17.2 volt Vmp panel and Victron MPPT controller
I have two 40-Watt solar panels on the roof of my boat and each one of them is fed to each battery (house and start) by a small cheap Chinese CMWD PWM controller that are sold as MPPT, but of course they are not.
My solar panels are Ozcharge 40-Watt Mono panels with the following specs:
Max. power (Pmax): 40W Rated Voltage (Vmp): 17.2V Rated Current (Imp): 2.33A Open Circuit Voltage (Voc): 21.5V Short Circuit Current (Isc): 2.5A
I was thinking of changing these cheap PWM controllers for the Victron SmartSolar MPPT 75/10 with built in Bluetooth.https://energyconnections.net.au/product/victron-shop/454/1461/81328/victron-smartsolar-mppt-7510-charge-controller-with-built-in-bluetooth
My batteries are wet cell century marine batteries.
This controller needs a difference of + 5 volts to begin the bulk charging phase and after it starts, this 5 volts is reduced to 1 volt over the battery voltage.
I spoke to the supplier of the Victron controller and initially he said that the panel voltage was too low at 17.2 volts but when I told him the VOC was 21.5 volts, he said it would be fine. I have checked the panels disconnected from the controllers and they did have an OC voltage of 19-20 volts on a cloudy day but it was my understanding that when connected to a controller that the VMP was closer to what the actual output is.
So my question, if you kind folks can help is, do you think this MPPT controller is a good match for these panels or will it be governed too much by the VMP and not the VOC. I suppose I am not sure if I believe the supplier and don't want to spend $300 on new controllers just to have them only work during the middle of the day and not much during winter when the sun angle is lowest. I am located in Melbourne Australia, which is latitudinally similar to Tennessee I reckon.
I mainly want to get rid of the CMWD controllers because I don't expect them to last and if they fault, they may cook my batteries, which I don't really need at sea.
Maybe I should just buy some better quality PWM controllers. Money is not a governing factor anymore.
I hope you guys can help.