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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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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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