Nobodybusiness
Solar Sponge.
That helps but doesn’t preclude cell imbalances.Exactly what I meant.
To prevent the 2V you mentioned: Use High Quality, Reputable Cells. Top Balance in parallel. Then Connect in Series.
Process is everything
That helps but doesn’t preclude cell imbalances.Exactly what I meant.
To prevent the 2V you mentioned: Use High Quality, Reputable Cells. Top Balance in parallel. Then Connect in Series.
Process is everything
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 ideaExactly what I meant.
To prevent the 2V you mentioned: Use High Quality, Reputable Cells. Top Balance in parallel. Then Connect in Series.
Process is everything
Well, it depends what you’re trying to accomplish.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
using a lithium nmc/lfp any lithium chemistry without a bms is not a resource of good practice.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.
Hello,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.
Hi @penguinairlines ,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.
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.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
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.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.
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.I keep on wondering why APC and other main stream UPS makers have not adopted new designs centered around using LFP batteries. Most of my UPS systems are older 1500W APC units, so putting in 4x LFP batteries is not going to work.
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.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.
A charger and inverter is really all you need, but what gets tricky (expensive) is a bypass circuit.Is there a DIY smart UPS/BMS board or even something that can be managed with a raspberry pi ?
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 +.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.
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 wastedI 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!)