Any recommendations or advice on LiFePo4 batteries for the typical 7Ah to 9Ah 12V sealed lead acid batteries for UPS?
We all know how important it is not to go with random cheap lithium ion rechargeable batteries, both for safety and performance reasons. At least LiFePo4 are safer technology, but I have seen virtually no information about the cells used in battery packs. Nor am I aware of the reputation of various brands of the replacement batteries, which is especially concerning on sites like amazon.
For example, impressions of this 10Ah unit at ~$90 CAD, and whether it is suitable for a UPS? Amazon.ca
They’ll drop in replace SLA “yes” — will they run your UPS— probably not — you need to know how much amp draw you’re using with your load applied — then you buy a battery accordingly — the first one you linked has a 10 amp max — that might run a moderate to small UPS — the second battery you linked, don’t bother trying
Then there’s the issue of what voltage your UPS float charges —— you really don’t want to continuously charge a LifePo4 at too high of a voltage
Good point about current ratings. I read reviews on some LiFePo4 batteries where people reported the BMS shut power when they exceeded the current limit. As for the charging voltage, wouldn’t the BMS handle that?
One UPS is a 550VA unit used for networking equipment. Typically only around 10W draw on that.
Another UPS is a 1500VA unit which has two batteries, I’m guessing in parallel, but not sure. That one runs a desktop computer and monitor, and typically has a load of ~100W but could go over 300W or more depending on use.
The BMS would handle both over charge and over amperage draw — It’s not really ideal to use the BMS in that way — better for the float charge voltage to be slightly under the cut off ( once it cuts out the voltage has to drop a certain amount below that voltage for it to turn back on )
I would suggest opening up the UPS and testing the amp draw with a clamp meter ( on battery power) then after it’s plugged back in and fully charged, check the voltage of the battery while plugged in
Dig around on DIY Solar Forum or Youtube —you should find some useful info
I plan on building me a battery for my two eventually, I have the cells — The grandkids powerwheels have come first in line though — I just built a 18v with 40/ VTC6 cells
Seems like “drop-in replacement” isn’t necessarily so drop-in and worry-free after all.
Although my toolset has been growing I don’t have a clamp meter yet. Still you raise interesting concerns. I’ve contacted some of the vendors about the suitability of their product for UPS; let’s see what they say.
Youtube DIY videos on the subject are interesting… and pretty sketchy! Feels like that’s a good way to incur dangerous liability. I wonder if anyone has caused problems like fire damage due to DIY batteries that insurance refused to cover.
Put it this way — I’ve been slow to convert my UPS to LifePo4 for that reason — Also I don’t have that many power outages —- I really don’t like the idea of constant charging of LifePo4 cells —— In a lot of ways (if you have the room) Just go with bigger SLA batteries outside the UPS
I’ve given this a try. The LiFePo4 batts that would fit the UPS boxes could not put out enough current when called on to run a load.
The BMS would shut them down.
Take a look at the max continuous current output of the prospective battery and come up with a watt rating. Many in the typical UPS size are like 8-10 amps max.
In most cases it falls way short of the UPS wattage.
8a x 13.5v=108w, even with 2 batts, that’s way short of the 500w (or more) needed.
This is true for the lower cost LiFePo4 batts.
Some of the high dollar ones might do the job.
If you do this, be sure to test the UPS under load.
All the 1500VA UPS I’ve serviced were 2x12 in series for 24v- except for one that 4x12 for 48v. Always liked that one until it was time to replace the SLAs.
All the Best,
Jeff
“In general, the LiFePO4 batteries offered by ROCKSOLAR are suitable as SLA replacements in a variety of applications.
For your application specifically, the 10Ah model can supply 120W and 1C (10A) of power/current. Your UPS likely requires more power than the 10Ah battery can offer, which is harmful to the battery. However, the 18Ah LiFePO4 battery should be suitable for your UPS.”
and
“From our research and testing, charging a LiFePO4 battery in a UPS with SLA batteries is the same as using a SLA charger to charge the LiFePO4 batteries externally. In general, they will only charge to 80% each time and will suffer capacity loss and degradation over multiple charge cycles. However, we have not found any serious risk posed by any individual charge (ex. Battery explosion).”
So it seems LiFePo4 batteries really aren’t ideal as a drop-in replacement for SLA-based UPS units. The biggest drawback seems to be the built-in charger designed for SLA batteries.
The, eg. 10A, max current might be a limitation that could be acceptable, as my units tend to be running at the low end of their capacity, nowhere near the maximum. But if I forgot for any reason and increased the load, it could be an unpleasant surprise.
I guess back to shopping for decent SLA batteries… So many choices, so few actually good options.
The problem with these SLA (LifePo4 replacements batteries is the size — most only have a 4S2P setup inside them. The cells usually can do constant output 1C and a surge up to 2-3C — that’s where the 10 amp comes from — Last year Battery Clearing house had these NEC LifePo4 (SLA 9AH size) batteries — I bought 5 for $100 —- 3 are currently in a 36v scooter that pulls 40 amps at startup —- the problem is, they’re only 5AH batteries —- Here’s the cells that are in them ( BADASS CELLS )
Oh my, that would be a dreadful cost, and expected every 3-5 years…
Hmm… they list max 70A for continuous discharge. And those are used cells to boot. The price is certainly compelling.
The manufacturers state 3-5 year replacement cycles for SLA batteries, and that’s the brand names. The off-brand ones I’ve tried don’t even last that long. $25 (CAD) is the best price I’ve found for local 9Ah no-name. For brands like CSB it’s minimum $55. I can’t even find Panasonic for any price. The OEM APC or Cyberpower replacements are closer to $100. Replacing 3-5 batteries like that every few years, it gets pricey, wouldn’t you say?
The appeal of LiFePo4 to me is the much longer lifetime (2X+ in time and 10X+ in cycles) as well as potentially increased usable capacity at moderate loads.
It’s the LiFePo4s many discharge cycles that makes them so appealing.
The biggest problem with SLAs is when the UPS gets used a lot for deep cycles.
I usually get 3+ -ish years out of the SLAs. Unless there are some long power outage.
Usually over a weekend. They time these things just to annoy me.
A few deep cycles and it’s time for new batts.
Depending on what the UPS is hooked to, setting the power down to like 50% helps.
But in some cases I’d rather give up battery life for longer run times.
Like on the bench where I do data recovery. Don’t want a power failure during a many hour disk scan on a failing drive.
That bench has an old 1500VA UPS hooked up to a couple of small car sized LA batts.
It’s funny, the UPS original batts always seem to last longer than any replacements including the uber expensive OEM packs.
I always put a sticker on the UPS with the battery date. So I know when to start doing a safe run time test using a test load instead of critical equipment.
If replacing a multi battery setup with generics (and making up the pack myself) I always do a charge in parallel to balance the batts before hooking them up in series.
All the Best,
Jeff
Also meant to say that the UPSs I’ve measured seem to put out enough charge voltage that the the LiFePo4 BMS should be happy to fully charge the battery. At least as far as the couple of 12v LiFePo4 I tried according to the manufacturer.
“Funny” indeed. So I’m not the only one who noticed this. Any preference of brands in SLA batteries?
I noticed most are made in China, but some like CSB are made in Vietnam. There’s virtually no other external differentiating factor.
And then I wonder if paying 2X the price is going to net 2X the lifetime. Maybe not even.
The especially annoying part is not knowing the state of battery health until it fails to perform in an outage.
I have an automotive variable resistive load tester that I might try, but it’s a hassle to have to remove the battery from the UPS, plus the load tester will put wear on the battery too.
This is disappointing, especially since I too use UPS as backup power, for keeping networking equipment running, so when the battery is used, it’s usually a deep or even full discharge. That’s another reason why LiFePo4 is appealing, as lithium ion batteries seem to last forever. Even at ~60% of original capacity, my old laptop cells are still somewhat useful after nearly 15 years.
phouton,
The OEM replacement packs seem to be more consistent than the packs I make up out of generic batts (life wise).
But I’ve had some aftermarket batts work very well indeed. The problem is finding some good replacement batts.
There used to be a local place that sold Panasonic SLAs and they had a high turnover in stock so the batts were fresh.
Then they switched to something else and raised the prices and I went looking for another source.
Heck, I’ve even used electric fence batteries from Academy for single batt UPSs with good luck.
For a while I used PowerSonic with good luck, then that source dried up too.
Shipping is what kills the deal for many of the replacement sources.
It’s hard to trust Amazon for any SLAs. No telling how long they have been sitting or if they are re-shipped from a return item.
In the multi battery UPSs the batts are in series and are charged without any kind of balancing. Eventually one battery drops low and the pack needs replacing.
How hard could it be in this day and age to add a balancing BMS ?
Most of the UPS designs have been static for decades. Just the cosmetics and the monitoring and control “Smarts” have been improved for use in server environments.
Sure wish there were some UPS boxes big enough to take a few larger LiFe of suitable current output.
Somebody is/was making a LiFe UPS a few years ago. It was Stupid expensive.
For long term reliable power, if cost is not an object, I wonder if something could not be done with one of the ECOFLOW type of power sources and just charge it from the wall power and have it run all the time. No Switchover.
Oh and meant to say 2X (or more) the price for the OEM replacements never get 2x the service life.
I wish that were true.
Usually for bigger $$ clients I get the OEM packs, just so much easier to swap out and they have no problem with the price.
For individuals of small biz clients, I’ll save them a few bucks to a hundred bucks by making up the packs myself.
Making up the packs, most times one of the 2 batteries in a “dead” pack is still good (if we catch if quick enough).
I’ll use these in some of my own UPSs in non-critical apps.
As you mentioned - One thing to always be aware of, particularly with the lower priced consumer UPSs is that the unit often thinks the battery is just fine until called on to use it. The power hiccups and the UPS just quits.
This is often the case where the UPS is on all the time.
After a few years, it’s good to actually test the things.
I made up a load with 6 100w light bulbs in parallel in those cheap single bulb sockets with pull strings… Each with it’s own switch. Total cost less than $20(?).
I power down the equipment nicely - unplug everything. Then hook up the test load.
After I unplug the UPS from the wall. I’ll switch on the lights one at a time to see how the UPS behaves itself.
I know this is not the “approved” test method as it breaks the ground line. But I’ve done it for many years. Always meant to add a proper hot only disconnect switch to the test setup, but never got around to it.
600w is enough to check out most any normal UPS.
I’ve got a 1500w heater if I’m really feeling frisky with some of the 3000w server UPSs.
There’s plenty of options for Power Backup other than these UPS devices — Size and Cost is what really determines what’s popular — I fool with solar and have lots of batteries — But at this stage of my retired life, as long as I have time to shut down my PC and not loose files a regular UPS is fine for me —- Besides I have the shop and one bedroom taken over with all kinds of crap — If my wife sees a big battery contraption in the office, she might leave me or even worse, Shoot Me
This battery will run a 500 watt load for around 7 hrs
I’ve figured out a way to test SLA batteries ( might not be accurate but seems to work weeding out bad ones) I charge one fully ,then I use a 300 watt inverter with a 100watt light bulb — I plug a watt meter into the inverter first, it gives me time and kilowatt hrs — I’ve done this on several occasions with 24v scooters and has worked well for me
chops,
I edited my previous comment to describe the test setup I use. Your way is a good way to test batts from alternate sources.
I’ve made up external packs for my own use.
I’m not comfortable putting these in someplace where a fire marshal/building inspector might pay a visit to the business.
Never know what code violation might get stepped on.
Or someplace where the user is basically clueless. (And that would be most places)…
All the Best,
Jeff
- unplug everything. Then hook up the test load.