The reason that it drops just suddenly is that LifePo4 cells have a flat discharge curve so all of a sudden one of the cells drops directly from 3.3 volts to 2.5 or less in a matter of seconds this means that it has like 10%-20% capacity left so if one cell drops bellow 2.5 or it may vary due to different BMS's the BMS itself is shutting of the connection to the negative terminal. U will not hear beeping or anything just will stop suddenly. The other cause is related to the first one if you are running without BMS it will work just fine but if one of the cells drops with 0.7 volts the ups doesn't have time to beep for low voltage. For example the Lead Acid batteries have a more curved like discharge curve so it will steadily drop from 13 to 12.9 to 12.8 to 12.7 and so on so the ups itself has time to beep. Cheers and be careful of what you are doing man u almost needed a fire extinguisher !

good choice using LiFePO4 as a replacement. This chemistry is the only viable option when needing a replacement for 12v PB. LiFePO4 has a lower nominal voltage, where other chemistries, such as Li-NCA or Li-NCM, voltage can be too low at 3S or too high at 4S.

A home computer UPS is a "stand-by" (as opposed to the more expensive "continuous"} power backup. This means that devices connected to it run directly off the grid mains until an interruption of current is sensed, at which point the battery-driven inverter is switched on (in a "continuous" UPS, the output is always from the inverter and the battery is constantly under load while the device maintains its charge and the grid mains is isolated from the connected equipment). The switching is nearly instantaneous, happening in five milliseconds or less, at which point the battery will begin discharging. This state will exist until the UPS senses a return of house power or the unit shuts down to avoid over discharging the battery. Once the unit again is powered by the grid mains, a charging sequence is initiated to bring the battery up to full charge which returns the unit to a back-up stand-by status mode with the house current again passing through to the connected device(s). The important consideration here is any UPS is designed to work with a specific battery chemistry, in this case the AGM lead acid. There are numerous articles available that explain in depth why one should not misuse a charger meant for one type of battery to charge a different battery chemistry. I would advise researching them to at least gain an understanding of what is good practice in this regard and realizing that just because one can does not mean one should. It may result in fewer houses burning down.

The reason your UPS shutsdown suddenly is because your bms have higher voltage cut off than your ups.

Nice Video. Have you experienced any drawbacks of using these LiFePo4 batteries instead of Lead Acid batteries in the last year and a half since you started using it? Thks.

This is not just an educational video but a motivational as will for he shows his mistake and still take video

I made a successful DIY Lifepo4 12v 32650 batteries to replace the lead lead acid battery of my APC 800.with 3S BMS of 40A. When tested UPS started with peeps amber lead., where as out put AC voltage is 275 v the.condition of batteries and BMS are normal. May I know the reason for high voltage?

I'm wondering how those two short-circuits influenced cells internal resistances. I was once replacing ni-mh cells in old cellphone's battery, and I shorted one cell for good 5-10 seconds. From that point on, this cell had significantly higher resistance than other two. The capacity didn't suffer significantly though. Just a thought.

So the ups is gonna cut off before bms would cut off huh? Any method to mod ups ?

Hello great video could you tell me if you had any problems since you made it

you can now buy an exact size LiFephosphate as those in a UPS. will that work as well? I don't have the skills to build a battery cell as u did. thankx.

Looks like you got a nice 3rd degree burn on your finger. Am glad you used the BMS. Not sure how the BMS and the UPS work together on charging. You may consider putting a fuse in place to limit the amp draw as the UPS doesn't appear to have a fan. Have heard that you need to manage the heat output on the UPS to keep it from overheating (because of no fan). Have seen others recommend limiting UPS to 20% of capacity to mitigate heat build up .

The speed at which he yanks the pack out, Is nothing but astonishing..

Hello, you can create one for a 24v UPS with 8 batteries, I have the 8 batteries and the BMS lifepo4 8s 24v bms, but I don't know how to make the connections for the bms ???

Thank you so much

Hilarious short circuit fire! but this is EXACTLY what I need to do - thankyou and I'll be sure to insulate the terminals. You could easily just add an external, larger battery the same way I expect. Nice work. And Lithium battery voltage is very constant, until it hit's 10% or so left, then it plummets. Lead Acid is a longer curve down.

Will the UPS give a accurate uptime and capacity estimation after replacing the Lifepo4 batts? Vital for UPS with automatic shutdown.

Hi. Is the UPS still holding up?!

Good explain thank you so much

I have 2 UPS with 12 Volt 5AH Lead Acid Batteries and 12 Volt 7AH Lead Acid Battery, if I buy these Batteries then in the 5AH UPS the 6AH Lithium Batteries will probably undercharge, and in the 7AH UPS the 6AH Lithium Batteries will probably overcharge, what to do and why did not you use the Battery Case ??

Just to help you on your future battery projects, BMS Leads should all have equal lengths.

The 15 amp BMS at 2:30 will provide only 190 watts or VA (12.7V X 15A).

should add a mppt solar charge controller also to it but . #NOTE make shore it can be programed to the right voltage so not have issues with the ups charger . test the max voltage of the battery at all times to see if it has a equalization charge so you dont blow up the battery / cells. other then that ill hope to see that you made an update of this ups conversion

For 2000va 24v ups, How many battery i need and what Amp bms for say almost 500w load for at least 10 min ? Plz answer bro. I have this Power Guard PG-2000VA UPS which has a Display buit in and can hold 4 lead acid battery which is total of 24v 18ah.

great video....I have lots(15+) apcs that I have to keep replacing the batteries. I think I will try this on the next one that fails.

You have to change the Macs power down features.. As they are manually set..As APC does not make a PowerChute application that runs on a Mac...Without hacking the through the terminal window..

Are you sure you did the right thing ?! I think the bms input voltage is exactly 12.6 volts. And in the old battery it is charged between 13.8 and 14 volts. Can't your bms burn or more ?! By the way I thought to put some diodes directly to the ups, and put an external charger of 12.6 volts. I would be happy if you answer me in full detail.

At the prices the components are currently at for the build, I'm not sure this makes sense. Probably better off going with an external lead acid battery of much higher capacity which could have it's water levels checked. $60-$70 for this (following supplied links and some known pricing) seems pretty high, not to mention the unknown reliability factor of overseas components. I can get a 12 volt utility battery right now for $20 that will plug right in and work - although it will not fit in the case because it's a much larger battery.

Is there any update on how long it lasts after a full charge?

Thank you so much this is the video I was searching for 1 Since its lead acid battery UPS battery will be continuously charging does battery will destroy or fire due to overcharging 2. This battery capacity is how much AH. Can layman like me try to build battery of course i wont do short like you did And please let me know the how is your battery performance now

very cool!

Honest Question: Doesn't the old case have its own BMS?

“Charging normally”8:53 Oh boy can’t wait to see where this goes

Keep us updated i want to do that same just not sure it would be safe

Hey, going on a year later...is it still working?

excellent video! only one suggestion: as good as your english is, Lead-Acid is pronounced Led-acid... as Pb in enlish is pronounced "led" not "Leed" otherwise, GREAT! any thoughts on how to increase the capacity limit ie increasing the 1050VA limit?

Umm, how long will it take for the UPS charger to kill the Lithium?

Don't forget that if you ever turn your UPS on its end, side or upside down after a couple of days, that masking tape will do nothing to stop your batteries from moving around inside that UPS case.

better with active balancer....ang voltmeter to monitor the voltage of battery....for you to know if it is already low battery ....

I knew something was wrong with the setup.. UPS requires high discharge battery source and PB acid battery allows for really thigh discharge for a short period, while LFP (lifepo5) has significantly lower discharge capacity so you'd need lots of parallels to make it effective.

Similar scenario is happening to me "My UPS shuts down without warning and Battery BMS goes to OFF mode as well then I have to open UPS reconnect BMS wire only after that my UPS starts". Other than that UPS and Battery are functioning pretty normal.

Voltage drop of sharper than lead acid

go to wallmart and get a 105 amp hour deep cell lead acid for about $90 bucks and run that for hours and hours. We have a lot of outages here so I picked up a few of these UPS units for free. people trow them out rather than the hassle of buying a new battery and taring them apart to replace it. They are literally everyplace for free or next to nothing. when the lights go out, your stay on. lead acid can last up to 5 years if you check the water every month. The UPS units charge 24/7 and cook batteries. check water levels and cycle once a month.

Put an external switch for the speaker.

Bms wire should have the same length.

You should remember that lifepo4 can only discharge at 1c continuasly and at 2c for few seconds. Using 6000mah cells is a bad idea. Ups will consume more than 15amp if u plug in a 100w load. And a 300w ups can consume upto 30amps. So u should go for 25ah lifepo4 at minimum. Or lithium ion. These batteries will explode or die early if u discharge them so hard..a monitor and pc st idle does not really consume much power. U should have run a cpu and gpu stress test to really see how long the battery takes to puffup😂

Links not expired

haha, I hope your wife doesn't watch your KZfaq channel 🤣

pb is pronounced led

just so we are clear "Lead-Acid" refers to the metal LEAD (pronounced LED).

🤣🤣🤣🤣🤣 nice control burnout

No,you can't replace the VRLA batteries with lithium batteries on your existing UPS. Lithium ion batteries have different charging regimes and voltages. If the UPS came with a standard gel type lead acid battery, it will have voltage regulation and charging cycles specific for that type of battery.

I know English has a lot of words that are hard to pronounce, Lead is pronounced Led like Led Zeppelin. Thats why they spelt it like that so it wouldn't be pronounced Leed. 😀

I’m super surprised no one else is annoyed by how he is pronouncing “lead” as “leed” instead of “led.” No one else?

Some real schoolboy errors here. I am very surprised you didn't monitor the battery voltages as you tested it to get a better idea of how the unit is treating the cells. You are very lucky you didn't fry the PCB on the second short. I think the only reason you didn't have a VERY serious problem is due to using LiFe Po4 cells. Lucky escape! The UPS is expecting Lead Acid voltages to determine run time and shutoff levels which your BMS is not set to correctly. This whole project is good for a cheap & nasty way to get it to work longer but that's about it.

You are pronouncing lead wrong.

you gonna burn all that battery and UPS dude ..put a insulator before anything dude for safety

If it smells like BBQ chicken when you're connecting up the batteries... you are doing it wrong. I bet you were awake after that.

DANGER!!!! If your UPS has not started your house on fire yet then it is only because of luck. I just tried the same setup using the same Daly BMS. Mine is a cyberpower pure sine UPS. The problem is the charging circuit is designed for a lead acid profile and it will not charge LiFePO4 batteries correctly. Lead acid chargers are over 14v and the maximum voltage tolerated by LFE batteries is 14.6V but this will SIGNIFICANTLY reduce their lifespan (more than 50%). If you charger runs over 14.6V (different for each UPS) then you run the risk of your battery offgassing to prevent an explosion. Since your charger doesnt realize this happened, it will just keep charging and charging until something catastrophic happens. Your cheap BMS doesnt cutoff the charging soon enough to keep the batteries healthy, it let's you charge then batteries up with the expectation that you are going to use them right away and not let them sit on the charger eternally. Now, here is where your house is at risk of burning down........ when MOSFETs on the BMS fail, they fail open. This means your BMS is no longer protecting your batteries and you will have no idea this happened. There is no alarm, there is no warning whatsoever. Your lead acid charger will just keep charging and charging your LFP batteries until there is a catastrophic failure. These batteries arent as dangerous as LiPo fortunately but you do still risk toxic chemical release offgassing (I dont know what happens when you abuse LFP batteries this bad maybe it is possible to start a fire). In my case with my UPS, it just did not work when I connected fully charged LFP batteries, I suspect the BMS shut off because the lead acid charger was trying to force too many volts- I will test it some more later today. The proper method is to learn how to disable the charge circuit, and connect an external charger that keeps each cell under 3.4V for longevity 3.2V is even better but this isn't a full charge. The external charger can be solar or electric, and it should support LFP battery charging profile. ** The proper way to charge these batteries is with constant current and slowly increasing the voltage as the battery charges **

it's spelled Lead but has two ways of pronounciations and two definitions. you're mispronouncing leed it should be pronounced "LED" lead VS leed. You did an awesome job, just that my ears cringed with wrong pronunciation. Death, dead VS deed, red, read VS reed, read and so on.... my goodness I've become a grumpy 'ol man "time for my meds!"

300w / 12v = 25 amps, i doubt your soldering will hold that power when UPS will be on battery. More solder wont hurt and be more safe :)

rip that beeper OUT. it is useless. you will know when it is going off.

Looks extremely dangerous setup.

After 1month of use i can pretty much tell it already exploded

06:57 Fireworks! 🧨