MPPT + DC/DC converter

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djl asked Sep 29, '23

MPPT + DC/DC converter

Hi, i am new to all this and i have a simple system, but having troubles making it work.

MPPT + battery + solar panel + DC motor as load

my batteries are 36V but my load needs just 29.4V, so i usually use a DC/DC converter to lower it down to the requested voltage.

As i read here, it doesnt work with the MPPT system (it works when the solar panel is actually producing electricity, but it doesnt as soon the voltage of the solar is lower than the battery one.

Any suggestions/solutions?

I know that i can connect the load directly to the battery (bypassing the MPPT)

Thanks
Dario

MPPT SmartSolar dc-dc charger

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Answer 1 · 2023-09-30T00:03:03Z

Mike Dorsett answered · Sep 30, 2023 at 12:03 AM

Presumably you have one of the MPPT's that can be set up for 36V - not all of them can.

A schematic of how your system is set up would help. None of the 36v enabled MPPT's have load outputs, so your dc/dc converter for the load needs to be connected to the battery.

The solar panel connects to the pv input of the MPPT and needs to have a voltage of 5V more than the battery voltage for the MPPT to start, there after it will work down to 1v above the battery voltage. So you need to check the open circuit voltage of your solar panel.

Which bit of the system is not working with the MPPT?

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djl commented · Sep 30, 2023 at 08:35 AM

Dear mike, thanks for your time, i am absolutely not an expert, so sorry if the scheme here is not as professional as you might expect ;)

i have a Victron Energy SmartSolar MPPT 100/20 bluetooth with has a load output for a dc motor (like one used in an electric bike) using an ESC, 2 power tools batteries of 18V in series and 3 solar panel on the other side.

the DC/DC converter is not working IF the solar panels are not over the 5V+, but i need it because from the App i can not tell the MPPT to down the electricity from 36V to 29.4V required by the ESC (I haven´t tried to connect the ESC without it, because i dont have the specifics of it).

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mppt-scheme-a1.jpg (189.3 KiB)

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