Solar Blocking Diodes? Help

[Dean Anderson]

I have a 20A Redarc Solar regulator connected to two folding solar panels (2x2 panels).
The combined output is 4A. The individual output is 4A. When I test the output when in parallel each Folding Panel gives out 2A.
Why not 8A when both connected?
Is this the regulator doing its job because the battery is full or do I need blocking diodes?

 

[DRW]

mmmmmm sounds a bit strange, I would suggest either the batteries are full or the panels may not be getting the full amount of sun

 

[Axl]

What size are the panels? you say you have 2X2 which I am assuming is four panels, 4amps/hr seems low for this many panels and a 20amp reg unless they are only small panels say 20w X 4=80w something just doesn't sound right.

I have a set of folding120w panels with a 10amp MPPT reg that in the right condition will produce 6-7amps/hr so I would have thought that a bigger reg such as your 20amp unit would deliver more than 4amps/hr a set of panels.

How are you testing the delivered current? again some thing doesn't sound right to test current delivered you need a reg that will give you this info or a watt meter of some sort, you can do it using a multi meter but the meter needs to be installed inline. As for blocking diodes if there are none on the panels then yes you will need them, see here http://pvcdrom.pveducation.org/MODULE/Array.htm

Even if your battery is full the reg will still deliver power from the panels to the battery, they simply go into float mode.

Do yourself a favour and have a search around over here http://www.myswag.org/index.php?board=9.0 type diodes into the search function on the home page http://www.myswag.org/index.php and sit back a have a read, there are several guys on here that really know 12v stuff and how it all comes together.

 

[Dean Anderson]

4x60w. Just seems funny that its exactly the same output whether one pair (120w) or two pairs (2x120W)are connected. I'm not an electrician, but from my logic, without a load the amps isn't going to travel down the cable. Half an uninformed idea can be a dangerous thing but.

 

[Axl]

4x60w. Just seems funny that its exactly the same output whether one pair (120w) or two pairs (2x120W)are connected. I'm not an electrician, but from my logic, without a load the amps isn't going to travel down the cable. Half an uninformed idea can be a dangerous thing but.

True @Dean Anderson if you can apply a load it would be better to test out what is going on. With 240w of solar and a 20amp reg you should be seeing around 12-14amps/hr maybe higher so maybe what you are seeing is the reg in float mode but, if they go into float the delivered amps/hr and watts will be jumping all over the place.

Do the panels have diodes? because from what I have read they seem to need them. I am no spakry either @Dean Anderson everthing I have learnt about 12v stuff has come from Myswag I managed to wire up my soft floor camper trailer with info from these guys.

 

[OZTRITON]

To put things simply think of 12 volt power like a recirculating water system, that tank is your battery, the hose is your wire, the tap is your switch.

Voltage = how full your tank is
Wiring size = how big your hose is
Amps = Flow through your hose
You cant measure Amps if there is no flow (load)
The bigger the hose (wire) the better the flow (amps)
The fuller the tank (battery) the better everything works

Imagine if you cut the hose and put a water wheel (lamp) in the hose and turned on the tap (switch) the water would flow from the tank through the switch(tap), through the water wheel (lamp) which would turn and then back to the tank.
This is a simple 12v circuit.

If you took the water wheel (lamp) out of the system and turned it on the water would flow through the system and with nothing to slow it down eventually, because of the speed of the water the system would explode.
This is what is know as a short circuit, this can and will cause fires and explosions.

Simple rules
The circuit has to be complete for everything to work
The circuit must have some form of load in it to avoid a short
The circuit must have a fuse placed in it

I am not calling myself an expert but 35 years as a motor mechanic/auto elec. I have learnt a few things.

 

[Dean Anderson]

Pushed a few buttons on the regulator panel and it says the battery is full, so I'll assume the low Amps is due to no load. Will see how all goes when I finish installing in the van and try it out for a week or so free camping in a couple weeks. or I could install, plug the fridge in and try it for a couple days in the back yard before I go.

Just thinking, it was set to 25Hz and the Amps was jumping between 2 and 4 every couple seconds so it probably was on float.

 

[Dean Anderson]

All Ok suns out alls wired up and with a 6B&S 11m lead..........back at the van I get 8.3Amps at 16.1 Volt per panel..............It's actually better than specified by the supplier.. I turned the Waeco down to -15 with the lid off and turned on all the lights, both bed fans, another 3amp fan and the Makita charger and I have more power than needed (for a bright cloudless day at 27degrees anyway).

 

[Dean Anderson]

The both panel output was limited by the regulator to 12Amp.

 

[Dobbie]

A good outcome.

I managed to check ours yesterday with our portable 120 panel and had similar readings so I'm happy.

Van is in the shed so roof solar is covered. It brought the battery up from 12.2 to 14 easily. I'm now confident it works effectively so definately don't need another battery.