Solar Panels

[bigmart]

I've just aquired an Exide 15 Watt Solar Panel.

The big question is do I need a Charge Regulator if I connect it to a 105 Amp Hour Battery between sails?

Martin

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[Shanty]

Rule of thumb here is that if the rated output of the panel in watts is less than 10% of the battery capacity in amp-hours, you don't have to have a regulator. On the basis of that, your panel is big enough to need a regulator.


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[johnsomerhausen]

The American magazine "Practical Sailor" ("practicalsailor.com") did a survey of owners of solar panels and found out that those who had installed small panels without regulators had fried their batteries in some cases. So it would be a good idea to fit one, just to be on the safe side.
john

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[William_H]

And just to be contrary ....No If you find it is overcharging the battery you will find the battery needs more water than usual assuming you can check the water leve. The 15 watt panel will give about 1 amp under best sun conditions say about 8 or 9 amp hours per day in best weather summer. Natural discharge will dispose of a portion of that. It should keep your batteries ready for action if you leave the boat for some time but no I think the regulator may limit some of the charge ability and I can't see your battery being fried. I wouldn't hesitate to leave a 15 watt on 105a/h battery directly connected no reg. here in west Oz summer. Of course I may be wrong. regards will

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[Dave_Knowles]

Hi Martin,

I would suggest that you fit regulators especially as they are not all that much compared to a new battery.

I have two panels one for each battery and they are the best investment I have ever made. I have a separate regulator on each one and the system keeps the batteries topped up all the time.



<hr width=100% size=1>Cleopatra Boats at
http://www.MyCleopatra-chandlery.co.uk

 

[jerryat]

Hi Bigmart!

I agree entirely with William H, no, you do not need a regulator for exactly the reasons he states. In the UK, it's extremely unlikely IMHO that you would get more than 7-10 amps even on a brilliantly sunny day AND with the panel exactly oriented towards the sun at all times. Your weekly useage, combined with the natural discharge of the battery, 'shadowing', and misalignment, will easily cope with the 'full' output of a 15w panel.

I wouldn't hesitate to leave it unregulated and connected to a 105amp battery.

Good sailing!

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[charles_reed]

Surely you mean..

0.7 - 1.0 amps. After all it's only a 15 watt panel.

Still it underpins the comment that a regulator is superfluous.

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[jerryat]

Re: Surely you mean..

Hi Charles!

Oooooops!! Hanging head in shame! Quite right, mental decimal point in the wrong place!

Good sailing!

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[bigmart]

Re: Thanks

Thank for all the responses everyone. I actually have two batteries, one 90 Amp Engine Starter & the other 105Amp Domestic deep cycle. I suppose you could call them a battery of batteries.

My original intention was to charge one with the new 15 watt panel & one with my old 5 watt panel. From what I have read here maybe I will charge them both together.

Anyone got any comments on connecting both panels together in parralel?

Martin

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[Benbow]

Re: Thanks

Charge them separately unless you want to get into cunning regulators which seems a bit daft for 20W.

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[silverseal]

Re: Thanks

OOps, I have been charging 3 x 110 amp batteries with a single regulator with all three batteries in parallel for 3 years.. they all pan out at between 12.6 and 12.85 volts, with a 18 watt solar panel

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[VicS]

Re: Thanks

Couple the panels together but retain the separate diodes for each one. That will prevent a panel in the shade pinching current from one in the sun, but be prepared for one to do most of the work if they do not match. If you then want to charge both batteries simultaneously connect each via its own blocking diode. You do not need diodes with high current ratings like you would for charging from an alternator and you will probably be able to get something suitable from Maplins. ALSO FIT A FUSE as close to each battery as possible.

The snag will be when one battery gets past it it will pinch all the current leaving the good battery not charging. So on that basis one panel for each battery is the safest option as you will still have one charged battery.

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[onenyala]

Re: Thanks

Regarding the fitting of a fuse. Presumably this is on the positve wire from the solar panel. I guess on my 18 watt panel a fuse of 2amps would be sufficient.
I have had an 18 watt solar panel for about 12 years without a regulator and the batteries have not boiled or required topping up very often.


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[onenyala]

Re: Thanks

Regarding the fitting of a fuse. Presumably this is on the positve wire from the solar panel. I guess on my 18 watt panel a fuse of 2amps would be sufficient.
I have had an 18 watt solar panel for about 12 years without a regulator and the batteries have not boiled or required topping up very often.


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[VicS]

Re: Thanks

Yes in the positive connection and 2amps would be sufficient for an 18watt panel.
I'll repeat, fit the fuse as close to the battery connection as possible because its purpose is to protect the the wiring between there and the panel. If you were to get a short somewhere in that wiring and did not have a fuse then several hundred amps could flow from the battery probably resulting in a fire.

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[onenyala]

Re: Thanks

thanks for that

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