UPC Uninteruptiable Power Supply Battery Replacement

[marionw]

Actually, many with 2 SLD batteries operate at 24 VDC with both batteries in series, many of APC's UPS's use 2 X 12 volts batteries in series

 

[pollenface]

I can tell you from experience lfp @ 29.2v all day everyday kills them within 18 months.

(From when i first started out and used a single stage pwm reg to charge everything)

 

[AntronX]

I can tell you from experience lfp @ 29.2v all day everyday kills them within 18 months.

Australian temperatures? 3.65V and 35°C would be tough. At 15°C should not be so bad.

 

[pollenface]

Australian temperatures? 3.65V and 35°C would be tough. At 15°C should not be so bad.

I clarify, 18 months of 29.2v in Australian temperatures, 5 to 45c

 

[mciholas]

How? The term constant current is being misused in this example. Unless the UPS is putting out more than 14.4v or so, it can't overcharge as the LFP will reduce the current draw to zero. The UPS can't "force" current into the battery unless it raises it's voltage about 14.4v or so.

Many SLA float charging stages are simple resistors to higher voltages like 15 or 16 volts.

Again, you can't force current into a LFP without raising the charge voltage.

That is correct but SLA is so tolerant, that a crude float charger could end up exceeding the voltage on an LFP. A properly designed charger shouldn't do that, but SLA is tolerant of bad charger design, so they are out there.

Mike C.

 

[mciholas]

I thought floating for LFP isn't recommended...

It isn't.

Lithium batteries (including LFP) suffer the most stress at 100% SOC (SLA is at 0% SOC, they like to be constantly float charged). This is why folks with EVs often terminate charge at 80% or 90% to extend the service life of their batteries.

Lithium also wants very precise termination voltages, SLA is very tolerant of sloppy voltages.

I worry that with the wide variance in SLA charging designs and tolerances, an LFP pack will be abused.

Mike C.

 

[meetyg]

I don't

Do you have any real world observations to prove that it doesn't hurt the battery?

Is the same true if floating at lower voltages than 100% SOC ?

 

[timselectric]

Do you have any real world observations to prove that it doesn't hurt the battery?

Only my own personal experience.
I haven't overcharged (above 3.65v per cell) , or over discharged (below 2.5v per cell) . And I don't push them hard (I stay at or below 0.2c rate). Or let them get too hot/cold.
But I do charge to the top of the knee (3.56v percell) , and float there (3.5v per cell) daily.
The only degradation I have seen is calendar aging (1% per year).
I also have one battery that I used to charge to 3.625v per cell, daily.
Which is now part of a portable system that doesn't see much use. And just floats 24/7 at 3.5v per cell.
I have only been running LFP for a little over 2 years. But I see no reason for the results to suddenly deviate from the expected.

Is the same true if floating at lower voltages than 100% SOC ?

Yes
But you will limit capacity if you don't balance the cells regularly, in the upper knee (Above 3.45v per cell).

 

[meetyg]

Only my own personal experience.
I haven't overcharged (above 3.65v per cell) , or over discharged (below 2.5v per cell) . And I don't push them hard (I stay at or below 0.2c rate). Or let them get too hot/cold.
But I do charge to the top of the knee (3.56v percell) , and float there (3.5v per cell) daily.
The only degradation I have seen is calendar aging (1% per year).
I also have one battery that I used to charge to 3.625v per cell, daily.
Which is now part of a portable system that doesn't see much use. And just floats 24/7 at 3.5v per cell.
I have only been running LFP for a little over 2 years. But I see no reason for the results to suddenly deviate from the expected.

Yes
But you will limit capacity if you don't balance the cells regularly, in the upper knee (Above 3.45v per cell).

Interesting...
Did you notice any bloating of the cells?
What cells are you using (brand, Ah, etc...) ?

 

[timselectric]

Did you notice any bloating of the cells?

No

What cells are you using (brand, Ah, etc...) ?

EVE 280ah and EG4 LifePower4

 

[Texas-Mark]

I thought floating for LFP isn't recommended...

It depends on what voltage it is floating. I would float a 12v LFP at 13.6 forever and not give it a second thought. And I'm pretty sure Bluettis and similar float too while left plugged in. What good is a power station if it's not ready to go?

 

[wpns]

And I'm pretty sure Bluettis and similar float too while left plugged in. What good is a power station if it's not ready to go?

I'd say they don't really care as long as it outlasts the warranty. On the other tentacle, you _should_ be able to fully charge it and leave it for a year, no?

 

[Texas-Mark]

On the other tentacle, you _should_ be able to fully charge it and leave it for a year, no?

Well, there are those who also say not to leave LifePo4 fully charged, so.....

 

[2Big2B]

The idea to use LPF as UPS batteries has appealed to me too. Wondered about it.
I am glad to have found this thread.

I guess SLA, AGM and LPF each has its own place.

 

[thepartyhound]

The idea to use LPF as UPS batteries has appealed to me too. Wondered about it.
I am glad to have found this thread.

I guess SLA, AGM and LPF each has its own place.

We use UPS at customer's houses to keep their phone service working in the event of a power outage. Back in the days of copper we only had to fire up a generator at the CO and everyone's dial tone would continue uninterrupted. Now, in the days of fiber, the backup power has to go at the CO as well as at the customer's premisis. Lead acid varieties of UPS do not seem to last more than a few years on average. It would be great to find a good LFP solution.

 

[Delmar]

Is there any reason that I could not remove the worn out SLA battery from a small APC battery backup and replace it with a LFP battery? Obviously the UPS was designed for use with a SLA battery, but the BMS in the LFP replacement should keep everything happy...or at least safe, right?

Here we go again. First investigate the specs of the UPS before throwing money at it. Most have a garbage stepped-wave output that your protected electronics will hate. Additionally the H-bridge is designed to overheat just as the standard battery runs out of power. Adding expanded batteries will not extend the runtime. Even if you run at a fraction of the rated power, the internal timer may ignore the battery voltage and shutdown the UPS anyway.

If you are going to spend money, I would instead look into an “all-in-one” unit that already has the solar input. You can grow the system into a proper prepper. Watch this:

 

[50ShadesOfDirt]

At a slightly higher cost, you could go the route of building a diy solar generator, good for daily protection of your equipment (computer, tv system), and good for camping or such.

Basically, just need LiFePO4 battery, inverter, battery charger (pulls from your grid) ...

Advantage is more functionality, good diy project, we aren't reverse engineering UPS internals, etc. Just replacing older tech with newer tech.

Hope this helps ...

 

[bolhuijo]

Here we go again. First investigate the specs of the UPS before throwing money at it. Most have a garbage stepped-wave output that your protected electronics will hate. Additionally the H-bridge is designed to overheat just as the standard battery runs out of power. Adding expanded batteries will not extend the runtime. Even if you run at a fraction of the rated power, the internal timer may ignore the battery voltage and shutdown the UPS anyway.

Yep these things are all possible. In the case of my Cyberpower 1500, it's a pure sine wave model. I saw it had a temp sensor on the output transformer and a fan that ran when inverting. Then I tested the bigger battery while keeping a close eye on it. At a mere 10% load it didn't generate much heat. The estimate of time remaining was comically bad for the whole 4 hour runtime but in the end it only cared about going until it hit the low voltage cutoff.

 

[Delmar]

Yep these things are all possible. In the case of my Cyberpower 1500, it's a pure sine wave model. I saw it had a temp sensor on the output transformer and a fan that ran when inverting. Then I tested the bigger battery while keeping a close eye on it. At a mere 10% load it didn't generate much heat. The estimate of time remaining was comically bad for the whole 4 hour runtime but in the end it only cared about going until it hit the low voltage cutoff.

Most but not all are bad. Love my APC “XL” models that are pure sine, low-frequency for starting motors, rated for continuous operation and have external battery connectors. Getting difficult to find nowadays. Downside they are heavy, loud and not very efficient at low loading.

 

[dfw_dude]

Most but not all are bad. Love my APC “XL” models that are pure sine, low-frequency for starting motors, rated for continuous operation and have external battery connectors. Getting difficult to find nowadays. Downside they are heavy, loud and not very efficient at low loading.

I do love my APC unit - the external battery config units are getting harder to find it seems. I picked up one of those "twin" sets where there's a whole addon battery designed for it a few years ago. Luckily I have another year or two before I need to rotate the batteries out of it.

I have two cyberpower 1500va units in my living room running my synology and PoE/security gear. And (feels good to be able to say it now) whole home is running on UPS backup from two EG4 Indoor units, so I'd need to burn through 28kWh worth of battery before the smaller UPS's even get touched.