Clipping more than 1 solar panel to the battery?

[duggybuggy]

I'm a bit new to boating, in particular solar power. I purchased a 100watt mono crystal panel with controller and clipped it on the battery. This was at the beginning of summer. It worked well. I never needed to run the generator. However, I didn't reckon on the great different that winter brings, and the battery went very flat.

The tv, which draws 2amps would not work off the battery as it was too flat. I'd charged it with the generator in the evening, but it hadn't held the charge. But when the sun came up (very over cast and low light), the tv would work, but only just, from what the solar panel was generating, so I knew that in these overcast winter conditions the panel must be giving 2amps. So it was obvious that there wouldn't be anything left to go into the battery to charge it up.

Only 6 hours of daylight, and 17 hours dark. What a dramatic change from how things had been in summer.

So I thought about it and reckoned that I would need 300watts of solar panel: 2amps to use, and 4amps going into charging, which should carry me through the 17 hours of darkness.

Anyway, I bought a new battery (230ah), and two more 100watt panels, identical to the one I had, with its own controller.

My plan is to connect all three panels to the battery with the clips supplied, but be sure that they can only connect with each other via the battery, and in this I hope to minimize any interference they may create for eachother.

I'm going to do this tomorrow.

Does anyone think this is a good or bad idea?

[leftbrainstuff]

I suggest you do some more research. Your numbers are way off. Determine your power budget in terms of Ahr. Then realize that you only want to consume about 30% of your available Ahr per charge cycle.

Put an mppt controller with cutoff in place and determine whether you want your panels connected in serial or parallel.

sv Sedoza Sakona Liberty 458 hull 12

[Herreshoff]

I would suggest ditching the old battery that wasn't holding charge. If it's not holding charge from the generator it's probably dead. Maybe get another 200ah battery on top of the one you bought already. Try and have somewhere around 400ah. If you have small batteries then it doesn't matter how much solar you collect you will go through it all at nighttime. More batteries means more stored power. Then you have your new panels. If you have a small boat maybe get a solar charge controller which has a digital screen. In Australia powertek make a cheap one. This will tell you how much solar is coming in an how much power is going out into your telly.
You can just hook all the solar panels together. Positive to positive. Negative to negative. You don't have to run seperate cables for each one.

[ErikFinn]

hi duggybuggy and welcome to the forum.

I recommend you start by reading one of our highly regarded member's articles at

Welcome To MarineHowTo.com Photo Gallery by Compass Marine How To at pbase.com

and especially the "What is a "deep cycle" battery?"

Understand please that if you have used an automative start battery for your tv and continuous draw you may expect only a few weeks or months life out of that battery.

Maine Sail also has some good articles about solar (among other things); very very much worth reading.

Best regards,

Erik

[noelex 77]

Originally Posted by duggybuggy

My plan is to connect all three panels to the battery with the clips supplied, but be sure that they can only connect with each other via the battery, and in this I hope to minimize any interference they may create for eachother.

I'm going to do this tomorrow.

Does anyone think this is a good or bad idea?

The three controllers won't interfere with each other. If by the "clips supplied" you mean alligator clips, these are a very bad idea and need to be replaced with a more secure connections such as ring terminals. Try to avoid lots of wires connected directly to the battery and it is very important that each wire is correctly fused.

[duggybuggy]

Thank you everyone. Erik I will have a look at that info. Noel, thanks. I also thought that the controllers wouldn't interfere with each other. But I don't know enough to have any kind of certainty about electronics. So it has been reassuring to run it past you all.

[bsurvey]

the controller should accommodate more than one panel.


without a controller you can ruin the batteries. I have tested my panels and bright sunshine and I get well over 12 volts 20VDC


so always use a controller before the panels to monitor the system and they will automatically shut off most at 12.9 vdc

[duggybuggy]

I replaced the old (18months only) battery with the new one. It was charged up and so I clipped the 100w panel to it and left it at that.

Then I metered the old battery which showed 12.2, so it seems to be charging and holding a charge, as it was 9.9v when I left it. So with the 2 new 100w panels I clipped both of them up onto its terminals and then metered the battery, which showed 12.24 (but it was vary dismal daylight, so low you'd think of putting your headlights on. I am sure that with better daylight the voltage would go up, of course).

So I am hoping that I have done it, and that it is as simple as that: if you want more charge going in then just add another panel or two. Each panel having its own controller, leads and fuse and clips.

The thing I am going to do differently this time with the new set up is to go off the hydrometer as to know the true state of charge, as volt meter might read 12.9v, but the hydrometer could be showing the electrolite as in the amber range when it should be kept pretty much in the green.

The old battery showed a low amber reading. I'm hoping the two panels will charge it up to the top, and then i will check the hydrometer reading, and if it still shows amber when it has had chance to get to green, then i will put in some sulphuric acid...carefully and monitor it and test it. (I use this acid in my work), or I will use the little battery tablets.

[foufou]

12.2V or even 12.9V while charging is not even close to charged up. When charging the voltage should get to close to 14.4V. Then settle down to float at 13.3V. Keep at it, you are getting there

[robbievardon]

Just remember when you buy a solar panel that the salesman may be a little economic with the truth. The output is based on sun at maximum summer height, with the panel at right angles to the sun and clear sky. To maintain full output the panel must track the sun in direction and angle.