Nobodybusiness
Collecting the leftovers of the Great Sky Reactor.
That helps but doesn’t preclude cell imbalances.
Replacing UPS lead acid batt w LiFePO4
- Thread starter JWLV
- Start date
If you top balance the best cells available, it does not guarantee that all 4 cells will hit 2.5v at the same time the first time you discharge to 10v and it will drift further apart with every cycle even worse with a 8s 24v. Do not compare the duty cycle of batteries in a ups to that of a solar system that is properly sized. Lifepo4 cells have a hard life in a ups even if it has a bms connected, without a bms is just a bad idea
Well, it depends what you’re trying to accomplish.
1. Take care of a Ferrari
2. Make a usable battery that last “Only” three times as long as a lead acid for cheaper.
Dont need “exactly “
Regarding the harsh life you mention. The ups charges at 13.6v which is the voltage that battle born recommend to float their batteries in a RV. So it’s more of a R&R life, that don’t get cycled much.
Please use this information as a Resource.
Not a blank Statement or vague opinon. Its coming from my own personal experience working with these units over a long time. The resource is for people wondering if it can be done and how.
Last edited:
using a lithium nmc/lfp any lithium chemistry without a bms is not a resource of good practice.
And i'm speaking of my professional experience in converting ups'es 12v, 24v, 48v, 72v, 96v lead acid to lifepo4, I do probably more than 100 conversions yearly. I stay in south Africa and we have scheduled blackouts almost weakly which last for 2hours sometimes 4 times daily (google south african loadshedding) and this situation really puts these batteries to the test in a ups, most of the ups'es ive encountered have a low voltage cut off in the region of 2v - 2.5v and without a bms that starts its balance circuit at 3.4v you will have a unbalanced battery sooner than you think.
al the experience i have accumulated and the literature regarding lithium batteries ive consumed, just corroborates that its a bad idea to go without a bms, it is certainly doable but i would not do it.
We
Yeah, you really live in a third world country. That kind of power interruption is hardcore and will stress the batteries like a solar power wall would.
The applications where Im installing the LFP Batteries have a Auto transfer Genset as part of the Office Complex. So the UPS would never shut down before the Genset kicks inn.
Regarding the BMS & LFP, it just depend on que quality of components and expectations of performance.
Safety wise, Never bring NMC into this conversation. That is just a Dynamit TNT Stick.
Hello,
Yeah, you really live in a third world country. That kind of power interruption is hardcore and will stress the batteries like a solar power wall would.
The applications where Im installing the LFP Batteries have a Auto transfer Genset as part of the Office Complex. So the UPS would never shut down before the Genset kicks inn.
Regarding the BMS & LFP, it just depend on que quality of components and expectations of performance.
Safety wise, Never bring NMC into this conversation. That is just a Dynamit TNT Stick.
penguinairlines
New Member
- Joined
- Apr 6, 2022
- Messages
- 2
Hey folks,
I think I understand what everyone is saying, and can understand the value of BMS making sure that each battery is properly attended to across its lifecycle. My question is, most of these LiFePO4 batteries such as what the OP mentions have their own BMS integrated, so wouldn't that be enough? I'll put a link at the end with an example LiFePO4 with integrated BMS.
For my use-case, I currently have a CyberPower GX1350U that needs new batteries imminently. These CyberPower UPS have worked great for me until they don't, and it's always been the fault of the battery. I'm wondering if I can replace the AGM batteries with LiFePO4 ones, which cost about 2x, but should have a much longer operating life among other benefits. I understand to look for the max output and make sure it matches the UPS spec, or at least the max output I need. I understand that if I get a battery that accepts a similar float voltage that the AGM takes, that the LiFePO4 integrated BMS should handle the power ingress to the battery to be sure it charges appropriately. My question is again as stated above, would the integrated BMS in these LiFePO4 be acceptable to maintain each cell? In this case, the job would involve a 2 battery replacement.
I'm looking at these for example. https://www.amazon.com/LiFePO4-Secu...3/134-0637064-2960942?pd_rd_i=B09MFGS4TX&th=1
After I get all this sorted out, I'm looking forward to getting a NUT server set up so that I can get some better statistics out of the UPS, but the primary objective is to get the network equipment back on battery for those .5s power blips in my area.
I think I understand what everyone is saying, and can understand the value of BMS making sure that each battery is properly attended to across its lifecycle. My question is, most of these LiFePO4 batteries such as what the OP mentions have their own BMS integrated, so wouldn't that be enough? I'll put a link at the end with an example LiFePO4 with integrated BMS.
For my use-case, I currently have a CyberPower GX1350U that needs new batteries imminently. These CyberPower UPS have worked great for me until they don't, and it's always been the fault of the battery. I'm wondering if I can replace the AGM batteries with LiFePO4 ones, which cost about 2x, but should have a much longer operating life among other benefits. I understand to look for the max output and make sure it matches the UPS spec, or at least the max output I need. I understand that if I get a battery that accepts a similar float voltage that the AGM takes, that the LiFePO4 integrated BMS should handle the power ingress to the battery to be sure it charges appropriately. My question is again as stated above, would the integrated BMS in these LiFePO4 be acceptable to maintain each cell? In this case, the job would involve a 2 battery replacement.
I'm looking at these for example. https://www.amazon.com/LiFePO4-Secu...3/134-0637064-2960942?pd_rd_i=B09MFGS4TX&th=1
After I get all this sorted out, I'm looking forward to getting a NUT server set up so that I can get some better statistics out of the UPS, but the primary objective is to get the network equipment back on battery for those .5s power blips in my area.
Hi @penguinairlines ,
The problem with All these blade terminal LFP batteries from amazon is that their continuous discharge is pretty low. In this case is 12v X 10 Amp = 120 watts.
You would need to make your own and slap a 50 amp bms to get the 500 watt rating to match the sealed agm.
Regards
penguinairlines
New Member
- Joined
- Apr 6, 2022
- Messages
- 2
Got it, thanks. I suppose it may be okay for the UPS that just runs my router and switch, but there's no way that'll take okay on the one that runs my PC. I'll take measurements of the prior's usage before purchasing those LiFePO4 batteries.
For building my own, I'm open to any recommendations of good information about that. I'll search this forum in the evening when I have some time for research. Obviously I will need more batteries to get enough amps together on that BMS to handle my whole desk, but that could end up with a system that has a lot of Voltage, which is pretty exciting!
Last edited:
I am confused by this statement: Lifepo4 cells have a hard life in a ups even if it has a bms connected...
Why do you think this? In my situation, we seldom have power outages unless there is a fire or it gets very windy (unfortunately, a bit too often here in No Calif.) We do have the occasional 5-second outage. So my batteries sit at full charge for 99+ percent of the time. For my 24v APC system, that means they are just sitting at 27.38v (3.42v per cell) all the time. I do use a BMS. Is this really that stressful for the batteries? It would probably be best to keep the batteries at say, 50% charged, but that pretty much defeats the purpose of a backup that I want to last a long time when needed.
Why do you think this? In my situation, we seldom have power outages unless there is a fire or it gets very windy (unfortunately, a bit too often here in No Calif.) We do have the occasional 5-second outage. So my batteries sit at full charge for 99+ percent of the time. For my 24v APC system, that means they are just sitting at 27.38v (3.42v per cell) all the time. I do use a BMS. Is this really that stressful for the batteries? It would probably be best to keep the batteries at say, 50% charged, but that pretty much defeats the purpose of a backup that I want to last a long time when needed.
Looking at BattleBorn's website it isn't nearly as bad as I would have expected, at least if you trust them. The batteries are going to constantly be going from 100% to 90% and back though, which isn't their ideal operating mode as I understand at least. The little UPSs are really designed for a specific battery parameter, and with the expectation that the batteries are replaced every 3 years. They don't like additional capacity (thermal properties of the inverters are designed for the watt-hours of the included battery), unless the inverter is an online type and includes battery expansion jacks.
In the scheme of things, it isn't the end of the world, but you might not get as much out of the batteries as you would expect.
There isn't money in it for them at the moment. People (at least the mass market) aren't willing to pay a premium for it. They also like the people that pay them for replacement batteries.
robby
Photon Vampire
- Joined
- May 1, 2021
- Messages
- 4,154
I was thinking that it could be revenue from battery replacement but I really wonder how many people use OEM battery replacements. I have never purchased a single one in 20+ years! Several cheaper brands last just as long if you get them factory fresh. As for the price difference, the gap is really not that big between LFP and AGM.
I work for a large high tech company where there are many of these APC SmartUPSs around. The SLA batteries all last about 3 years and then fail. They bulge out so that they are hard to remove. I have see a trend where people just give up and throw the entire UPS away...and do not get a replacement because it is too much of a hassle (that is how I got mine!) I would think APC would redesign these to use LiFePO4 batteries and tout them to corporate customers that want long term reliability.
GavCol
New Member
ooooh. I would love to do this.
I've have been thinking about it for months and finally decided to search here if it was possible.
I've got 3 UPS' and don't get enough minutes during blackouts so I've been thinking of extending or replacing with LIFEPO4 cells and bms.
Is there a DIY smart UPS/BMS board or even something that can be managed with a raspberry pi ?
I've have been thinking about it for months and finally decided to search here if it was possible.
I've got 3 UPS' and don't get enough minutes during blackouts so I've been thinking of extending or replacing with LIFEPO4 cells and bms.
Is there a DIY smart UPS/BMS board or even something that can be managed with a raspberry pi ?
A charger and inverter is really all you need, but what gets tricky (expensive) is a bypass circuit.
Quoted from:
While we very much advocate for using batteries with a build-in BMS (without one the battery would be unsafe and likely fail very quickly!), manufacturers struggle to make their BMS as bullet-proof as it should and needs to be. Surge currents due to the input capacitors of large inverters, motors, and air-conditioners can and at times will kill the BMS, rendering the battery useless.
At least one well-known battery manufacturer is now enforcing their warranty conditions to the letter, and that requires the use of an external current limiter when their batteries are used with large inverters (“large” being defined as 3,500 Watt and up). This leads to the ironical situation where the BMS is there to protect the battery, and now a current limiter gets connected to protect the BMS. What will be next to protect the current limiter…
Seeing how the BMS has become the weak link, manufacturers should really work (hard) on hardening that. Nothing is 100% bomb-proof, but there certainly is room for improvement! Another solution could be to acknowledge that the BMS is the weak link and make it so it can be replaced without too much effort, for example a gasketed lid on the battery that is removable with a few screws, and a BMS that has connectors and bolted lugs, so a repair shop can swap the board. It makes no sense to throw away a battery where 90% of the cost is in the cells, and 10% in the BMS, just because the BMS failed."
www.solacity.com
The Weak Link - The BMS
"We now have a few years of experience with lithium-ion batteries, and what is becoming clear is that while the LiFePO4 cells hold up very well, that is not the case with the Battery Management System (BMS). Overall the number of prematurely failed batteries is small, but with 10,000+ batteries sold it is clear that in 99% of cases it is the BMS that fails, turning the battery into an expensive piece of gender-neutral-cave decoration!While we very much advocate for using batteries with a build-in BMS (without one the battery would be unsafe and likely fail very quickly!), manufacturers struggle to make their BMS as bullet-proof as it should and needs to be. Surge currents due to the input capacitors of large inverters, motors, and air-conditioners can and at times will kill the BMS, rendering the battery useless.
At least one well-known battery manufacturer is now enforcing their warranty conditions to the letter, and that requires the use of an external current limiter when their batteries are used with large inverters (“large” being defined as 3,500 Watt and up). This leads to the ironical situation where the BMS is there to protect the battery, and now a current limiter gets connected to protect the BMS. What will be next to protect the current limiter…
Seeing how the BMS has become the weak link, manufacturers should really work (hard) on hardening that. Nothing is 100% bomb-proof, but there certainly is room for improvement! Another solution could be to acknowledge that the BMS is the weak link and make it so it can be replaced without too much effort, for example a gasketed lid on the battery that is removable with a few screws, and a BMS that has connectors and bolted lugs, so a repair shop can swap the board. It makes no sense to throw away a battery where 90% of the cost is in the cells, and 10% in the BMS, just because the BMS failed."
How to Find Happiness With LiFePO4 (Lithium-Ion) Batteries –...
By: Rob Beckers You have just sold your first-born into slavery, remortgaged the house, and bought yourself a lithium-ion battery! Now you want to know how to take care of your precious new purchase: How to best charge lithium-iron batteries, how to discharge them, and how to get the maximum...
www.solacity.com
Slightly off-topic, but, isn't the only reason that UPS are "complex" because they need to do a live swap to transition power delivery from mains over to the output of the inverter in order to keep the powered devices online? And the reason for having that complexity instead of simply running off battery 100% of the time is due to the efficiency loss of going through the inverter when mains is up.
Just makes me want to try to implement a DC architecture for things more and more.
Just makes me want to try to implement a DC architecture for things more and more.
Bud Martin
Solar Wizard
- Joined
- Aug 27, 2020
- Messages
- 4,844
nifty-stuff.com
New Member
- Joined
- Oct 3, 2019
- Messages
- 126
I'm really enjoying this thread!
I have a UPS running on a LFP battery and it's been working great. I haven't dove into the charge profile (current, volts, upper/lower limits, trickle, etc.) but from what I've read, it *should* be fine swapping SLA battery with LFP.
If y'all have links to very detailed info about the pros/cons and what to look out for when swapping out SLA for LFP, I'd love to read more!
I think I'd like to keep an eye out at thrift-stores for them from time to time.
I have a UPS running on a LFP battery and it's been working great. I haven't dove into the charge profile (current, volts, upper/lower limits, trickle, etc.) but from what I've read, it *should* be fine swapping SLA battery with LFP.
If y'all have links to very detailed info about the pros/cons and what to look out for when swapping out SLA for LFP, I'd love to read more!
Yup, I think this! SLA keeps the price of UPS cheap, and I guess 99% of users won't pay 2x-3x or more for a UPS with LFP, even if the cycle (and year) life is going to be 10x +.
Exactly! That's how I got one of my UPS. Just tossed because it was "broken"... just needed a battery swap. I often wonder how many end up in landfill wasted
I think I'd like to keep an eye out at thrift-stores for them from time to time.
