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Solar panel over voltage

Saabpilot

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I inherited an unbranded solar panel when I purchased a camper trailer. Connected to a Renogy 50A DC-DC charger I measured 36volts at the panel which exceeds to solar input upper limit of 25.5volts. The over voltage protection cut in.
My question is, could I use a buck converter to step down the input voltage to be in range?

many thanks.
 
The Renogy DC-DC charger is. Intended for PV input only input?

The DC to DC chargers I looked at were intended to take a a 24 volt load off a battery and step it down to a 12 volt battery. If I upgraded to 24 volts, I would still need 12 volts to run a battery breakaway and the trailer jacks. I’m not sure that the 12 volt breakaway would need it, but the trailer leveling jacks can pull some amperage.

I’m just being sure you did not inherit a system where someone installed a DC-DC charger that should have installed a charge controller. Usually charge controllers have a pretty broad input, and the DC to DC chargers don’t. Some I looked at have a input less than absorption voltage, and closer to float voltage, which would do me no good.

My Batteries have an absorbtion phase of 14.6 and an absorption of 13.2, and usually 24 volt batteries have twice that, and that puts your charge not strong enough for that.
 
The charger in question has both DC-DC alternator charging and an MPPT solar charge controller limited to 25V input. He's proposing stepping the panel down to 24V for input into the Renogy's SCC.

 
Which may or may not serve to perform a MPPT function on the PV panel.
If buck converter is fed into MPPT input, charge controller will pull current to maximize power (unless it reaches its own limit.) Probably best if it doesn't reach current limit of the buck converter (size that large enough).

Be careful of the buck converter you select. Some switchers get killed by brownout (I've seen it with boost, not sure about buck; those ought to be more robust). First it will experience brownout as the sun gradually comes up. Then as the charge controller pulls more power than the PV panel can supply, voltage will drop.

A suitably rated MPPT charge controller might perform better.
 
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I'm looking at doing this too!

Was also considering a cheap MPPT controller (like this https://www.amazon.com/Controller-Regulator-Intelligent-Adjustable-Parameter/dp/B07STZSG9J ) in front of the DCC50 instead of a buck converter like this https://www.amazon.com/DROK-Adjustable-Regulator-Stabilizer-Transformer/dp/B0744BT79M or this https://www.amazon.com/Voltage-Converter-DROK-Regulator-Transformer/dp/B076TTBKFG.

Guessing it may be more efficient but not really sure! Definitely a bit cheaper..

I was looking at this 375W panel for instance which has a Voc of 39V https://www.itstechnologies.shop/products/375w-ja-solar-mono-mbb-percium-solar-panel
 
There is no such thing as a cheap MPPT controller. The one you linked explicitly states it's a PWM controller.

You need an MPPT controller to use that panel effectively.
 
There is no such thing as a cheap MPPT controller. The one you linked explicitly states it's a PWM controller.

You need an MPPT controller to use that panel effectively.
Doh - I guess theres ones like this then but becomes a bit more expensive that the buck converter.. https://www.amazon.com/Beleeb-Controller-Operation-Temperature-Compensation/dp/B08B7QS5XG

My question is then, would the buck converter work as well and be as efficient? I'm thinking not as I'm not sure either of those converters are set up to handle radically varying voltages and I'm not sure what would happen when the voltage was below the target output voltage.
 
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No. MPPT automatically sweep through the voltage and find the point where V * I = Pmax.

Buck converter doesn't do anything automatically besides maintain the set points.
 
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