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DC voltage reduction circuit needed

HANKMARS

Jul 28, 2019
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The latest charge controller I purchased for my PV system has a max input voltage of 25 VDC. My panels produce 36 VDC. I'm looking for a DC voltage reduction circuit to insure that controller never feels any voltage above 20 VDC. Does anyone have a bare-bones, bullet proof buck circuit handy?
 

Alec_t

Jul 7, 2015
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There are loads of DC-DC converters advertised online. Won't one of those do, if bought from a reputable source? No guarantee it'd be bullet-proof though.
 

HANKMARS

Jul 28, 2019
498
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There are loads of DC-DC converters advertised online. Won't one of those do, if bought from a reputable source? No guarantee it'd be bullet-proof though.
I did indeed order a 40A buck converter about an hour after posting this thread. However, this particular converter has a max input voltage of 35 VDC. My panels will reach 36.7 V, no load, therefore I will be using a shunt regulator that should guarantee that Vin,max is never exceeded. Quite a simple design by a friend. Shunt uses a power transistor, a zener diode and one carbon resistor. Zener will determine when shunt turns on.
 

HANKMARS

Jul 28, 2019
498
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Hi,
The DC-DC buck converter is the best-suited DC voltage reduction circuit that maintains constant voltage at 20 VDC for my panels with 36 VDC. The buck converter efficiently reduces the Vin while providing stable Vout. Buy a buck converter to step down the 36V input voltage of your panels to a constant 20V.
Hope this will help.
What I did find that I have on hand is a CV CC convertor which I will hopefully be testing with panels and charge controller, sometime this week. CV CC unit rated 40 A.
 

ramussons

Jun 10, 2014
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I did indeed order a 40A buck converter about an hour after posting this thread. However, this particular converter has a max input voltage of 35 VDC. My panels will reach 36.7 V, no load, therefore I will be using a shunt regulator that should guarantee that Vin,max is never exceeded. Quite a simple design by a friend. Shunt uses a power transistor, a zener diode and one carbon resistor. Zener will determine when shunt turns on.
Just make sure that the Shunt Transistor has an forced aircooled heat sink.
 
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