Lithium for UPS

[Zilacon]

I have many APC units that are old, have used them for 8 years and replaced the batteries 4 times.
Sick of replacing SLA batteries i chose to buy new APC units with a set of new LifePO4 batteries as replacements.
I read a bunch of articles, watched a lot of your videos, and others videos on placing lithium batteries into UPS units and them working.

But my experience has not worked out. 2 12v 10ah batteries in series should give 240wh yet it cant run a 35w lamp for over 2 hours, when the math should be atleast 6 hours runtime. Trying twice but charging for 48 hours, got the same results. I bought a different brand of batteries to test and got the same results.

Both battery packs in both ups units were at 26.5v or 13.25v per battery.
Any idea whats going on? Or is there a better consumer grade UPS i can get that had better support for Lifepo?

Thanks

 

[snoobler]

Welcome to the forum.

LFP is not typically a good choice for standby operations. They deteriorate when stored/held at full charge and cycled infrequently.

13.25V may be at a relatively low state of charge unless it was VERY recently charged to 14.4V.

Have you tested the batteries individually by charging to 14.4-14.6V and discharging to 10V to determine their capacity?

What is the low voltage cut-off of the inverter?

Have you measured the efficiency of the inverter?

Can the batteries you've selected handle the current needed? I would hope so, but it's worth checking.

Are the wires sufficient for the current?

What is the charge voltage of the inverter? If it simply floats them at 13.25V, then you're not going to get the battery fully charged - probably closer to maybe 70%. If you're not getting an accurate voltage reading, and the battery is closer to 13.1V, you might only be at a 40% SoC.

 

[Zilacon]

Welcome to the forum.

LFP is not typically a good choice for standby operations. They deteriorate when stored/held at full charge and cycled infrequently.

13.25V may be at a relatively low state of charge unless it was VERY recently charged to 14.4V.

Have you tested the batteries individually by charging to 14.4-14.6V and discharging to 10V to determine their capacity?

What is the low voltage cut-off of the inverter?

Have you measured the efficiency of the inverter?

Can the batteries you've selected handle the current needed? I would hope so, but it's worth checking.

Are the wires sufficient for the current?

What is the charge voltage of the inverter? If it simply floats them at 13.25V, then you're not going to get the battery fully charged - probably closer to maybe 70%. If you're not getting an accurate voltage reading, and the battery is closer to 13.1V, you might only be at a 40% SoC.

Oh, I'm sorry i forgot to list what units im using. Im using the APC BR1500MS2 UPS units. APC said they have a 98% efficiency from DC to AC and 89% from AC to DC.

I do not have a stand alone charger, i recently just ordered this to individually charge them https://www.amazon.com/gp/product/B07W8KJH44

As i said both batteries were left in the UPS for 48 hours to charge before i did a runtime test. So that 13.25v is the maximum the UPS has charged it in that time.

 

[snoobler]

From:

https://www.apc.com/products/runtime_for_extendedruntime.cfm?upsfamily=27

Run time of your unit with a 450W load is only 14.5 minutes.

450W for 14.5 minutes is only 108Wh of energy extracted from a 257Wh battery.

This is likely due to in large part to the Peukert effect, but I have to question if the published efficiency numbers are leaving something out. The unit consumes power itself, and that is likely not included in the efficiency numbers (nobody does).

UPS only charges at 16W and takes 16h to charge.

If the UPS is only charging the LFP to 13.25V, you're not likely to get fully charged no matter how long you leave them in the UPS.

 

[Zilacon]

From:

https://www.apc.com/products/runtime_for_extendedruntime.cfm?upsfamily=27

Run time of your unit with a 450W load is only 14.5 minutes.

450W for 14.5 minutes is only 108Wh of energy extracted from a 257Wh battery.

This is likely due to in large part to the Peukert effect, but I have to question if the published efficiency numbers are leaving something out. The unit consumes power itself, and that is likely not included in the efficiency numbers (nobody does).

UPS only charges at 16W and takes 16h to charge.

If the UPS is only charging the LFP to 13.25V, you're not likely to get fully charged no matter how long you leave them in the UPS.

Right but SLA batteries can only be discharged down to 50% right? So your not getting 100% of the batteries power.
All of APC's runtime data is based on SLA batteries. Oh and you were looking at the BR1500G numbers, not BR1500MS2. That ones 17.1 mins.
Not much of a difference though...

 

[John Frum]

I'm running a diy online ups.
The initial plan was to continually float the battery at 3.35 volts per cell.
For my battery 24 volt 280ah battery that means 200ah available.
There is still wear and tear(lithiation) at 3.35 volts per cell but according to @RCinFLA its the optimum value.
I ended up making a charge controller so that I could cycle the battery between ~255 amp hours and ~135 amp hours.

 

[Substrate]

Also consider that those two you slapped in series doesn't mean they are balanced to begin with unless you charged them first individually! (or used the parallel method and then rewired for series ops)

Even at this low CV voltage, unless they were balanced, you could have easily damaged them.

 

[snoobler]

Right but SLA batteries can only be discharged down to 50% right? So your not getting 100% of the batteries power.
All of APC's runtime data is based on SLA batteries. Oh and you were looking at the BR1500G numbers, not BR1500MS2. That ones 17.1 mins.
Not much of a difference though...

I see 14.5m



I doubt APC only runs them down to 50%. A decent SLA can be run down to 20% many dozen of times, which is probably realistic over a couple years unless your power is just garbage.

 

[snoobler]

Also consider that those two you slapped in series doesn't mean they are balanced to begin with unless you charged them first individually! (or used the parallel method and then rewired for series ops)

Even at this low CV voltage, unless they were balanced, you could have easily damaged them.

That's a really good point. BMS on one could just cut it out entirely.

 

[Substrate]

(Edited). Ok, the Noco with the LFP should do fine charging those 10ah batts up individually. It's what I use for my non-critical small projects with LFP. Although if those batts are rated at 0.5C max charge, hopefully the internal bms won't shut it down. Probably not, but you could have gotten away with the 2A unit.

Let's see how it goes once you get 'em charged up individually first.

 

[Zilacon]

Also consider that those two you slapped in series doesn't mean they are balanced to begin with unless you charged them first individually! (or used the parallel method and then rewired for series ops)

Even at this low CV voltage, unless they were balanced, you could have easily damaged them.

Both bats were balanced at 13.0v before placed in series in the ups.

 

[snoobler]

Both bats were balanced at 13.0v before placed in series in the ups.

That's useless. Balance can only be done north of 14.0V.

 

[OffGridInTheCity]

I have several APC 1500(s) and 3 x APC 30000s. The 1500(s) are 24v systems and the 3000 is 48v.
I use 18650 7s7p(s) for my API 1500(s) - and they fit inside and work well. The 1500(s) charge them up to about 3.94v/cell and cut-out at 3.0v/cell. Here's one with a Chargery 8S as the BMS



In the APC 3000s - with just a bit of rewire from 2 separate 24v Anderson connectors to a single 48v connector - I was able to fit a 14s12p with a Chargery 16S.



In my off-grid system, I consume power thru ATSs - e.g. when sun charges the batteries a bit the inverters come on and if the batteries run down to cut-off the inverters go off. These UPSs smooth split-second power loss during the twice daily ATS switchovers between grid and solar power.

I too was initially enthralled with the idea of big $ savings after many years of replacing lead acids in my APCs... but really, in hindsight, its a bit of work and cells + BMS not free

 

[snoobler]

I have several APC 1500(s) and 3 x APC 30000s. The 1500(s) are 24v systems and the 3000 is 48v.
I use 18650 7s7p(s) for my API 1500(s) - and they fit inside and work well. The 1500(s) charge them up to about 3.94v/cell and cut-out at 3.0v/cell. Here's one with a Chargery 8S as the BMS
View attachment 54823


In the APC 3000s - with just a bit of rewire from 2 separate 24v Anderson connectors to a single 48v connector - I was able to fit a 14s12p with a Chargery 16S.
View attachment 54824


In my off-grid system, I consume power thru ATSs - e.g. when sun charges the batteries a bit the inverters come on and if the batteries run down to cut-off the inverters go off. These UPSs smooth split-second power loss during the twice daily ATS switchovers between grid and solar power.

I too was initially enthralled with the idea of big $ savings after many years of replacing lead acids in my APCs... but really, in hindsight, its a bit of work and cells + BMS not free

That's about 13.8V/12V battery charge, and that seems normal for a system designed for SLA.

 

[time2roll]

I think you will have better luck if you charge the LFP batteries to about 14.0 and disconnect the charger. Restart charging at maybe 13.2 volts. I don't think the existing charging system in the UPS is doing you any favors. Probably killing the SLA batteries too.

I would probably be inclined to build my own UPS system.

 

[snoobler]

I think you will have better luck if you charge the LFP batteries to about 14.0 and disconnect the charger. Restart charging at maybe 13.2 volts. I don't think the existing charging system in the UPS is doing you any favors. Probably killing the SLA batteries too.

I would probably be inclined to build my own UPS system.

That's what I was thinking too... 26.5V absorption/float = dead SLA.

 

[Just John]

Oh, I'm sorry i forgot to list what units im using. Im using the APC BR1500MS2 UPS units. APC said they have a 98% efficiency from DC to AC and 89% from AC to DC.

I do not have a stand alone charger, i recently just ordered this to individually charge them https://www.amazon.com/gp/product/B07W8KJH44

As i said both batteries were left in the UPS for 48 hours to charge before i did a runtime test. So that 13.25v is the maximum the UPS has charged it in that time.

If you can return that Noco, a 10 amp 30 volt supply is about the same price and much more versatile (besides giving twice the charge current).

I think the biggest problem is what APC uses as a float voltage.

 

[sacalul]

hi to all
I have a similar dilemma and decided to avoid starting a new thread and try my luck here.
I was wondering if I can replace a VRLA battery 1st battery information link 2nd link with a lifepo4 battery.
The batteries will be used in a old 230v apc ups - link - don't know if the system is 24v or 48v, it has 4x12v batteries and they form 2 packs, each pack has 2x12v in series but maybe that is just for easy swap and further down the line after connecting them maybe the connections join again.
I do apologise in advance if some of my questions/observations are stupid, but after watching this youtube video I released that swapping batteries its not only about matching volts and amps.

 

[time2roll]

hi to all
I have a similar dilemma and decided to avoid starting a new thread and try my luck here.
I was wondering if I can replace a VRLA battery 1st battery information link 2nd link with a lifepo4 battery.
The batteries will be used in a old 230v apc ups - link - don't know if the system is 24v or 48v, it has 4x12v batteries and they form 2 packs, each pack has 2x12v in series but maybe that is just for easy swap and further down the line after connecting them maybe the connections join again.
I do apologise in advance if some of my questions/observations are stupid, but after watching this youtube video I released that swapping batteries its not only about matching volts and amps.

If you go LFP buy the battery at the correct voltage. LFP does not always work good in series.
Might be better starting a new thread and post a picture of what you are working on.
People may not see you way down here.

 

[PeSCaLo]

Welcome to the forum.

LFP is not typically a good choice for standby operations. They deteriorate when stored/held at full charge and cycled infrequently.

13.25V may be at a relatively low state of charge unless it was VERY recently charged to 14.4V.

Have you tested the batteries individually by charging to 14.4-14.6V and discharging to 10V to determine their capacity?

What is the low voltage cut-off of the inverter?

Have you measured the efficiency of the inverter?

Can the batteries you've selected handle the current needed? I would hope so, but it's worth checking.

Are the wires sufficient for the current?

What is the charge voltage of the inverter? If it simply floats them at 13.25V, then you're not going to get the battery fully charged - probably closer to maybe 70%. If you're not getting an accurate voltage reading, and the battery is closer to 13.1V, you might only be at a 40% SoC.

Check the Charging Voltage of the UPS by disconecting the Battery when the UPS is charging.

Charging voltage should be above 13.8 v

If its less, the you have a charging voltage problem .

I have made and sold over 20 batteries for UPS.
0 problems yet.

PM for more info