question

wrietveld avatar image

VE.Bus low battery alarm, why?

I am getting Low Battery warning at a voltage that is different than configured in the settings. The pre-alarm is set to 10.9V, the ESS assistant is configured to do a cut-off at 12V@0.005C, yet, I am getting alarms when voltage drops below 12.25V at a much higher discharge rate. The battery monitor Voltage reading = VE.Bus DC Voltage reading so it doesn't look like a cabling issue.


What am I missing?

I am using VE.Bus firmware 465.





VE.Buslow battery warning
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3 Answers
Leslieanne avatar image
Leslieanne answered ·

Hi there,

I think your system is behaving exactly as expected, given the observed voltage drops.

In an ESS system, low battery warnings (as distinct from alarms) are generated when the voltage drops below the dynamic cut-off level PLUS the restart offset (0.3V for a 12v system). Your “much higher” discharge rates when the alarms occur are only about 20 amps or 0.05C, so the relevant dynamic low voltage cut-off is not much below 12v, and so the alarm voltage is just a little under 12.3V, which is exactly what you are seeing.

In fact, when using ESS, it is recommended to set low voltage alarms/warnings to “alarms only" so that the warnings are not bothersome!!! The flashing red LED on the multi will then be the only outward sign of the warning.

BUT.....rather than concentrating on "inappropriate" warnings, ask why are you seeing such large voltage drops at those discharge rates? I would be heeding those warnings by checking connections, wire sizing, battery health etc

Hope these comments are helpful, cheers, Leslie


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Hi @Leslieanne,

Thanks for your response. It has been a while but I am still researching this issue. Battery connections, wire sizing and battery health should all be OK. I am seeing this at every location where I am using new or used Narada REXC (lead carbon) batteries.

I asked a consultant to research this for us and he was wondering if we could be dealing with the coup de fouet discharge phenomenon, which is an excessive voltage dip that occurs in the early minutes of discharge of lead-acid batteries that has been previously fully charged.

I do not know why the issue occurs with the Narada REXC Lead-Carbon batteries and not in our systems with regular Lead-Acid batteries. We could not find any information of the coup de fouet effect in lead-carbon batteries.

The following possible solutions were provided. They are theoretical, and I am not sure if they can be implemented with the Victron system, or the solution may not provide the desired overall system performance.

1. Place a minimum time required on the test for a low battery voltage, in which the coup de fouet effect will not trigger the alarm.

2. Reduce the voltage level for the low battery voltage alarm to not be triggered by the coup de fouet effect, but still provide a reasonable warning when the battery voltage is nearing depletion.

3. Don’t fully charge the batteries.


I am wondering if solution #1 can be accomplished in the inverter settings. Anyone?

wrietveld avatar image
wrietveld answered ·

Hi Paul,

Thanks for your suggestions.

We have no alarm rules configured in VRM, nor do we have anything configured in the BMV.

Just for additional information, in the example above, the first alarm was when SOC was 99.9% and then again when SOC was 89.3%.








It seems to be exactly when going through the 12.25v mark.


I have more of these systems installed, they all use Lead Carbon batteries and are all configured identical and they all give the same errors. As soon as the utility power goes off, it throws a low batt warning, then it recovers and then after a little while it starts flooding our mailboxes with low battery alarms. Unfortunately, we need these alarms because when the battery is actually low (which should never happen), we need to intervene so we rely on this to function correctly.


Anybody else have any ideas?


Thanks so much!

Wilbert






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Paul B avatar image
Paul B answered ·

More information is need as to what you have connected.

However I suspect you have a Venus unit and a BMV battery monitor if so then the battery monitor has its own allarm settings in it so check these settings


or

you could have a allarm set in the VRM thats being triggered.

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