Victron MPPT over panelling

[Hedges]

How does a PWM SCC self-limit current?

 

[sunshine_eggo]

In case it is useful, the bogart SC 2030 self limits to 30 amps, so you can over panel if you want to.

For better or worse, it is a pwm type, so it will turn on earlier in with a lower panel voltage, but is not as good when the panel voltage is high.

It is limited to 12 / 24 volt systems. Might be able to run 36 volt.

Only up to 45A per the manual.

 

[sunshine_eggo]

How does a PWM SCC self-limit current?

No idea, but it says it does (I didn't believe it, so I had to look it up):

http://www.bogartengineering.com/wp-content/uploads/docs/SC2030%20Technical%20Manual.pdf

2. Technical Specifications:
Regulation type...........................................PWM
Solar panel open-circuit voltage..................55V maximum
Solar panel nominal voltage.......................12V - 24V, matched to the battery voltage: Vpp about 16-18+Volts for 12-24V systems, Vpp about 32-36+ for 24V systems
Nominal Battery voltage............................12V - 24V
Required operational current.....................While sun shining: 25mA. Solar dark: 1mA max
Maximum Battery voltage............. ...........35V
Battery type...............................................AGM, Gel, or flooded lead-acid
Solar-panel peak current...........................Max 31A for full efficiency. May be safely used with panels up to 45A,however charging current will be reduced to protect charger

 

[HarryN]

Only up to 45A per the manual.

Thanks - will need to go through the manual again. It has been a while.

It has AGM and flooded battery parameters built in that can be selected via some pins. If you want to use Li batteries you just program the settings in yourself. I have built multiple 24 volt Lifeline and battle born setups with them.

 

[Hedges]

No idea, but it says it does (I didn't believe it, so I had to look it up):

Solar-panel peak current...........................Max 31A for full efficiency. May be safely used with panels up to 45A,however charging current will be reduced to protect charger

So the transistor can probably handle 45A, but not the heating of 45A continuous.
PWM to limit heatsink temperature, as well as to regulate voltage, is my guess. Resulting in reduced average current.
Likely lower average charge current than if some steady-state lower current. W(heating) = I^2R

 

[HarryN]

So the transistor can probably handle 45A, but not the heating of 45A continuous.
PWM to limit heatsink temperature, as well as to regulate voltage, is my guess. Resulting in reduced average current.
Likely lower average charge current than if some steady-state lower current. W(heating) = I^2R

It might, but for some reason I think that it actually measures current flow internally and regulates using that vs temperature. Might be my imagination.

 

[Hedges]

To reduce current requires impedance.
Linear regulator drops voltage and burns watts.
Switching regulator has an inductor; current ramps up over time, so switching on an off limits current (and relates to voltage conversion.)

PWM can't do either. So I don't believe it regulates current.
Max 45A array, it said.

Yes, it could measure current and PWM a calculated amount. But using temperature would be free, if it had temperature protection.

Most MPPT could take any size array. Even a battery (thousands of amps on tap.)

 

[Kiwi2000]

But since Victron has multiple voltage output options. It appears that it has multiple options for overpaneling. As long as you never exceed the ISC hard limit.

Even something like their 150/45 can be overpanelled on a 48V system.

At 48V it has a max output of 2600 watts. Entering the details of a particular panel I use, I could build an array of 6240 watts. That would be 240% overpanelled.

 

[sunshine_eggo]

Even something like their 150/45 can be overpanelled on a 48V system.

At 48V it has a max output of 2600 watts. Entering the details of a particular panel I use, I could build an array of 6240 watts. That would be 240% overpanelled.

Can do so on 12V as well... Could put that same array on a 12V system only outputting 650W... 960% overpanelled...

 

[Kiwi2000]

Can do so on 12V as well... Could put that same array on a 12V system only outputting 650W... 960% overpanelled...

Just pointing out as the other poster was trying to imply that they can be overpanelled on a 12V system because they are also capable of running 48V systems.

Yet they can be substantially overpanelled on 48V systems as well.

 

[timselectric]

So if a victron unit can handle more than twice the PV than it can output, it isn’t really limited? And in fact is over panel friendly.

Again assuming you stick to the published specs of VOC and ISC.

In my opinion it's not overpaneling, If you stay within its listed input specifications.
But if others choose to call it that. That's entirely up to them.

 

[Pi Curio]

In my opinion it's not overpaneling, If you stay within its listed input specifications.
But if others choose to call it that. That's entirely up to them.

But it is overpanelling.

The limits are there to protect the SCC, not to specify the actual power the SCC can deliver @ specific system voltage.

For example, 100/20 != to 2000W PV

It's the V and I limit you have available to work within to fit the amount of PV necessery to get the power output rating an SCC can provide at specific system voltage.

You can overpanel regardless of system voltage, as long the SCC has enough Voc and Isc headroom to do so.


Honestly, it's great to see this topic getting more traction. Just a year ago this wasn't the case.

This can help people upgrade to or design a more productive system, panels are cheaper these days.

 

[timselectric]

But it is overpanelling.

The limits are there to protect the SCC, not to specify the actual power the SCC can deliver @ specific system voltage.

For example, 100/20 != to 2000W PV

It's the V and I limit you have available to work within to fit the amount of PV necessery to get the power output rating an SCC can provide at specific system voltage.

You can overpanel regardless of system voltage, as long the SCC has enough Voc and Isc headroom to do so.


Honestly, it's great to see this topic getting more traction. Just a year a go this wasn't the case.

This can help people upgrade to or design a more productive system, panels are cheaper these days.

The reason for the high allowed ISC. Is to work with the low minimum voltage requirement. ( Vbatt+5v)
That's a good thing. It allows for a wide range of PV combinations.
But as long as you don't exceed the amperage than it's designed for (which is only limited by the ISC). I wouldn't call it overpaneling.
Most other MPPT's have a set amperage limit that it will use. No matter what the voltage is.
Like my Growatt's. They will clip at 18a, no matter what voltage the array is configured for.

 

[Pi Curio]

The reason for the high allowed ISC. Is to work with the low minimum voltage requirement. ( Vbatt+5v)
That's a good thing. It allows for a wide range of PV combinations.
But as long as you don't exceed the amperage than it's designed for (which is only limited by the ISC). I wouldn't call it overpaneling.
Most other MPPT's have a set amperage limit that it will use. No matter what the voltage is.
Like my Growatt's. They will clip at 18a, no matter what voltage the array is configured for.

But if you have more PV Wattage than SCC can deliver at specific system voltage, it will have enough to exceed the I rating of the SCC but the SCC will only use what it can.

That's overpanelling, yes?

 

[timselectric]

But if you have more PV Wattage than SCC can deliver at specific system voltage, it will have enough to exceed the I rating of the SCC but the SCC will only use what it can.

That's overpanelling, yes?

You are more than welcome to call it that, if you want.
I don't.

 

[BjornM]

To reduce current requires impedance.
Linear regulator drops voltage and burns watts.
Switching regulator has an inductor; current ramps up over time, so switching on an off limits current (and relates to voltage conversion.)

PWM can't do either. So I don't believe it regulates current.
Max 45A array, it said.

Yes, it could measure current and PWM a calculated amount. But using temperature would be free, if it had temperature protection.

Most MPPT could take any size array. Even a battery (thousands of amps on tap.)

A PWM regulator works just like PWM-controlling motors or other types of loads. It slices up the incoming voltage really fast, and together with an output filter capacitor the practical result is a lower voltage on the output. For a given output load, different duty cycles result in different output voltages. To regulate output current, all the regulator has to do is set the output voltage to whatever results in the target current. This is done automatically through a feedback loop.

 

[Pi Curio]

You are more than welcome to call it that, if you want.
I don't.

Fair enough.

Just to put it out there I wasn't trying to argue, merrly enjoying a constructive discussion with you.

Croatians are known to be direct, straight to the point, and sometimes it may come out the wrong way giving an impression of arguing etc. I hope you didn't take any of what I said in such or similar manner.

I'm open to being wrong at all times, why I find a productive discussion worth having, it's also a good way to learn new things and improve the understanding of concepts.


Just recently Sunshine helped me have a better understanding of what the term
overpaneling encapsulates.

If it weren't for him pointing out I'm pointlesly looking for a term that would describe increasing the PV wattage range to gain prolonged SCC peak production since it's overpanelling either way, I'd most likely still be separating the term overpaneling from that context.

That's not necessery the case here, why I'm always for a good productive discusion, where I could be easily proven wrong and I might learn something.

 

[BjornM]

The reason for the high allowed ISC. Is to work with the low minimum voltage requirement. ( Vbatt+5v)
That's a good thing. It allows for a wide range of PV combinations.
But as long as you don't exceed the amperage than it's designed for (which is only limited by the ISC). I wouldn't call it overpaneling.
Most other MPPT's have a set amperage limit that it will use. No matter what the voltage is.
Like my Growatt's. They will clip at 18a, no matter what voltage the array is configured for.

I think the common definition of over-panelling is when you have more nominal panel power than your charge controller and/or batteries can handle. You will regularly get into situations where not all your panel power can be harvested, because of limitations in your system.

That is not necessarily a bad thing. Over-panelling is a very common design choice. I've seen 130% as a typical value. My installation has 233% (5.6 kW array, 24 V/100 A controller). Panels are relatively cheap, controllers and batteries not. High latitudes have poor solar array performance in the winter, with the array very rarely hitting its nominal power. So the system is designed for those bad months.

 

[740GLE]

Nahh I’ve seen the light and jumped on Tim’s platform, over paneling is only when a SCC is able to exceed its published specs of VOC and ISC, argue with me all you want. ?

 

[Kiwi2000]

On grid tied feedback inverters, oversizing is when you have more watts of PV installed than the capacity rating of the inverter. Like 6kw of PV to a 5kw inverter.

It's the common definition of oversizing.