Cause of constant 'Battery Low Chemistry Voltage' alerts on new UPS/battery strings

[Anonymous user]

We have two EPS 6000's with four strings of batteries for each and battery monitors connected to each string.  We seem to get a lot of alerts that say string discharging from each string and sometimes see the voltage on some of the batteries drop from 13 volts down to 7 or 8 volts then jump back up over the course of a few minutes. The other alarms we get(but no where near as often) are Battery Low Chemistry Voltage, Disconnected Battery or Dryout or Sulfation Condition Exists.  Has anyone seen these errors before with this type of setup?  We have had multiple people go over the system and they cannot seem to find anything wrong and have had the batteries pass testing.

Any insight would be appreciated.

[BillP]

Is this by using your APC Battery Management System (AP9921X) or are these alarms directly from the UPS?

If this is from a Battery Management System - the first thing we always check to validate any alarms is if the user has done a calibration on the system so that we know we are not getting false alarms/readings. If you want to FTP to the AP9921X BMS and get me the config.ini, event.txt and data.txt files, I can see if it has been done. (Instructions on getting log files are here in the knowledge base -> http://www.apc.com/site/support/index.cfm/faq/ -> search for article ID FA156131)

[Anonymous user]

I have the files but would prefer not to post them on the forums, is there an email address i can use to send them to you?  We actually had APC install and configure the units and have had techs come out multiple times to check them but have yet to find a cause for the alarms.  We have been told that these battery monitors are used by other clients with the same UPS  system we have and they do not have the same issues we are experiencing. 

[BillP]

Do you already have a case in progress for this issue then where the logs are already available before I make you send them again? (also, I assume then this confirms it is a battery management system we are talking about here?)

[Anonymous user]

Our Facilities department opened a case but I do not have the number, I believe August Patrick is involved in the case, I will see if I can get the case number later.  I think my biggest issue is right now I don't think I fully understand how the UPS and the battery monitors interact with the batteries and what could cause them to show batteries at 12 volts that drop to 8 volts then jump back up to 12 in under a minute.  Sorry if this is very vague, I don't think I know enough about the system to know the right questions to ask.

[BillP]

To be honest, my weakness is batteries in general and I am good with the battery management system management card side and some of the specifics of how it works but maybe between us we can identify what is going on where the case is

If you cannot get the case number, I'll do a little more searching in our database and if I can't find anything, I'll tell you where to send logs.

[BillP]

I did find some cases from earlier this year but it'd be good to verify the on going case number so I don't duplicate efforts after understanding who is managing the case and what they're doing. From logs I did see, the systems have been calibrated but I have not verified that per the manufacturer's suggestions, battery cell voltages are setting according to their mins/max. That might be a moot point but I usually just ask these questions methodically, like I said, to ensure the alarms/values are accurate for the situation.

Many users of the BMS are in the same boat unfortuantely as far as understanding of the product because of the fact that the system shows "alarms" which probably should be reworded as "informational events" so this may not even be an alarm but more of an FYI.

Regardless, once I get a case number or more info on what August is working on and with who, I can try to help too.

[Anonymous user]

It looks like the current ticket is C1-4828119591 and the last previous ticket was C1-4641970090.  The last response was that they believed the alerts to be due to power bumps however the UPS doesn't show power bumps at the same times and it doesn't explain the extremely low drop in voltage on some of the battery managers that it is reporting faulty batteries for a minute.

[BillP]

Ok, I only saw C1-4641970090 before which did not really indicate the answer was not appropriate so it seemed pretty cut and dry to me. C1-4828119591 I do see that someone is going to go out to the site?

Anyway, the notes in the newest case indicate: the times on all the BMS are not synced, but based on the times these logs were downloaded which was probably close in time, both units  do show a power blip.  All the BMS on UPS A went at the same time and all the BMS on UPS B went at the same time.  This is an indication of a quick power blip.

Were they given the UPS logs to look at or I am just confused as why they would think this but you do not. I'll also follow up with the case owner as well.

[Anonymous user]

I just sent those in last night, they never asked for them before from me but they were working with a member from our facilities team who isn't with us anymore and were also on site multiple times.  The battery managers is sending us alarms that a battery dropped from 13.1 volts to 8 and back up to 13.1 in less than a minute is not possible for a healthy battery which I was told by the on site APC tech and our Facilities members.  The batteries were new when installed and have been tested by APC and have not had any fail testing. How much should the voltage drop when the UPS switches to battery?  On one hand we are told the batteries shouldn't drop to such a low level like that, but on the other we are told they are normal power bumps - that is why i would say it's not a good answer to our issue.

The BMS are set to use our NTP server with the same settings that our rack PDU's are using and the rack PDU's do not seem to have any issues keeping in sync.  No idea what to do with this issue

[BillP]

I will check into it further. I did not hear back from the case owner yet and have been tied up all afternoon.

The battery part is what I am weak with as well, especially on a 3 phase application. I would think that if the UPS went to battery then there was current draw which could've drawn the voltage down. That is all I know at a high level

I will follow up more tomorrow

[BillP · Accepted solution]

I spoke to the case owner today and he said he has not seen the UPS logs so they have not been forwarded or reviewed by all involved just yet.

Anyway, he seemed to indicate that for some reason, there was a discharge on every single battery so maybe the problem was that there was a discharge but the UPS did not log it?

Someone is going to the site soon though to review it more closely but we really feel there was something that happened to discharge the strings and that everything else on the system looked good and normal.

Unfortunately, to the fault of those that designed the alarm text, some things come across as "alarms" but are more so informational and that might be happening here.

I am not sure on the battery specific questions either though myself. (like how much voltage the voltage should drop) I assume it will depend on how much current/load on them?