I have a Q-on 6KS 6kVA UPS with an extended battery pack that I'm using to power some computer/screen/tv devices and LED lights during load shedding. The make is also sold under the brands Socomec, Eaton, Certa (and probably many more).

It works well on brand new batteries for the first year or so, but after approx 18 months of light use the batteries seem to have degraded severely. It's happened with 2 sets of batteries (the second set replacing the first).

I'm trying to figure out how to:
-  prevent this fast degradation - I was expecting the batteries to last at least 3 years
-  revive the batteries if it's at all possible. 

First set of batteries: 4 strings of 20x12V CSB 1272 28W (7.2Ah) = total 240V, 80x12x7.2 = 6.9kWh
replaced by 
Second set of batteries:  4 strings of 20x12V CSB HR 1234W 34W (9Ah) = total 240V, 80x12x9 = 8.6kWh

Runs: in "High Efficiency / Economy" mode, 230V, 50Hz output.
Extended battery pack has its own charger.
Typical load is around 500W, it never goes above 1kW when in battery mode.

At the start of the 18 months, as a once-off test, the UPS could easily manage 4h at constant(ish) 500W load without the voltage dropping close to 230V. At the end of the 18 nonths it didn't even last 30min.

What's possibly odd is that the voltage seems to be dropping slowly for a while and then suddenly drops off very quickly even though the load is fairly constant (around 7% of max) and low. See attached pics.
Individual batteries currently measure:
   13.85V when in the UPS and fully charged (taking UPS reported 277V/20)
   13.2V when left for 4 days after being fully charged (charged w. separate smart charger and left) 
   12.9V to 13.1V after the UPS switches off (20 x 13V = 260V)
 
 It's that last measurement that seems odd since the UPS reports <230V when it shuts down. So the batteries seem to "bounce back" 

 I tried removing any batteries that were below 12.9V (worst was 12.5V) after shutdown and using good batteries in 3 strings instead of a mix of good and weaker batteries in 4 strings. Unfortunately the performance was even worse. 

Any advice on what might be going wrong (if anything) and if there's any chance in reviving the (rather expensive) 80 batteries would be very much appreciated.

Hello Henty,

Usually using a UPS as a standby long duration power backup, more than +/-30 mins is generally not recommended, as UPS's are typically not designed to run for long durations, and also need a good few hours to recharge batteries once discharged, so if load shedding is frequent in the same day they probably wont recharge fully.

Also if the UPS has a Battery run test function, do not use it monthly or weekly as it basically emulates a power failure to determine the max duration the ups batteries will hold, however in cycling the batteries you are effectively using up cycles on them.

Is it possible to set the Depth of Discharge on the UPS? to what level of Discharge? Usually this is not somehting one can usually set? And the deeper the depth of discharge, combined with the battery chemistry, will determine the typical lifespan of the batteries. Typically deeper DOD = Shorter life (Many Less Cycles). Check the battery spec sheet for info on this.

I expect this ups problably uses Sealed Lead acid, or Sealed Gel Batteries, which should perform ok, provided a shallow DOD, maybe max 15-20% of capacity, if the DOD is closer to 50% one will expect a much shorter lifespan (no. of cycles) from the batteries.

Does this ups have a battery management system? (BMS) built in? The odds are with 20 batteries per string and 4 strings you are going to find the batteries get unbalanced, and add to the risk of sudden voltage drops, when taking load, and then the ups will tend to drop the load? If it has a BMS with the ability to balance each of the batteries per string then this would mitigate this risk, and help with battery lifespan.

Also with a string of 20 batteries, bear in mind that each battery adds resistance, so one typically finds that as one moves along the battery string each battery has a harder time getting properly charged, meaning batteries on the outer edges of the string will be less unbalanced, but as one works towards the center of the pack are more unbalanced, again increasing the risk of dropping the load as they become more unbalanced.

Other factors that influence performance are related to the battery specs, for example the Max.Discharge rate per battery not being exceeded and trying to keep the discharge rate at a battery in line with what the batteries are designed for? their standard discharge rate?

Typically once batteries get old they drop voltage quickly, under load, once load is removed the voltage will bounce back, this could mean a failing battery or that the battery is unbalanced?

Have a dig on the forum on lead acid batterys and battery balancers, as well as the BMV-702 units, it will give some insight into the challenges with lead acid, sealed lead acid, gel, agm batteries and why most solar users are moving to Lithium btteries, like pylontech, freedomwon, bsl etc.

We also use some small 1500va ups's just to carry a few pc's once the load drops, and we find we replace the 12v9ah batteries typically every 2 years. Each ups uses 2 x 12v 9ah, and we pretty much always find that one of the two battery's fails (Voltage drops dramatically when under load on one of the batterys) and then causes the ups to easily drop the small load of +/-100 to 200 watts after about 30 seconds, instead of holding for 2-3 minutes to shutdown.

Fortunately we only have to replace about 6 batteries on the 3 x ups's. My guess would be that with your 80 batterys being replaced evey 18 months they must cost you in the region of R16K to R31k for new batteries?  For that kind of money one would probably be better off looking at the pylontech lithium units. As every 18 months you could buy another pylontech unit or two, and add it to the pack, so effectively growing your capacity?

I hope some other forumites are able to give you further advice.

28 minutes ago, Arandoza said:

Hello Henty,

Usually using a UPS as a standby long duration power backup, more than +/-30 mins is generally not recommended, as UPS's are typically not designed to run for long durations, and also need a good few hours to recharge batteries once discharged, so if load shedding is frequent in the same day they probably wont recharge fully.

Also if the UPS has a Battery run test function, do not use it monthly or weekly as it basically emulates a power failure to determine the max duration the ups batteries will hold, however in cycling the batteries you are effectively using up cycles on them.

Is it possible to set the Depth of Discharge on the UPS? to what level of Discharge? Usually this is not somehting one can usually set? And the deeper the depth of discharge, combined with the battery chemistry, will determine the typical lifespan of the batteries. Typically deeper DOD = Shorter life (Many Less Cycles). Check the battery spec sheet for info on this.

I expect this ups problably uses Sealed Lead acid, or Sealed Gel Batteries, which should perform ok, provided a shallow DOD, maybe max 15-20% of capacity, if the DOD is closer to 50% one will expect a much shorter lifespan (no. of cycles) from the batteries.

Does this ups have a battery management system? (BMS) built in? The odds are with 20 batteries per string and 4 strings you are going to find the batteries get unbalanced, and add to the risk of sudden voltage drops, when taking load, and then the ups will tend to drop the load? If it has a BMS with the ability to balance each of the batteries per string then this would mitigate this risk, and help with battery lifespan.

Also with a string of 20 batteries, bear in mind that each battery adds resistance, so one typically finds that as one moves along the battery string each battery has a harder time getting properly charged, meaning batteries on the outer edges of the string will be less unbalanced, but as one works towards the center of the pack are more unbalanced, again increasing the risk of dropping the load as they become more unbalanced.

Other factors that influence performance are related to the battery specs, for example the Max.Discharge rate per battery not being exceeded and trying to keep the discharge rate at a battery in line with what the batteries are designed for? their standard discharge rate?

Typically once batteries get old they drop voltage quickly, under load, once load is removed the voltage will bounce back, this could mean a failing battery or that the battery is unbalanced?

Have a dig on the forum on lead acid batterys and battery balancers, as well as the BMV-702 units, it will give some insight into the challenges with lead acid, sealed lead acid, gel, agm batteries and why most solar users are moving to Lithium btteries, like pylontech, freedomwon, bsl etc.

We also use some small 1500va ups's just to carry a few pc's once the load drops, and we find we replace the 12v9ah batteries typically every 2 years. Each ups uses 2 x 12v 9ah, and we pretty much always find that one of the two battery's fails (Voltage drops dramatically when under load on one of the batterys) and then causes the ups to easily drop the small load of +/-100 to 200 watts after about 30 seconds, instead of holding for 2-3 minutes to shutdown.

Fortunately we only have to replace about 6 batteries on the 3 x ups's. My guess would be that with your 80 batterys being replaced evey 18 months they must cost you in the region of R16K to R31k for new batteries?  For that kind of money one would probably be better off looking at the pylontech lithium units. As every 18 months you could buy another pylontech unit or two, and add it to the pack, so effectively growing your capacity?

I hope some other forumites are able to give you further advice.

Thanks for the info Arandozo

You've convinced me (I was 80% convinced before you answered) that it's not going to be worth the effort of keeping this old-tech UPS going and spending yet more money on new batteries. I should just bite the bullet and go with Lithium. Was hoping to eek out another year from the current batteries somehow. 

To answer your questions:

The more recent set of batteries (CSB HR 1234W) are AGM. The previous set (CSB GP 1272) seem to be AGM too, although I didn't realise that until googling a few minutes ago.

The DOD of the UPS is not configurable or listed but it seems to shut off at 230V, which is below 50% based on the tables I've seen. With the fairly low load I don't think I ever got close to this in the first year though, before the battery capacity started falling (so maybe I somehow did get close in the first year, else why did it fall?) after which I must have hit it frequently. That explains why they've degraded so rapidly in the last few months.

There is no BMS and having checked individual batteries in each string with a multi-meter, their voltage is not 100% consistent, but didn't seem crazily bad to my layman standards.  Once discharged they were almost all between 12.9V and 13.1V.  I removed the few that were below 12.9 by reducing from 4 strings (of mixed batteries) to 3 strings (of only stronger batteries), but it didn't make much difference.

 

 

 

 

 

It's strange that the UPS manufacturer's have not yet started moving to lithium or lifepo4 type batteries, but as with all lithium there is always a fire and disposal risk, this maybe one of the reasons, along with cost. But i do see that Powermode offers the Q-on dropin lithium replacement pack, it maybe an idea to chat to them?

https://powermode.co.za/q-on-ionbank/

For the price of a 5 or 8 kva inverter/charger/mpptt unit and some pylontechs, you can effectively have a UPS  and once you add solar panels later you will smile, but also bear in mind that the Solar inverters, some switch and have a 20 -40 ms switchover time so for sensitive eletronics you might still need so small ups's just to handle the switching so that the Pc's are not adversely affected, appliances are not really bothered by the 20-40ms switch, and or to carry your pc for 5-10 mins max should not be that expensive  

 

I also found that with the APC ups's the RBC batteries that are APC branded are definately a higher quality and durability, however they come at a Premium price, so one has to keep the run time and load on battery low and as short as possible for the longest lifespan. (SmartUPS 2200)

On 2021/10/17 at 8:25 AM, Arandoza said:

Hello Henty,

Usually using a UPS as a standby long duration power backup, more than +/-30 mins is generally not recommended, as UPS's are typically not designed to run for long durations, and also need a good few hours to recharge batteries once discharged, so if load shedding is frequent in the same day they probably wont recharge fully.

Also if the UPS has a Battery run test function, do not use it monthly or weekly as it basically emulates a power failure to determine the max duration the ups batteries will hold, however in cycling the batteries you are effectively using up cycles on them.

Is it possible to set the Depth of Discharge on the UPS? to what level of Discharge? Usually this is not somehting one can usually set? And the deeper the depth of discharge, combined with the battery chemistry, will determine the typical lifespan of the batteries. Typically deeper DOD = Shorter life (Many Less Cycles). Check the battery spec sheet for info on this.

I expect this ups problably uses Sealed Lead acid, or Sealed Gel Batteries, which should perform ok, provided a shallow DOD, maybe max 15-20% of capacity, if the DOD is closer to 50% one will expect a much shorter lifespan (no. of cycles) from the batteries.

Does this ups have a battery management system? (BMS) built in? The odds are with 20 batteries per string and 4 strings you are going to find the batteries get unbalanced, and add to the risk of sudden voltage drops, when taking load, and then the ups will tend to drop the load? If it has a BMS with the ability to balance each of the batteries per string then this would mitigate this risk, and help with battery lifespan.

Also with a string of 20 batteries, bear in mind that each battery adds resistance, so one typically finds that as one moves along the battery string each battery has a harder time getting properly charged, meaning batteries on the outer edges of the string will be less unbalanced, but as one works towards the center of the pack are more unbalanced, again increasing the risk of dropping the load as they become more unbalanced.

Other factors that influence performance are related to the battery specs, for example the Max.Discharge rate per battery not being exceeded and trying to keep the discharge rate at a battery in line with what the batteries are designed for? their standard discharge rate?

Typically once batteries get old they drop voltage quickly, under load, once load is removed the voltage will bounce back, this could mean a failing battery or that the battery is unbalanced?

Have a dig on the forum on lead acid batterys and battery balancers, as well as the BMV-702 units, it will give some insight into the challenges with lead acid, sealed lead acid, gel, agm batteries and why most solar users are moving to Lithium btteries, like pylontech, freedomwon, bsl etc.

We also use some small 1500va ups's just to carry a few pc's once the load drops, and we find we replace the 12v9ah batteries typically every 2 years. Each ups uses 2 x 12v 9ah, and we pretty much always find that one of the two battery's fails (Voltage drops dramatically when under load on one of the batterys) and then causes the ups to easily drop the small load of +/-100 to 200 watts after about 30 seconds, instead of holding for 2-3 minutes to shutdown.

Fortunately we only have to replace about 6 batteries on the 3 x ups's. My guess would be that with your 80 batterys being replaced evey 18 months they must cost you in the region of R16K to R31k for new batteries?  For that kind of money one would probably be better off looking at the pylontech lithium units. As every 18 months you could buy another pylontech unit or two, and add it to the pack, so effectively growing your capacity?

I hope some other forumites are able to give you further advice.

Get a generator sir. UPSs are used to hold the load while you start the generator manually or Auto Start. Running your UPS till the batteries collapses is a sure way of killing your batteries faster than anything. Also when you have multiple load shedding in a single day, your batteries wont fully charge so by the time another power failure comes, your batteries take a serious beating. Im surprised they lasted 18 months.