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Old 21-09-2011, 19:17   #1
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Cut-Off Point for Solar Panel to Battery

I have a 200watt panel charging my battery. I have set the regulator to cut off the panel input at 13.1v as to not damage the battery. Is this too low. Can the battery handle more?
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Old 21-09-2011, 19:19   #2
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Whoops with the title... Bloody iPads. Meant to say 'cut off point for solar panel to battery'
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Old 21-09-2011, 19:38   #3
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Re: Cut-Off Voltage for Solar Panel Going into Marine Battery

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Whoops with the title... Bloody iPads. Meant to say 'cut off point for solar panel to battery'
Title repaired, Nikos.

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Old 22-09-2011, 04:38   #4
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Re: Cut-Off Voltage for Solar Panel Going into Marine Battery

13.1V is too low.
As you only have one voltage set point it will need to be a compromise.
To give you an accurate recommendation you will need to tell us the battery type and how the battery is used.
It will be somewhere between 13.8-14.5V, depending on the above factors.
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Old 01-10-2011, 01:20   #5
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That sounds about right. I am using two 6v newton power batteries. 200ah each and the power is used for cabin, nav, top lights as well as fridge' bilge pump and radio. Nothing big like an anchor winch. I do that by hand.
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Old 01-10-2011, 01:50   #6
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Re: Cut-Off Voltage for Solar Panel Going into Marine Battery

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That sounds about right. I am using two 6v newton power batteries. 200ah each and the power is used for cabin, nav, top lights as well as fridge' bilge pump and radio. Nothing big like an anchor winch. I do that by hand.
Newton power seem to make AGM, Gel and flooded batteries.These require different voltages
The only 6V 200AHr battery I could that they made was AGM.
If your batteries are AGM I would set the regulator to 14.3V, but if you leave the boat unatended with little load on (no fridge) I would reduce this to 13.8V
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Old 04-10-2011, 01:07   #7
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Thanks for that. Strangely at the moment they are not going much past 13v even with a 200watt panel attached. They had been sitting in a factory for a year so I wonder if that is a problem. Do you know? Brand new but a little cheaper (20percent) because of this. They have only been plugged in for a few days so maybe i will just wait and see. Perhaps blasting them with some power from a generator would boost them up.
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Old 04-10-2011, 01:21   #8
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Re: Cut-Off Voltage for Solar Panel Going into Marine Battery

If the voltage is not rising much past 13v as a maximum it indicates the batteries are reasonably discharged or your output current is close to solar panel input, or something is wrong
In Sydney this time of year you should be getting about 50AHrs a day from 200w, but it will be very viable given the fickle weather.
From this 50AHrs you need to deduct how much you are using.
A good battery monitor is really essential to know what is going on with system.
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Old 04-10-2011, 01:33   #9
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Well yes the weather has been painfully cold and cloudy. I do have a battery monitor as part of the regulator I have for the panel. It's been on and off but it's pulling in between 3-7amps at any one time. I'm not using much power at the moment during the day. Do you think that giving them a kick by hammering them with a generator is a good idea or should I just give them some more time. After a few consecutive sunny days if not at 14v then will start to worry. Plenty of power anyway even at 13v for me but always best to figure out the problem.
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Old 04-10-2011, 03:13   #10
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Re: Cut-Off Voltage for Solar Panel Going into Marine Battery

For reasonable battery life try to keep the battery above 50% capacity and get it fully charged (100%) every few weeks.
Your battery monitor should count AHrs in and out and give you some idea of the state of charge. The good monitors are quite acurate, but the simpler ones are only acurate for a few days after the battery is fully charged.
I would use your generator to get the batteries to 80% in the morning and then let the solar bring them up to 100%. This will give you a starting point and help show if the batteries are OK.
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Old 04-10-2011, 04:36   #11
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Re: Cut-Off Voltage for Solar Panel Going into Marine Battery

I'd set around 14.2, derated by 0.022v per degree C over 20
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Old 04-10-2011, 09:56   #12
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Re: Cut-Off Voltage for Solar Panel Going into Marine Battery

A lot depends on the type of regulator you have. Some have a relay control, which cuts the panels off when the voltage goes above some setpoint, then switches them on when the voltage drops below some level which is typically at least 0.5v below the cutoff setpoint. Other regulators use Pulse Width Modulation to reduce the current when the voltage goes above the setpoint. You should set the relay type at least 0.25v above the PWM type.
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Old 07-10-2011, 05:53   #13
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I still can't get it to go above 13.1v. I had 18amps come in through the panel today however more would have if the battery were to go to 14 no? It says I've used 13 amps and am now sitting on 12.6v. Does that sound right? On my regulator I am able to choose at what point the panel cuts out (mine at 14.3v) and at what point the load cuts off and on etc. What I need answered is whether or no I can try blasting some higher amps into the batteries through a generator. I got the batteries slightly cheaper (2 X 6v 200ah each) because they had been sitting in a factory for a year or so. Therefor I figure they had a build up of sulfite or whatever it is on them. This can be stripped by heavy charging can't it. If not can nothing be done. is a max of 13.1v just not enough? thanks.
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Old 07-10-2011, 07:44   #14
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Re: Cut-Off Voltage for Solar Panel Going into Marine Battery

Your batteries are fine--they are telling you that they are still NOT fully charged. You SHOULD charge them up with another source TODAY. When the alternator brings them up above 14.1, monitor to make sure that the solar reg cuts off.
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Old 07-10-2011, 08:00   #15
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Re: Cut-Off Voltage for Solar Panel Going into Marine Battery

...just a thought...the 13v reading may also be telling you there are other load on the system while you are charging.IE:a panel connected to battery all charged up=14+ volts.But a panel connected to a battery that has a fridge/a pump/a light ON= 13v or whatever...

Tell us the battery is ONLY connected to the panel OR that you KNOW everything else is OFF.... that would help filter out the obvious
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