Solar charging while storing boat.

mgarr682

My boat is currently stored in a storage yard along with my travel trailer since my acre of ground is too steep to park the boat or travel trailer on. Right now to keep my batteries charged when not using the boat I have to remove them and bring them home to be charged periodically in the garage and then returned to the boat before use. I'm wondering if one the solar chargers I've seen advertised would produce enough of a charge to keep the batteries charged up during storage periods.

My boat has two batteries, both group 24, one a cranking battery and the other a deep cycle battery, both wired through a BEP VSR cluster. There is no drain on the batteries when stored, simply turn two switches to off on the VSR cluster and pull the two fuses on the only items connected directly to the batteries (bilge pump and Wallas stove) so I shouldn't need to account for any draw from electrical devices, just the voltage drop over time that lead/acid batteries experience.

I've seen some of the travel trailers and a MacGregor 26 at the storage yard with small solar panels attached, approx. 1'x1.5'. Do these small panels provide enough of a charge to keep the battery topped up during storage periods? Would I need two, one for each battery? Would a solar panel over charge the batteries?

Any help or suggestions appreciated!

rogerar · Posted: Mon Feb 18, 2013 11:21 am Post subject:

You should be safe with no voltage regulator(solar controller) as long as the output of the panel(s) is 10% or less than the batteries' amp hour rating. I have a 10 watt panel directly hooked to each of my group 24 batteries, no problems.
Roger

thataway · Posted: Mon Feb 18, 2013 12:32 pm Post subject:

I like to disconnect the battery negative (or positive) cables, to be sure that there is no parasitic draw. Also the AGM have less self discharge. Occasionally there are memories on radios, GPS etc, which use small amount of power. Also the VSR may have some draw--from your post I believe that you are aware of this, and are sure that both terminals are disconnected.

I kept both the C Dory 22 and 25, and Road Trek stored both in S. Calif and in Las Vegas, with one of the small solar panels for each battery. I would leave the units as long as 6 months and the batteries would be up and ready to go when I returned. I got a cheap steel sawhorse, and cabled the solar panel to that, then chained the saw horse to the trailer frame or truck frame--just to prevent "sticky fingers".

Robert H. Wilkinson · Posted: Mon Feb 18, 2013 2:49 pm Post subject:

Mike, agree with Roger and Bob - just make sure your batteries are fully charged to start with. A 10 watt panel/per battery should be OK. Point them south and bear in mind - a prolonged snow load will compromise their current output. Some light will get thru 1-2" of snow and after about 8 continuous hours of full sun it is usually melted off.

Regards, Rob

colobear · Posted: Mon Feb 18, 2013 4:11 pm Post subject:

I have a 20W panel connected to my two GP24 house batteries wired in parallel. It keeps them charged in storage and also allows me to use them more while anchored cruising or moored without shorepower. I do have a 7A controller connected in series with the panel just to make sure there is no reverse flow. The panel does not, I think, provide enough charging to completely top off the batteries but does keep them from discharging too much.

mgarr682 · Posted: Fri Mar 01, 2013 10:35 am Post subject:

I think I've found my solution. Northern Tool sent me a few coupons in the mail the other day so I used the $20 coupon on the purchase of two NPower 7 watt solar panels.

http://www.northerntool.com/shop/tools/product_200578631_200578631

I hooked them up to my two batteries for a few hours and according to my meter both batteries showed an increased voltage (0.5 volt on one, 0.6 on the other).

Norther Tool says they are 7 watt chargers but when I did the math (volts x amps = watts) on the specs in the documentation it came out between 5 and 6 watts.

This may solve my problem. Thanks for the advice and suggestions!

thataway · Posted: Fri Mar 01, 2013 10:57 am Post subject:

Barry, The twenty watt panel should easily keep your batteries fully charged in storage, if there is no drain--and the controller is almost essential with that large a panel

The "watts" are with direct 90 degree sunlight--if you are getting 75% of that over a day, it is very good. Even with my 180 watt solar panel in the Keya I am only probably running about 60% efficiency--with clouds, angle of sun etc over the 12 hour light period.

jkidd · Posted: Fri Mar 01, 2013 10:19 pm Post subject:

So could you hook the solar panel to the cranking battery and let the acr trip and combine the batteries and keep them charged with one panel?

mgarr682 · Posted: Sat Mar 02, 2013 8:32 am Post subject:

thataway · Posted: Sat Mar 02, 2013 12:56 pm Post subject:

I used two small solar panels, rather than combining the two batteries. With even a large solar panel--it would depend on the controller as to what voltage, and how much of the day that voltage was reached. I felt that the two solar panels, with completely isolated batteries was safer, no chance of both batteries going bad, and you arrived on the spot--with no way to start the engine. These were both in an RV and C Dory which were left unattended for up to 6 months at a time...

mgarr682 · Posted: Tue Mar 12, 2013 4:36 pm Post subject: It works.

Just an update. After plugging a 7 watt solar panel into each of my batteries via 12 volt outlets I'm finding my battery voltage at 12.59 to 12.63 on each battery every time I check. I just lay one solar panel on the dash in front of the steering wheel and the other on the driver's seat. So far it's working great.

potter water · Posted: Tue Mar 12, 2013 5:46 pm Post subject:

Hmmm...me thinks you are not keeping them topped up. If you were, they would be reading several tenths higher if the batteries are in good condition. But considering, if I read your last comment right, you are just laying the panels behind the window on the instrument panel, you are lucky to be getting any decent charge time at all. The small cheaper solar panels are particularly sensitive to angle to the sun and you are cutting the U.V rays out almost all together. Solar panels are mostly tuned to the U.V. spectrum, however, most glass, such as in your windows cut the U.V. way down. So I guess I'm a little mystified that you are getting any charging. The panels, when connected and metered with the right sun load on them should be putting out in excess of 13 volts if the batteries are low and not less than 2.8 or so with the panels removed on fully charged batteries.

I'm not an expert on these panels, but that is what my own reading has indicated.

A. 90 angle to the sun.
B. No intervening medium such as window type glass.
C. Panels will provide pretty good power even on cloudy days because the U.V. gets through moderate cloud layers.

All that and 2 cents gets you my expertise on anything and I'm sure it is worth every penny.

mgarr682 · Posted: Tue Mar 12, 2013 6:32 pm Post subject:

thataway · Posted: Tue Mar 12, 2013 6:35 pm Post subject:

Harry is correct, but I have seen reasonable charge with a small panel inside of the windshield on the dash, angled toward the sun (slightly to the South), and getting charges at mid day of 13 volts with bright sunlight. You will do much better with the panels outside, with a mount (just blocks) to angle toward the sun.

You would be best served with the batteries floating at a level of at least 12.7 volts. The 12.53, is a little lower than you would expect with a fully charged battery in good condition.

Sea Wolf · Posted: Tue Mar 12, 2013 10:06 pm Post subject:

Question (as long as we're at it):

Do deep cycle wet cell batteries typically charge up to the same voltage levels as their starting battery cousins and dual purpose type batteries?

My personal experiences cause me to doubt that they reach quite the same levels, but I don't have lot of data to go on.

I'm curious to know.

Joe. Teeth