,940
Thanks: 0
Thanked 14 Times in 14 Posts
Rep Power: 7
Barquito is on a distinguished road
Another related question: Would I still need a controller for a smaller 24 volt panel (5W for a 12 volt house and starter batt)?
Reply With Quote Share with Facebook
  #7  
Old 01-04-2012
nickmerc's Avatar
Senior Member
 
Join Date: Nov 2008
Location: O'Fallon, MO
Posts: 563
Thanks: 0
Thanked 1 Time in 1 Post
Rep Power: 6
nickmerc is on a distinguished road
Yes
Reply With Quote Share with Facebook
  #8  
Old 01-04-2012
Bene505's Avatar
Glad I found Sailnet
 
Join Date: Jul 2008
Posts: 3,579
Thanks: 5
Thanked 39 Times in 38 Posts
Rep Power: 8
Bene505 will become famous soon enough Bene505 will become famous soon enough
For starting batteries, I'd use a very small 12v panel and no controller. If your panel is small enough, you don't need a controller, just make sure it's small enough.

It's not like you are using your starting battery for any loads between engine starting, so you only need enough to maintain that battery. Years ago I had a panel that was about 4" x 12". I used it to maintain a starting battery.

There's an article by Don Casey on boatus.com that talks about this:
Installing a Solar Panel to Maintain Batteries by Don Casey
Quote:
...
Wet-cell batteries self-discharge at about 1% per day-more in hot weather, less when it's cold. So to float charge the battery, i.e., maintain a full charge, we need an equivalent charge rate. For a 100-amp-hour battery, that means a solar panel with a daily output of about one amp-hour.

Solar panels, however, are rated in watts. To determine the output current in amps, divide the watt rating by 15-the approximate true output voltage of a typical solar panel. Thus a five-watt panel has a maximum output of about 0.33 amps. But rated output only occurs at high noon; the rest of the time, the panel puts out less. Expect average output to be the equivalent of about five hours of rated output per day. That makes the expected daily output of a five-watt panel about 1.65 amp-hours (5 x 0.33).

Allowing for recharging inefficiencies, this is still about 50% more than necessary to float a 100-amp-hour battery. A good rule of thumb is 3.5 watts per 100 amp-hours of battery capacity. But throw in an occasional sunless day, put blocking diodes in the circuit, and let the bilge pump run once in a while, and five watts will be about right. A small amount of extra capacity won't damage the batteries as long as you maintain the water level in them. ...
I would err on the side of fewer watts for a starting battery, and use a maximum of 2 watts of solar power for each 100AH of battery. It's a simple solution requiring no charge regulator.


Depening on the size of your batteries, your 5w solar panel could possibly be used if you split-up the charging between the house and starting batteries, using diodes. Casey talks about that too.

Regards,
Brad
__________________
.
.
Great minds discuss ideas;
Average minds discuss events;
Small minds discuss people.
.
The best minds discuss sailing.
.

Last edited by Bene505; 01-04-2012 at 09:49 PM.
Reply With Quote Share with Facebook
Reply


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

 
Posting Rules
You may post new threads
You may post replies
You may post attachments
You may edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is On


Similar Threads
Thread Thread Starter Forum Replies Last Post
solar panel alan_21_us Gear & Maintenance 12 07-31-2008 10:18 PM
New davit with wind and solar charging dsbentley Gear & Maintenance 17 08-03-2006 10:33 AM
Charging with Solar Power Kevin Jeffrey Gear and Maintenance Articles 0 07-28-2003 08:00 PM
solar panel maestro Gear & Maintenance 3 11-20-2002 11:02 AM
Charging with a Solar Panel Sue & Larry Gear and Maintenance Articles 0 11-22-2001 07:00 PM


All times are GMT -4. The time now is 08:36 AM.

Add to My Yahoo!         
Powered by vBulletin® Version 3.8.7
Copyright ©2000 - 2014, vBulletin Solutions, Inc.
SEO by vBSEO 3.6.1
(c) Marine.com LLC 2000-2012

The SailNet.com store is owned and operated by a company independent of the SailNet.com forum. You are now leaving the SailNet forum. Click OK to continue or Cancel to return to the SailNet forum.