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hydrogen asked

SmartSolar Datasheet - Max PV short circuit current

Trying to understand the "Max. PV short circuit current 2)" line item from page 2 of the following SmartSolar datasheet:

https://www.victronenergy.com/upload/documents/Datasheet-SmartSolar-charge-controller-MPPT-150-70-up-to-150-100-VE.Can-EN.pdf

It reads "50A (max 30A per MC4 conn.)" for the 150/70 VE.Can model, and "70A (max 30A per MC4 conn.)" for the 150/85 and 150/100 VE.Can models.

The "2)" footnote at the bottom of page 2 reads:

2) A PV array with a higher short circuit current may damage the controller.

So I understand 30A is the limit of an MC4 connector, but I am considering "Tr" connection models, so 30A is irrelevant.

Everything I read online 'sizes' these MPPT units to the rated charge currents, not this Maximum PV short circuit current, yet this datasheet reads as the short circuit current rating is what must not be exceed.

Lastly, what is the point of purchasing a 150/100 unit, if it shares the same 70A Max. PV current limit of the 150/85?

Thanks!

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mrhappy answered ·
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hydrogen avatar image hydrogen commented ·
@MrHappy thank you for sharing that. I appreciate your response. It took reading through the thread to properly understand that, even though the Max PV short circuit current (IsC) is less than the charge current, if you get the PV array up to a high enough voltage via a series string, as long as you do not exceed the voltage of the MPPT, you can actually have more total power to draw from (watts) and thus, effectively achieve a higher charge current (because the bank is at a lower voltage). Is my understanding correct?

Thanks!

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mrhappy avatar image mrhappy hydrogen commented ·

Yes.

Theoretically: Consider the 150/100 model. If it charges a 60V battery bank with 100A that is 6 kW. In that case, you would have to deliver 6 kW into the PV side. For example strings of 3 x 40V panels, =120V which would mean 50 Amps @ 120V. Safe. But if you would connect the same panels in strings of 2, =80V, you would end up with 75 Amps on the PV side and probably burn out the mosfets exceeding the PV current limit.

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