Solar charge controllers specifications

The controller only needs to be as strong as the panels.

Joe

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it

If it is not capable of dealing with the batteries it will eventually fry.

?-)

why, the batteries aren't going to over-current it., and the solar cells are too weak.

While in a high altitude blast, the EMP is a real issue, but for ground blasts, much of the EMP is canceled.

Protecting solar panel array against EMP (NEMP/LEMP) and also possibly against strong geomagnetic storms can be hard, if the panels are daisy chained across the roof or other large area, since the cabling would form a large area loop, through which the magnetic field will go, causing large interference currents.

The OP might start by reading

On a sunny day (Fri, 30 May 2014 10:52:04 +0300) it happened snipped-for-privacy@downunder.com wrote in :

The whole story assumes nuc[u]lear bombs. In present times power plants have been bombed by conventional means, or taken over by enemy forces, or simply their operators killed or to scared to go to work, or their fuel supply interrupted. or no money for fuel. System disruptions. Hackers, I forgot hackers. :-)

This is true both for a big battery or a smallish battery with some on-line loads consuming the rest of the available power.

The V/I curve drops _very_ rapidly, if loaded above the maximum power point, so the controller is quite well protected against too much current.

The other question is how the panel likes to be overloaded with a more or less short circuit.

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current

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fry.

If the battery is large and a cell or two shorts it might very well kill the charge controller.

?-)

how's that going to hurt the controller?

A 100 W panel (8 A @ 12 V) will be able to deliver 9 or 10 A at short circuit, thus any decent controller should be able to handle that.

With a 12 V panel directly connected (no controller) to a 12 V battery with two shorted cells (8 V), the panel will deliver about 8.5-9A at 8 V. So even if you put a simple controller in between, this is what you get.

With a real MPPT, the panel would deliver 8 A @ 12 V (100 W) and the battery would get 12 A @ 8 V.

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eventually fry.

kill

That depends on the quality of the controller. If it has been heavily muntzed the output would be 8.8 V @ 7.5 A and the controller subsequently fries.

?-)

If one really is concerned with this, just make sure that one of the cables from the solar panel is lead on the back of the panels, following the exact path as the internal bus bar wires. It costs a lot more cable, but minimises the loop area. Question is: will it become sufficiently small?

joe

That short circuit will just carry the photo-current, and the panels will be fine with that. It's not an 'overload'.

joe

Yes, that is: the voltage of the batteries. The solar panel can only supply as much current as it is rated to, so a charge controller, well dimensioned to the size of the solar panel, will not 'fry', as the current will never exceed the maximum solar panel's value.

joe

Please explain _how_ exactly it will fry? Because I don't see how it would.

joe

You are correct. I have here a 40W panel with the following rating plate:

Peak Power: 40W Max Power Voltage: 17.8 Max Power Current: 2.3 Open Circuit Voltage: 21.6 Short Circuit Current: 2.5

literature

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Overdissipating the pass transistors.

?-)

With what size of current, 10% more than the maximum-power current of the panel? I still don't see that happening in a well designed device.

joe

the

But i am including overly Muntzed devices explicitly.