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Solar Panel

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WindDancer
1st Mate

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USA
34 Posts

Initially Posted - 03/20/2006 : 23:37:53

I have just purchased a 15W panel with controler. I plan on installing two batteries running them through a battery switch. Is it best to install a volt meter on the battery switch common along with the solar panel as to read the status of each battery and the output of the panel. I plan on installing an isolation switch for the panel. Do I need to install a diode or is the controller good enough? Secondly, is it a good idea to install a bypass switch around the controller so that I can charge both batteries at the same time without damaging the batteries. I understand while charging individual batteries I will need to use the controller. Lastly, is it ok to mix battery types, and has anyone had trouble with the batteries venting in the cabin during charging

Lots of questions.....

Thanks,
Bruce

Bruce and Suzette
Five O' Clock Somewhere
2006 C250WB #861
Clearlake Ca

Edited by - on

OLarryR
Master Marine Consultant

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USA
3467 Posts

Response Posted - 03/21/2006 : 05:29:54

I have some photos of my setup on my website. I can't answer all your questions but from what I went thru, I'll offer some comments:

Normally, they indicate that one can get away without a solar controller if you have a 5 watt panel for one 12 volt battery. But when you use more than 5 watts per battery, most reference material will indicate that a solar controller is recommended. Solar controllers can be bought for low cost if only doing the basics (controlling/limiting the solar charging when batteries are fully charged). But you can also spend a lot more and get one with a lot of features that incorporate a diode preventing some power trickling back out thru the panel (ie @ night), also provide real time readout of the charging amps of the panel and also the voltage of each/both batteries. My setup uses the Morningstar Pro 15M Controller and by using the battery switch that was on my boat for the two batteries, I can monitor and charge either battery or both at same time.

The basic setup goes thru a 12 volt accessory plug and/or directly to the battery switch. You can also hook it right up to the batteries. I used the 12 volt accessory plug for starters but probably will hook it up directly to the battery switch if for no other reason but to hide the wires and free up the accessory plug for other uses. However, there are more sophisticated setups recommended for battery banks. The best setups utilize isolators, diodes or actually have separate solar panels for each battery. There are a number of reasons that justify going to a more sophisticated setup and mostly has to do with more effective charging and use of batteries when one is weaker than the other. However, once you make the investment into buying the panel and then a good controller that has the readouts you may desire if you desire readouts, you have by then made quite an investment along with adding the extra battery and battery switch. So...you may want to just utilize a battery switch and forgo the more sophisticated setup for now...or bite the bullet and go for it all.

Edited by - on

JohnMD
Navigator

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USA
207 Posts

Response Posted - 03/21/2006 : 08:51:32

These sites have a lot of information on solar charging and controllers.

http://www.solar-electric.com/

http://www.morningstarcorp.com/products/FAQ/

I think most controllers come with a blocking diode to prevent power drain at night(mine did).

The tech at Morningstar told me to make sure I fused my panel and controller to prevent costly problems.

I would wire the volt meter in such a way that I could check the voltage on each battery and the panel seperately. If you check them as a group, one battery could be bad and the panel output and other battery would hide that fact. One thing I never thought about when I was doing my system is that a volt meter, if left hooked up to a battery, will actually use power. You have to have a way to disconnect the volt meter from the circuit.

If you use the panel to charge both batteries at the same time (very normal thing to do), they should be the same size/type and age.

The controller will keep from overcharging your batteries which will keep your batteries from creating excessive amounts of gas and fumes.

I have a 20w panel and two batteries wired together. In two years I have never had to add water to the batteries or smelled the batteries. I leave my panel/controller hooked up 24x7x365 and it keeps my batteries full without ever needing any additional charging.

Edited by - on

OLarryR
Master Marine Consultant

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USA
3467 Posts

Response Posted - 03/21/2006 : 10:55:19

Hey John !

That link you provided, I assume that is where you bought your solar panel ?
In any case, that is same place I bought my panel and controller - Arizona Wind and Sun.

Your comments regarding the voltmeter: While it is true that a voltmeter will use a slight bit of power, maybe the analog/needle type voltmeters use more than the digital ones. In any case, I purposely bought the Morningstar Pro15M so I would get the voltage readings and since it is hooked up thru the battery switch, you can flip back and forthe between the batteries and get readings on either battery. The digital voltmeter must be very low load since it is common for the higher priced solar controllers to have the amp and volt readings on the display and they always read when the controller is on.

I have found that the volt readings do not reflect actual battery voltage unless read after the sun goes down or at least the controller indicates no amps. otherwise, the volts read higher when the solar panel is charging. Same goes for when the outboard motor is on, the volts will read way higher. But once the chargers are not charging, then the battery voltage settles down to stable reading.

By the way, as far as amps go, i experimented with different conditions to see how well the panel charges. if the panel is left flat on the cockpit seat, then the 20 watt panel puts out about .4 amps/hr. Tilted at less than perpendiculr to the sun and it then reads approx .6 - .8 amps/hr. if the panel is mounted directly perpendicular to the sun, then it gets the rated 1.2 amps/hr. Wave a hand over the panel and it drops signficantly. if a dock support pole or etc shades the panel, the panel amps can drop down all the way to zero.

Edited by - on

JohnMD
Navigator

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USA
207 Posts

Response Posted - 03/21/2006 : 14:13:01

Arizona Wind was out of the panel I was looking for, so, I got it elsewhere. You're probably right about the drain being minimal from a volt meter. Before I had a solar panel, I noticed that just leaving power to a volt meter plugged into my lighter outlet or leaving power to my stereo drained the battery after a few weeks. I also understand that some solar panels are more tolerant of shade than others (thats what the brochures say anyway). There's an excellent article on the Arizona Wind site about 'fully charged voltage' which is ~12.7 volts and 'charging voltage' which can be all the way up to 15.? volts. At night, my battery reads about 12.7. During the sunny day with nothing on and the battery charged, it reads about 13.5. The solar panel makes quite a difference.

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The Officers, Staff and members of this site only provide information based upon the concept that anyone utilizing this information does so at their own risk and holds harmless all contributors to this site.