Waveform Clipper

Red_Fir

New Member
Joined
May 8, 2022
Messages
1
So I have a Flexmax 60 working well.
But working on the philosophy of "panels are cheap, and charge controllers less so" it keeps tickling around the back of my mind that Flexmax is way under utilized!
Specs give me a shutdown voltage at 145v and damage ensues at 150v so a constant input at 144v would be ideal.
Has anyone ever attempted a diode clipper at these voltages to limit Voc or cold weather exuberance?
Or any other voltage limiting scheme?
 

efficientPV

Solar Addict
Joined
Sep 24, 2019
Messages
634
I have one, it is called a water heater. When voltage gets above a set level it will draw just enough power to bring the voltage down to the set voltage. Not to protect controller, just to get free hot water (I have two tanks so in theory it will never shut off). One issue with these schemes is you can never know if it will work when it is needed.
 

AntronX

Solar Enthusiast
Joined
Oct 24, 2021
Messages
103
Wrong way to go about it. It's better to add solar panels by paralleling more of them versus maximizing series string size. MPPT charge controllers like FM-60 use buck DC-DC converter to do voltage conversion down to battery voltage. This type of converters run more efficiently if the difference between input and output voltage is small. For example it's better to wire your 60 cell solar panels in 2P configuration for 62Vmp while your 16S LFP battery pack will only need max voltage of 55.2V (3.45V per cell) to reach 99% SOC. During most of bulk charge state battery will be at 53.2V and FM-60 input at 59V after voltage drop on PV wire for a 1.1 : 1 input to output voltage ratio. Another benefit is you can bypass the charge controller in an emergency in case it fails and charge your battery bank by directly connecting PV output to battery while monitoring battery voltage to avoid overcharge. The MPPT mismatch loss will be minimal in that configuration.
 
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