Idiots guide to 12 volt solar trickle charging

[eastcoastbernie]

Spare me the ohms and amps and suchlike as I have no idea.

I live an hour and a half away from my boat. During the winter I have to do a 3 hour round trip to run the engine to maintain the batteries. Tedious and expensive on fuel.

So I was thinking, could I buy a solar thingy that I could plug into the cigarette lighter 12 volt (don't want to have to do any wiring up) and would it look after the batteries while I was away? What should I be looking for that would supply just enough to keep them healthy? Is there any risk that they would fry if left unattended for weeks on end?

Only a little boat so I'm not running a fridge or anything. Nothing drawn when I'm not on the boat, and when I am, only needed for engine starting, cabin lights, instruments, etc.

Any advice - as long as not too technical - would be extremely welcome.

 

[TopDonkey]

4.5 watt solar panel

this is what you need, glue it to the roof, plug it in and forget it, it will maintain your batteries for you

 

[VicS]

If you only want to keep a charged battery maintained one of the small panels around 2 watts would do. Maplin often do them on special offers but they may not be weatherproof. They can be fixed up inside a window though.

Cigar lighter sockets are not the best choice of connector.


If you have more than one battery bank use a panel on each bank and clips to connect but include inline fuses as close to the batteries as possible.

By connecting direct to the batteries you can leave your isolator switches off.


With no load your batteries will be Ok for up to 6 months without any charging.
But surely if you only live 1½ hours away you'll visit once or twice during the winter anyway.


Do not ever run the engine for a short period for charging batteries. If you start it run it under load until it is fully warmed up to normal working temperaure

 

[sarabande]

OK, so questions.

Is the cigarette lighter conected directly to the batteries and not via the ignition ?

Then, does it have a fuse on the positive side ?


Cigarette sockets are rated normally at maximun 15 amps. So any panel should up to about 12 amps should be OK. That is 144 watts, which is a big panel.


Really, then, a panel of about 40 watts would supply enough energy to keep the batteries on most saily boats well charged up during winter, and more than enough in summer.

The caution is that you then need a controller which limits the amount of power going into a battery (i.e. stops the battery overflowing with voltses). The controller should be placed in a cool, non-sunny place so that it can disperse its heat easily.


EDIT I agree with VicS. Cigarette sockets are not the best input. And the panel will not need to altered every day to optimise the orientation towards the sun, so could be left vertical or horizontal.


A small panel would be of limited use in the sailing season when your use of power is much greater because of boat use.

 

[Topcat47]

I have a cheapo Maplin solar panel linked to each battery (start and service). They are inside the boat, behind the window, so no problem with the "unsuitable for prolonged external use. With the boat moored roughly e/w the panels are erected on the "sunny side" of the vessel. Not only will they maintain battery charge but are capable of topping up the charge, even over winter. However, I don't run an electric bilge pump and when the boat's ashore for a winter refit, both batteries are connected to an "intelligent" charger in my garage which works the batteries, thus extending their life.

 

[LadyInBed]

I live an hour and a half away from my boat.
During the winter I have to do a 3 hour round trip to run the engine to maintain the batteries. Tedious and expensive on fuel.

So I was thinking, could I buy a solar thingy . . . . Nothing drawn when I'm not on the boat, and when I am, only needed for engine starting, cabin lights, instruments, etc.

Any advice - as long as not too technical - would be extremely welcome.

Easy! forget all about solar, take the battery home with you and return it to the boat charged when you want to use it.

That's not too technical, is it?

 

[eastcoastbernie]

Easy! forget all about solar, take the battery home with you and return it to the boat charged when you want to use it.

That's not too technical, is it?

Not too technical, but quite an ordeal. Firstly the batteries are too heavy for me to womanhandle, secondly they can only be accessed through the cockpit locker which has to be completely emptied before I can climb in. Not really an option I want to consider.

 

[eastcoastbernie]

I have a cheapo Maplin solar panel linked to each battery (start and service). They are inside the boat, behind the window, so no problem with the "unsuitable for prolonged external use. With the boat moored roughly e/w the panels are erected on the "sunny side" of the vessel. Not only will they maintain battery charge but are capable of topping up the charge, even over winter. However, I don't run an electric bilge pump and when the boat's ashore for a winter refit, both batteries are connected to an "intelligent" charger in my garage which works the batteries, thus extending their life.

That sounds like the sort of thing. My windows are quite heavily tinted. When inside the boat looking out, they appear clear, but when outside looking in, they look almost black. Would a solar panel work behind heavily tinted windows?

 

[eastcoastbernie]

OK, so questions.

Is the cigarette lighter conected directly to the batteries and not via the ignition ? Don't think they are direct to the batteries.

Then, does it have a fuse on the positive side ?

No idea.

Cigarette sockets are rated normally at maximun 15 amps. So any panel should up to about 12 amps should be OK. That is 144 watts, which is a big panel.


Really, then, a panel of about 40 watts would supply enough energy to keep the batteries on most saily boats well charged up during winter, and more than enough in summer.

The caution is that you then need a controller which limits the amount of power going into a battery (i.e. stops the battery overflowing with voltses). The controller should be placed in a cool, non-sunny place so that it can disperse its heat easily.


EDIT I agree with VicS. Cigarette sockets are not the best input. And the panel will not need to altered every day to optimise the orientation towards the sun, so could be left vertical or horizontal.


A small panel would be of limited use in the sailing season when your use of power is much greater because of boat use.

Not worried about charging when boat is in use as motoring in and out of the marina is all I ever need to charge the batteries .

 

[sarabande]

in that case it's best to have the panel wired directly to the controller and then to the battery, with appropriate fuses. If your normal power requirements are met by motoring on and off, then a 20 to 30 watt panel would be OK just to put a refreshing charge and top up while you are away.

That size panel will be about 20 inches by 15.

If you have a big multiple battery bank, say > 200Ahr, you could get away without having a controller, but some detailed specs would be needed to say definitely yes or no.

 

[onesea]

With no load your batteries will be Ok for up to 6 months without any charging.
But surely if you only live 1½ hours away you'll visit once or twice during the winter anyway.

Keep it simple, is my tough...

 

[BAtoo]

My 2p

Sounds like you need a 5w or 10w panel attached directly to the battery(ies), fixed (cable clipped) to your guard wires/backstay, appropriate fuse on +ve side. Take it off in the summer if its in the way.

Size depends on your battery size - under 10% of battery AH rating & you can attach directly and forget.

Don't get too involved with orientation of panel etc, point it towards the docks/Shotley & not the trees and you will be fine.

Here:- http://www.ebay.co.uk/itm/5-W-Monoc...00753595685?pt=UK_Gadgets&hash=item2ebdd8c525

 

[eastcoastbernie]

My 2p

Sounds like you need a 5w or 10w panel attached directly to the battery(ies), fixed (cable clipped) to your guard wires/backstay, appropriate fuse on +ve side. Take it off in the summer if its in the way.

Size depends on your battery size - under 10% of battery AH rating & you can attach directly and forget.

Don't get too involved with orientation of panel etc, point it towards the docks/Shotley & not the trees and you will be fine.

Here:- http://www.ebay.co.uk/itm/5-W-Monoc...00753595685?pt=UK_Gadgets&hash=item2ebdd8c525

I like the look of your recommended product as it says it's waterproof! Next thing would be to work out how to connect directly to the batteries as they are situated BEHIND my engine and my arms aren't long enough to reach crocodile clips onto the terminals.

Any time I have to get at the batteries it is an immense ordeal involving emptying out capacious cockpit locker, climbing in, removing small inspection hatch then carrying out tasks in a sort of cramped up, upside down orientation. Which is why I had hoped I could just plug it in the cigarette lighter thingy.

In the past, I have tried to get down to my boat once a month in the winter to check her out, but I'm having a job to get down once a month in the summer at present, so I'm just thinking ahead to the winter and thinking if the batteries were being safely trickle-charged I could save myself a bit of travelling and a bit of worrying.

 

[Boreades]

I've been through the same situation, and tried various products and setups. I started with a 10W panel - that does fine when you're not onboard and only want a tiny trickle charge to one battery. I always connected to the engine battery via a charge controller like this.

The main problem with that setup is the domestic battery doesn't get charged, unless you have a second panel charging the domestic battery seperately. But SWMBO didn't want me sticking extra panels all over the boat. So I stuck with a single larger semi-flexible panel. Swings and roundabouts. I didn't mind starting the engine occasionally when that was the only option.

That worked fine for three years before my children started insisting on bringing their Nintento Wii, iPad and phones with them. They seem to need charging every five minutes. Starting the engine more and more often to keep the domestic charged started to grate on my nerves, so I changed the charge controller for one like this that can split the charge between two batteries.

In real-like testing last month, with 10 days cruising in Cornwall, (all with cloudy days with only occasional direct sunlight) that setup produced enough charge to trickle charge the engine battery plus keep a 120W inverted permanently connected, powering a small domestic DAB/VHF radio (so SWMBO can get Ken Bruce, The Archers, etc) and USB chargers for the electronic toys. Plus occasionally plugging in a laptop power-supply to keep the laptop battery topped-up.

 

[dleroc]

I have used the £9.99 solar panel from Maplins since May with the panel stuck inside a window. Works fine in keeping the battery topped up. Come with croc clips or ciga lighter plug. I use the croc clips.

 

[Modulation]

I like the look of your recommended product as it says it's waterproof! Next thing would be to work out how to connect directly to the batteries as they are situated BEHIND my engine and my arms aren't long enough to reach crocodile clips onto the terminals.

Any time I have to get at the batteries it is an immense ordeal involving emptying out capacious cockpit locker, climbing in, removing small inspection hatch then carrying out tasks in a sort of cramped up, upside down orientation. Which is why I had hoped I could just plug it in the cigarette lighter thingy.

In the past, I have tried to get down to my boat once a month in the winter to check her out, but I'm having a job to get down once a month in the summer at present, so I'm just thinking ahead to the winter and thinking if the batteries were being safely trickle-charged I could save myself a bit of travelling and a bit of worrying.

...............so why not fit a new lead from your batteries up through your locker to a point where you can access them easily and connect your solar charger leads to that? Then you could connece and disconnect your charger to your hearts content. That's what I did with my mains charger as I wanted to be able to switch it between 3 batteries, all in remote location. You have to be certain that the ends of the leads cannot short circuit and are well protected, mind.
Simples!!

 

[Burnham Bob]

agree with brendan. i use a small solar panel just to keep the starter battery topped up becuase as long as I can start hte engine, I can charge tie domestic battery. i used crocodile clips to take a lead to a convenient place in the locker, added a cigar lighter socket and can plug in the solar panel when i leave the boat. the very thin wire comes easily up wth the locker lid down.

 

[MudShipper]

KISS

+1 for keep it simple.

If you only want to keep a top up, then the 1W job from Maplins does a reasonable job - it kept my starter battery up at 13v through the winter.
Siting could be difficult with tinted glass, but try it and see. At £10 it is not a big investment.

If you feel the need for more, there are a range of panels available. I notice that Maplins have a 44W kit, including charge controller, for a mere £80. This is a crystalline cell and is weather proof.

 

[BAtoo]

...............so why not fit a new lead from your batteries up through your locker to a point where you can access them easily and connect your solar charger leads to that? Then you could connece and disconnect your charger to your hearts content.
Simples!!

+1

Or you could connect to the appropriate terminals on the back of your battery isolator switch(s), or run a cable from there to a new socket in a convenient place.

 

[VicS]

Regarding the criticism of cigar lighter type plugs and sockets.

What is far better, but compatible with the standard ones, are these Marico ones which when used together lock together

Click on the pictures to see the decriptions