Good afternoon, all today i'm going to look at this and this. So this is a bms i bought it on ebay. I think it was 21 pounds or something like that. It's a daily bms, so dongguan, daily electronics, co-limited uh.

This is a life po. For eight s, eight cells in series 24 volts bms discharge. Current 20 amps charge current 10 amps with balance, so this has built in cell balancing not sure how effective that's going to be, and it has a common port, and i have no idea what that means. Um, this is the nine way balance charge, not balanced charge, but balancing lead.

Well, it's also a detecting lead because it detects the voltages of each of the eight cells and if any one of them is lower than the minimum it'll cut off the discharging atmosphere. If any one of them is higher than the maximum it'll cut off the charging mosfet um, this is not a jst xh. It looks like two millimeter pitch, so is that a jst ph i'll check? Yes, ph appears to be the two millimeter pitch, so i'm going to plug that into here now the only uh thing i can think of for common port is this uh. You can see from my dmm that black on the balance charge lead is well, let's put it on continuity, and so that's beeping is connected to the same point as blue on the high current side and that's b minus that's battery negative well.

This, of course, is also battery negative i'll. Stop that beeping, let's put it on ohms um, so these two are connected together internally from there across to there. It seems now what about continuity between black and blue um. Well, it's quite high resistance.

16 meg ohms uh. We could try the other way around. I guess yes, let's do that. Actually i'll swap them on my dmm.

That's probably easier so tell the way around. Oh that's interesting! That's infinity! Megomes uh! Try that in diode setting, so that's ol one way around. Let's put it other way around and it's old, so yeah definitely no conductivity between these two wires, although one way around there is a measurable resistance uh as against the other way around. So what i really want to do is switch on the mosfets in here to allow charging well.

That will be from pack negative through to battery negative so from black to blue and also switch on the mosfets for discharging that'll, be from battery negative from blue through to black and out to the load. And i think the only way i'm going to be able to do that is to connect all nine of these leads uh, i'm gon na solder them to some little solder tags and connect them to the eight cells of my lithium ion phosphate bike battery. I think i've got a funny feeling this is going to be powered from the balance lead and i think if it sees a sensible voltage between each of these cables, then it will allow the mosfets to turn on here and therefore a circuit to be uh or Current to flow from p minus to b minus and also in the other direction. If now, let's get this right, if one of these cells is too high, then it's going to turn off charging, which means it'll turn off the mosfet from p minus to b minus.

If any one of these cells go below goes below the minimum, it'll turn off, discharging that's from b minus to p minus. So let's get soldering to my iron-on solder, nine of these little solder tags onto these wires and get them attached to my battery so tinning. The tag tinning a wire ah stay there, uh making sure we've got a piece of heat shrink on there, soldering the wire to the tag and sliding the heat shrink up over that times. Nine right here are the nine wires with the solder tags.

I'll just do the heat shrinking and come back when that's all done right, i don't need the high current connections uh just at the moment, so i'm going to take those off being careful not to bridge this wrench or spanner across the terminals. Now, to make this a 24 volt pack, i've got to connect the positive point here to the negative point here: um and then my outer positive and negative will be these two. So let's get this bolt through there and into there try and do that up such that it doesn't short anything out. Okay, tighten that up and now it's simply a case of getting these nine ring terminals onto my little balance, charge studs there all around the pack in the correct sequence, most negative! Is that point there so i'll start with the black and work my way through right.

Halfway through a little more than halfway through that one goes on there, which is slightly awkward to get to i'm biasing these upwards, so that all the wires gon na come off the top. Let's tighten that one up again watching for shorts. Okay, next wire! Is this one which is wire number eight that goes right over to this side, where's most positive? That's there! That's right with the black balance charge lead with these balance. I want these ones as well, so that i can put my little measuring device on there, and these ones, of course, are for the bms.

So let's put that one on there tighten it up and finally, most positive is this one which goes on there? If i can undo that nut, which i can't very easily so let's get some voltage measurements off, this balanced charge lead first cell 3.3, second cell 6.6, third cell 10, fourth cell 13, 16.6, 20, volts 23, volts and 26 volts, so they're all in the correct sequence. Let's plug in the bms right, let's plug it in i've, got my dmm on diode across this across the black and blue and when i plugged this in, it should provide a continuity, get this the right way around across these output mosfet switches. So, let's give that a try, and yes it does - that goes to zero, indicating closed circuit there. Let's put that there now.

Does this work in both directions so i'll turn these around and yes, it does and in continuity mode we get a beep. So this has turned on because it can see eight voltages across this nine-way cable, which are all within spec, because these have all settled down. I think this one's a lot more charged than this one, this one actually hasn't been charged since it came out of the bicycle this one i did put on charge and take it all to the top, but that does seem to work. There are no lights on here, which is a a bit of a shame now.

This should also be doing its balancing um center balancing is very ineffective on lithium ion phosphate, because the curve comes down quite sharply and it's very flat in the middle so to trans position, all the centers to match is virtually impossible, but it does. It has balancing. I could watch that taking place on these, but it it's highly likely that this is going to balance incredibly slowly. One thing i could try is detaching.

One of these balance leads. Let's actually do the one here next to the meter: let's just loosen it because then it should see strange voltages which it can't make any sense of. Let's take that nut off yes, and that goes to ol, so open circuit effectively. The bms put that back on and, yes, it closes the switch.

So let the voltage on here drift to something that isn't within spec. It goes open circuit, put it back on the pack and it goes back to zero volt drop across this switch excellent. So i put a little battery checker on these four cells with the five-way balance, lead yeah, nothing to see there really they're all 3.34. I don't think that's by virtue of the brilliance of this balancing circuit in the bms.

I think they've just settled to that um. What i really need to get is my five plus four-way connector to a nine-way, and then i can see all the cell voltages on this little checker. Now here's the question when i charge this pack from solar and i'm going to use a 60 cell panel because they have an open circuit voltage of about 30 volts. When this connects the solar panel to this pack, which is a about 26 volts.

The panel voltage will, of course, immediately pull down. Do i need a solar charge controller? Well, i don't think i do because if you take the simplest form of charge controller, which is pulse width modulation, when the battery pack is below its target voltage, the mosfet for charging is just on 100 and that will be the equivalent of this switch in the Bms being on so i think i can take my solar panel and connect it directly across positive of this pack, which i think is there yeah. That's right because that's the link between the two pack halves and um blue will go to pack negative and then i'll connect the other end of the solar panel, the negative end of the solar panel to p minus black and then, when the first of these eight Cells reaches top, which is a voltage beyond which this doesn't like 3.65 volts for lithium-ion phosphate. This should switch the mosfet off the battery cell voltage will settle down.

This will switch on again and will effectively work a bit like a slow pulse width. Modulation, it'll just switch on and off until um, well by virtue of the balancing in here all the cells reach top. But even then this will just continue to connect when this pack voltage is low and dis, actually not the pack voltage. But when one of the cell voltages well, when not any of the cell voltages is over the 3.65, this will connect and then we'll disconnect when the first of the eight cells goes over 3.65.

So i don't think i need a charge controller. I think i can connect it straight to the bms and charge this pack that'll be the next thing i do, but for this video, that's all i really wanted to do just get this bms connected understand how it works and get ready for the next stage, which Is to solar charge this pack, so for the moment, cheerio.