Back-UPS XS 1300 LCD - Battery percentage goes down at full charge.

[Anonymous user]

Back-UPS XS 1300 LCD - Battery percentage goes down at full charge.

[BillP]

Hi Matt,

Do you know the approximate age of the unit and whether or not the battery is original? There is no direct way to reset the information held in the eeprom. There is a process for manual runtime calibration, however this is generally performed with a new battery and only if the runtime available does not display properly.

Secret Squirrel

[Anonymous user]

The unit is 9 years old.  However from my haphazard testing it seems that the battery pack is defective?  I bought the pack nearly a year ago and it failed to function when it was incidentally tested 3 months in multiple times.  The pack works, but when I decided to take a set out of some 900Ms (same size) and install them the issue does not persist.  I've only gotten to it now because I had to move and for the most part power is extremely stable here.

I have a feeling due to the age of the unit I doubt I can get the batteries replaced.

[Anonymous user]

Hello Matt,

I can assure you beyond a doubt that it is quite possible for your batteries  to  show "full charge" and yet be very low on "capacity"

Voltage is by no means a very good way to determine the health of a battery.   It's is one way, but it leaves the capacity to question.  And a battery is nothing if it has voltage but no capacity.

Voltage is simply the potential  difference in voltage between the negative and positive terminals of the battery.   It does not require that the full surface area of the plates be in 100% condition to pass full voltage.    But when the plates have  become  sulfated  or  otherwise  damaged, then the plates can not store the electrons needed to supply "capacity"

Simply put....a 12v battery could read 13.2volts on a VOM, yet barely have the capacity to run a 10 watt bulb for a few minutes.    Similarly, two 12v batteries in series (as those in your battery backup) could read 26.2volts, yet not have enough capacity to power much of anything.   The lack of capacity could cause the battery's voltage to drop quickly or resist full charge.....or the battery backup could "sense" full charge at 27v even though the battery can't retain enough charge to hold that voltage level there for long.

I have a feeling your unit would work fine with new batteries.

[Anonymous user]

I think you may of misunderstood my post.  My batteries do not show full charge and it lasts what is fairly normal given the load.  It stalls at 26.8V and begins to drop rather quickly.  The makeshift set I made with the 900Ms reached 27.4 and floated around there for a couple of hours before I returned them to their proper units.

I was able to RMA the batteries cause it is 11 months old, so I hope that will resolve the issue.

[Anonymous user]

Oh ok.  Just trying to help.

I just measured the one month old batteries on my XS1300 and they both are at 13.16v

A fully charged 12v battery will read 12.80 volts or slightly higher.  You don;t want them idling much higher than that because that is over-charged and will shorten battery life.

When you said "my XS 1300 seems to be dropping from 100% to around 80% or so despite it being fully charged", it sounded to me as though you were saying they were fully charged.   You also said they idled at 26.2v....so at least one of them has to be fully charged.

Maybe you have one weak or bad battery?  Why are you certain it's the unit itself?

BTW.....my XS1300 does the EXACT same thing.   It occasionally drops to 80% also...even though the batteries test fully charged with a meter.

But then later when I check it it will be back at 100%.   Same load.   Note that I have my batteries EXTERNALLY connected which makes it MUCH easier to test the individual batteries periodically.  I'm also using much larger 35AH batteries so my run time on batteries is days instead of minutes or hours.   I USED to run two Werker 80Ah batteries (for 6 years), but they are so expensive now (over $200 ea) I went with smaller, 35Ah batteries.   If this unit could hold up to maintaining 80Ah batteries for 6 years, it can easily handle 7-8Ah batteries for a LONG time.

Also, My XS 1300 is more than 9 years old and still works fine.   I have 4 APC units and 2 CyberPowers.   The APC units are made MUCH better IMO.  I only buy APC units when I buy new ones now.

I love these older work horses because they are bullet proof.   And if and when I do have problems with one and it's out of warranty, I simply open it up and repair any components that have malfunctioned. 

[Anonymous user]

If you've got PowerChute installed it relays voltage information via its driver back to the PC.  With the right programs (namely, HWMonitor) it tells me what voltage the UPS says it is.  When I rigged a set of 900M batteries the issue wasn't replicated, so I do not believe my unit is faulty.  However the batteries that were in there before those did routinely fail to operate when it was tested so even though it works now I don't anticipate the batteries to last a few more years.

I can understand it happening once in a while but this happens 3 times a day, usually only when the UPS is loaded.

[Anonymous user · Accepted solution]

The only problem with this is that it can not give you the actual voltage of each battery.    It gives you a combined interpolated voltage.

It is quite possible, if not, normal that two the batteries will not age identically.   In almost all cases, one battery will, due to manufacturing variations, rise in internal resistance a bit faster than the other.  

This was my point in the above post.

The battery pack in the unit is 2 individual batteries joined together in series.

The ONLY way to actually determine the true health is to separate them and test their capacity with a tool specifically designed to do that.

I own such a tool.   It applies a specific load to the battery and calculates the capacity in Ah.

So you're getting the combined voltage.   Not the voltage of each individual battery.   And that's the ONLY information that can truly tell you the true health status of the battery.    OTH - if APC has developed and integrated some new technology that does measure each battery independently then I am not aware of that at this time but would be thrilled to learn of it and which units have this new tech installed.