Batteries for Home Backup, 14s 48v (51.8v) LG Server Rack Lithium

most of the time when you purchase 48 volt lithium batteries they're going to cost you an arm and a leg in this case we have a 48 volt lithium battery made for server racks now it's a used battery it's got a tough steel case and it is really heavy we're going to bust it open and find out what it takes to use it in a home powerwall backup system here we go [Music] hi everybody i'm dave and welcome to my channel where i like to diy renewable energy and energy efficiency projects this video we're going to bust open this really heavy server rack battery now this thing is over 90 pounds it looks like 94 pounds for this lg pack the cells inside here are arranged as 14 s which means they're going to work really well with 48 volt inverters and 48 volt charge controllers now this one is used and it's going to have some degradation we're going to find out how much i purchased two of these packs from battery hookup using my discount code which is davidpaws and that gets you 10 off any of your orders from battery hookup you could stack one on top of the other probably floor to ceiling without worrying about crushing the one underneath according to battery hookup's website this has about two 2.2 kilowatt hours remaining out of the original 3.2 kilowatt hours now we're going to test that and confirm it now this pack has a maximum continuous discharge of 100 amps maximum continuous charge of 50 amps according to battery hookups website so we'll be using a 100 amp bms with it 22 and a quarter to the outside of the orange plastic we have about 20 inches from the outside of the handle to the outside of the handle over here and standing tall it looks about 4 and 7 8 almost 5 inches tall now this is the only spot where we had some damage from shipping now this unit was palletized really well it looked it had about a dozen straps on it battery hookup tried their best not even the studs got damaged or any of the plastic is cracked so you know i mean shipping happens and we have 53.3 volts at the outside terminals so if there's a bms inside it's not shut off but i don't know exactly what's built into this so we're going to find out we're going to take off all these phillips head screws and get the top cover off this battery there we go inside the cover it looks like there is a bunch of open cell padding according to battery hookups website half of this is a 7s and half is a 7s so if you wanted to use them as 24 volts that should be possible i want to take off these orange covers and i'm going to have to slip something in here so as not to break the little tab that's in the inside i'm going to try this very little flat head screwdriver [Applause] oh broke one of them so if this is the main negative it looks like it comes up to this side it must travel through then we have a positive bus bar over here which jumps to the negative side and then the main positive i'm going to take this 300 amp fuse off and these might be 10 millimeter let's go find out yep 10 millimeter [Applause] wow that's quite the setup look how thick that copper is 26.7 and this half reads 26.7 oh six nine wow nearly perfect that's awesome well balanced a bms like this that i'll be adding this has protection circuits built in so if something goes wrong with the cells this bms will shut off the pack and it does that with little mosfets inside here but this unit doesn't look like it has a traditional bms inside it looks like this is just a communication port where it's taking the information of the cell voltages probably some thermistors built in and it's going to send that data packet up to the higher level computer and say whether it's good or bad and if something's bad then the higher level computer could shut down it looks like a couple of phillips head screws and then a bolt up top and we should be able to get this unit out i'm going to call this a bmu or battery management unit [Applause] okay so there we go if anybody is interested on the part number on that actually let's go ahead and take it apart looks like we have some phillips head screws and we can go inside and look at the circuit board okay so let's take a look inside now i'm not a computer engineer so i don't know exactly what we're looking at here but to me these little things look like they're probably resistors a pair of resistors for each cell and this board is keeping the cells balanced so this is a balanced board and a communication board but it's not a safety protection board so this is this doesn't cut off the battery pack itself looks like our two halves are separated right down the middle now thank you to you guys on youtube as well as a few people on the facebook group who've already taken these apart they've identified that not every bolt needs to be removed to take the cell modules out of the housing so that will save me some time so i'm going to flip this over and let's take a look at which bolts look like they go all the way through and which ones might just be for the plastic housing there's a threaded stud right here so this bolt is going to go all the way through and screwed to the housing but this bolt has no nut on the back side right there so this one doesn't come out this will be just used to hold together the plastic housing [Applause] looks like there's even feels like aluminum let's see yeah so they have an aluminum sleeve inside the plastic [Music] that should be all of them let's go ahead and lift it out see if we can lift it up now up here oh i see that i missed a couple of phillips screws there we go well fit together like a puzzle so in the middle of this module it looks like there's some plastic covers here so let's go ahead and pop them out okay so we're seeing one side of the cells here these wires come over here to a thermistor so that's going to tell us the temperature you can see down into the cells and over here we're seeing half the cells that's neat how they're oriented okay let's flip it over so that's all of four millivolts difference between them it's pretty clear at this point that you don't have to pull it apart this far uh you could leave this inside the tray with the sides attached but i'm interested in just how far we can take this apart so let's keep going i got the two copper bars off now i'm going to go through and remove these and this little temperature sensor it just pulls out from in between the cells and these are just phillips head screws so take them off and then remove these little copper bars on each side well that was pretty neat these series connections can pop out like that so now these are going to be the cell tabs in the interest of fun let's keep going and we'll take these bolts out now the packs might expand and i might not be able to get them back together but i'm willing to do it just because i'm so curious as to see exactly how they're built okay here we go yep quite a bit of expansion there it looks like all the connections are being made right here in the middle inside i can see two cells so that means that this is a 4p so there's two cells here and two cells here all in parallel to this so if anybody wants to look that up that means that i would guess these are 15 amp hour cells if you have a unique application where you want to take the individual cells apart and then reorient them into your own thing you should be able to do that you should be able to come in here and just pry up the tab and that will break the spot weld looks like that whole thing can come up so all four cells have been paralleled here in the middle so we have a negative and a positive so we have a threaded nut in there so it makes this all all these cell tabs are welded to this copper plate on both sides giving you a threaded nut to connect to so right now these get series connected so positive to negative positive to negative positive negative and then opposite on the other side potentially you might be able to rotate this whole upper pack around so if you oriented this whole thing around so i'm taking this cell group and i'm rotating it and it looks like it probably would work just like that so right here i just flipped the top one but you could see how that could just uh parallel right there so you could flip every other one and do one parallel connection down the whole line you could do that on each side so right here you could parallel these and all these silver tabs would line up making all the parallels so you could turn this whole thing into one giant cell pack this would be what would that be about one and a half kilowatt hours of a 1s and that's so neat right now i'm just compressing the cells that i can get them back into the case when i saw that you could flip every other cell around i got very excited and i wasn't making a whole lot of comprehensive sense trying to explain it so i'm going to refilm that and put it up at the end of the video with an excel spreadsheet so stick around to the end if you want to see why i think turning the cells around makes a lot more sense if you're going to use these modules we got the case back together exactly the way it was the next thing to do is focus on attaching the bms so at this point all you had to do was remove the lid and the bmu unit which isn't necessary but these are the voltage sense wires which go to every positive of the cells we need to get to these wires and then attach the bms leads to it when we go to attach all these wires we don't want the wires attached to the bms just in case we short something and this is clearly showing which one is the main negative and the main positive i'm going to start by cutting away this extra sheath all right that's as far as we need to go with it i don't need to take off any more than that because at this point that will allow me to take this plastic loom off there we go so with that out of the way we now see this is a temperature sensor and we don't need the temperature sensor so that's going to go away with this plug which we don't need but all these other wires they go down to the voltage sense so we're probably going to have a few that we don't need but most of these we will need is something to watch out for you don't want to just go ahead and cut this whole thing because you'll wind up shorting these wires out now because these wires run down to a ring terminal directly on the tab what will happen is you'll burn out the wire somewhere between here and there and then you'll have to take this whole module out to replace it so i'm not going to do this anything fancy here i'm just pulling them off one at a time and there we go now i'll take the temperature sensor off with the plug we don't need that and we're left with all these wires coming out and it looks great now this bms wiring harness this is all 24 gauge it says 24 on the wire this stuff looks a little bit thicker so it might be 22 gauge so we need to figure out which wire goes to which so what i'm going to do is i'm going to jam the main positive in here that way the negative is free and we have 26.7 but now this hand is free so what i'm going to do is check these individual leads until i find the 26.7 that way i know that i have found the main negative wire that goes all the way over to here i happen to remember that when i took apart this module and checked the back side there were two wires leading to the screw that was the main negative and i just went through and checked every single one of them and it was these two white wires showing 26.7 and the blue wire is also showing the same 26.7 so they're both connected to the same ring terminal back there so in the interest of just keeping kind of things organized what i'm going to do is use the white wire as the main negative so since i don't need the blue wire i'll cut the blue wire down a little bit and then just tape it over so now i go back to my bms harness and i have the main black wire right here this is the main negative so it needs to attach to the main negative of the lg server pack so i'm going to take this white one and connect these two together let's see if i can trim it with a 20. yep this can be a very time consuming process doing all this wiring to try to make it quicker for myself i picked up these low melt solder connections and i picked up a big pack of them and i'll leave a affiliate link to these in the description below now i should be able to just use a heat gun and have that the next wire in the bms harness is going to be this one now this needs to connect to the positive side of cell number one this is the negative of cell number one so what we need to do is switch our probes over now we'll jam in the negative probe just get in there tight and now with the positive probe we're going to go through and check these until we can find one that reads about 3.8 which is about what we're at right now but it'll be somewhere between 3 and 4.2 so we're going to go through and find one that reads 3.8 and we know that's the positive of the first cell here it is so it's the brown one so here's our brown wire that's going to be the positive of the first cell i'm going to take this little heat shrink solder connection and i'm going to slip it on down past the end now we'll take the bms harness we've already done the black wire which is the main negative now we'll take the second wire in the harness we'll slide it down through our fingers until we reach the end now we need to strip some of this insulation we're now going to twist these together now i'll slide the heat shrink down so we'll slide this down until the solder so now the solder is over the middle of that twisted connection and now we heat it [Music] and you could actually see that that solder flow inside the wires now we'll go back to this one and we'll give this a little tug now it's cooled off yeah it's not coming apart so that's the procedure it's boring but that's what we need to do i notice the main positive of this module also has two wires we have 26.7 on the purple and 26.7 on the red with a white stripe now since i already have a red one over here i'll fold back this red one with a white stripe and we'll keep just the purple this tessa loom tape and i'll leave a link to this in the description below if you want to get some now i'm not going to tape up more of this until i have the other side done because i'll probably tape them together but now we've protected all the splices leading back to the system now we just have the other half to do at this point i've cut the plug off and we have all the wires exposed i'm going to temporarily put this fuse back in place that doesn't have to be on here very tight so i'll just put it on by hand now if you remember our last reading was 26.7 so the next reading should be about 30 volts something like that so the brown one is the next one over that we need so again we'll just slip on our heat shrink so we're going to go through and check these one at a time make sure we haven't crossed anything 3.8 7.6 so we're just looking to make sure we go up by 3.8 every time without skipping any numbers make sure we haven't crossed our leads anywhere this is important to do every time you make a new wiring harness before you plug this into the bms because if something's wrong you could short the bms so it looks like we're all good so now this is good to go move my board out of the way now the bms has two things on here we have a charlie minus and over here we have a bravo minus now the bravo is for the battery side so this needs to go to these this copper bar right here so i can put it in a ring terminal and put it on that post and then this is the side where we take off to all of our loads and charge controllers now i'm going to cram this bms kind of down in this area so that it'll be hidden by the cover and it'll be nice that way the output of this whole block is already protected now to put it in there i think i'm going to cut this piece of plastic from the bmu because it already lines up well for these two screw holes and i'll use that as part of securing this so i'm going to start nibbling away i'm going to take away some of this plastic and i'm going to be checking the fit as i go so i've been cutting this up and i think i'm on to something here as far as mounting this bms but i'm finding that this little threaded stud back here is getting in my way now i don't need that anymore that was part of holding in the end of the bmu that i just cut off so i'm gonna see if i can break that off i put the bolt back in place now underneath is this see a couple of little spot welds there we go there's the the nut well on the inside so i think that'll probably work so i'm going to tape the bms on here some more make sure it's nice and rigid and not going to go anywhere and then i'll cr i have to crimp on a splice to come over here to this lug for the b minus and this lug can just come out the way it is so i melted the plastic a little bit next time i'm going to have to do all this outside of the plastic case i i had already taped this up and i just didn't think it was gonna melt that so i put some zip ties and heat shrink on there as a strain relief so now we can tug on this you know not go anywhere so on this bms there are two temperature sensors so i'm going to fish the temperature sensors down in between the cells so here's the fuse and it gets secured with these serrated flanged head nuts this is the welded stud that i broke off from the bottom and it happens to be the same thread size so i'm going to use a little loctite and use this to charge it i'm going to be using this boost converter so i'm going to connect this anderson plug to it because that is what i currently have on the boost converter i mentioned in a previous video i have a collection of different plugs going on so over here we'll just throw this on so i'm pulling power off of my big battery bank to this boost converter i have it set to 10 amps and 58.8 which would be fully charged for this battery pack so we're going into the bms and right to the positive post over here so let's go ahead and turn it on so 10.5 amps on that side we're coming in i'm borrowing the bluetooth dongle from my other battery because uh battery hookup was sold out of the bluetooth dongles for this so let me borrow my wife's phone because that's an apple and we'll be able to check what the bms is doing here's the app open connected to the bluetooth dongle and the bms so we can see what the cells are doing okay it's been charging for a while and one cell is now balancing so the way that this bms is pre-configured from the factory is it'll start balancing when you're in a charging cycle and when you have more than a 30 millivolt difference so you see when it pops over 30 millivolts that's when it's balancing and then when it drops below 30 millivolts it stops balancing again and this boost converter is not getting hot i can touch it i do have the fan running but it doesn't get hot when you're really close to the same voltage and right now my battery pack is at 53 volts you can see right there and i'm charging and it's currently at 55.7 yep 55.8 so the two voltages are very close to each other so there's not a whole lot of dissipated heat when you have a wider range then it gets hot we're showing 58.83 on the bms and our highest cell is 4.224 now it's important to note that this is actually fairly common a lot of bms's won't shut down until you hit 4.25 volts this is 4.22 right now so we haven't actually hit the bms cut off and they allow that little bit extra for that balancing top end terrific we're ready to start the discharge test we have the battery the bms is still hooked up to the bluetooth dongle the app on the phone we have our watt meter this is going to tell us how many watt hours we pull if you're curious how i built this i have a video on it then we have an inverter and the inverter is connected to two space heaters and we have a few watt hours left over from the last time we use this so i'm going to reset this and i'm just grabbing the closest thing that's small we press and hold this little button all right we're completely zeroed out on everything we have 58.7 volts uh the switch is on so we're using the battery to power this meter we're currently connected here and here so let's go ahead and turn it on we'll start with the switch right there uh oh oh nope i'm sorry okay i was worried that i just fried my inverter i forgot that i added a circuit breaker on the back side of my meter all right so we turned the circuit breaker on turn that on that was close and the space heaters are now on all right all right let's see what we're doing the cells are fairly well balanced if i was to allow this more time to balance out it could get them a little bit better but this will probably take i'm guessing around four hours to do the discharge so we'll find out there is an hour meter here so we'll be able to see exactly how long it took five hours would be the ideal time frame for a discharge test but we'll see how many kilowatt hours we get out of this battery all right we're at the three hour mark and we've done 1.67 kilowatt hours it's only been 20 minutes since i last checked and what's interesting is when you get down towards the bottom of the voltage curve how much more deviation you start to have between the cells we're now at 170 millivolt delta between the highest and lowest and so you start to see which cell groups are the weakest when you get into this down at the bottom and that's because we top balance the cells or the bms right here is programmed to top balance and so then when you get towards the bottom you start to find out which cells are the weaker ones and so we already have the weakest cell here is at 3.3 so when i put this into service in my own home that means that i'm going to be using these numbers uh 34 amp hours for the programming so i'm going to assume that i have a usable 1.8 kilowatt hours out of this pack now i'm going to keep the test going and find out what our total is but i don't want the weakest cell group going under 3.3 and it only uh it was actually the bms that shut off you see the under voltage protection there so our grand total is 1.93 kilowatt hours or 36.2 amp hours we are fully charged once again the cells are a little bit more balanced what i've been doing is a few short cycles right at the top end between 4 volts and 4.2 volts per cell and so we've been able to balance out better all right so at this point we're done charging this we're going to try one more discharge test the max oak blue eddy so i'm going to use this as a load because it has an mppt input right here so anything from 16 to 60 volts and this barrel plug fits in right here so this wire came with the max oak all right everything is zeroed out so i'm going to go ahead and flip it the lights just clipped on you hear the fan for the blue eddy and it'll ramp itself up now we're discharging and we can see that over here says 412 watts this says 419 watts and this says 390 watts so this is reading a little bit low we've now verified it with two other meters all right so it looks like the math says that whatever this is reading i have to multiply by 1.07 what that tells me is the last time that i got 1.93 out of this battery if i multiply that i get just a hair over two kilowatt hours out of this pack so that would be a little bit more reasonable exactly what they're advertised as they're advertised between two and two point two kilowatt hours well we finally shut off and the alarm is under voltage protection so that would would have been 2.8 and now we're just bouncing a little bit back so the bms shut itself off at 2.8 volts for the lowest cell we got 1.95 kilowatt hours so we did just a little bit better but nothing to write home about after running two tests i think it's fair to say that these are two kilowatt hour modules that means they have two-thirds of the original capacity left in them let's run through some numbers together as built as you see it in the video i bought two of these batteries from battery hookup i used my discount code david paz and i paid the 350 for shipping now these worked out to 230 dollars per kilowatt hour as you see it in the video now let's go back to something that i did during the teardown when i was showing that you could rotate the cells and parallel the cell groups together i got really excited the reason is that we could actually put these together so this giant module becomes a 2s 7p and i would regroup all of these to be parallel and all of these to be parallel and that would make it a 2s look at cell number 1 through 7. you see how they vary well all of those would be averaged out at this point if you paralleled these then you get more capacity overall and you'd average out this cell group so that's really exciting because then you could stack seven of these modules together to create a 14s battery it would be then a 14 kilowatt hour battery and you could use one giant bms like this to compare it in size to the 100 amp bms here you go they're quite a bit different in size but you could purchase one large one it would be mounted externally and you would run the voltage sense wires with ring terminals straight off from the posts now when you do it that way you're saving a little bit on shipping per module because it's still a fixed 350 dollars and it will come out to 143 dollars per kilowatt hour now that's a savings of 38 percent over the way that i built it here in this video if i did this again knowing what i know now i would go that way i think this would be really well suited for a home backup system where your house is on the grid most of the time 99 of the time but every so often you get power outages and this could be hooked up to an automatic transfer switch and not probably built into the inverter but once in a while you have a power outage and this can then uh back that up i think that's a really good situation for these however if you are completely off grid and fully charging them with solar every day and fully discharging them with every night that's a full cycle i don't think you're going to get more than two years out of these they're pretty well degraded and i don't think they're best situated for that for that daily hard cycling well please let me know in the comments below if you like the video if you like the longer format i really try to answer all these questions i keep getting over and over about wiring the bms and how to do capacity testing so i hope this video helps you all out thank you so much like subscribe comment and share really does help the channel thank you you

Channel: DavidPoz

Views: 214,019

Rating: 4.9448276 out of 5

Keywords: battery, battery hookup, LG Chem, LG, server rack, lithium, li-ion, li-nmc, home, backup, off grid, off-grid, solar, 48v, 51.8v, DC, 14s, 2.2kwh, kwh, capacity test, testing, capacity, wh

Id: 2tbHFdqng5A

Length: 36min 11sec (2171 seconds)

Published: Sat Dec 05 2020