Understanding VE Direct Output

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vishnu-venkatesh asked Dec 1, '22

Understanding VE Direct Output

Hello,

I recently started having to maintain someones solar power system. They are using the MPPT 75/10 charge controller and the BMV 700. They managed to hook up all the connections and are getting data output on one of their computers. They appear to be tracking a number of values and I wanted to get some clarity on what exactly they represent. I have been thorugh the VE direct datasheet but I have some further questions.

The values being collected are as follows.

V - This appears to be the voltage of the battires, that is clear enough.

P - What is this the power of? Is this the net power = (power in - power out)?

CE - I am assuming this is the cumulative power consumed, but it is not clear since when. is there a way to reset this value?

VPV - This is clear, it is just the voltage accross the solar panel leads.

PPV - Is this simply the power in from the solar panels?

I - Battery current has an explanation in the document

iL - I guess this is simple the current draw of the load.

Apologies if this question is very basic and vague. I just want to get the terminoology clear so I can understand this system better.

Thanks a lot!

VE.Direct

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Answer 1 · 2022-12-01T10:05:39Z

Thiemo van Engelen (Victron Energy staff) answered · Dec 01, 2022 at 10:05 AM

Hi,

> P - What is this the power of? Is this the net power = (power in - power out)?
This is indeed the net power, so V * I.

> CE - I am assuming this is the cumulative power consumed, but it is not clear since when. is there a way to reset this value?
This is indeed the cumulative power drawn from the battery. This will count up when current is drawn from the battery and it will count down when the battery is charged. It is reset to 0 when the synchronization conditions are met, so when the SOC is reset to 100%.

> PPV - Is this simply the power in from the solar panels?
Yes.

> IL - I guess this is simple the current draw of the load.
Yes.

Kind regards,

Thiemo van Engelen

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vishnu-venkatesh commented · Dec 02, 2022 at 10:13 AM

Hey, thanks for the help!

Need a bit more clarification.

This is are a couple of lines of the output from the computer, one from eariler when it was charging, and now when it isnt.

 P,     CE, SOC, TTG,     V,    I, CS, ERR, LOAD,  IL,   VPV, PPV
20, -49414,   0,   0, 12110, 1840,  3,   0,   ON, 700, 16280,  32 
-8, -46955,   0,   0, 11810, -610,  3,   0,   ON, 800, 16010,   2

What is 'I' exactly? I read the VE Direct document again, but it just says that if I > 0 its charging and I < 0 its discharging. Is this the current to the batteries? or is it net current = (current in - load current)

I did a quick check, V * I was close to, but not always equal to P. Im guessing there are some fluctuations, but I wanted to understand it.
eg. 12.11V * 1.84A = 22.26W

My CE value has been a fairly high negative value for a while, what does that mean? To me that would mean that it was discharging for more time than it was charged.

What is the difference between CE - consumed amp hours and H6 - cumulative amp hours drawn?

Thanks so much!

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Thiemo van Engelen (Victron Energy staff) ♦ vishnu-venkatesh commented · Dec 02, 2022 at 11:27 AM

Hi,

The output you provide here is a combination of the data of the BMV and the MPPT as it has both VPV and CE in it. It is very hard for me to comment on this kind of data as I don't know where it comes from or what has been done with this data. So when you provide the raw output from the devices it is easier for me to provide answers.

Then more specifically on I:
For the BMV this is the measured current through the shunt. The P in the data from the BMV should always be the same as V*I.
For the MPPT, I is the current through the battery connection of the MPPT.

Then CE and H6:
CE provides a different view on the current state of the battery. CE being high negative means that a lot of energy was extracted from the battery.
H6 is how much current has been extracted from the battery over the lifetime of the BMV. So this will only decrease (be more negative) and never count towards zero.

Kind regards,

Thiemo van Engelen

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vishnu-venkatesh Thiemo van Engelen (Victron Energy staff) ♦ commented · Dec 03, 2022 at 04:39 AM

Thanks for the response, its been a great help.

Ah, this is how the data was output in the system. I just copied a couple of the lines as examples.

But things are a bit clearer now.

Best,

Vishnu

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