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jakudo avatar image
jakudo asked

VRM values - explanation

Hi,

can anybody please explain, what the values on PV Charger mean?

I've got a bit confused what those values are. I have MPPT 150/100 on 48 V system, so I would expect that one of that numbers should be max 4800 W (100 A x 48 V = 4800 W). However, one is 4958 W and the second is 5067 W. What are those?


Thanks,

Jakub

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VRM
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2 Answers
kevgermany avatar image
kevgermany answered ·

First number is the maximum input voltage from the panels, never to be exceeded.

Second number is the max output current. Actual depends on power from the panels and the willingness of the battery to accept charge.

There isn't a power in these numbers, as it's dependant on battery voltage at time of charge.

You can get an idea of power by multiplying battery voltage by max current. But remember that as battery voltage is nominal and depends on state of charge, this is a guideline, not precise value.

Depending on where you're looking in VRM, you will see power, voltage, current. And in some cases for the panels as well as the battery.

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jakudo avatar image jakudo commented ·

Hi, thanks a lot, however, I must have explained my question wrong (sorry). I What I would like to know are the values on the other side of the picture in the box "PV Charger":

screenshot-2024-04-05-at-55108.png

There I would expect that one of the values should be max 4800 W and not 4958 W or 5067 W as on the picture since I have MPPT 150/100.

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Alexandra avatar image Alexandra ♦ jakudo commented ·
Those are solar panel statistics. So voltage and current from that side.
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Alexandra avatar image
Alexandra answered ·

@jakudo

Those are solar panel statistics.

So PV voltage and Current on the solar panels side.

Panels are rates at 25°C if they are colder they produce more.

Also the MPPT is tracking where it gets the most power so those vary.

Then your battery voltage is not at 48v all the time. Some 48v systems charge up to 56v so the power output since it is amp limited can vary as well


48v x 100A is 4800w

100A being the max output of the mppt... But if battery terminal voltage is higher....

55v x 100A is 5500w

Maximum Power Point Tracking hence the name.

Dont forget you are also running loads so again it can produce more for that.

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jakudo avatar image jakudo commented ·
Hi @Alexandra , ok, thanks for explanation. My understandings were that if the MPPT is 150/100, it can always produce max 100 A and if the system is set as 48 V so max 4800 W no matter how many panels and no matter what the temperature and other circumstances are.


Thanks a lot.

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pwfarnell avatar image pwfarnell jakudo commented ·
If your MPPT output terminal is actually at 50.5V then it can deliver 5,050W, if you are at 52.5V then 5,250W.
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jakudo avatar image jakudo pwfarnell commented ·
Thanks for explanation. Now it make more sense :)
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Alexandra avatar image Alexandra ♦ jakudo commented ·

You are correct in saying that the max is always 100A. But it is max amps at the battery terminal voltage. Or the DC bus voltage.

How the system is physically connected can also affect how well it produces.

To charge a battery a voltage potential has to be created to make the power flow that way. So the MPPT is outputting a higher voltage than the battery voltage at this point.

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