Using Photovoltaic Panel to Maintain Boat Battery

Electrical and electronic topics for small boats
afinelli
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Using Photovoltaic Panel to Maintain Boat Battery

Postby afinelli » Tue Aug 24, 2021 9:15 am

Is it practical to use a Photovoltaic panel to maintain a 12-Volt boat battery?

Where would you install one on a open center console boat like [what was later clarified to be an 18-foot] c.1989 Boston Whaler OUTRAGE?

BACKSTORY Sometime two weeks will elapse between use of the boat. The boat has an automatically operating sump pump wired directly to the boat battery. Battery discharge hasn't been a problem so far.

I cannot envision where a photovoltaic panel would be mounted.

I have no idea what physical size panel and what electrical capacity photovoltaic panel would be involved.

Any thoughts or recommendation will be welcome. Thanks.

Jefecinco
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Re: Using Photovoltaic Panel to Maintain Boat Battery

Postby Jefecinco » Tue Aug 24, 2021 10:10 am

If you are using a wet slip with an electrical power source a battery maintainer connected to shore power would be a good choice. If you are storing your boat on it's trailer a boat cover would be good investment. It should keep your boat protected from harmful UV light and atmospheric pollution. It should also prevent rain from filling the sump thus saving your battery from cycling. Turning off off disconnecting the boat battery would also work.

If your boat is kept at a mooring a small solar charger should work for you. I would prefer a temporary mounting location for the solar array. A mount that makes it easy to to remove and store the array when the boat is in use. The controller and battery connection could be permanent or temporary. the design could be as simple as using velcro to mount the controller conveniently and a battery connection could use a pair of "dragon clips" to connect to the battery terminals.
Butch

afinelli
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Re: Using Photovoltaic Panel to Maintain Boat Battery

Postby afinelli » Wed Aug 25, 2021 11:21 pm

I appreciated the helpful input.

During the boating season we tie up at the float of our own dock, but there is no practical access to electric power there. The sump pump is wired to only battery and by-passes the battery switch.

Would mounting something on the float itself be crazy?

Any idea what physical size and charging capacity panel we'd be looking at?

Thanks.

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Phil T
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Re: Using Photovoltaic Panel to Maintain Boat Battery

Postby Phil T » Thu Aug 26, 2021 8:25 am

What size Outrage are we discussing?

Most boat I have seen mount the panels on a bracket on the console rail, or lay flat on the bow platform.

Boats will full covers usually have a bracket off the aft side rail with a cutout in the cover.
1992 Outrage 17
2019 E-TEC 90
2018 LoadRite 18280096VT
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Jefecinco
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Re: Using Photovoltaic Panel to Maintain Boat Battery

Postby Jefecinco » Thu Aug 26, 2021 10:00 am

Mounting a solar charger to the float seems like an excellent solution to the panel array mounting.

The charger controller may or may not be weatherproof. That would determine where and how it should be mounted.

I would consider a weatherproof plastic box, also mounted to the float, for the controller if the heat generated would not cause damage to either the box or controller.

Otherwise a console mounted controller could serve.
Butch

afinelli
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Re: Using Photovoltaic Panel to Maintain Boat Battery

Postby afinelli » Thu Aug 26, 2021 10:05 am

Phil T: the boat is an OUTRAGE 18.

Bow platform sounds interesting. I'm assuming the panel would be stowed when under way.

How might panel be secured when boat is tied up at float?

In this configuration the bow platform is largely taken up by a hatch cover.

Thanks for your input.

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Phil T
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Re: Using Photovoltaic Panel to Maintain Boat Battery

Postby Phil T » Thu Aug 26, 2021 12:26 pm

The panels tend to be small.

See this as an example. Not an endorsement.

https://www.westmarine.com/buy/nature-power--8-watt-semi-flex-solar-charger--19683952?recordNum=1
1992 Outrage 17
2019 E-TEC 90
2018 LoadRite 18280096VT
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jimh
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Re: Using Photovoltaic Panel to Maintain Boat Battery

Postby jimh » Thu Aug 26, 2021 4:31 pm

afinelli wrote:Is it practical to use a Photovoltaic panel to maintain a 12-Volt boat battery?
Yes. This is done everywhere there are boats and sunshine.

afinelli wrote:Any idea what physical size and charging capacity panel we [need]?

The amount of charging current you need is unknown. Apparently you do not need much because your narrative mentions that the boat battery does not become deeply discharge to the point where it won't crank over the engine even after sitting for two weeks. On that basis, ANY charging current is going to be useful, and you really do not need a lot of capacity.

The electrical voltage and current output of a photovoltaic panel depends on the intensity of the sunlight falling on the panel, the orientation of the panel with respect to the sun, and the weather. When the manufacturer specifies a current, that is the MOST current possible. The typical current will not constantly be the MOST possible.

Jefecinco wrote:The charger controller may or may not be weatherproof.

A charge controller is used with large panel arrays that produce perhaps 50-Volts of output. The charge controller converts whatever voltage and current is provided by the photovoltaic array to the appropriate voltage and current to match the attached battery terminal voltage.

Generally with a little panel {like the one Phil linked) that might produce 1-Ampere of current at best there will not be a charge controller. The battery itself will be the charge controller. The panel will just dump all the current it can into the battery.

If you mount the photovoltaic panel on land you can orient the panel to optimize its exposure to the sun. If the boat is on a mooring and swings around into random orientations, the panel can't be optimized in its orientation.

Around me are many docks with boat hoists operated by a 12-Volt battery. Most of these docks have a little photovoltaic panel connected to 12-Volt battery to provide charging current. It takes quite a bit of electrical power to operate the electrical motor in a boat hoist, and these rather small 1-foot x 2-foot panels seem to be sufficient to maintain the battery charge between hoist operation. (Although I do note that most of these boats on hoists seem to get used about once a week or less often.)

Keeping the battery charged by non-120-VAC devices is a good safety measure. Having 120-VAC on a dock is an invitation to problems with leakage current into the sea water.

afinelli wrote:Where would you install one on a open center console boat like [what was later clarified to be an 18-foot] c.1989 Boston Whaler OUTRAGE?

The exact location for a small photovoltaic panel on your particular boat will have to be solved by you. Because the panel output current is going to be low, there will not be a huge concern about voltage drop in the wiring from the panel to the battery, as long as you use a reasonable conductor size. With a small panel, with low voltage and current output, the panel should be close to the battery and connected by suitably chosen conductors so that most of the electrical power winds up in the battery, not in power lost in the cables.

For advice on choosing a conductor size see

https://continuouswave.com/whaler/refer ... tion1.html

Oldslowandugly
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Re: Using Photovoltaic Panel to Maintain Boat Battery

Postby Oldslowandugly » Fri Aug 27, 2021 11:26 am

For many years I used a [photovoltaic panel to charge the battery] on my boat. The panel was a small, 1.5-Ampere panel whose dimensions were about 4 x 12-inches. To mount the panel at the bow I used a bungee cord. My 30-HP engine always started.

Later when I upgraded to a larger 48-HP engine, I needed more battery charging. I changed to a charger [that employed a photovoltaic panel] that was 12 x 12-inches {i.e. three times larger] and rated for 2.5-Amperes output The photovoltaic charger worked better [than the smaller and lower current output panel mentioned earlier], but I found this panel was hard to mount; I broke several.

Now while the boat is at a dock with 120-VAC power, I use a charger that operates from 120-VAC shore power.

I still use the 2.5-Ampere photovoltaic charger. I mounted the photovoltaic panel to the forward side of the helm console of the boat. The 2.5-Ampere photovoltaic charger helps a lot [to maintain the battery charge] while the boat is drifting or is at anchored during angling.

With photovoltaic panels, the bigger [the panel] the better [the current and voltage output from the panel].

You may use a hinge-mounting method and then fold down the photovoltaic panel when you are on board.