question

Alex Pescaru avatar image
Alex Pescaru asked

Battery consumption when no need to ? Possible software/hardware bug ?...

Hello All,

Rookie here, so please go easy on me. I have a strange situation...

Multi RS Solar, without PV solar panels, used as an UPS, with 3 x US2000C Pylontech batteries.
Multi RS connected with the batteries' BMS through a Cerbo GX.
Both inverter and Cerbo with latest firmwares. (1.15 and 3.13)
Multi RS "internal" ESS configured as Keep Batteries Charged.

Without any consumption from AC-OUT, the batteries consumption is 0 (zero), batteries being all the time in IDLE state.
On the picture below, you can see that the BMS considers to replenish the batteries once at about 9 hours to keep them charged.
Before replenishing, batteries voltage dropped to about 49.8V and after recharging is 52.4V, 2.6V difference, all normal here.

What I don't understand, is that after I begin to draw power from AC-OUT, the batteries consumption begins to be 0.2A (!!), also seen on the graph below...
Of course, the batteries are not on idle anymore and therefore, this leads to a much often recharge of the batteries, once at about 1 hour.
Also, the voltage excursion is from 50.4V (before recharging) to 52.4V (after recharging), with only 2V difference this time.

Why is that? Why a consumption from batteries when power is drawn from the AC-OUT?
For sure a 400W average consumption from AC-OUT will not warrant a battery "help"/consumption, isn't it?

Again, the inverter is set as "Keep the batteries charged" and Victron makes it clear "Utility grid failure is then the only time battery power is used".

I confirmed all of the above with a DC clamp meter, to be sure that is not a glitch... It's true, the current draw from batteries increases when AC-OUT consumption is present.


Thanks in advance for any help/advice!

consumption.png

Multi RS
consumption.png (107.1 KiB)
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3 Answers
Alexandra avatar image
Alexandra answered ·

@Alex Pescaru

The saw tooth graph you have there happens with pylontec especially when they are new.

I have seen it on quite a few Pylon systems and not just with the Multi RS but with MP2 as well. More noticeable on the keep batteries charge set ups.

All it is doing is going between just under float to absorption. And it is the batteries telling the system to do that. I am fairly certain Pylon know what they are doing with their batteries and they cover their warranty.

On a different note, they are not so good at picking up the smaller current draws of the battery

Notice the voltage drop with 'no current draw'.

1000014204.jpg


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Alex Pescaru avatar image Alex Pescaru commented ·

Thank you for your answer.

Indeed, "no current draw" is in fact a very small current draw, about 2W, for the Cerbo which is connected on DC bus. This is why the batteries are still charged/refilled at about 9 hours.

But the same Cerbo current is consumed, of course, when there is a load on the AC-OUT and then, for sure there is an additional current draw from batteries, because now they are charged/refilled at about 1 hour. Clear indication that there is a bigger current draw from batteries.

What I was wondering is in fact why the inverter is increasing the current draw from batteries when the AC-OUT consumption is present and also the grid is present and the inverter is set as "Keep the batteries charged". Victron makes it clear "Utility grid failure is then the only time battery power is used".

Is it possible that when they detect a consumption on AC-OUT to start the inverter in a "low power" mode to be ready to quickly take over on an eventual grid failure?

Thanks!

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netrange avatar image
netrange answered ·

Check the "Battery monitor" setting in the Remote Console. Can you find the Pylontech there?

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Alex Pescaru avatar image Alex Pescaru commented ·
It is set on "Automatic", with "Auto selected" being "Pylontech battery on CAN-bus"
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netrange avatar image netrange Alex Pescaru commented ·

Are all your loads connected to the AC Out or do you still have some connected on the mains side?

Remote Console - ESS - ACOutput used ?

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Alex Pescaru avatar image Alex Pescaru netrange commented ·

All loads are on AC OUT.

There is no ESS in Cerbo's Remote Console, because the ESS is implemented directly on the inverter.

Anyway, there is only one AC-OUT at the inverter's output. The other one is directly coupled with AC-IN. But again, all loads are on the inverter's output.

Also, in this moment, with the current firmware, there is no possibility to feed in.


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Alex Pescaru avatar image
Alex Pescaru answered ·

Is there any hardware/software engineer from Victron here who can confirm (or infirm) this consumption from batteries despite the fact the inverter has quality grid present and is set as "Keep the batteries charged" ?

Thank you in advance!

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