SMX3000 + SMX120: Which battery failed?

[BillP]

This question was originally posted by Ruppert on APC forums on 1/1/2016

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Hello,

we do have an SMX3000RMHV2U. About half a year later we added one SMX120RMBP2U. Now we are going to add another one.

Question:
The SMX3000RMHV2U got an indicator that shows us that we need to replace the battery and shows battery failures (& via NMC2).
In this setup we have many batteries and these batteries are of different ages and in different enclosures - but they are all connected together.
How can we tell which battery we do have to replace? There does not need to be a correlation between age and failure.

It seems very uneconomical and environmentally absolutely unacceptable to replace all batteries, only because we can not tell which battery needs replacement.

Can anyone tell us how to find out which battery to replace? (Without changing/replacing batteries one by one, which is unacceptable, too.)

Thanks a lot!
-RT

[MarkC_apc · Accepted solution]

This was originally posted on APC forums on 1/4/2016

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The SMX3000 has an interesting battery pack of 10 small AGMs - all in series with relatively (to other APC UPSs) complicated interconnecting wiring and spacers (nominal 120 volt DC).  WARNING - this is a high level of DC voltage and can be very dangerous/deadly with powerful arc potential.  Replacing individual batteries (if you can determine which are bad) in this pack can be a challenge!

Adding the extended battery units essentially adds multiples of these packs in parallel with the one contained in the main unit.   This arrangement of the packs in parallel - with each containing many batteries in series requires that all batteries be essentially the same in their electrical characteristics - otherwise the weakest battery in the entire system will essentially drag the entire battery system to it's (weak) level.  

Running an identical load test on each fully charged pack individually might tell you if one of the three packs you currently have is bad (or substantially reduced energy), but could require a significant time without the protection of the UPS if done with a known external load.  If the age of the original pack is nearing it's life expectancy (2-3 years?) and/or has been through many power failure cycles, you might try a new pack in addition to the new SMX120 unit. 

Of course, if any warantees exist - see what Schneider can recommend.  There may also be a recommended testing procedure for multiple packs as you have.

There are methods to determine if individual AGM batteries are bad.  However, in usual critical services, it is best to replace the entire pack as explained in the second paragraph.

Let me know how you resolve this.