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Old 26-03-2016, 09:46   #1
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How test solar system with dummy load

With a controller that has solar input, and battery and load outputs, how do you test the system to see the maximum output?

I'm not sure how you test for the maximum output, other than running your batteries down which takes time and is not necessarily a good idea.

One problem is that If your batteries are at say 80% charge, they'll only accept a certain amount.

So do people put a dummy load on the load outputs, or battery outputs?
What do you use for the load?
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Old 26-03-2016, 10:02   #2
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Re: How test solar system with dummy load

Watch your meter and start turning stuff on of known values until you no longer see a positive power reading from the panels then just do the math.
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Old 26-03-2016, 10:09   #3
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Re: How test solar system with dummy load

I have a 12V to 220V converter. I ordered a cheap chinese 700-800W immersion water-heater to measure maximum available amps after topping up my batteries. My idea is just to plug in the heater from the converter, read out amps supplied by the panels (subtract eventually amps drawn from the batteries) and voilà. Gives me an idea of the available amps to use for additional equipment eg watermaker.
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Old 26-03-2016, 10:37   #4
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Re: How test solar system with dummy load

Dave, at best I think this is an academic concern. If I'm reading your question correctly.

Look at your battery, or its paperwork. It should be rated in A/hrs. Amp/hours. If you have more than one battery on the same circuit, add those values. Example: my battery is rated at 130 amp/hrs. That means I can run a 1 amp load for 130hrs, 2 amp load for 65 hours, etc.

There are a couple reasons why this is not really reality based. First, as your battery ages it will no longer have the amp/hr capacity it did when it was new. Secondly, we almost never have a 100% charge on the battery. There is a point of diminishing returns that any charger can work once the battery is above 90% charged. So most of the time we're not using the full capacity. Lastly as end user consumers, we cannot predict the effects of things like ambient temperature or battery voltage on an appliance's drain on the system.

The good news: get yourself a good quality voltmeter and wire it in where you can click it on/off to monitor the voltage state of the battery. You're close to full when reading 13.8 to 14v and FND when it reads 11.5v I start charging at anything approaching 12v.

cheers
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Old 26-03-2016, 12:11   #5
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Re: How test solar system with dummy load

why are you using controller load outputs on boat? I see no reason. this is for cabin use and other weird things. with nobody around to monitory battery levels.


as for the max panel output.

just turn on lights and things on the boat. when the total battery draw is neg (you have a battery monitor right?...) the panels are maxed out. put clamp meter on wire between controller and battery to see solar amps. that is your max for that sunlight / conditions.


batteries can be full or any state. (turn charger off)
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Old 27-03-2016, 09:19   #6
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Re: How test solar system with dummy load

Quote:
Originally Posted by smac999 View Post
why are you using controller load outputs on boat?
I'm not, just thought it might be part of an easy approach for the test. However, since
they have sunlight / time programming options for the load outputs, I might use it for a dedicated LED anchorlight. These controllers are used for some streetlight installations.

Quote:
Originally Posted by smac999 View Post
just turn on lights and things on the boat. when the total battery draw is neg (you have a battery monitor right?...) the panels are maxed out. put clamp meter on wire between controller and battery to see solar amps. that is your max for that sunlight / conditions.


batteries can be full or any state. (turn charger off)
And your easy solution will encourage testing in the variety of conditions. I knew there was a reason to leave a few incandescent bulbs in the cabin.
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Old 27-03-2016, 09:44   #7
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Re: How test solar system with dummy load

Drain your batteries to about 50%. If you do not have a battery monitor that is about 12.2 volts resting. Using a clamp multimeter measure solar output of positive wire from controller to batteries.

Forget the load outputs of the controller.
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Old 27-03-2016, 10:55   #8
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Re: How test solar system with dummy load

You can test your panels with a dummy load but not at the controller out put. Only at the output of the panels. So in full sunlight you can test with an amp meter how many amps the panels are outputting. For example if you have a 23 volt panel connecting a 100 ohm 10 watt resistor to it will yield around 2.3 amps. Check the specs of your panel to see if this is accurate.

But that just tells you that your panel is working you would have to keep a log and test under the same conditions over many years to see if the panel is weekending.

Not sure this is fruitful. as the gentlemen wrote earlier a quick test is to load your batteries with lights for example check the boat current meter you should have one installed if not. and when the current goes to 0 amps then that is what the solar panels and controller are putting out. With the controller disconnected the load on the batteries may be minus 3 amps. Connect the solar controller and what ever reading you get on the amp meter is the difference between the controller and the load. If it's positive 1 amp for example then the solar panels are putting out 1 amp more then the load. 4 amps that is a large solar panel and all is well.
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Old 27-03-2016, 11:36   #9
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Re: How test solar system with dummy load

Quote:
Originally Posted by smac999 View Post
why are you using controller load outputs on boat? I see no reason. this is for cabin use and other weird things. with nobody around to monitory battery levels.
.
Actually when I install my next refer system I am considering using the load output to run a power relay to power the fridge. If the fridge shuts off due to low power it must be manually reset via disconnecting the power and reconnecting it just set the load cutout point about .1 volt above the system cutout and when batteries are charged enough it will reconnect power to the fridge so I wouldn't have to worry about it when off boat for a few days.
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Old 27-03-2016, 14:59   #10
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Re: How test solar system with dummy load

I have pondered on a system which would allow a quick check of the panel/regulator/battery system a number of times over the sixteen years I have been living with solar power and have yet to dream up one which does not require excessive complexity. The last occasion was only a couple of weeks ago and inspiration has yet to strike.


The analogue panel meter is a good suggestion and I have used an expanded voltage meter for about 25 years now. The meter is expanded by placing a 10V zener diode in series with it. The meter I use has two scales, 0 to 5 and 0 to 3. I changed the 0 to 5 to 10 to 15 using those little transfers one could buy from drafting supply shops (don't know if they still have those in the computer age)


Once you get yourself into the habit of glancing at the meter every now and then you seem to acquire the skill of instinctively knowing something is not right from the battery voltage behaviour during the day and night.
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Old 27-03-2016, 23:39   #11
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Re: How test solar system with dummy load

Like posted before, use the inverter to create the load. You can use lamps, heaters, fans etc.
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Old 28-03-2016, 00:43   #12
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Re: How test solar system with dummy load

Testing solar panel could be a bit complex, as you figure out from previous replied.
Solar panel output is very variable depends on load, shade, temperature, angle of the light source, etc. Sure I wont to known how my solar performing.
It's not difficult at all, disconnect solar panel and directly connect your amper meter.
Yes you can test Solar short circuit and reading is maximum current available in particular light condition. Real current for charging batteries would be about 10% less.
This is the only test eliminating all variables, like different load, different stage of batteries discharge, simple and working. Try and see.
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Old 29-03-2016, 14:25   #13
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Re: How test solar system with dummy load

I have a Victron blue solar Mppt controller for my panel.

Plug in a usb cable and run the Victron software and it data logs and stores everything for the past 30 days. It also runs live data.

My panel is a 345w sun power and I have reading coming in at 340-360w at 68volts the yield for the day being 1.8kw the best to date


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