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all right let's talk about batteries new load a whole palette of 21 700 cells so 2170s that's what tesla calls them right but check these beauties out these are inr 21 700 m50 l they're all brand new in the box they're naked so they don't have a wrapper right so these are because they were from a car manufacturer uh that decided to sell them and we ended up with them and so now here they are these are premium cells they're brand new i think they have like a 20 late 2021 uh code i think where's the thing let's see um where is it where's the 2021 721 2021 there you go so these are cool but what do you do with them i know that's what you're asking yourself it's like okay but if i buy a bunch of these cells how do we use them well i'd say let's make a module i'll show you how to make a module so you can use them all right so first we start by using this holder here we got this holder for the 2170s and you measure the thing and so in the screen now here's what we drew that's the four cell holder and then this is the three cell holder right and so once you got those measurements you put them in here in this board then you can make a pcb around those right so put because it's 48 volts so basically you need 14 cells there's seven on this side and then seven on the other side so that'll do 14. so now that you have those now you can do the border outline and that's a border right there it's got corner uh rounded corners in here because that's how you know they're easier to handle that way and stuff and so after that what you can start doing then um you can start putting in uh the top layer for example there we go so that's how the top players are right so negative this is the most negative positive and then that has to connect to the negative and the the reason why we're doing that is because they're that way it's easier to whoever is going to populate this boards with battery cells uh if they're all the same so all the pluses are over here all the positives are over here and all the negatives are over here and then on this board is the exact same thing all the positives and all the negatives it would be easier if they flip around electrically to design that board but i there would be more chances of you making a mistake so that's why i like to do these board this way so that all the cells are facing the same direction so if you got the first one right then chances are that the rest of them are going to be okay right and we mark them positive and the holder itself has positive and negative and unlike other versions of these boards these ones have all the positives to the one side and all the numbers to this some of the other boards they would alternate positive the negative then positive the negative but these ones are already the way we want them to be and so this is the that's what you do right so this is what the electrical traces right so the one cell is here another cell is here and these are the interconnects between the cells and then it just jumps to the other side so the positive of the most positive of this side will connect to the most negative of this side and then it'll zigzag back and forth and then you'll have your positive then here we put a fuse in there so in order to see the fuse uh let's see multi-layer maybe that's what we have to do okay so multi-layer now it added the little holes in here and all you have to do is just measure between the pins there and then i made them long elongated like that because these sometimes when you get them they come like this like this is a perfect example see how that one's bent so if if you put like a tiny little hole that is round then you're gonna end up spending a lot of time uh straightening out all those pins and you might break those pins because they are kind of brittle and so if you put them elegated like that now you could just place it in there and it'll just be a little bit crooked it doesn't matter because you're just going to solder into that board and so that eliminates a long a lot of time when you're assembling when you're populating these boards and that's why these are elongated that way so now we have our little 30 pin connector over here there's the fuse right here and then these are the mounting screws the mounting brackets or whatever and then you do the opposite side and the opposite side uh it's almost the same but it'll you need to add a few more things like now all the traces you see this the 14 uh traces for the balance leads so the basically every single one interconnect the two ends and then every single interconnect has to be connected in there and so that's how we did this um how is that one connected that one is connected oh this one's not connected there that one's connected over here so so these might seem like they're not connected but they are because that remember connects up to this one and since this one is connected here then that's how it is so you have to do every single cell in interconnect right and so that's what we're doing half of those are going across and then half of those are going just down this route right here so that is kind of self-explanatory if you know what we're doing here then you connect the top uh bottom actually this is not that important bottom paste and top paste this is the areas of the board that need to be exposed the copper cannot be painted over right because like this is copper trays but it's going to be painted over to whatever color you decide to have the board made right and then this is paint but this is just some other like type of paint there's two different types of paint and though and if you want to see what it looks like you do the 3d render thing here and then that's what it shows it to you and you can change it here this is the blue color that is but you know a lot of the times they're going to be green boards or you can change the color over here to the black one i usually like black but black it's uh you can't really see the traces i think blue is one of the best ones that still allowed you to see where the traces are at and see what's exposed oh by the way here when you're gonna do this i'm missing a part of where it needs to be exposed copper exposed copper so that it's easier to solder it'll make the difference between it takes in you like a minute minute and a half maybe two minutes to solder this to like it takes 30 seconds to solder that so let's add that right now because i kind of forgot about it so what we have to do is put it on the bottom see here we go so the bottom this this uh pink stuff is not across so what you do is you go over here and then you add it there there we go and then you added another one over here and now when you render this again on the top side is fine but on the bottom you see that you see how those now are exposed copper so now when you're gonna solder that in there it's gonna be so much easier and it makes sense um other than that i think i just need to put some instructions in the back here uh letting people know that they're going to put these together that all the cells have to be exactly the same uh voltage and just like little things like that so let's add that in there there it is let's put it together you're gonna need you're gonna need holders right uh two for the four and two for the three 10 amp fuse 30 pin idc connector dash the the little key to the outside even though in the thing i have it on the inside it doesn't really matter i just i did another board and already started this way so it's not as long as you do them all the same it's not that critical how you do it they just have to match then we start your thing 400 degrees make sure it's hot enough clean the tip and then you start soldering this guy right here all right so now that we have those two now we just do these and you gotta pay attention to the positive and negative these ones have the positive on the one side right so here we go here we go and now it's fully put together now we got to do this five more times to build our little thing and here we go we just did it five more times this one goes right on top here and then this guy goes in here okay now we gotta populate it with batteries so the cells come in the original factory box it comes with this desiccant and this is very important because it will remove any of the uh any moisture that will that can get inside this box and because these are naked they're not naked they're they're unwrapped so they're still in the steel any moisture will create some corrosion in the cells okay another thing to point out here is that these are very very powerful cells and that you could very easily short them so you have to be very very careful we order some uh isolators and wraps and we are gonna need seven eight cells so we're gonna wrap 70 cells so again these are very very powerful cells this is what's in my ribbon this is what's on the model three now what we're going to do i recommend you taking one at a time because if you touch them like this they will short out so once you take them out you take one of these isolators you stick it in the front right and these have adhesive and then you take one of these little wrappers put them there and now what you do is you hit it with the gun all right okay there's the first one now we gotta do 69 more okay now is time to populate the cells into the boards first things you got to do you got to isolate the bottom of this board because this is all exposed and if you sit this with batteries on a metallic surface you're going to burn everything it's going to melt in them so what you need is these little plastic uh feet that isolate the bottom of this board so that you don't short it out okay second when you populate this is very helpful if you are checking these are brand new cells so there should all be exactly at the same voltage but just in case sometimes you get some that are uh off right just a bit off of spec and so you want to catch on before you build this giant battery module you want to know and so one quick easy way to do that is by using a couple of these uh vg 8s and i think we sell these uh this little connector on uh and so it allows just to connect it onto the ribbon cable here and then as you're mounting the cells you'll be able to see the actual voltage here within you can reject anything that's out of spec so let's try that right now we'll put the first one and by by the way the first cell should always be the most negative so this is the cell here one two three four five six seven eight nine 10 11 12 13 14. this is a 14 s pack so this is a positive side of the cell right the one that's got the little green and that goes to the inside because that's where all the positives are so uh i think you need at least two cells to uh power boom yeah so at least two cells to power that up they're exactly at 3.5 volts uh you have to change this to battery type lithium ion back boom there we go so now it shows you that they're very uh about 30 to 40 percent state of charge because that's what these ship right the factory ships them at that so there's a one millivolt zero millivolts difference between those two cells so yeah they're perfectly balanced uh those two anyways here's the third one oh okay this one's about 25 millivolts difference so it's a tiny bit different 24 but still you know that's almost perfect uh the fourth one fifth one sixth one seventh uh the biggest difference between all of these right here are 11 millivolts so they are very very well balanced let's do uh this one so it needs two to uh do the next one there we go now the second one same thing 16 millivolts difference between that will change the battery type to lithium ion oh 32 29 they're kind of evening out that's the first module so now you just do that times five all right after you've done that now you just gotta make sure that they're all exactly the same voltage all of these modules right because you're going to connect them now in parallel each one of these ones is his own battery uh 14s 1p right so as soon as you put another one in here now that becomes 2p 14 s2p and so if there's too much difference between the one module there's going to be a lot of like there's going to be a lot of energy transfer and you don't want that you want to be able to control that right so because these are all new brand new cells then there's none of that i actually already checked just in case so you should be fine there we go look at that no sparks obviously because they are the same voltage now you just put the uh standoffs these uh they just need to be finger tight don't over tighten them because you can break stuff and the only ones that are gonna be transmitting power are these the front ones the back ones are just there for mechanical to hold these they serve dual purpose here we go the third one now even if you did make a mistake here and had it backwards these all have a fuse in here so uh you would be safe i mean it would make some sparks but the fuse right here would blow and uh before you melt it and you know burn a bunch of stuff right so then you could just replace it and uh you have learned a valuable lesson and then you could recover from that very easily okay so those two are a bit too close there that can be problematic i guess now what's the voltage in here you know you could touch it you won't get shocked but if your hands are extra sweaty for example you might be able to feel that it's right there at the threshold where you might feel stuff or not the nominal is 48 volts on this one right but the actual voltage right now let's see 50. that's 50 volts in there so as long as your hands are dry you shouldn't feel any of that but if yeah you spit on them or you you know you touch them with your elbow and it's sweaty you will feel that a little tingly sensation so be careful all right so here we go this is our battery pack fully assembled right now there is uh i am building a uh bms module that's gonna go on top of this is a board that's why it's got these over here but for now to charge it and test this we're just going to use these guys here just to monitor each cell group each of the 14 cell groups right they're represented right here and what we're going to do is we are going to charge i have i made this cable that just goes and clamps in there on the uh standoffs there right um and so what we're going to do is going to use a variable power variable voltage and power uh power supply to charge it so fully charge this uh 14 times 4.2 58.8 so we're gonna set this to 58.8 um 58.5 and we like that's what we're going to do oh we're not going to be able to do it because this only goes to 50.

all right so now we're back here and now we put a uh power supply that goes all the way to 50 80 volts or whatever so now i don't like it it's not as good as the other one because you can't set the power level only the voltage so we're gonna set it at 50 which is the same as the battery and then raise it up because i don't want this to uh go bad there we go let's see we're gonna measure uh amperage here it's doing at the max this is only a six amp power supply and it's doing six amps all right so a few hours later and it's at 58.3 uh is no longer putting almost uh yeah no power in there the these guys have done a very good job at balancing the entirety 20 millimeter millivolts difference on that 12 milli volts 13 millivolts difference there so these this is pretty balanced as it is now we can test it uh put a load in there okay so now we have the load here uh going through the shunt it's fully charged at 58 volts we're going through these two 2000 watt grid inverter all right here we go i just set it up to a thousand watts this thing i think is capable of 2 000 watts but i set it to a thousand watts because that'll do 23 amps uh about 25 amps that's what you should be able to get out of this five amps per board right so 5 10 15 20 25 uh 25 amps which means that it will load each one of these contacts here with 5 amps i think that's the maximum that we those are able to support due to the temperature now the batteries are not sagging too much all right and here is the thermal camera the thermal view of how those boards are doing each one of those little hot spots there are the connections right so the the little terminals on each cell and those are just basically press fit so they are limited by the amount of pressure that each one of those has uh and so that's why that's the weak link there even though those cells are capable of much more than five amps we're limiting to five amps here on this application here all right at 20 82 percent uh the temperature is at 53 c so ambient temperature is about 33 i think 32 about 20 degrees celsius above ambient that's not bad all right so this battery is done we were able to remove about 90 i think there's three amp hours left in there because uh this thing has a 45 volt low voltage cutoff so this one at you know when it's completely depleted is uh when it's at three volts it's 45. so that's why it is not able to remove just that last like 10 of the battery right so if you're gonna build this battery they do work with this but it's a bit close there right but other than that a 14 s 48 volt system like this could work with pretty much any 48 volt inverters and so you just a lot of them you have the ability to adjust the voltage and stuff um yeah this is a 1.2 kilowatt hour battery pack right here if you put 10 of these boards in those same stack then you have twice that right so almost two and a half kilowatt uh they're very very very compact and very light compared to others um this is this the an equivalent to like a 12 volt battery 100 amp hours right it's not it's a 48 volt 25 amp hour right uh but it does the same amount of energy so that gives you an example of the the the difference right and it's about the size of my hand and it's about half the weight of like a 100 amp hour battery uh 12 volts right so there you go i have the list of all the components i have links where you can buy the batteries or you can buy you know the fuses all the connectors ribbon cable stuff in the description of this video i want to thank pcbway for being a sponsor of this video and if you need to buy these boards you can go and follow the link and get all those boards there and all your board needs they make and they deliver boards really quickly and they give you a bunch of different abilities to make all kinds of cool projects there so thank you for watching this video we'll see you guys on the next one bye all right before i go completely i am working on a bms module for this one particular board it's going to look like that and it's going to use some really affordable 48 volt uh bms's that i've found uh so that's coming up soon uh i'll just upload this thing and add it to the description of the video once it's done okay thank you bye.

5 thoughts on “Finally – 48v 21700 cell modules”
  1. Avataaar/Circle Created with python_avatars Skeptic Fucker says:

    36-42v better or worse?

  2. Avataaar/Circle Created with python_avatars Gann Dolph says:

    Nice haul Jehu – great you guys can make these kind of cells available!

    However, the 21700s still seem to command an enormous premium over 18650's — in terms of $$$ per kilowatts hour. I guess they make sense for someone who needs the absolute maximum power density/ minimal volume and weight..

  3. Avataaar/Circle Created with python_avatars Grand Solar Minimum Solutions says:


  4. Avataaar/Circle Created with python_avatars Charles Ostendorf says:

    No link to buy them ?

  5. Avataaar/Circle Created with python_avatars Ajay Naidu says:


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