Hello today! I'm going to build a battery using these cells. I've got eight cells here. They're lithium-ion phosphate. l I F E p04 Um, they're 32 650s.

Sometimes they're called 32 700 depends how you measure the length. I suppose 32 millimeters diameter and 65 millimeters in length. That probably doesn't include the two screw studs. but I'm going to assemble these into some frames which are these things which have a 32 millimeter diameter hole and little stops here to stop the cell when you place it into the hole.

Sometimes these tight, sometimes they're loose. There's slight variation in the diameter of these cells, but uh yeah, let's start to assemble my battery pack. So let's start with one of these holders. Now these are I can get them apart.

They are two cells little holders and they've got these little dovetail uh connectors and so you can build these into however big an array you want. I'm going to do a 4x2 array and I'm going to put four cells in series but with two cells in parallel so it's a 4S 2p battery. Uh, so I need to connect that like that So that's what I need for one end and then I'm going to need the same thing again for the other end. and I've just realized I've done them slightly differently.

It probably doesn't matter, these are all in a line and these have been done in a square formation. But never mind, that's fine. So let's start populating one of these ends with cells. Now these are male male cells.

They've got a male I think it's M4 threaded stud on each end a lot of the ones you see on AliExpress In fact, I think all the ones I've seen so far have a female threaded insert, a hex nut type thing welded on the positive end and then a male on the negative. and the idea is that you screw them in long lines and then assemble these cells into big frames to make your series. But I'm not going to do it like that I'm going to do it a different way. So I wanted mail to mail.

um I'm going to put some details in the description below this video where I got these cells. it was a company called. well they're called Aerotech Projects Limited and they have a website. um which is Lithium Battery Shop dot UK So yes, I'll put the details of um, that place I actually went there.

they're in a little village outside. Ipswich I Went there to pick up these cells I Thought it'd be a nice little drive up to Icharidge. Quite a lock drive, but it was worth it. and I do have um 40 of these cells slightly more actually because ultimately I intend to build an eight by five array.

But in this video, I'm just going to build a very simple 4S 2p. So positive is this assembly here? negative is just flat. so let's put a couple of positives face down at this end and then of course the next cell. I Need the positives facing up like so and then positives down for this one and then positives up here and then I'll put the other end cap on now like I say some of these are an interference fit, but some of them are a bit loose so these end caps don't actually hold themselves on very well.

I'm going to turn it round uh, that way so that my dovetails are both on this side and act as little feet so the battery can sit down like that. So that's it. I've got my positives negatives. Positives: uh oh, is that the right we run? Yeah, that's a negative side.

The positive is on that side. so that's the array of cells now. I need some means of connecting them together and for that, I'm going to use these printed circuit boards which I made a little while back. Um, so this: these two holes will connect my two cells in parallel and then these two will connect my negatives here to my positive.

So I can place that one on there and similarly place that one on there. and then I have a whole set of washers and nuts here. Uh, which I will place down on here. tighten them up and that's um, that's these two linked and then on the other side, I'll link across the middle here.

now. What I absolutely cannot do is Place Another of these boards in that position because that would create a dead short around there and these cells would discharge rather quickly. I Had an interesting chat with Um Gary it was at um, that's a bit dodgy um, Lithium Batteryshop.uk and he was saying that these cells are of such a size that actually if you short them, they don't have enough. and I mean they will get hot and they will vent, but they don't have enough energy in them to get so hot that they would combust, so they're considered fairly safe.

This particular 6 amp hour size Six thousand milliamp hours for things like Transportation shipping them um, you know, between countries and um, just static batteries in packages simply because they're unlikely to get to that combustion stage, right? These M4 nuts require a seven mil uh nut spinner, so I'll do those up finger tight and then put washers and nuts on this side like so. And he was telling me all about the phase change properties of these cells and how the charge curve is very sharp at first and then it's very flat in the middle. So as these cells are charging, the voltage barely changes in that middle section. and then once they get charged, of course, the voltage shoots up at the end and that's the way to detect whether they're fully charged or fully discharged.

But because the voltage curve is so flat in the middle, it's very difficult to determine state of charge from the cell voltage. So again, use the nut spinner to tighten these nuts onto those boards. Now when I flip it over to the other side, I'm safe to put a board there, but definitely not. Um, across those four or those four, but across the middle? That's fine.

So these will be my most negative points. and what I'm going to have to do is put a cell a PCB a connector a bus bar if you like sticking out the side because of course I need to parallel up these two cells. And similarly, I'm going to have to have a board sticking out that side. So my ultimate positive and negatives will be on these sides.

Better get the nuts on these and then you can see the flow. Yeah, let's get the nuts on. First thing that I can show you what I'm doing. Now this idea of using printed circuit boards as cell interconnects.

Um I Haven't done that one yet. Um I've tested these up to 10 amps and there's no temperature rise on the Pcbs and this is one ounce copper so it's no special copper thickness on these boards. I do have one of these boards actually doing 20 amps now. Whether there's a temperature rise on that board, it's hard to tell because I know that the wires running into that board do get warm, so if the board's warming up, I can't tell whether it's heat transferred from the wires or heat being generated in the copper.

So I'm going to have to do more tests on that. Oh am I a nut short yeah, appear to be missing a nut I'll have to get another one and uh, yeah, there it is. So this is my most positive connection. so I can connect onto these two holes to go to other things like BMS or um, whatever my load is and whatever my charging system is I'm not going to do anything on charging and loads in this video actually I will get a couple of light bulbs and just make sure that this works so you can see.

I've got the three boards on this side and then on the other side. I've got two boards. So let's get, um, a light bulb and check that it lights up. So this pack is uh, nominal.

3.2 times four. So that's 12.8 volts. and this is where lithium-ion phosphate is a bit nicer to work with than lithium ion Nmc, Nickel, Manganese. Cobalt Because the cell voltages on those are uh, 3.7 volts.

No one. I Think these are 3.2 volts. which means that you get when you put four in series, you get 12.8 When you put 18 series, you get 25.6 volts nominal. Now, of course, when these cells are fully charged or being charged, they will push up I Think the upper limit on these is 3.65 typically the lower limit? I'm not entirely sure something like two and a half volts.

but anyway, um, 12.8 volts nominal. So this is a 24 volt vehicle brake light bulb. for trucks. they tend to have 24 volt systems, so I should be fine putting that across these two outer connections.

So let's do that and that lights up at about half brightness. That's fine now. I'm going to also try it with this 12 volt bulb. This is a 55 watt 12 volt headlight bulb H7 type headlight bulb.

so that should light up nice and bright. In fact, I think what I'm going to do is plug that into these two, um, four millimeter banana sockets and then I can use these ends. They're actually not big enough to go under the nuts, but I can just poke them in the holes. Let me just get that lined up ready to go.

make sure that we can see that bulb resting it. There's probably not brilliant, but we'll see how we go, right? So connect it to the most positive and most negative ends of the battery. and uh, yeah, that lights up really nice and bright. So 55 Watts 12 volts that's taking oh, at least four amps, isn't it? 48 watts would be 4 amps because this is a bit more than 12 volts.

This is 12.8 volts. But yeah, that lights up at pretty much full brightness. So my battery pack seems to be fine now. my pack capacity I Got two cells in parallel, so we've got 12 amp hours.

and then if we multiply the 12 amp hours uh, by 12.8 volts, let's get a calculator. So, 12 amp hours multiplied by 12.8 volts is 153 Watt hours. Um, so approximately 150 watt hours is the capacity of this pack. Let's compare that with a couple of Power Tool batteries.

Um, these are fairly clearly smaller. These, of course, have, um, Lithium Nickel, Manganese Cobalt cells in them. So this 4 amp hour is 72 Watt hours. Uh, this 5 amp power is 90 watt hours and the pack that I've just built is 153 Watt hours.

So that was just a quick video on. A nice easy way to assemble these. uh 6 amp hour lithium ion phosphate cells. Make sure that you've got mail studs, threaded studs at each end.

Buy a few of these plastic holders, which you can get on eBay and AliExpress The PCB is slightly more difficult. you can have to make these Pcbs. The spacing between these cells is some really bizarre measurement I Think it's 34.4 millimeters. but what you can do is you can create an array of cells and then measure the distance over a wider distance and then simply divide it down to work out what this measurement is across here.

But it's not a nice neat measurement like 35 millimeters. No, it's something awkward, like 34.4 And uh yeah, you can very quickly build yourself a 12 volt Ish, it's 12.8 volts. Uh, 150 watt hour lithium-ion phosphate battery pack using essentially these three parts: the cells, the cell holders, and the Pcbs. And that's all I'm going to do in this video.

So cheerio!.