LiFePo4 - UPS gets a small but important upgrade! 

I recently swapped the 7Ah lead acid for LiFePo4 cells and encountered this very same problem. So I will try this fix over the weekend. Hopefully it solves the issue. Makes total sense! 😊

Great stuff, an obvious solution when pointed out. Maybe add a low voltage cutoff relaY before reaching the bms low low safety cutoff as well. Now nee to address the difference between LAb charge curve and LFP charge (doesnt need or invite equalisation period charge - that should be minimised somehow?

thank you so much for the tip, i needed it!

Thank you, khun Roland. Congratulations on your 1k plus subscriber. I'm your room no.2 guest at resort. (My old account have trouble to be premium status so I use this new one)

I have a similar problem on an old APC Smart UPS 1400. I was able to use the COM port to connect to the UPS and enter PROG mode. From there you can set the voltage calibration. What you can do is to start with a 12V lead acid battery and measure the voltage both fully charged, and then run the battery down till the UPS shuts off. Using a voltmeter at the battery posts you can directly see what the UPS fully depleted voltage is. You can then adjust the calibration constant in the UPS firmware up so that the calibrated depleted voltage in the UPS creates an actual voltage at the LFP battery posts that is above the BMS disconnect voltage. The only downside is that the UPS never registers fully charged and is likely continuously try to overcharge the LFP battery, but the BMS is cutting off the top. The other way I've tried it is to set the calibration such that the top of the voltage window is the top of the UPS pre-programmed charge window. When I do this, I need to be careful to set the maximum % allowable discharge such that the LFP battery voltage on the posts never gets below the BMS cutoff (ie: set the UPS to start shutown at 35% instead of 10%). This happened to me when I was first setting up the LFP module. Couldn't get the UPS to take a charge to turn back on. Had to rig up 24V to get the battery over the minimum UPS turn on voltage. If i was to do it again, I'd use 8 bare LFP cells for 24V and only use a balancer not a full BMS, and make sure that the top of charge window calibration was set correctly to not exceed the max charge voltage.

Nice fix I just boost with another battery.

ouch !! I just ordered 3 kits with LiFepo4 batteries from AliExpress. The UPS are installed at a remote location with no human presence for a couple of weeks / months. Hopefully my UPS has a higher low-voltage cutoff. alternatives i can think of are: 1) the management software (APC powerchute) can be configured for a higher low-voltage cutoff 2) replace the BMS with a "Smart BMS" which can be configured with a higher cutoff. (expensive alternative).

Hi i had purchased 12v 12ah lipo4 battery for ups, but my ups is not able to charge it more than 14 v so it never fully charged the battery so, i can only switch on the ups using grid power, and it gives backup if grid power cut after switching 9n the ups, but problem is that is i have already power cut from grid, then i can not switch on my ups directly 9n this battery. The ups is ok as it was designed for 12v 7 ah lead acid battery and if i put old lead acids battery then it work normally. Help me to overcome this problem

i belive the best batteries to use for UPS are headway's 38120 HP. they are plenty powerfull and rated for 100% DOD compined with a simple active balancer would do the job i belive

Hi Thanks for a great video. I can get a 12v Lifepo4 battery that looks like the lead acide battery and the BMS is sealed inside. How can I do the modification without cutting open the Lifepo4 battery to do this ? Thanks

Eaton UPS available for stock，Happy cooperation.

If using a larger capacity LiFePO4 battery that the original fitment use an additional charger direct to the battery to charge in a reasonable time and charge regardless of the BMS.

Thanks! I've been looking for this exact fix. I'm just getting into electronics and am very cautious. I was thinking of buying a DC to DC charger. Good one from Renogy to put between the ups and lithium battery with built in BMS...... anyone rolling their eyes yet?😅

I want to convert my 750VA APS ups into an LFP powerwall (24V x 280 Ah). So I run my day day pc load (ca 250W) off UPS and run mains/recharge ups on 8 hrs night time rate (which is 1/3rd of day time). I wonder if the UPS could handle continuose usage given that its only intended for a 15min operation on its 24V 5Ah LABs. Would be very good if it could do duty like that as a Victron equivalent is ca £750

I tried changing my stock battery with lifepo4 but I have similar issue.. when I connected the positive and negative wires.. my ups beeps like normal (yellow light) indicating it is running on battery. When I try to plug it in.. it lights to green which is normal too. Problem is power switch seems not working. It is always on and I cannot turn if off. Also, when I try to insert a load (charger to charge my phone)... my ups lights to red and continuously beeps (monotone and irritating beep). Since switch not does not turn off. I open the ups again.. and remove the ground (black wire) so the ups turn off as well as the irritating beep. Not sure why my ups turns red with irriting monotone beep. Btw, I bought a LiFePO4 battery which looks like my original lead battery. I am not sure if there is BMS included on my bought battery.

Thank you, can you still use the existing lead acid charger inside the ups to charge the lithium ion phosphate cells, how does it work?

Hi i have a SyberPower ups that usess two lead acid batterys in series, can i use LFP batterys and will it charge? I am buying two LFP batterys with built in BMS. And how do i get to hook the switch up on thoese batterys?

Thanks for the video. Can you not just parallel a small lead-acid battery with the LIFEPO4/BMS? Since they have similar charging profiles, the LA battery should have enough juice available to trigger the UPS?!?

also.... i don't agree on your cost comparison ( at least for the long term) cause LiFePo4 batteries have many more times the cycle capability hence you dont have to replace the batteries often like lead acid. also... less of trouble for many years. hence in the long terms cheaper then Lead Acid.

how to charge the lifepo4 4s? how many voltage ups did to charge the battery

HI !!! i built 4s1p with bms XH-4S-F30A for lifepo4 same video but it can't load the computer even for 1 minute. is it a bms problem? Can't start ups without grid, and UPS can start while no plug rear 220v, PC under 250W. Please help...thankyou verymuch

Seems like a hassle, cant you use a relay instead of a manual switch?

Which bms did you use , is it 4s or 3s

its been a year since you created this project, so how was it now after a year??? still working/? did it blow up? update us.thanks

Hi i had purchased 12v 12ah lipo4 battery for ups, but my ups is not able to charge it more than 14 v so it never fully charged the battery so, i can only switch on the ups using grid power, and it gives backup if grid power cut after switching 9n the ups, but problem is that is i have already power cut from grid, then i can not switch on my ups directly 9n this battery. The ups is ok as it was designed for 12v 7 ah lead acid battery and if i put old lead acids battery then it work normally. Help me to overcome this problem

Hi i had purchased 12v 12ah lipo4 battery for ups, but my ups is not able to charge it more than 14 v so it never fully charged the battery so, i can only switch on the ups using grid power, and it gives backup if grid power cut after switching 9n the ups, but problem is that is i have already power cut from grid, then i can not switch on my ups directly 9n this battery. The ups is ok as it was designed for 12v 7 ah lead acid battery and if i put old lead acids battery then it work normally. Help me to overcome this problem