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Solar Trickle charging batteries over winter

deaglan1

Hi all, my next newbie question relates to solar panel trickle charging of a boats batteries during Winter. There seem to be numerous solar panels out there that have different wattages. What is recommended to keep 12V batteries charged if a boat is off grid & unused for the Winter? I note that some units are supplied with suckers to attach them to windows and long wires with crocodile clips that attach directly to the battery? But as the wattage of the panel increases, so does the price.

So, my questions are:

(1) is there a minimum wattage required to keep 12V batteries charged? I note that solar panels have wattages varying between 4.5 to 100 or more, with even the 4.5 watts being recommended as good for battery charge trickle supply maintenance.

(2) Do these solar panels require a controller unit to prevent overcharging of the battery?

Thanks all for reading this.

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spaceHopper

I've read but don't hold me to this that if you say under 10 W you don't need a charege controller, if you go over that you do or you will damage the batteries. If can take them out and give them a fill charge then store them with the negative disconnected, then if you want connect a low wattage pannel 4.5W should be plenty it will keep the battery over winter or even fill charge it.

When ever you are working with batteries always take the negative off first that way if you make a mistake woth the positve and touch it off metal work the battery is isolated, this mostly applies to cars and vans but its best practice.

deaglan1

OK, sounds good, spaceHopper, but here I show my ignorance again.

There are two batteries connected to each other.

I will not be removing the batteries from their hold. It all looks too complicated

There is a shut off switch (Blue Sea systems E23) which is in the off position

(1) Do I attach the crocodile clips to just one of the batteries - if yes, which one or does it matter?

(2) Do I really need to to disconnect the negative

spaceHopper

deaglan1 wrote: »

OK, sounds good, spaceHopper, but here I show my ignorance again.

There are two batteries connected to each other.

I will not be removing the batteries from their hold. It all looks too complicated

There is a shut off switch (Blue Sea systems E23) which is in the off position

(1) Do I attach the crocodile clips to just one of the batteries - if yes, which one or does it matter?

(2) Do I really need to to disconnect the negative

One is the engine starter battery the other is the house battery. The switch is probably to seprate the engine battery from the house battery so that you don't flatten both if you leave light on.

If both are connected then a pannel should keep them both topped up. For that to work both negatives wires need to be connected. If you aren't sure ask somebody to check it and to show you

Ubbquittious

deaglan1 wrote: »

OK, sounds good, spaceHopper, but here I show my ignorance again.

There are two batteries connected to each other.

I will not be removing the batteries from their hold. It all looks too complicated

There is a shut off switch (Blue Sea systems E23) which is in the off position

(1) Do I attach the crocodile clips to just one of the batteries - if yes, which one or does it matter?

(2) Do I really need to to disconnect the negative

If the batteries are connected in parallel then crocodile crips on one battery will do. If they're in series you'll have to connect a solar panel to each battery or come up with a different solution

fergal.b

Here is a very good video from Driftwood on solar power on a boat in Ireland

W1ll1s

Solar Panels, everything you need to know.

https://www.pbo.co.uk/expert-advice/solar-panels-everything-you-need-to-know-24455