Solar power output question etc

Submitted: Tuesday, Dec 16, 2008 at 16:25

ThreadID: 64322 Views:5401 Replies:5 FollowUps:5

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Solar Power

This article covers every aspect of solar and its design and installation in RVs (camper trailers, caravans and motor homes). It shows how much power solar panels really produce,

Featherfoot

A few questions for the solar and electrics gurus on this forum.
I have a Photowatt PWX 400 solar panel 40 / 45 watt I think, on a van I bought 2nd hand. If I put a multimeter across the wires before they enter the controller I get a reading of approx 17. 8 volts. After connecting the wires to the controller and putting a multimeter across the wires exiting the controller I get no reading at all. The wires are not connected to a battery. The controller is a morningstar Sunguard. Not sure of the age of this gear could be as early as 1994 as that's the age of the van. My thoughts are the controller's kaput. What's yours? If that's the case what should I replace it with. Also I need a battery to connect it to. What would best suit my needs? Battery will need to power the 12v flush toilet, Shurflo water pump, a couple of small fluros and maybe a 12v tele.possibly for a week or two. I have a 2 kva Honda genny also.
Next question.
On the floor behind a pot drawer is a Meanwell ESP-120 12volt power supply unit powered by 240 volts. Is this also a battery charger as well as a power supply unit.
To connect the van battery power supply to the 12 v van circuit I pull the trailer plug out of the tow vehicle and plug that into a female plug on the drawbar this makes the connection using the normal hot wire pin ( no 2 ). When the Meanwell power supply is turned on it would then be connected to the battery through the 12v van wiring, so I'm thinking this will charge the battery. Can you charge a battery from another 12v supply either by alternator or other means as well as have the solar charger connected at the same time, or will one cause
the other grief.
Sorry it's a bit long winded .

regards
Gary

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Reply By: Foxhound (WA) - Tuesday, Dec 16, 2008 at 16:47

Tuesday, Dec 16, 2008 at 16:47

If you have the wires connected to the voltage regulator correctly you should have a reading of around 14 Volts. If its an old unit it maybe faulty. Re the battery I would use a deep cycle of around 100 Amp Hrs, you can`t have too much battery storage.
Your 240 AC 12 volt power supply is not a battery charger and would be wired into the 12 volt light circuit to run the caravan lights only. You would have to fit a battery charger wired to the battery and run by 240 volt off the van power points. You can run your Solar and 12 volt feed from your vehicle at the same time... Regards, Foxhound.

AnswerID: 339992

Reply By: Member - Ed. C. (QLD) - Tuesday, Dec 16, 2008 at 16:56

Tuesday, Dec 16, 2008 at 16:56

I think you will find that you need to have the solar controller connected to a battery in order for it to work...

I'm not familiar with the Sunguard, but I have a (Morningstar) Sunsaver MPPT, and it requires a minimum of 7 volts (at the battery terminals) to power the controller....

your other concerns, I will leave for others more knowledgeable;-))

Confucius say.....
"He who lie underneath automobile with tool in hand,
....Not necessarily mechanic!!"

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My Profile Send Message

AnswerID: 339995

Follow Up By: Best Off Road - Tuesday, Dec 16, 2008 at 17:24

Tuesday, Dec 16, 2008 at 17:24

Ed,

Same with mine. Outlet from regulator doesn't kick in until there is some load.

Easiest way to check it Feather, is

1. check the voltage of a battery with the multi.
2. connect panel, via regulator, to the battery
3. check battery voltage with multi again

If there is an increase reg is working.

Jim.

FollowupID: 607543

Reply By: Dunaruna - Tuesday, Dec 16, 2008 at 17:27

Tuesday, Dec 16, 2008 at 17:27

The only way to accurately test your sunguard is to connect a battery and perform some resistance tests. The main thing that kills this type of controller is reversing the wires, diodes tend to have a meltdown.

The 17.8v test you did confirms that the panel is operating correctly.

Go here for the controller test procedures -

http://www.energymatters.com.au/images/morningstar/SG_FieldTesting.pdf

AnswerID: 339999

Reply By: Member - Mike DID - Tuesday, Dec 16, 2008 at 20:33

Tuesday, Dec 16, 2008 at 20:33

Connect the Solar Panel Output directly to the car battery with the engine and accessories off .

With the panel in the sun, the battery voltage should rise above 13.0 volts if the panel is working.

AnswerID: 340024

Follow Up By: Best Off Road - Tuesday, Dec 16, 2008 at 20:49

Tuesday, Dec 16, 2008 at 20:49

I don't agree with the 13 volt theory Mike.

When I get up in the morning, camping, my aux batt may be showing 12.1 vlots. I attach the 64 watt paneland it may show iwth the multi, about 12.4 and grows as the day gets longer. This tells me the panel/reg is working.

It as all about a substantive increase rather than concrete numbers. Any immediate voltage increase indicates the panel is working.

Cheers,

Jim.

FollowupID: 607596

Follow Up By: Member - Mike DID - Tuesday, Dec 16, 2008 at 21:29

Tuesday, Dec 16, 2008 at 21:29

I did write "car battery"

It will not be discharged like an Auxiliary Battery may be in the morning.

Connecting the panel directly to the battery eliminates all other components and connections as a source of your problem.

FollowupID: 607616

Follow Up By: Best Off Road - Wednesday, Dec 17, 2008 at 06:56

Wednesday, Dec 17, 2008 at 06:56

I hear what you are saying Mike, but, let's assume the car battery is not 100%, say only holding 12.4.

If he sticks the panel (45 watts) onto that he will not see it jump to 13 volts immediately. Possibly 12.6 and climbing.

My point is that as long as he sees some relative increase, he'll know the panel is working.

For him to think the panel/reg is knackered because he doesn't see 13 volts may result in him pursuing a problem that does not exist.

Cheers,

Jim.

FollowupID: 607644

Follow Up By: Maîneÿ (wa) - Wednesday, Dec 17, 2008 at 09:44

Wednesday, Dec 17, 2008 at 09:44

What he "sees" is the CHARGING Voltage, not 'actual' battery voltage.
Yes, any increase in the Voltage NUMBERS indicates the battery is receiving the charge from the Solar panel via the reg.

Mainey . . .

FollowupID: 607665