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bjornm avatar image
bjornm asked

Does the SmartSolar 250/100 have a hard limit on max array power?

I can see in the manual that there is a max array short circuit current of 70 A, and that there is a max array voltage of 250 V. Those numbers make sense to me, to avoid damaging the controller.

Then it says "Nominal PV power, 24V: 2900 W". Not sure what that "nominal" means in this context. I assume it means "normal", i.e. a suitable array size for this controller.

If I use the MPPT Calculator, I can't get it to accept an array size of more than 3760 W for this controller.

https://www.victronenergy.com/mppt-calculator

I'm curious about the reason for this power limitation. Could be that the calculator is just hinting that you will waste a lot of your array capacity, you should get a larger controller (or get two). But then that hint should come at a much lower power. Or it could be that the calculator thinks the controller will break above certain array power. That doesn't make sense either, because the controller only draws as much current as it can handle. An array of 200 V, 50 A is 10 kW. A lot of wasted power to use with this controller, but still has a voltage and current within specs.

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Alexandra avatar image
Alexandra answered ·

@BjornM

For the 250/100, no matter how much you connect to it it can only charge with 100A @ the battery voltage. Same goes for the 70A

So yes a limit in that regard.

The only hard limits on the input are the max voltage at min temps and the short circuit amount. Over panelling is ok if you can live with the 'loss' if your system ever operates at STC conditions.


100A at 24v is 2400W. But most 24v batteries charge to 27v so 2700W output there. But with irradiance and panel temps you can go over that.

For example where we are on average we only see about 70% of installed capacity. So tend to oversize a bit (without breaking the input rules) to compensate for that.

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bjornm avatar image bjornm commented ·

Thanks Alexandra, that makes sense.

Could have been explained a bit clearer in the manual and on the MPPT calculator. Some people will think it is an actual hard limit on the array size.

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Alexandra avatar image Alexandra ♦ bjornm commented ·
Well to some degree there is a hard limit. In th tech specs it is explained. There is training on the Mppts on Victron professional open to all. And on you tube. So plenty of aid.



With so many variations on solar panels and batteries and design it is difficult to state exactly what that could be in wattage.

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bjornm avatar image bjornm commented ·

The MPPT calculator apparently thinks I can use this controller for a 3760 W array. That's 39% oversize. So apparently Victron thinks an oversize of 39% is ok, but not more than that. They need to explain why, or it looks like an arbitrary number. A technical limitation in the controller? A friendly suggestion, so that you don't lose valuable array power? We have no way to know their intention.

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Alexandra avatar image Alexandra ♦ bjornm commented ·

The mppt is rated at nominal battery voltage. Like I explained before, batteries charge to all different voltages and this since the rating is amps based (output of amps is fixed max) will affect rating.


Then the voltage and output of panels is affected by temperature as well. So in some circumstances you probably will be over paneled.

That is the nature of solar. Nothing is constant.

The RS series allows 100% over panel. But in low light conditions this is a great help.

But for some shaving and peaks off their solar is unacceptable. You find this true if space is limited and you can't waste a watt in any circumstance.

At the end of the day you need to evaluate what you can live with. The responsibility is yours. So yes it is a friendly warning that if that is not what you want then you need to change your design. You decide if that is a good or bad thing for yourself.

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