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Solar Panels for winter battery Charging


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#1 husky

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Posted 21 August 2013 - 07:49 PM

Every year I leave my boat in a marina for approx 6 months over winter and return home to Australia.  I have 2x100W solar panels on my boat - would these 2 panels be sufficient to keep the batteries fully charged over the period I am away without the use of shore power?  I have 1 x  90 AH and 4 x 110 AH batteries and these would be the only draw on the solar panels.  The panels are fitted flat on the roof and the boat is stored in the Northwich area.  Any thoughts please?


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#2 Ally

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Posted 21 August 2013 - 08:09 PM

Except for a total of 5 hours external genny charging (no alternator) we kept charged last winter via 2x135a panels, & we live aboard. 4x125 agm leisures.
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#3 blodger

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Posted 21 August 2013 - 09:06 PM

As long as you are not moored in the shade of trees or buildings 200 watts solar even in Winter would more than combat the tendency of the batts to self discharge IMO.

The age and type of the batts may also be a factor  and a more sphisticated charge controller might do a better job if it equalises a bit every now and again.

I presume that you would be commoning your starter battery with the domestics while you are away or better giving the starter battery its own feed from the controller with a diode in the lead to maintain its isolation?


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#4 trackman

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Posted 22 August 2013 - 10:09 AM

I can confirm that you should find this works OK. We now have doubled up our panels, but until this summer we had only one 68W panel glued flat on our roof.
We didn't leave the boat long very often but when we did, this panel kept our Smartgauge showing 100% consistently even in winter.
Do make sure that both battery banks are linked to the panels though. Our setup doesn't do this as it is, even though the Smartbank closes the relay when there is good solar power. The problem is the isolator switch wiring arrangement. When we isolate everything this cuts off the starter battery from the relay, preventing the solar charging it!
I need to devise a way to work round this that doesn't defeat the charge splitting and isolation inappropriately. A use for a diode perhaps?
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#5 husky

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Posted 22 August 2013 - 04:59 PM

I can confirm that you should find this works OK. We now have doubled up our panels, but until this summer we had only one 68W panel glued flat on our roof.
We didn't leave the boat long very often but when we did, this panel kept our Smartgauge showing 100% consistently even in winter.
Do make sure that both battery banks are linked to the panels though. Our setup doesn't do this as it is, even though the Smartbank closes the relay when there is good solar power. The problem is the isolator switch wiring arrangement. When we isolate everything this cuts off the starter battery from the relay, preventing the solar charging it!
I need to devise a way to work round this that doesn't defeat the charge splitting and isolation inappropriately. A use for a diode perhaps?

Thanks for all your replies- looks like the panels are a good option. Yes Blodger, my intention was common all the batteries.  The negative terminals are already common so I was going to attach some 17A wire to the +ive terminal of the start battery and run this to the leisure batteries +ive terminal.When I turn off the battery isolation switch, hopefully this shouldn't make any difference and still leave them all connected together. But I'm curious to know why you think giving the start battery its own supply might be preferable.

Trackman we have a "Smart Charge" system(Smartguage + Smartbank) which gives a readout of the voltage on the leisure batteries so commoning the batteries should include the start battery in this reading.  When the smartbank relay closes it will not charge the start battery(it will be isolated by the switch) but the start battery will be charged by being commoned with the leisure batteries - does that make sense?


Edited by husky, 22 August 2013 - 05:00 PM.

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#6 blodger

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Posted 22 August 2013 - 07:12 PM

I have three banks of batts  plus starters so I have made up a box of diodes, switches and voltmeters so that when the batts are isolated at the isolators they each get charge from the solar.

 

It just seems that when so much effort goes into keeping the starter circuit separate from the domestics it is wrong to connect them together.  Giving the starter battery a feed from the same source, solar, with a diode the right way round in the line just maintains the electrical isolation somewhat.


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#7 Laurie.Booth

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Posted 22 August 2013 - 08:12 PM

I have just installed this on my boat, have I done the right thing?

 

http://www.maplin.co...riefcase-348061

 

Now worried


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#8 blodger

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Posted 22 August 2013 - 09:40 PM

I have just installed this on my boat, have I done the right thing?

 

http://www.maplin.co...riefcase-348061

 

Now worried

 

What's to worry about.  I do not know how waterproof they are but I would be tempted to put some blutack around the connector to keep water out.  It will do a better job than the 1/2 watt ones sold for cars that you sometimes see mounted around the stern for the starter battery.


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#9 Arthur Brown

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Posted 22 August 2013 - 10:08 PM

The OP's rig sounds great, should keep up with bilge pumping etc easily.

 

Yes I would consider keeping the starter battery separate, with it's own solar panel but the cost per watt of small panels rather spoils the idea, but I like the idea of having two separate ways to start the engine lest one should fail


It is reputed that a 1 watt panel can be left unattended connected to a 100AH battery without the need for a controller -especially over the winter.. At this rating the panel never puts enough into the battery to overcharge it, but will put in enough to replace natural self discharge.


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#10 Laurie.Booth

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Posted 22 August 2013 - 11:07 PM

 

What's to worry about.  I do not know how waterproof they are but I would be tempted to put some blutack around the connector to keep water out.  It will do a better job than the 1/2 watt ones sold for cars that you sometimes see mounted around the stern for the starter battery.

I was worried about the water proof bit, so I have put it in my kitchen window.


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#11 blodger

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Posted 23 August 2013 - 08:19 AM

I was worried about the water proof bit, so I have put it in my kitchen window.

 

I think you will find the orientation and glass intervening will cut down what you might have otherwise got but the ones for cars are designed for just lying on the dash board so I suspect it will achieve its purpose.

 

To be honest I would recommend 10watts minimum and I must admit to having two of those 4w jobbies because they were cheap for portability and emergencies


Edited by blodger, 23 August 2013 - 08:22 AM.

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#12 Laurie.Booth

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Posted 23 August 2013 - 10:22 AM

 

I think you will find the orientation and glass intervening will cut down what you might have otherwise got but the ones for cars are designed for just lying on the dash board so I suspect it will achieve its purpose.

 

To be honest I would recommend 10watts minimum and I must admit to having two of those 4w jobbies because they were cheap for portability and emergencies

The instruction book claims it works well behind glass but I'm sure you are right about the loss of power, still at £16 I think it is worth the money. When I go boating now I intend to put it in the car cigar lighter socket.

:)


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#13 blodger

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Posted 23 August 2013 - 10:28 AM

The instruction book claims it works well behind glass but I'm sure you are right about the loss of power, still at £16 I think it is worth the money. When I go boating now I intend to put it in the car cigar lighter socket.

smile.png

 

Yes we went boating on the Thames for a month leaving the car a Thrup (Kidlington) when we got back the car was dead as a dodo.  Had to take a batt off the boat to get it started.  Since I have had soal panels even on top of the car.  Saved replacing a battery last winter!


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#14 Mike the Boilerman

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Posted 23 August 2013 - 10:46 AM

 

Yes we went boating on the Thames for a month leaving the car a Thrup (Kidlington) when we got back the car was dead as a dodo.  Had to take a batt off the boat to get it started.  Since I have had soal panels even on top of the car.  Saved replacing a battery last winter!

 

That's a different problem. Cars draw power these days even when parked and locked up. The alarm, immobiliser, remote key fob detector all need to stay energised. My scooby will self-discharge it's battery in about three weeks if left unused too!

 

This is not the battery self-discharging naturally, it's actually being flattened by being lightly loaded. The boat batteries only need against self-discharging, which takes months on end.

 

Having said all that I'm amazed how much the output of my solar panels varies with light levels. At midday I can see 12 amps charge rate. An hour after dawn , like proper daylight, it can be as low as 0.2amps.

 

MtB


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#15 kevinl

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Posted 23 August 2013 - 11:45 AM

Every year I leave my boat in a marina for approx 6 months over winter and return home to Australia.  I have 2x100W solar panels on my boat - would these 2 panels be sufficient to keep the batteries fully charged over the period I am away without the use of shore power?  I have 1 x  90 AH and 4 x 110 AH batteries and these would be the only draw on the solar panels.  The panels are fitted flat on the roof and the boat is stored in the Northwich area.  Any thoughts please?

You don't mention any sort of controller I assume you have one as 200 Watts (although you won't get that too often) is too much to leave unregulated. You could probably keep your 4 battery set up maintained on a tenth of that. It depends on the type of panel but some work perfectly in just daylight not just direct sunlight and even in winter the days can be quite bright. If you don't have a controller I'd be tempted to disconnect one of the panels or you could end up with boiled batteries.

K


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#16 husky

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Posted 23 August 2013 - 05:23 PM

You don't mention any sort of controller I assume you have one as 200 Watts (although you won't get that too often) is too much to leave unregulated. You could probably keep your 4 battery set up maintained on a tenth of that. It depends on the type of panel but some work perfectly in just daylight not just direct sunlight and even in winter the days can be quite bright. If you don't have a controller I'd be tempted to disconnect one of the panels or you could end up with boiled batteries.

K

Hi Kevinl - yes I have a controller, a 20Amp Duel Controller which allows me to divide the current from the panels to feed 2 different sources.  Also the instruction book that came with it is pretty sketchy on exact details(it's Chinese) but shows charge voltage, boost voltage and float voltage so presumably it will do all these things. I have used it for 3months now and I have only connected one of the controller output to the leisure batteries(set to 100%) and having a Smartcharge system this will connect all the batteries shortly after the motor is started.  I am now thinking, before I leave, of connecting the second controller output to the start battery and setting this to receive, say 20% of the available output.  My start battery sometimes struggles so it may be an indication that it is nearing the end of its life and if I leave it for 6 months commoned to the leisure batteries it may drag down the voltages of all of them. 


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#17 blodger

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Posted 23 August 2013 - 05:59 PM

Hi Kevinl - yes I have a controller, a 20Amp Duel Controller which allows me to divide the current from the panels to feed 2 different sources.  Also the instruction book that came with it is pretty sketchy on exact details(it's Chinese) but shows charge voltage, boost voltage and float voltage so presumably it will do all these things. I have used it for 3months now and I have only connected one of the controller output to the leisure batteries(set to 100%) and having a Smartcharge system this will connect all the batteries shortly after the motor is started.  I am now thinking, before I leave, of connecting the second controller output to the start battery and setting this to receive, say 20% of the available output.  My start battery sometimes struggles so it may be an indication that it is nearing the end of its life and if I leave it for 6 months commoned to the leisure batteries it may drag down the voltages of all of them. 

 

That sounds about right.

 

 

That's a different problem. Cars draw power these days even when parked and locked up. The alarm, immobiliser, remote key fob detector all need to stay energised. My scooby will self-discharge it's battery in about three weeks if left unused too!

 

This is not the battery self-discharging naturally, it's actually being flattened by being lightly loaded. The boat batteries only need against self-discharging, which takes months on end.

 

Having said all that I'm amazed how much the output of my solar panels varies with light levels. At midday I can see 12 amps charge rate. An hour after dawn , like proper daylight, it can be as low as 0.2amps.

 

MtB

 

That's reminded me to stick a panel on the dash of the Rover I have just laid up awaiting the scrap man as I'll take the batt off before it goes


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