Who is successfully using a small solar panel? (less than say, 30 watts)

[chriscampbell]

BTW, love this forum! Thanks to everyone for your help.

I'm researching my solar panel options. I want something small and as simple as possible to keep my single battery going and recovering from weekend use. I only have lights, bilge pump, and electric start. I've heard from some of you that I should avoid small wattage systems. But I keep running into comments and reviews from people saying how they are running something like a 15 watt panel and it keeps them charged up perfectly.

So, who out there is successfully running a small solar panel and what is your setup?

 

[rgranger]

This is what I did on my H26

 

[chriscampbell]

This is what I did on my H26

View attachment 199747

So what is that - 10 watts or so? What is your usage and how does it do keeping your battery charged?

 

[berner73]

Not sure what you're definition of 'successful' is, so I wont make that claim. I still haven't found the time to write up the project - but based largely on the article found below, I built a similar system (BTW, if you find value in the information linked below, please consider donating to Rodd's stroke recovery fund @ https://paypal.com/donate/?hosted_button_id=NLBJAT2KVK4RQ&source=url).

Maine's small solar panel article

I used a 30 Watt monocrystalline Renogy panel, a 4A Genesun MPPT controller and appropriate connectors/wiring/fusing. I also fabricated a collabsable stainless steel bracket to mount the panel to. This setup has done a great job at keeping 2 'Group 31' batteries topped off on a mooring for the past 2 seasons.

 

[dlochner]

There are many folks who will claim their small panels are successful at keeping the battery charged. The question to ask is how do they know their panel is successfully keeping the battery charged? And what is the definition of successful? The other question to ask is how much power is actually drawn from the battery each week and what percentage of the full rated battery's capacity is being used?

The article @berner73 links to delves into this a bit. Rod's advice is, as always, spot on. Although he is a bit more optimistic than Nigel Calder and his assessment of panels production.

To really understand how well a charging system is working, a good State of Charge battery monitor is essential, although for a lightly used single battery system in a small boat it may not be cost effective.

Advances in Onboard Solar - Professional BoatBuilder Magazine

Advances in onboard marine solar technology improved efficiency and lowered the cost. But they also introduced more complexity.

www.proboat.com

 

[rgranger]

So what is that - 10 watts or so? What is your usage and how does it do keeping your battery charged?

I think it was a 10W. I also had a 6A alternator on the Tohatsu so between the two sources, I never had issues. All of my bulbs were switched to LED and I had a VHF and some fans. The only other thing that I used the electrical system for was to charge my iPhone. That is all of the electrical I needed. I had two deep cells (probably overkill) so... it worked just fine.

Here are some more pics

 

[Stu Jackson]

The other question to ask is how much power is actually drawn from the battery each week and what percentage of the full rated battery's capacity is being used?

Actually, Dave it should be the ONLY question.

Ahs removed vs. ahrs returned (including whatever inefficiencies, etc.). Small loads on weekends vs. small input over a long (relatively) period of time can work quite well.

I have an old 11W (gasp!!!) panel. When I left SF to move to BC in 2016, I bought a $20 controller and hooked it up to my house bank. When I returned month later, all was well.

When this panel finally dies, and it will, I will just get a bigger one. The controller is good for 20W.

Otherwise, Dave, you're right about learning how to know your battery bank actually got FULLY charged. Unless one does the math, one simply won't know. But it's rather simple math, after all, like balancing a checkbook.

 

[berner73]

@dolchner's point is absolutely spot on.

"To really understand how well a charging system is working, a good State of Charge battery monitor is essential"

I installed a 1st generation Balmar Smartgauge on the boat a couple of years prior to the solar panels, so in our case that's what's used to measure SOC. I've read varying opinions on the Balmar battery monitor, and I've never verified our bank's SOC independent of the Smartgauge.

 

[Richard19068]

BTW, love this forum! Thanks to everyone for your help.

I'm researching my solar panel options. I want something small and as simple as possible to keep my single battery going and recovering from weekend use. I only have lights, bilge pump, and electric start. I've heard from some of you that I should avoid small wattage systems. But I keep running into comments and reviews from people saying how they are running something like a 15 watt panel and it keeps them charged up perfectly.

So, who out there is successfully running a small solar panel and what is your setup?

I thought a lot of your question was covered in your post from October 7.

I had a 25 watt panel for years that I used similarly to what you describe and it served me well.

I think the bottom line is that as mentioned above, yes, you should know what your usage is. But, with the low cost of small panels these days why don't you just get a 25 or 30 watt panel and a 10 amp controller and hook it up and use it. I wired mine permanently and put it in the sun when anchored/moored/slipped and put it below when sailing. Easy.

It will either work for you or not and you have little to lose. It seems like the worst things that could happen is you would have to use the pull starter on your engine and/or get some reduced battery life from possible undercharging. If you get 2 or 3 or 4 years from a battery rather than 3 or 4 or 5 it isn't that big of an expense.

Just my 2 cents.

 

[TomY]

BTW, love this forum! Thanks to everyone for your help.

I'm researching my solar panel options. I want something small and as simple as possible to keep my single battery going and recovering from weekend use. I only have lights, bilge pump, and electric start. I've heard from some of you that I should avoid small wattage systems. But I keep running into comments and reviews from people saying how they are running something like a 15 watt panel and it keeps them charged up perfectly.

So, who out there is successfully running a small solar panel and what is your setup?

I am successful!

I have a 20-watt panel charging 2 grp 27 LA batteries. It's primarily doing what you're looking for; trickle charging the batteries when the boat is on the mooring for a week or two between uses. It has a small (cheap) solar regulator.

Basically, this allows me to use the boat for a few days and not have to worry about running the engine to charge. I can sail in and out of anchorages, sit for a few days, etc.

But this is more about how we like coastal sail; no refrigeration, LED bulbs below for lighting, small devices doing most of our e-navigation, and a third battery for the engine starter/windlass. Bottom line; our batteries are never discharged very far and live in a fully charged state. I predict this may get me another year out of them, say 6 as opposed to 5 seasons. (whoopie,..).

Once we're on board for several weeks of course it won't keep up. But I'm surprised how much it helps.

I'd bet you'd do well with a 20-30 watt panel, small regulator, and that's it. You have a perfect battery alarm; your outboard starter won't work but you have back-up - your arm to pull the recoil starter. Before going to a bigger panel, I'd consider adding another battery.

Enjoy your lack of energy complexity.

 

[Stu Jackson]

Before going to a bigger panel, I'd consider adding another battery.

Not necessarily.
Unless and until he does an Energy Budget, adding batteries will NEVER address a situation where what is going out is larger than what is coming back in (between uses, in his case).
Having more "storage" is utterly useless unless it can be refilled.

 

[JamesG161]

Having more "storage" is utterly useless unless it can be refilled.

Same as your onboard fuel tank.
Jim...

 

[chriscampbell]

I am successful!

I have a 20-watt panel charging 2 grp 27 LA batteries. It's primarily doing what you're looking for; trickle charging the batteries when the boat is on the mooring for a week or two between uses. It has a small (cheap) solar regulator.

Basically, this allows me to use the boat for a few days and not have to worry about running the engine to charge. I can sail in and out of anchorages, sit for a few days, etc.

But this is more about how we like coastal sail; no refrigeration, LED bulbs below for lighting, small devices doing most of our e-navigation, and a third battery for the engine starter/windlass. Bottom line; our batteries are never discharged very far and live in a fully charged state. I predict this may get me another year out of them, say 6 as opposed to 5 seasons. (whoopie,..).

Once we're on board for several weeks of course it won't keep up. But I'm surprised how much it helps.

I'd bet you'd do well with a 20-30 watt panel, small regulator, and that's it. You have a perfect battery alarm; your outboard starter won't work but you have back-up - your arm to pull the recoil starter. Before going to a bigger panel, I'd consider adding another battery.

Enjoy your lack of energy complexity.

That's great - thanks for your feedback. That's about the size I'm thinking about.

 

[chriscampbell]

I thought a lot of your question was covered in your post from October 7.

I had a 25 watt panel for years that I used similarly to what you describe and it served me well.

I think the bottom line is that as mentioned above, yes, you should know what your usage is. But, with the low cost of small panels these days why don't you just get a 25 or 30 watt panel and a 10 amp controller and hook it up and use it. I wired mine permanently and put it in the sun when anchored/moored/slipped and put it below when sailing. Easy.

It will either work for you or not and you have little to lose. It seems like the worst things that could happen is you would have to use the pull starter on your engine and/or get some reduced battery life from possible undercharging. If you get 2 or 3 or 4 years from a battery rather than 3 or 4 or 5 it isn't that big of an expense.

Just my 2 cents.

Ha, yeah. You've all been great answering my questions. I should probably just start buying stuff and figure it out. Every time I think I'm close to pulling the trigger I get sidetracked on something. For instance, the panel has 16awg leads but most of the connector wire options are 12 or larger. The inline fuse holders have short pigtails so I'll need to buy butt connectors and shrink wrap. etc etc

Anyway, I appreciate you weighing in! I'm enjoying learning on this site.

 

[chriscampbell]

Actually, Dave it should be the ONLY question.

Ahs removed vs. ahrs returned (including whatever inefficiencies, etc.). Small loads on weekends vs. small input over a long (relatively) period of time can work quite well.

I have an old 11W (gasp!!!) panel. When I left SF to move to BC in 2016, I bought a $20 controller and hooked it up to my house bank. When I returned month later, all was well.

When this panel finally dies, and it will, I will just get a bigger one. The controller is good for 20W.

Otherwise, Dave, you're right about learning how to know your battery bank actually got FULLY charged. Unless one does the math, one simply won't know. But it's rather simple math, after all, like balancing a checkbook. View attachment 199761

Thanks for the example.

 

[chriscampbell]

I think it was a 10W. I also had a 6A alternator on the Tohatsu so between the two sources, I never had issues. All of my bulbs were switched to LED and I had a VHF and some fans. The only other thing that I used the electrical system for was to charge my iPhone. That is all of the electrical I needed. I had two deep cells (probably overkill) so... it worked just fine.

Here are some more pics

View attachment 199748

View attachment 199749

View attachment 199750

Very helpful - thanks! That sounds pretty close to my power needs - but no VHF and only one battery. I'm starting to lean toward just getting a 10 or 15 watt panel and some alligator clips. It's a slippery slope.

 

[chriscampbell]

There are many folks who will claim their small panels are successful at keeping the battery charged. The question to ask is how do they know their panel is successfully keeping the battery charged? And what is the definition of successful? The other question to ask is how much power is actually drawn from the battery each week and what percentage of the full rated battery's capacity is being used?

The article @berner73 links to delves into this a bit. Rod's advice is, as always, spot on. Although he is a bit more optimistic than Nigel Calder and his assessment of panels production.

To really understand how well a charging system is working, a good State of Charge battery monitor is essential, although for a lightly used single battery system in a small boat it may not be cost effective.

Advances in Onboard Solar - Professional BoatBuilder Magazine

Advances in onboard marine solar technology improved efficiency and lowered the cost. But they also introduced more complexity.

www.proboat.com

Thanks for your help, Dave. I appreciate all of your responses.

 

[chriscampbell]

Not sure what you're definition of 'successful' is, so I wont make that claim. I still haven't found the time to write up the project - but based largely on the article found below, I built a similar system (BTW, if you find value in the information linked below, please consider donating to Rodd's stroke recovery fund @ https://paypal.com/donate/?hosted_button_id=NLBJAT2KVK4RQ&source=url).

Maine's small solar panel article

I used a 30 Watt monocrystalline Renogy panel, a 4A Genesun MPPT controller and appropriate connectors/wiring/fusing. I also fabricated a collabsable stainless steel bracket to mount the panel to. This setup has done a great job at keeping 2 'Group 31' batteries topped off on a mooring for the past 2 seasons.

Thank you - I have found his information helpful! Donated.

 

[Stu Jackson]

I'm starting to lean toward just getting a 10 or 15 watt panel and some alligator clips. It's a slippery slope.

Chris, I understand your "slope" and raise you one toboggan. But please, don't do this. Alligator clips are poor connectors. And if you leave a panel connected to your battery without a controller you'll kill your battery by overcharging it. Wattage doesn't kill batteries, over voltage does. I hope you've read Maine Sail's solar article, if not here it is again, with a bonus link:
Solar Systems: Selection, Installation & Controllers by Maine Sail SUPERB

Installing A Small Marine Solar System by Compass Marine How To

Do I Need a Controller for Solar?

Do I Need A Solar Charge Controller ??

Chris, this is an engineering issue, not an emotional one. Wanna join two different gauges of wire? They make stepped butt connectors:

Step Down

www.ancorproducts.com

If, OTOH, you're just being nice by answering individual posts, then you're welcome!

 

[chriscampbell]

Okay, okay - fair enough. I’m convinced on the controller issue.

So I need:

• Panel (20-30amp)
• MC4s to put on the panel leads
• MC4 adapter to the controller
• 10amp controller
• Battery terminal cables to the controller
• In line fuse holder and 10amp blade fuse
• Butt connectors and shrink wrap to splice in the fuse holder
• Crimper

Cheers!