Solar panel connection-need advice

Jun 17, 2012
201
C&C 35 MKIII Manitowoc, WI
We are currently sailing our 2002 356 in the Great Lakes for the summer. To help battery life while on the hook-I installed (2) 100 watt panels. My battery bank consists of (2) separate 12v batteries wired in parrellel. And I can select 1,2 or both with the battery selector switch. So I connected the combined output from the solar panel to controller and then connected the controller output to battery 1. That seems to be working fine, but since the solar panels are putting out 20v in good sun I would like to charge both batteries. My problem or question is how can I do this. Since the negatives of the 2 12v batteries are already connected it would be simple to simply jump a lead from the solar panel conductor positive lead at battery 1 to battery 2. Thus charging both batteries. However unless I’m missing something-doing this would then make my battery selector switch useless because the battery positives would the be always be connected. I need advice. Thanks
 
Feb 6, 1998
11,667
Canadian Sailcraft 36T Casco Bay, ME
We are currently sailing our 2002 356 in the Great Lakes for the summer. To help battery life while on the hook-I installed (2) 100 watt panels. My battery bank consists of (2) separate 12v batteries wired in parrellel. And I can select 1,2 or both with the battery selector switch. So I connected the combined output from the solar panel to controller and then connected the controller output to battery 1. That seems to be working fine, but since the solar panels are putting out 20v in good sun I would like to charge both batteries. My problem or question is how can I do this. Since the negatives of the 2 12v batteries are already connected it would be simple to simply jump a lead from the solar panel conductor positive lead at battery 1 to battery 2. Thus charging both batteries. However unless I’m missing something-doing this would then make my battery selector switch useless because the battery positives would the be always be connected. I need advice. Thanks

1 - Where is the controller in all of this?

With 200W of array you NEED a solar controller!

2 - Do you have 1 starting battery and 2 house batteries physically wired in parallel?

3 - Or do you have 2 12V batteries total that are only in parallel when the switch is on BOTH?

DO NOT make a parallel jumper between two banks for the solar unless that jumper is intended to permanently parallel the banks and is LARGE GAUGE wire (same gauge as the starter motor cable on-board). If you do this with solar gauge wire you run a very, very high risk of starting a fire.
 
Jun 17, 2012
201
C&C 35 MKIII Manitowoc, WI
Thanks Maine Moderator. Yes there is a solar controller in my system. And no there is no aux starter battery. I only use the 2 -12v batteries utilized together or separately via the battery selector switch. Currently the 2 combined solar panels charge only 1 of the batteries. My original question is they any way to connect the solar panels to continually charge both batteries simultaneously? Thanks for your comments
 
Jun 17, 2012
201
C&C 35 MKIII Manitowoc, WI
One more thing. Obviously if I did use the large AWG conductor to permit my solar to charge both batteries simultaneously that would render my current battery selector switch ineffective. Is that correct?
 
Feb 6, 1998
11,667
Canadian Sailcraft 36T Casco Bay, ME
One more thing. Obviously if I did use the large AWG conductor to permit my solar to charge both batteries simultaneously that would render my current battery selector switch ineffective. Is that correct?
Correct.

I would suggest placing the two existing batteries in parallel as house and purchasing a small "aux" or reserve battery for emergency use/starting.

You can charge both banks together with a voltage sensing relay otherwise known as a VSR, combiner or ACR. For solar applications the Sterling ProLatch-R is one of my favorites. It draws almost no current off the system when the solar is not producing. It will also charge both banks anytime the alternator or battery charger is operating. These are sized based on how many amps your charger or alternator are. For example if you had a 100A charger or alternator you would want to choose the 160A model. If your charger and alternator are both well under 80A then the 80A unit would be fine..
 
Sep 25, 2008
957
Macgregor & Island Packet VENTURE 25 & IP-38 NORTH EAST, MD
Could he just keep the battery selector switch in the "all" position when letting the boat sit?
 
Feb 6, 1998
11,667
Canadian Sailcraft 36T Casco Bay, ME
Could he just keep the battery selector switch in the "all" position when letting the boat sit?

Sure, but you've now got potential loads on when you don't want them or intend for them to be on. As an example, earlier this spring I had a customer leave his battery switch ON, thinking everything was off. He had forgotten about his engine room light being ON... He ruined almost $1700.00 worth of AGM batteries. If he had just spent that extra few seconds he'd still have that $1700.00....

Shutting off a battery switch when you leave a boat is just a good practice.
 
Oct 27, 2016
0
Seattle
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Aug 15, 2013
193
Hunter 35.5 Legend 003 San Carlos, Sonora, Mexico
OK, I have to share here. The ACR relay, yes, that is a solution, not one I would use for this application. That would be more for something using extremely large DC currents. 200W of solar, not so much....It's a little brute force in my onion.
My suggestion would be to use either two separate charge controllers or a charge controller made to charge two batteries. The last thing you want to do is cheap out on taking care of your batteries.
1. They are expensive.
2. They are a pain int he ass to replace
3. If you overcharge them you will ruin them and burn down your boat.
4. If you undercharge them they will not last you a year.
5. If you kluge something together, unless you really know what you are doing you may burn down your boat.
6. No electricity sucks on today's boats, take care of your batteries and they will take care of you.
7. Fuse anything you connect to the positive post as close as possible to the positive post. Use Marine Grade wiring (https://gregsmarinewiresupply.com/). If you crimp, solder the connection. Use heatshrink.

So go take a look at this controller:
https://www.morningstarcorp.com/products/sunsaver-duo/
There is also a remote meter kit for it I highly recommend. I am on the 4th year of leaving my boat in Mexico for 6-9 months at a time and my batteries are as strong as there were when I bought them. I have 4-220Ah 6V for house & 2-220Ah 6V for backup/starting on 100W of PV. The controller has a periodic boost feature that ensures the batteries are fully charged, electrolyte mixed and not stratified, without continuous overcharging. Seriously. I get nothing from this other than to share what I know, but I do know what I am talking about. Google my name Steve Harrington and Charge Controllers.....
I like my Ice Cubes for my Gin & Tonic while sailing the Sea of Cortez - that requires electricity. All good.
Fair winds and good charging....
 
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Mar 20, 2012
3,983
Cal 34-III, MacGregor 25 Salem, Oregon
The ACR relay, yes, that is a solution, not one I would use for this application.

That would be more for something using extremely large DC currents. 200W of solar, not so much....It's a little brute force in my onion.
My suggestion would be to use either two separate charge controllers or a charge controller made to charge two batteries.
I would agree that IF it was only solar that was ever giving a charge, a dual output solar controller may be a fair option, but when one has other charge sources, an acr makes the most sense for dependable multiple bank charging for ALL sources..
its my opinion that just because two solar controllers are more expensive than an affordable ACR, it is not better or simpler in this type of simple application.
the acr type devices are very affordable, and very simple to install it... and afterwards, one can then forget about it and let it do what it was designed for.

1 ACR can take care of allowing incoming current to pass into both banks, while keeping them isolated from each other.... and not only the output from the solar, but from ALL charging sources, no matter how many they may be.. (alternator, solar, wind, shore power charger, water current generator)

200 watts (rated) may be as much as 16amps in ideal conditions, but more realistically an average of 6-8 amps when using non tracking panel mountings, and in a 12v system there really is not a "too low of input" to make an acr type device NOT be a good choice.....

solar controllers and ACR devices have 2 very different purposes, but the end result is keeping the batteries charged properly with the least amount of cost and equipment, and yet the most dependability. the ACR answers this call.
 
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Aug 15, 2013
193
Hunter 35.5 Legend 003 San Carlos, Sonora, Mexico
Disagree. Crimp alone is fine, if it's a proper crimp.
If the crimp is covered with heatshrink that is sealed with adhesive, then yes, that is fine. If the connection is exposed to the air (or worse - salt air) it will only be a matter of time before corrosion takes place and you start to develop a voltage drop across the connection reducing the voltage your batteries will charge up to because of that additional voltage drop. In addition, if there is enough corrosion this connection will get overheated and could potentially start a fire (especially in connections to inverters or chargers).
 
Aug 15, 2013
193
Hunter 35.5 Legend 003 San Carlos, Sonora, Mexico
Centerline, good point on the multiple charging sources. I suppose I was just looking at it from the strictly solar person's perspective. There are pros and cons to both ways but they will both work. I appreciate your opinion.