question

Ingo avatar image
Ingo asked

ESS slowly discharges my battery with Keep Batteries Charged

My system slowly discharges my managed battery over a couple of days even while the Keep Batteries Charged option is selected. Currently it's down to 94% and doesn't seem to stop any time soon. My PV Charger is out of commision (Panel Maintenance) so the only charge source is the Grid - which is fine.

Quattro/478

VenusGX/2.60

Freedomwon 10/8

SmartSolar 150/35/1.54

ESS/Keep Batteries Charged

No Power Assist or anything strange selected. Pure UPS at this point in time.

Any ideas why it would keep on discharging my battery? At some point I am going to need the capacity for grid failures.


venusgx-status.png

ESS
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4 Answers
seb71 avatar image
seb71 answered ·

Your Quattro inverter and other DC powered devices are discharging the battery, not ESS.

Is the charger enabled in Quattro? If yes, what are the settings?

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Ingo avatar image Ingo commented ·

You are correct, it's the Venus and Quattro itself. My charger is enabled and set to the battery manufacturer's specifications.

charger.png

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seb71 avatar image seb71 Ingo commented ·

I use ESS with the "Optimized (without BatteryLife)" mode, but for testing I switched to "Keep batteries charged".

My Multiplus II disabled the inverter and immediately started to charge the battery from grid (it's after Sunset, so solar chargers are off).

The battery was at about 87% when I switched modes.


I see that your inverter apparentlly has the inverter enabled (the LED is on). It can either invert or charge from the grid. Not both.


If you check in VRM, is the "System - ESS battery life state" shown as "Kep batteries charged"?


Or maybe it is caused by the batteries BMS.


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Ingo avatar image Ingo seb71 commented ·

Yes, it shows Keep Batteries Charged. I must confess that I've seen this with my previous Lead Acids also, it just keeps on draining a drop at a time and never charges to 100% If I set it to Optimized with Battery Life then a weird thing happens, it charges to 100% but the battery voltage drops down to 52V which is shouldn't. In the old lead-acid days I disabled ESS and then everything was perfect.

The battery expert says it must get up to 55-55.8V for proper operation. I also upgraded the VenusGX to the latest Release Candidate but it made no difference, something is telling the charger not to charge or the charges behaves this way when in ESS mode which is not right.

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seb71 avatar image seb71 Ingo commented ·

A BMS with cell-level monitoring could disable the charging of the battery if one cell gets too high (and that can happen even if the battery voltage looks normal).

But I do not know if your battery BMS acts like this.


If the same thing happened with lead-acid batteries (so without BMS), then most likely the cause is something else.


Another thing: you do not list a shunt. Without a shunt, the calculated SOC is very inaccurate. And with LiFePO4 the voltage is not a good indicator for SOC, either (especially in the middle zone).


In fact, from where does come your SOC value? From the inverter?

What you have in Settings-System setup-Battery monitor?

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Daniël Boekel (Victron Energy Staff) avatar image
Daniël Boekel (Victron Energy Staff) answered ·

Hi @Ingo

What parameters does the BMS send? (devices, BMS, Parameters)

You can also enable those values in a widget on VRM 'advanced' page

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Ingo avatar image Ingo commented ·

Hi @Daniël Boekel (Victron Energy Staff)

VRM id: 985dadcac66b

The below has been enabled on VRM portal. On the actual Venus Console there are a few more. I think the Freedom Lite batteries have one of the more comprehensive BMS' around.


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Daniël Boekel (Victron Energy Staff) avatar image
Daniël Boekel (Victron Energy Staff) answered ·

Hi @Ingo

Your battery tells the system at what voltage to charge, and the system does just that: charge to 55.2 volt. I'ts the battery that tells the sytem the SOC, and that SOC is incorrect IMHO, you can see cells are at 3.45V / cell and that is 100% charged.

screenshot of BMS limits:

screenshot-2021-01-22-102352.png


So best to ask your battery supplier if this can be improved (or just don't worry about it now you know what is going on).


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Ingo avatar image Ingo commented ·

You are absolutely right @Daniël Boekel (Victron Energy Staff). I also just came back from a session getting the battery firmware updated to the latest. The vendor said we must give it a day or so to 'adjust' and it should eventually hover around 99.X% SOC and a slightly higher charge voltage. I will report back on Monday with the results.

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Ingo avatar image Ingo Ingo commented ·

Ok, this is more like it. With the updated firmware the voltage increased to 55.5V and the SOC toggles between 99% and 100%

So if anyone finds this post in future, please make sure that the battery manufacturer has loaded the latest firmware - it looks like my issue has been resolved.

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seb71 avatar image seb71 Ingo commented ·

You said it did the same thing with your old lead-acid battery (so without a BMS).

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Ingo avatar image Ingo seb71 commented ·

Yea, could be something unrelated to this issue.

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Robert Boerescu avatar image
Robert Boerescu answered ·

I have the same issue, I have keep battery charged selected but SOC has been drifting down ever since I set it, now at 83%. I have a smartshunt and generic lifepo4 without a smart BMS.drift.png


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derrick thomas avatar image derrick thomas commented ·
You appear to be in float with a voltage of 51. What are your charge settings in the inverter? Is dvcc enabled? What are the voltage/amperage settings in dvcc? With a voltage of 51 your SOC is going to keep dropping.
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Robert Boerescu avatar image Robert Boerescu derrick thomas commented ·

The battery is 15S and the recommended charging voltage on it says 54V. However I have been doing a lot of reading and listening to youtube videos on the subject and I decided to set the charging voltage to 52 and float to 51, similar with pylontec batteries. It has been working fine like this. I do not need a lot of capacity, this is only 100Ah, mostly for critical loads in case of power cut. The way I use it lately is to keep it charged. The only issue I see is that SOC goes down every day. Yesterday I set it to optimized with battery life and this morning charged again to 100%. Not sure what is causing to go down. DVCC is enabled.

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