In this Video i show the basics on how you would swap out your old lead acid batteries in the 48 volt configuration to Lifepo4. UPS is a Emerson GXT4-2000RT120 .
I will have to remember this video, Because I need to find some good Rack mounter Server UPS for my well server's, and network equipment. Be nice if they just make a 48 volt battery to just replace the 4 batteries. With LIthium being able to have up to 30AH in then same foot print of just one of those 12 volt battery's. Be nice to put a 48volt 20AH battery in place of the old lead acid so the UPS can last a lot longer during a power outage. But I do like this video. Also I wonder if they make those battery's in higher AH other than 6AH when most of those Lead acid ones are usually 7AH
I am about to do another video on building your own battery . Got all the cells in this week and will begin working on the video ! Also i will go over capacity and cell sizes There are some limitations but I'm going to try and make something work
Yes that sounds about right. Limited to the discharge capabilities of the BMS's. Still for the use intended it will be a hell of a lot better than lead acid
Great idea. Very cool video. Do you anticipate any issues with how the ups charges the lifepo4. I would assume the ups still thinks it’s lead acid and keep them topped off all the time which lead acid like. Without being able to control the charge profile on the ups, the lifepo4 may get damaged or degraded prematurely. Can you do a follow on capacity in 6 months or a year? Thanks
So long as the voltage profile of the lead acid charger is not above the 3.60Vpc or 3.65Vpc of this 15S or 16S 48V (often 51.2V nominal 16S in the industry but you'll have to measure your UPS's charge profile to understand what works best) then the battery should be fine. It's not ideal to have LiFePO4 constantly "floating" above 3.45Vpc as most LiFePO4 cells will eventually rest at 3.35Vpc to 3.45Vpc (larger cells seem to rest lower)....but it won't do too much considering most LiFePO4 is going to have a cycle life of 3000+ cycles depending on the cell manufacturer. Worst case scenario would be 58.4V in a 16S where the max cell voltage is 3.65V.....I'd guess you'd get half the number of cycles to 80% if the battery was forever floated at that tippy top voltage. If you can bring it down to 3.55V you can probably get much closer to the datasheet rating and anything at 3.45V or under for the float voltage would be ideal....because even if the charger only charges the cells up to 3.45V you are getting 90%+ capacity....probably more like 92%-95%....there's really nothing left in the last 200mV and the only reason why we use the last 200mV is for balancing since you can at least assign a SOC percentage to a voltage number whereas from 3.20V to 3.30V you have NO CLUE what your state of charge is at all. If there's no load on your battery at all you can make a guesstimate but you could be off by 20% or more. This is why all proper balancing circuits for this chemistry don't start balancing until the cells hit 3.45 because below that you are NOT balancing the cells to have an equal number of Ah in each cell...you are just matching voltages which doesn't mean Cell A has 70Ah in it just because it is at 3.28V and Cell B is also at 3.28V and you know it has 70Ah in it. If you're using new, matched cells from the same batch it should theoretically be pretty close but if you're using used cells, especially if from different batches and MOST definitely if from different manufacturer then 3.28V on one cell could be 60Ah and on another it could be 72Ah Sorry long rant but LFP is kind of a unique chemistry due to the flat voltage curve and its differences from NMC and NCA lithium ion. NMC/NCA hates sitting above 4.0Vpc or 4.1Vpc for extended periods of time but LFP is much more tolerant to it and the insanely long lifespan makes the limited degradation it causes a lot easier to swallow since most LFP batteries would have to be cycled once a day for 8-10 years to hit their 80% of original capacity "end of life" metric....where you still have an equal number of cycles life roughly before the cells become pretty unusable or start dying completely more than 50% of the time* (rough estimate but this is generally what people have seen with NMC/NCA lithium ion....old laptop cells can see another 500+ cycles and even 1000+ cycles after already being at 80% of their original capacity depending on how hard you cycle them. Lots of people don't use the full 2.50V (or 2.75V, in rare cases 3.00V) to 4.20V range and instead cycle them 3.00 to 4.00 or 3.20 to 4.00 where you'll still get 75% of their remaining capacity but double or triple their cycle life. Its said that every 0.10V you cut off the top of the voltage range doubles the cycle life. So never charging above 4.10V gives you 1000 cycles instead of 500 to 80% of original capacity...Charging to 4.00V could give you 2000 cycles to 80% of its original capacity.....the lower end of the voltage range is not quite as easy to put in words because the discharge curve starts to get steep below 3.00V so I generally say if you stop at 3.00V you can double capacity just like 4.10V does. Then it would be stopping at 3.15V or 3.20V would double the capacity againt like 4.00V would)
yea custom built pack would double the max output of 300ish watt or double the runtime whichever you choose to go with, if you can get cells at a price that isn't redicilous vs batteries , could probably fit 12ah in the same space, doubling the runtime well have actually seen a 12ah battery in that size but if this is all you need great stuff
I agree , Maybe ill try and get ahold of some 26650 lifepo4 cells and build a pack for a more advanced video , ill have to get another UPS , but i could always use more! Be good to do it and do some good testing for simulated outage.
I will have to remember this video, Because I need to find some good Rack mounter Server UPS for my well server's, and network equipment. Be nice if they just make a 48 volt battery to just replace the 4 batteries. With LIthium being able to have up to 30AH in then same foot print of just one of those 12 volt battery's. Be nice to put a 48volt 20AH battery in place of the old lead acid so the UPS can last a lot longer during a power outage. But I do like this video. Also I wonder if they make those battery's in higher AH other than 6AH when most of those Lead acid ones are usually 7AH
I am about to do another video on building your own battery . Got all the cells in this week and will begin working on the video ! Also i will go over capacity and cell sizes There are some limitations but I'm going to try and make something work
You are limited to the max discharge rate of the battery, in this case 307.2W
Yes that sounds about right. Limited to the discharge capabilities of the BMS's. Still for the use intended it will be a hell of a lot better than lead acid
Great idea. Very cool video. Do you anticipate any issues with how the ups charges the lifepo4. I would assume the ups still thinks it’s lead acid and keep them topped off all the time which lead acid like. Without being able to control the charge profile on the ups, the lifepo4 may get damaged or degraded prematurely. Can you do a follow on capacity in 6 months or a year? Thanks
Yes i can , However the Bms in the batteries should protect the units and since it would never been a full cycle should not be too bad !
So long as the voltage profile of the lead acid charger is not above the 3.60Vpc or 3.65Vpc of this 15S or 16S 48V (often 51.2V nominal 16S in the industry but you'll have to measure your UPS's charge profile to understand what works best) then the battery should be fine.
It's not ideal to have LiFePO4 constantly "floating" above 3.45Vpc as most LiFePO4 cells will eventually rest at 3.35Vpc to 3.45Vpc (larger cells seem to rest lower)....but it won't do too much considering most LiFePO4 is going to have a cycle life of 3000+ cycles depending on the cell manufacturer. Worst case scenario would be 58.4V in a 16S where the max cell voltage is 3.65V.....I'd guess you'd get half the number of cycles to 80% if the battery was forever floated at that tippy top voltage. If you can bring it down to 3.55V you can probably get much closer to the datasheet rating and anything at 3.45V or under for the float voltage would be ideal....because even if the charger only charges the cells up to 3.45V you are getting 90%+ capacity....probably more like 92%-95%....there's really nothing left in the last 200mV and the only reason why we use the last 200mV is for balancing since you can at least assign a SOC percentage to a voltage number whereas from 3.20V to 3.30V you have NO CLUE what your state of charge is at all. If there's no load on your battery at all you can make a guesstimate but you could be off by 20% or more. This is why all proper balancing circuits for this chemistry don't start balancing until the cells hit 3.45 because below that you are NOT balancing the cells to have an equal number of Ah in each cell...you are just matching voltages which doesn't mean Cell A has 70Ah in it just because it is at 3.28V and Cell B is also at 3.28V and you know it has 70Ah in it. If you're using new, matched cells from the same batch it should theoretically be pretty close but if you're using used cells, especially if from different batches and MOST definitely if from different manufacturer then 3.28V on one cell could be 60Ah and on another it could be 72Ah
Sorry long rant but LFP is kind of a unique chemistry due to the flat voltage curve and its differences from NMC and NCA lithium ion. NMC/NCA hates sitting above 4.0Vpc or 4.1Vpc for extended periods of time but LFP is much more tolerant to it and the insanely long lifespan makes the limited degradation it causes a lot easier to swallow since most LFP batteries would have to be cycled once a day for 8-10 years to hit their 80% of original capacity "end of life" metric....where you still have an equal number of cycles life roughly before the cells become pretty unusable or start dying completely more than 50% of the time* (rough estimate but this is generally what people have seen with NMC/NCA lithium ion....old laptop cells can see another 500+ cycles and even 1000+ cycles after already being at 80% of their original capacity depending on how hard you cycle them. Lots of people don't use the full 2.50V (or 2.75V, in rare cases 3.00V) to 4.20V range and instead cycle them 3.00 to 4.00 or 3.20 to 4.00 where you'll still get 75% of their remaining capacity but double or triple their cycle life. Its said that every 0.10V you cut off the top of the voltage range doubles the cycle life. So never charging above 4.10V gives you 1000 cycles instead of 500 to 80% of original capacity...Charging to 4.00V could give you 2000 cycles to 80% of its original capacity.....the lower end of the voltage range is not quite as easy to put in words because the discharge curve starts to get steep below 3.00V so I generally say if you stop at 3.00V you can double capacity just like 4.10V does. Then it would be stopping at 3.15V or 3.20V would double the capacity againt like 4.00V would)
yea custom built pack would double the max output of 300ish watt or double the runtime whichever you choose to go with, if you can get cells at a price that isn't redicilous vs batteries , could probably fit 12ah in the same space, doubling the runtime well have actually seen a 12ah battery in that size
but if this is all you need great stuff
I agree , Maybe ill try and get ahold of some 26650 lifepo4 cells and build a pack for a more advanced video , ill have to get another UPS , but i could always use more! Be good to do it and do some good testing for simulated outage.
i have noticed those 26650 cells have gotten way more expensive in the past two years
Where (in MD) do you take your lead acid batteries for recycling? / scrap money?
Either Maryland Recycle or Owl Metals