Schneider electric is a fantastic company. They own APC. Their commercial equipment is great, to include their larger UPS’s. They make some of the equipment that I work on professionally.
Their “home grade” stuff is no better than AliX junk IMHO. I had the APC UPS in the first post, and the sine wave was so bad it wouldn’t turn a motor properly, and fried 2 separate AC to DC converters plugged into it on the first power outage.
Making your own UPS is pretty easy, especially if you can stick with DC and skip the inverter.
As in hooking a bunch of batteries together with a charger?
19v DC for a laptop, but it already has batteries.
Kinda tough to power a desktop with DC.
I’ve got some LiFeO4 batteries on the way from Amazon. Replacement for the 12v 7Ah sized jobbies.
The seller says the BMS can handle 2 in series if the charge voltage is the correct range.
Which I just tested a Cyberpower 1500VA and it’s good to go.
Finally got cheap enough to risk giving them a try.
Sure would be nice not to have to buy new SLAs every 3 years or so.
LifePo4 cells are the way to go — to start with you get full AH rating not like SLA only being half discharge — The thing you want to check is the float voltage and that the 2 batteries are pretty much in balance —- hopefully 28.8v or lower float and both batteries are under 15v —- the best thing to do with LifePo4 is to top balance them —- Hook them up in Parallel ( make sure their voltages are fairly close beforehand) —Then fully charge them to 14.4v — Then they are in balance with each other and can be connected in Series —- Really these steps should be done even with SLA batteries/ any series connections
Yeah,
I always hook the SLAs in parallel before installing them. Unless they are sealed in a pack like most of the UPS OEM replacement batts are shipped.
Depending on the customer, I make up my own from the parts from the old OEM packs, or just do the OEMs cause it’s often way less grief.
The LiFeO4 seller says anything between 24.5-29.5 is good for their BMS in series. The Cyberpower is 27.5v
Didn’t want to spend big bucks, but the price has dropped enough that I’m ready to drop the lead batts forever if these work out.
All the Best,
Jeff
Right now I’m having an issue with a pair of LifePo4 batteries in my grandson’s Razor Quad —- I capacity checked them (they’re close) and resistance checked them (they’re close) — but when I series connect them and use the factory charger (29v ) , one battery goes above 15v —- when I use a adjustable PS and stay around 28v , they stay balanced— with LifePo4 cells anything above 3.5v per cell (14v for 12v replacement) is very minimal
Well, I got a couple of 12v 6Ah and 8Ah LiFeO4 batts to experiment with.
This is the size that fits in my UPSs and many many others.
Tried to pick the ones with the least negative reviews.
Ampertime 6Ah. $26,
Recommended charge current 1.2a. (6a max) Why the huge difference?
Max Discharge recommended 76.8w (!) Max 6a.
6a BMS.
Well this one won’t power jack sh*&.
And the damn thing has been charging forever on my 750mAh charger. I could get out the hobby charger and push more, but I’m too lazy.
Chins 8Ah, $36,
Max charge 4Ah
Max Discharge 8a, 102W.
So a pair of then will run 204w. This is still way low for a UPS.
The 1500VA UPS uses 2x 12v 8Ah SLA batteries. So figure 1200w, that’s like 50a or so per battery.
So these liths are not even close to being able to power a larger typical office UPS. (If I did the math right)
The lower power UPSs use smaller sized batts - so nothing to be gained.
I looked around a bit more, and did find a Dakota 12v 10Ah that will fit inside the UPS for ~ $100 a pop that can push 20a max.
Better, but still less than half of what’s needed.
So at this point, I don’t see anything other than a DYI solution for a lith battery for a UPS of any wattage.
Got to build your own battery and BMS. Or get a pre-built battery of like 100Ah and put a pair outside the UPS. Which is what I’ve been doing for my own use (with lead batts).
I would never do something like this for a client. OEM packs or packs rebuilt by me to OEM specs.
Have you tried to run a load on them — most SLA batteries aren’t rated much higher on the label —- I bought some NEC 12v 5AH from battery clearing house — I’m using them in scooters and a quad for my grandson —- in the quad at startup is 25amps
With LifePo4 batteries I try to charge some where in the middle —still about .5 C just like I do for Li-ion —- LifePo4 will charge full current for around 90% of the charge and then be full almost right after —not like Li-ion that will take a good while to finish up the charge
Haven’t tried them under load yet.
But the first one with a 6 amp BMS isn’t going to put out much.
It just finished charging and I’m letting it rest to see if the V drops off.
Have better hope for the Chins brand.
But since output C is controlled the BMS, I don’t think it will be able to handle a UPS load.
The SLAs, naturally, have nothing limiting current other than the design of the battery.
At full rated output, the SLAs will only power the UPS for a few minutes.
I’m just so sick of lead batts. I have dozens of UPSs I keep after. Total pain in the butt.
All the Best,
Jeff
LifePo4 will settle some where between 13.4 - 13.8v — most of their energy is between 3.2v - 3.34v X 4 of coarse for a 12v battery — that’s the true benefit of LifePo4 — the almost flat discharge curve —- The problem with a small UPS size battery — you only have 4S2P inside the box — 2 cells in series is only going to put out a certain amount of amperage
The two Chins cells (8Ah) I decided could live in a UPS that powers a router. Plenty of juice for than. And I’ll never have to fuss with SLAs in that corner of the office again.
Except - The Battey pack consists of 2 of them stacked on top of each other.
Put together like that, the pack is about 1mm too big to fit in the UPS.
Harrumph! Back to Amazon they go.
All the Best,
Jeff
I am thinking that a UPS could be designed around the upcoming 4680 li ion cells, it would only need one battery and a slight redesign to the circuitry.
I would like LiFePO4 just becasue of how many cycles it can take but i would add the option to charge either chemistry to a pre-selected percent as you don’t want to store lithium batteries full for long periods.
Do if i had a 25,000mAh 4680 cell UPS i would want to charge it to 60% which should make it last a decade or more.
I’m still thinking of making a DYI LiFePO4 pack up for my own use. A ready made solution is still too pricey for the output I need.
The batts are getting cheaper, I just need to find a BMS that’s reliable.
Trouble is there are so many durn choices and all the reviews on Amazon are mostly bogus…
All the Best,
Jeff
I’m surprised no one has suggested refurbished / used UPS units. I’ve been buying from RefurbUPS for my office for 15 or so years and have had good luck with them. They’re not the cheapest place to buy them from, but they do bother to test and recalibrate the units and slapping new batteries in before selling them.
Also, if you’re near an office park or university, keep your eyes out. In college I picked up 20+ APC SmartUPS over the years, left in the trash. Anyone who is familiar with the APC SmartUPS line will know that the controls are actually powered by the batteries. So, if the batteries go tango uniform, the whole unit will appear dead. Replace the batteries and they’ll come right back to life. Made a nice little profit off these guys.
Had not heard of RefurbUPS before.
Prices are reasonable but shipping is kind of tough. $84 for a 1500VA SMART APC.
Thanks for the link.
All the Best,
Jeff