How to bench test a Solar Charge Controller without a panel array

I would like to see a simple set of guidelines for "How to bench test a Solar Charge Controller without a panel array" - for the general interest and benefit to us Beginners.

I have searched for a concise definitive instruction for how to test a used Solar Charge Controller from ebay to verify it before the Returns Accepted thru <date> runs out. It is a straight forward enough question seeking a not so technical answer. Not how to build a clock, but how to see if it works... Videos after videos seem to elaborate too much or go off in some tangent explanation or scenario.

In my case I have ordered a used Victron 100 30. I do not feel like assembling an array to test it.
I have a variable 24v 1.8a HP desktop power supply that I used for pre charging 3.2v LiFePo4 cells for my 24v 100A DYI BATTERY projects, as well as any number of AC adapter 12v DC power supplies ov various amperages.

All of the discussions I have seen here so far have debated using Regulated power supplies and how they aren't great at mimicking a solar array. Too confusing. I just need to verify that I didn't buy a burned out lemon and that the CC isn't dead. OK ?

Does the type of DC power supply make any difference? -More importantly, as long as polarity and maximum VOC and amperages are respected on hooking up a power supply to the PV input connections, what are some valid voltages/amps and are there any hazards in doing so?

I might want to further experiment later with different voltage/amp power supplies. What if I hook up a 12v car battery to the PV input of a Victron MPPT 100 30 CC ? Or, what if I use the variable power supply's output adjustments to mimick shadows and clouds that an array would be subject to? That way I could probably test to see if the tracking is functional?

I also just got a free Eco-Worthy 12A boost charge controller I might want to test as power supply source ...

Is it ok to do this, or is there a "Gotch'a" I am ignorant about? I am a little nervous about that and my lack of confidence is my biggest hurdle.

So, how about a simple guidelines in testing and experimenting with a new charge controller?

Anyone?

"In my case I have ordered a used Victron 100 30. I do not feel like assembling an array to test it."

Well, then, anything you do won't be "real world". Just an approximation thereof. MPPT algos operating against a fixed input power supply can't "do their thing". You're on the right track with variable power as the input, but when the CC "looks" back at that, it still isn't going to be seeing how a panel/array would behave. It would normally determine the VOC of the array, then incrementally ramp down from there while watching current and determine where the MPPT point is. It can do that with a fixed input, but it's not the same.

It only takes one panel and a battery to make this happen. They don't need to be anything special, just functional.

For a go/no go (you say "I just need to verify that I didn't buy a burned out lemon"), I suppose that if you connect a bench PS in place of the array and a battery that needs charging to the CC output, and see that the input voltage is being converted to the battery voltage and the current proportional to the input, that would be better than nothing.

I don't think you will every get a test on a bench top as good as real world. But I can't see a problem using benchtop supply as the PV to see if you get voltage out the other end.

If the supply has a variable voltage and current you could adjust them indepently and see with DMM and shunt hooked to a battery that it adjusts the current as you change the input but the voltage stays steady.

That wouldn't fully op check it but it would prove it to be functional. Better would be to have a panel in the sun hooked up and a battery on the end.

I assume if you are buying new SCC you are either swapping one out or you have the other parts laying around.

v_green57 said:

"In my case I have ordered a used Victron 100 30. I do not feel like assembling an array to test it."

Well, then, anything you do won't be "real world". Just an approximation thereof. MPPT algos operating against a fixed input power supply can't "do their thing". You're on the right track with variable power as the input, but when the CC "looks" back at that, it still isn't going to be seeing how a panel/array would behave. It would normally determine the VOC of the array, then incrementally ramp down from there while watching current and determine where the MPPT point is. It can do that with a fixed input, but it's not the same.

It only takes one panel and a battery to make this happen. They don't need to be anything special, just functional.

For a go/no go (you say "I just need to verify that I didn't buy a burned out lemon"), I suppose that if you connect a bench PS in place of the array and a battery the needs charging to the CC output, and see that the input voltage is being converted to the battery voltage and the current proportional to the input, that would be better than nothing.

Click to expand...

robbob2112 said:

I don't think you will every get a test on a bench top as good as real world. But I can't see a problem using benchtop supply as the PV to see if you get voltage out the other end.

If the supply has a variable voltage and current you could adjust them indepently and see with DMM and shunt hooked to a battery that it adjusts the current as you change the input but the voltage stays steady.

That wouldn't fully op check it but it would prove it to be functional. Better would be to have a panel in the sun hooked up and a battery on the end.

I assume if you are buying new SCC you are either swapping one out or you have the other parts laying around.

Click to expand...

I bought a used Victron MPPT 100 30 from JB-Tools, an ebay vendor. They sell some really good bargains on Victron CCs now and again. I got this one for $85. Not bad. Look them up on the Completed Items and you will see what I mean.

It just arrived via Fedex, - very fast shipping in spite of some bad feedbacks. It looks brand new and should probably have been listed as Open Box. My new 130w flex panels are still in boxes, and my intention was to just store it all away in the closet until a hurricane grid failure happens, then yank it all out and set it up. I am just being lazy and I suppose I should really test/verify each panel independently too. That would be at least some peace of mind that I have a survival plan.

Maybe tommorow...

robbob2112 said:

I don't think you will every get a test on a bench top as good as real world. But I can't see a problem using benchtop supply as the PV to see if you get voltage out the other end.

If the supply has a variable voltage and current you could adjust them indepently and see with DMM and shunt hooked to a battery that it adjusts the current as you change the input but the voltage stays steady.

That wouldn't fully op check it but it would prove it to be functional. Better would be to have a panel in the sun hooked up and a battery on the end.

I assume if you are buying new SCC you are either swapping one out or you have the other parts laying around.

Click to expand...

What if I plug the speaker output of my 200 watt tube amp, dime it, and play it into the PV inputs of my Victron MPPT and play "SMOKE ON THE WATER" ? or maybe play a little more of a mellow jazz standard like "Smoke Gets in My Eyes" ?...

Wouldn't an un-attenuated audio wave pattern make a good simulation? Rain, sunshine, shade, tornedo ... hurricane.
Definitely a good hurricane simulation anyway ...

. .. . .. . . . hmm? .

There are special power supplies that are designed to mimic the output curves of solar panels under various conditions. They cost 100x more than your solar panels. They also weigh more.

There is a "wood workers motto" that goes something like "when in doubt, drill a hole". I find it to be remarkably useful to push me through morning procrastination and to start building / assembling things.

Maybe for solar hobbies, it is more like "when in doubt, attach a wire".

Easy use 2 lead battery in series and connect it on the input.
Thats is about the same like a 24 volt panel .
Its the cheap way to do it .
Normal it will pull the max amps out of the battery and it done.
Do use a fuse in the input .

You can use 19volt charger from a laptop and use that to.

Really a mppt or pwm is nothing more than a dc tot dc systeem with a smart unit in it to use the max of the input.

Thank you. This is exactly what I am trying to do:

I want to better understand what it is device functions and what it can do. Sort of like a transistor radio, when they first came to appear in the '60's.
I was not as concerned with how the transistors worked, but more about how to use the radio. I don't need to know how a watch works, I just want to use it.

Hence I need to play with it a little without wrecking it.

I speculate that in some ways I could almost use it as an adapter. For instance, if I needed 19.5 volts for, say a CPAP machine or some oddball piece of equipment that wants a specific DC voltage at a specific amperage that are within the settable voltage ranges, will it do that? Not that I need to, but if I know that it can, then I have a better understanding of how to apply it to any solution for any array situation I can use it for. - or I can just go with whatever I think the manual and everyone else says and take it at face value, but not really understand it.

Suijkerbuijk said:

Easy use 2 lead battery in series and connect it on the input.
Thats is about the same like a 24 volt panel .
Its the cheap way to do it .
Normal it will pull the max amps out of the battery and it done.
Do use a fuse in the input .

You can use 19volt charger from a laptop and use that to.

Really a mppt or pwm is nothing more than a dc tot dc systeem with a smart unit in it to use the max of the input.

Click to expand...

Well here is a detail I need to clear up:

On the the Victron MPPT 100 30, it is my understanding that the "100" is the maximum input voltage . 100v. A Hard limit.
Exceeding 100v will will fry the MPPT.

As for the "30", isn't 30 amps also a Hard limit ???
Won't exceeding 30A of current fry the MPPT?
What are the rules about that really?

For example,
- will 200v @ .0001A damage it?
- will .0001V @ 500A damage it?
I wouldn't really think so. So how does that work?

I have a pair of worn out 12v @55a AGM batteries that I retired off of my smaller house power wheelchair. I keep them for running 12v stuff and led lights in power outages.

So. if I were to use those, never mind a hot 12v car battery @ 600 Starting amps, and present that as input to my Victron MPPT 100 30, wouldn't that let out the genie's magic smoke?

Doesn't a higher than 30A current, damage this device?
Does the excess current get shunted off somehow?

Not knowing, I would go out of my way to neither exceed 100v (at any amperage?) or 30A (at any voltage?) for fear of releasing the magic smoke...

Or is that silly?

100/30 means 100volt in put max 30 amper out .
Thare is no really a max amp in .
In the victron Manuel it even tell you that if you set more watts the unit will not use it.

Other mppt can be not protected for it.
But Victron do .

The 100v is the input limit. The 30 is the max amps it can output. You draw from the panels as if the are a barrel of water. What you draw is equivalent of turning the spigot more or less

Thank you for clearing that up!

So, I could hook up three 12v car batteries in series as PV +/- through the Victron MPPT 100 30 to charge my 24v 100a Lifepo4 as long as the batteries have the voltage headroom to charge @ 29.2v - Right?

2Big2B said:

Thank you for clearing that up!

Click to expand...

And meanwhile, when I get the physical energy and motivation I am planning my first test platform.

I have a workbench desk in front of my spare bedroom window where I can set it up. I will hang one of my 130w flex panels as a big window shade inside the window, facing out. I will put one of my old 12v 55a agm batteries there, hooked up to that bonus Eco-worthy 12a Solar Charger I got and use it to kick up enough voltage from the one 12v ( panel, to charge that battery, and see how well that works, if at all.

If that works, I could set up 3 panels outside the window facing up to the southern sky to test that out set to 29.2v on the 24v 100a Lifepo4 battery pack. After I have proved that works, add the 4th panel for 520w and use the Victron. I might get a 6' folding table or something to lay them out flat or tilted into the sun on if more practical. Its a makeshift emergency power station, like a MASH sort of thing ...

2Big2B said:

So, I could hook up three 12v car batteries in series as PV +/- through the Victron MPPT 100 30 to charge my 24v 100a Lifepo4 as long as the batteries have the voltage headroom to charge @ 29.2v - Right?

Click to expand...

I am not 100% sure, but I don't think that is correct.

There are two limits to the "input" of the V 100 / 30 solar charge controller:

1) The max input voltage into the controller - which is more obvious - 100 volts absolute max.

2) Max input "power", which requires a calculation.

( 24 volt battery pack ) x ( 30 amps max output rating ) ~ 700 watts.

So the "power coming into the solar controller needs to be limited to 700 watts of solar panels or whatever the source of power is. AFAIK.

____________

3 each 12 volt batteries will look like:

1) Max voltage ~ ( 3 ) x ( 14 volts ) ~ 42 volts, so no problem

2) Max power delivered into that controller would be easily ( 42 volts ) x ( 100 amps for a short period of time ) ~ 4200 watts vs 700 watt rated.

This would result in the magic smoke inside that makes all electronics work - escape.

I could be completely wrong, but this is my understanding.

_________________

There are specific units sold that are for battery to battery charging for this reason.

I recently tested a 100/30 MPPT with a 30V/10A power supply. I simply hooked it up as if it were a panel.

Since it's limited to 300W, and I'm charging to 14.4V, I had to limit the 100/30 output to (300/14.4=) 20.8A. I rounded down to 20A.

Charged the battery right up. It's been floating @ 13.5V consuming about 3W for several days now.

sunshine_eggo said:

I recently tested a 100/30 MPPT with a 30V/10A power supply. I simply hooked it up as if it were a panel.

Since it's limited to 300W, and I'm charging to 14.4V, I had to limit the 100/30 output to (300/14.4=) 20.8A. I rounded down to 20A.

Charged the battery right up. It's been floating @ 13.5V consuming about 3W for several days now.

Click to expand...

I get the impression that this Victron 100 30 is still a poorly understood mppt device.

Here's how I have been figuring it:

I have (4) 12v 135w flex panels that each has a POV of 24.5v

I can't use a Victron 100 20 with all 4 panels because:

Watts=Amps x Volts => Amps= watts / volts

if; Watts/POV = Amps (?)
then;
1 panel: 130w/24.5 pov = 24.5v @ 5.31a
2 panels: 260w/24.5pov = 49v @ 10.61A
3 panels: 390w/24.5 pov = 73.5v @15.92A
4 panels: 520w/24.5 pov = 98v @ 21.22A --> Victron 100 20 ??? (too much current?)

Technically I could string all 4 panels in series @ 98v and not surpass the 100v hard voltage limit on the MPPT.
However, the total amperage being put out @ 21.22A exceeds WHAT I THOUGHT WAS A 20A HARD LIMIT
my understanding is that this would overload the Victron 100 20, but not the Victron 100 30.
- or do I have that wrong? Is that extra 1.22A shunted to ground (?) and lost, thus not overloading the Victron 100 20?

So, could I have really used all 4 panels with the Victron 100 20?
and what if they were 200w panels w/24.5 pov each. 800w/24.5= 98v @ 32.65A
could I use 4 of those panels with the Victron 100 20? or the Victron 100 30?
my understanding/misundrertanding is that total amp output beyond 30A on the Victron 100 30 will fry it.

- and -

Just to throw another monkey wrench into it, I have that "24V/36V/48V/60V/72V Boost 12A MPPT Solar Charge Controller Regulator"



I know that their 390W Golf Cart Solar Kits are sold with that solar charger:




Hence the 3 panels = 390w/24.5 pov = 73.5v @15.92A --> that is more than 12A, which contradicts my logi.,
That is, assuming...it works the same way as the Victron.
Does it?
I believe It just boosts VOC and passes it out, but only 12A, but I am uncertain.
Excess amperage is discarded?


I think I need to "RTFM" ... (Read That F###! (fine) Manual) !!!

2Big2B said:

I get the impression that this Victron 100 30 is still a poorly understood mppt device.

Here's how I was figuring it:'

I have (4) 12v 135w flex panels that each has a POV of 24.5v

I couldnt use the Victron 100 20 with all 4 panels because:

Watts=Amps x Volts & Amps=watts/volts

if; Watts/POV = Amps (?)
then;
1 panel: 135w/24.5 pov = 24.5v @ 5.51a
2 panels: 270w/24.5pov = 49v @ 11.02A
3 panels: 405w/24.5 pov = 73.5v @16.53A
4 panels: 520w/24.5 pov = 98v @ 21.22A

Technically I could string all 4 panels in series @ 98v and not surpass the 100v hard voltage limit on the MPPT.
However, the total amperage being put out @ 21.22A exceeds WHAT I THOUGHT WAS A 20A HARD LIMIT
my understanding is that this would overload the Victron 100 20, but not the Victron 100 30.
- or do I have that wrong? Is that extra 1.22A shunted to ground (?) and lost, thus not overloading the Victron 100 20?

So, could I have really used all 4 panels with the Victron 100 20?
and what if they were 200w panels w/24.5 pov each. 800w/24.5= 98v @ 32.65A
could I use 4 of those panels with the Victron 100 20? or the Victron 100 30?
my understanding/misundrertanding is that total amp output beyond 30A on the Victron 100 30 will fry it.

Please Expain.

Click to expand...

Yes on the victron you can
By Victron its a hard limit and will not use it.
Its in you manuel .
Attach file i have select it.

a) If more PV power is connected, the controller will limit input power

I use a current limited power supply and set the amps to some value below Impp and a resistor in series. Volts is set to below Voc and above Vmp. Resistor softens the transition of the power supplies current limiter and capacitor bank. For resistor, a start is (V power supply - V power point) divided by desired current. With a battery I would always use some resistance.

I don't know what this test actually proves other than the switching section of charge controller is functioning. Every method works till it doesn't. The risk is that supply or device will fail if a bad decision is made.