 |
26-05-2016, 05:20
|
#1
|
Registered User
Join Date: Apr 2014
Location: Ft Lauderdale Florida
Boat: Catalina 320
Posts: 142
|
Emergency solar control
My solar controler went out and FedEx won't have my new one to me till Friday. I want to connect one 100 watt panel direct and cover 4 cells to lower the voltage to 14. Will this work or is it time to start the engine up and let it run?
Thanks in advance, Woody
Sent from my SAMSUNG-SM-G890A using Cruisers Sailing Forum mobile app
|
|
|
26-05-2016, 06:22
|
#2
|
Senior Cruiser

Join Date: Oct 2007
Location: 29° 49.16’ N 82° 25.82’ W
Boat: Pearson 422
Posts: 16,307
|
Re: Emergency solar control
I'm not an expert on solar panels but from my limited knowledge it will depend on how your panel is wired and which cells you cover. Solar panels, like batteries, can be wired in series and parallel but panels are generally wired in a combination of the two.
Also a question, what's the voltage of your panel uncovered? Specs might call it open circuit voltage or Voc.
I think the safest option is to disconnect the panel from your batteries, hook up a volt meter, cover some cells and look at the voltage on the meter.
__________________
The water is always bluer on the other side of the ocean.
Sometimes it's necessary to state the obvious for the benefit of the oblivious.
Rust is the poor man's Loctite.
|
|
|
26-05-2016, 06:46
|
#3
|
Registered User
Join Date: Aug 2014
Location: Astoria, NY
Boat: Sabre 38
Posts: 566
|
Emergency solar control
This same question was asked and answered by Maine Sail and Stu Jackson just a few days ago. See if you can find that thread.
I believe the answer was that you would be running with scissors if you connect the panels directly to the batteries. You in theory can connect them and manually monitor voltage at the terminals till they hit 14.4 (or whatever bulk voltage you batteries call for) then manually disconnect the panels. But if you don't pay attention and disconnect at the right time or will fry your bank.
Converting panel cells may slow things down or give you more headroom to make an error...
Good luck.
Sent from my iPhone using Cruisers Sailing Forum
__________________
Stephen
s/v Carpe Ventum
1983 Sabre 38
My Intro
|
|
|
26-05-2016, 07:03
|
#4
|
Registered User
Join Date: Apr 2014
Location: Ft Lauderdale Florida
Boat: Catalina 320
Posts: 142
|
Re: Emergency solar control
I checked the open voltage and it's at 18.6 now. This is more experimental then necessary, going to West marine after lunch.
I'll look for Stu's thread on the subject.
Sent from my SAMSUNG-SM-G890A using Cruisers Sailing Forum mobile app
|
|
|
26-05-2016, 18:51
|
#5
|
Moderator Emeritus

Join Date: Sep 2006
Posts: 4,663
|
Re: Emergency solar control
Covering cells will not reduce the output voltage in a controllable manner, and it will reduce the current, also not easily controlled. All I can suggest is to connect the panel directly and monitor the battery voltage, disconnecting when you hit your target.
__________________
Paul Elliott, S/V VALIS - Pacific Seacraft 44 #16 - Friday Harbor, WA
www.sailvalis.com
|
|
|
26-05-2016, 19:08
|
#6
|
Registered User
Join Date: Jan 2012
Location: St Pete
Boat: Sabre 34 , Island Packet 38
Posts: 745
|
Re: Emergency solar control
I would think that the size of the battery bank would be important to know before giving an opinion , but.......
If you have a decent size bank of 300 or 400 amp hour capacity, connect it up until your batteries get to 13.6 , then turn on the fridge. I would have to believe that with normal power usage, the single 100 watt panel won't get you above 13.6. If you are leaving the boat and can't moniter then I would not leave it connected.
__________________
All that is necessary for the triumph of evil is that good men do nothing. Edmund Burke
|
|
|
27-05-2016, 07:30
|
#7
|
Registered User
Join Date: Apr 2014
Location: Ft Lauderdale Florida
Boat: Catalina 320
Posts: 142
|
Re: Emergency solar control
It worked without any problems. I left both 100 watt panels exposed to full sun and the batteries pulled the voltage down. After checking the voltage every half hour, it never went above 13.8 at the posts.
Sent from my SAMSUNG-SM-G890A using Cruisers Sailing Forum mobile app
|
|
|
27-05-2016, 11:15
|
#8
|
Moderator Emeritus

Join Date: Sep 2006
Posts: 4,663
|
Re: Emergency solar control
Quote:
Originally Posted by Drift Woods
It worked without any problems. I left both 100 watt panels exposed to full sun and the batteries pulled the voltage down. After checking the voltage every half hour, it never went above 13.8 at the posts.
Sent from my SAMSUNG-SM-G890A using Cruisers Sailing Forum mobile app
|
But, unless you have a load that magically draws just the right amount, the batteries will eventually over-charge. You will need to regularly monitor the voltage to avoid an extended over-charge.
__________________
Paul Elliott, S/V VALIS - Pacific Seacraft 44 #16 - Friday Harbor, WA
www.sailvalis.com
|
|
|
27-05-2016, 17:17
|
#9
|
Moderator
Join Date: May 2008
Location: cruising SW Pacific
Boat: Jon Sayer 1-off 46 ft fract rig sloop strip plank in W Red Cedar
Posts: 21,562
|
Re: Emergency solar control
Quote:
Originally Posted by Drift Woods
It worked without any problems. I left both 100 watt panels exposed to full sun and the batteries pulled the voltage down. After checking the voltage every half hour, it never went above 13.8 at the posts.
Sent from my SAMSUNG-SM-G890A using Cruisers Sailing Forum mobile app
|
Fancy that! Despite all the doom predicted, it worked, just like you thought it would, and like I reported (in that other thread) we have done for years.
Obviously, it does require some monitoring, and is not suitable for long term unattended, low load usage. For a typical cruising boat, the ongoing loads help avoid overcharging. Undercharging is a far more prevalent worry!
Well done!
Jim
__________________
Jim and Ann s/v Insatiable II, lying Port Cygnet Tasmania once again.
|
|
|
27-05-2016, 20:02
|
#10
|
Registered User
Join Date: Apr 2014
Location: Ft Lauderdale Florida
Boat: Catalina 320
Posts: 142
|
Re: Emergency solar control
Quote:
Originally Posted by Jim Cate
Fancy that! Despite all the doom predicted, it worked, just like you thought it would, and like I reported (in that other thread) we have done for years.
Obviously, it does require some monitoring, and is not suitable for long term unattended, low load usage. For a typical cruising boat, the ongoing loads help avoid overcharging. Undercharging is a far more prevalent worry!
Well done!
Jim
|
Yes Jim I read the thread you are referring to, it was suggested above. This morning after resting all night the 320 house bank was almost 80% after changing the previous day. So instead of buying a backup I plugged my panels in and turned on the fridge ( also mentioned above.)
Thanks for the help, Woody
Sent from my SAMSUNG-SM-G890A using Cruisers Sailing Forum mobile app
|
|
|
28-05-2016, 17:32
|
#11
|
Moderator Emeritus
Join Date: Aug 2005
Location: Carlsbad, CA
Boat: 1976 Sabre 28-2
Posts: 7,505
|
Re: Emergency solar control
Left one panel hooked up to brand new 300 amp hour battery bank with no current load for a couple of days. Now know for certain you can blow up batteries.
Would only do it in conjunction with a volt meter and frequent checking with hydrometer. Definitely wouldn't leave panels unattended while hooked up. A relatively constant load like refrigeration would probably suffice to keep from overcharging the batteries but be careful.
__________________
Peter O.
'Ae'a, Pearson 35
'Ms American Pie', Sabre 28 Mark II
|
|
|
28-05-2016, 17:55
|
#12
|
Moderator
Join Date: May 2008
Location: cruising SW Pacific
Boat: Jon Sayer 1-off 46 ft fract rig sloop strip plank in W Red Cedar
Posts: 21,562
|
Re: Emergency solar control
Quote:
Originally Posted by roverhi
Left one panel hooked up to brand new 300 amp hour battery bank with no current load for a couple of days. Now know for certain you can blow up batteries.
Would only do it in conjunction with a volt meter and frequent checking with hydrometer. Definitely wouldn't leave panels unattended while hooked up. A relatively constant load like refrigeration would probably suffice to keep from overcharging the batteries but be careful.
|
Hoping to never find out for myself, so would you mind telling us what the actual failure mode was? I assume that the term "blowing up" was not literal (I hope).
Jim
PS How big was the panel?
__________________
Jim and Ann s/v Insatiable II, lying Port Cygnet Tasmania once again.
|
|
|
 |
Thread Tools |
Search this Thread |
|
|
Display Modes |
Rate This Thread |
Linear Mode
|
|
Posting Rules
|
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts
HTML code is Off
|
|
|
|
Advertise Here
Recent Discussions |
|
|
|
|
|
|
|
|
|
|
|
|
Vendor Spotlight |
|
|