Power Difference between values shown by Smartsolar and Smartshunt (Battery Monitor)

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lorenzo asked Sep 18, '20

Power Difference between values shown by Smartsolar and Smartshunt (Battery Monitor)

There are huge differences between the Values I get from the MPPT and the battery. Everything is luke warm to ambient temperature. Cables are not an issue - they are total overkill.
The Smartshunt values are independently verified by a very good BMS.

Anyone can shed some light on the situation for me?

Power Solarpanels: 34.07V * 13.4A = 456W

Power Battery: 27.27V * 16.30A = 445W

MPPT efficiency loss: 2.4% That's ok

Meanwhile, the Smartshunt shows verified 407W!!

Where are the missing 38Watts??

I am using LiFePo4 at low C rates - so round trip efficiency is virtually negligible in light of the losses I am trying to figure out.

Update: I've measured everything, thank god that I've the equipment for that since values vary in the milliseconds.

The only thing that does not match at all is the purported Solarpanel amperage output. Voltage seems pretty accurate. As such 1.4A were reported, when there were really 1.1A. A 21% difference!

That makes me really fed up and unless that is my specific unit I am gonna make sure that other people will become aware of the kind of product they are really buying.

But that doesn't explain everything. The only thing certain is that there are no real physical losses present.

battery charging smart solar set-up help power meter

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screenshot-2020-09-18-15-23-13-967-comvictronenerg.jpg (53.0 KiB)

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Answer 1 · 2020-09-19T07:42:30Z

jeroend answered · Sep 19, 2020 at 07:42 AM

Difficult to assess without knowing what the equipment is setup like and what controls the charging of the battery yet I do see a NRN (Nice Round Number) as an output value on the Shunt screenshot for the Current. Shunt report 100% SOC so battery is full. Given that you state you are using LifePo4 at low C-rates, could it be that you are limiting the Watts as a result of limiting the current of the battery? P=U*I

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Answer 2 · 2020-12-06T14:35:00Z

lorenzo answered · Dec 06, 2020 at 02:35 PM

The equipment is of course setup in the most direct and comparable fashion. A battery solar panels and a smartshunt in between. No loads.

Go measure first and assess the Smart Solar accuracy yourself, before hypothesizing upon the setup. I have a realtime current meter and it reflects the values of the smartshunt, not the ones the Smartsolar reports on the current that supposedly goes in.

Victron must know this, which is why the abstain from a clarification here.

What I don't understand? Don't you have a current meter to carry out measurements on your own setup rather than hypothesize?

So far not a single person has vouched for Victron's SmartSolar.

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Fra commented · Jan 15, 2021 at 08:17 PM

personally I have no difficulty in believing that it is Smartsolar who is wrong.

I have read other people complaining about this.

I also saw a comparison between a Victronenergy Smartsolar and an Epever TracerAn in which the Smartsolar detects a little more watts than the TracerAn, with the same panel and in all conditions.

The comparison was made without a current meter, based only on the apps of the two brands.

So there is no telling if it was reliable.

I who have compared two instruments of different brands (Victronenergy Smartshunt and Epever TracerAn) can only bet on the good precision of the Smartshunt (and consequently of the TracerAn).

When 2 instruments say the same thing, they are quite likely to be telling the truth.

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Answer 3 · 2020-12-06T14:42:24Z

lorenzo answered · Dec 06, 2020 at 02:42 PM

I regoogled and the answer is here: https://community.victronenergy.com/questions/1858/innacurate-smartsolar-current-measurement.html

Victron isn't even claiming a 5% Tolerance ( i wish it were that low), they are just saying that any reported value is fine with them (as long as the shown value is positive).

Tolerances will vary by surrounding EM fields, heat, peak power point and may well be higher than 5%.

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Answer 4 · 2021-01-15T19:17:11Z

Fra answered · Jan 15, 2021 at 07:17 PM

I recently bought the Smartshunt.

And I own an Mppt Epever 3210 controller and a 300 watt panel.

The power detected by the Epever and Victronenergy Smartshunt controllers is surprisingly almost identical !!!

As well as the measurements of Voltage and Amper, of the "LOAD" output of the Epever Mppt controller are identical to those of the Smartshunt.

In these case:

Victronenergy Load current 2.72A

Epever Load current 2.67A

Victron power 34 watts

Epever power 33.77 watts

Victron voltage 12.66 volts

Epever voltage 12.65 volts

And i think Epever mppt controller dont detct its own consumpitions (Lcd display and wifi module). And Victron Smartshunt detect these micro-consumpions and result.

I've never tried over 200 watts. Because it's winter!

So in my opinion the difference you notice is a bit too much.

Especially considering that the victronenergy MPPT controller costs more than 1/3 more than the Epever MPPT controller. And it can't be explained by tolerance.

screenshot-20210115-192333.png (131.3 KiB)

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Answer 5 · 2021-01-15T20:19:21Z

lehrling answered · Jan 15, 2021 at 08:19 PM

It looks like you are using the app and switching from the controller to the shunt screens and expecting the numbers to be identical on the shunt to what they were on the controller when you last viewed it.

Even the phone clock in the screenshots are a minute apart.

I think simultaneous measurement is necessary.

How about comparing shunt current and amp clamp readings?

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Fra commented · Jan 16, 2021 at 10:16 AM

You're right ... I also took the photos in a hurry last night.

However the load was constant so it didn't vary much over time.

I will calmly redo them using 2 phones or the PC to avoid time differences.

I don't have a clamp, however trust me, looking at apps on two phones a lot of times, the measurements are pretty similar.

And this is good.

I wanted to "show" that the difference that the author of the post notes, in my opinion is really very high.

In fact, my Epever regulator and my Smartshunt are always almost identical.

Clearly the Smartshunt resistor is even better than the small resistors that the Epever controller uses as a shunt.

So I think the Smartshunt values are the more truthful of the two.

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Fra commented · Jan 16, 2021 at 10:23 AM

Where do you see a minute of difference in the phone? Maybe in the "filename"?

Because in the screenshot it marks 19.23 in both.

In the "file name" you see 20 seconds of difference.

19.23.13-19.23.33

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Answer 6 · 2021-01-16T10:55:31Z

Fra answered · Jan 16, 2021 at 10:55 AM

Now that I think about it .. There is definitely something wrong with the Smartshunt setting. (Charging efficiency, capacity, tail current, "battery charged" voltage.

How is it possible that the panel still charges 13A and the Smartshunt detects SOC 100%?

This indicates that the SOC 100% sync settings are wrong.

With solar charge, on the Smartshunt a very low tail current (1.5 / 2%), a high "battery charged" voltage (13.5 / 13.6v .. almost as much as the floating voltage of the mppt controller) must be set.

Otherwise the Smartshunt will sync to 100% Soc long before reality.

I have set a tail current of 1.5%, a "battery charged" voltage of 13.6 v and a "battery charged time" of 8 minutes.

In this way, the Smartshunt syncs every day at 100% Soc, precisely when the mppt controller(or alternator) has finished charging. That is when it charges less than 1.5A while floating.

And when the Smartshunt scores around -1ah in the battery.

Instead, with the default settings, it would sync to 100% soc, much earlier ...

That is when the battery still lacked 5/6 ah .... and the mppt controller was still in the absorpion phase.

This obviously has nothing to do with the difference in detections.

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