Got my NEW Headway BMS - It's finally all working!

[Sacman]

Here... let me simplify the diagrams for the power wires only.
On the left side is bikeelectric's working 48V BMS (from bikeelectric's description above).
And on the right should be the power connections to the 72V BMS (reverse side).
Again, notice the similarities in the 3 connections.

[patrickza]

how did you get the picture to be so wide? mine always are about half that size.

I have no idea. At first only the first two pictures were that wide and the third half the size. I tried re-sizing the third but that didn't help. Eventually I just dropped the quality and reloaded the picture. That worked, but I'm not sure which part did it.

Anyway, onto the other side of the BMS.

[dnmun]

ok 25, the left most pin is connected to B- by that trace going all the way around the perimeter, and they run a separate lead out to the pack B-. and the top of the shunts is over on the far right, comes up from the underside and that pin on the far right is connected to the top of the battery and then all in between in sequence.

20 ohm, 183mAa shunt current. when each of the shunts is active, .67W powerx24=16W total, so it will get hot. that is why they have the heat sink cover them i bet so other stuff doesn't have chance to touch them.

[Sacman]

Thanks for the pics showing the other side of the 72V BMS.
The layout and lables of the power wires match the ones on bikeelectric's working 48V BMS.
So it at least confirms the power wire connections.


Now on to the ballancing wires.

[Sacman]

Okay and after thoroughly studying the balance wires on bikeelectric's BMS and 48V battery pack. This is what the balance wires for the 72V BMS should look like. The balance wires connections to Cell 1 (C1), Cell 2 (C2),...etc. are labled on the battery diagram as well.

[dnmun]

i was surprised that the P- lead does not go to the pack and the B- lead go to the motor controller. that is how the signalab BMS works i think, will eventually check that, but i would expect the current from the motor to go through the shunts before it goes to the source leads on the n channel FETs, if they are, which i assume they are. wonder why they hooked it up that way, but it is obvious from that picture that the headway pack has the negative lead from the pack going to B-. curious.

[patrickza]

Hello helpful ES people. Thanks for those pictures, I've just finished a box for my BMS and will be wiring it up soon, but now for the charger.

I've got a matching plug, but now I need to wire it up. As you can see in the attached pictures there are 4 plug, two with red wires connected to them on the left and two with black wires connected on the right. Now do you think they've just used two wires to cope with the amps like they did with the BMS? Do I need to wire up all 4 plugs or will 2 be enough. The charder puts out 5 amps so I can't imagine it needs thick cables.

Any ideas, or has anyone used a charger like this from headway?

[Sacman]

It's most likely they are giving you 2 pins to run your your (+) thru the plug and likewise ... another 2 pins to run the (-). That is a 5A charger at 48V right? So that's like 5 x 48 = 240 watts going thru that plug. See what I mean? So wiring it that way would be safer and less likely to melt your plug.

You really should only have one (+) and one (-) coming from the charger. Verify that the 2 red wires are coming from the same spot on the board inside the charger, and do the same for the 2 black wires. You're going to have to do this because we can't see it even in your nice pictures. All we see is loops of black and red wire. We can't see how it connects to the board.

[patrickza]

It's most likely they are giving you 2 pins to run your your (+) thru the plug and likewise ... another 2 pins to run the (-). That is a 5A charger at 48V right? So that's like 5 x 48 = 240 watts going thru that plug. See what I mean? So wiring it that way would be safer and less likely to melt your plug.

Yeah that's what I thought, you can't tell with a voltmeter though as it reads 0 without a load. I'm running 72v though, the charger is marked 550 watts.

[reagle]

Mine came with a mating cable that ends with an IEC connector, like the one you plug int the back of PC. I am sure UL would love that
Other observations- a few large toroids are only held in place by the wires (lower right on your picture), so I epoxied them to the board a bit. They were just too wobbly. And finally, there were metal shavings in the box from the screws that hold heatsinks- may want to vacuum or blow those off before something gets shorted. Otherwise charger (at least in my case) seems to be of better asembly quality than the BMS

[patrickza]

Mine came with a mating cable that ends with an IEC connector, like the one you plug int the back of PC. I am sure would love that
Other observations- a few large toroids are only held in place by the wires (lower right on your picture), so I epoxied them to the board a bit. They were just too wobbly. And finally, there were metal shavings in the box from the screws that hold heatsinks- may want to vacuum or blow those off before something gets shorted. Otherwise charger (at least in my case) seems to be of better asembly quality than the BMS

Thanks for the info reagle. Have you used the charger yet. Mine turns the end red light on when I plug it in to the wall, then when I plug it in to the bike the other LED flashes red. Eventually this turns green and stays on, at first I though it was done at this point, but it seems like that is when balancing starts, as that's when the BMS gets warm, it cycles from about 87.0 to 88.0 at this time, turning on and off. After a while the BMS cools and voltage drops again. I imagine it's done then, but there's no way to tell other than checking the voltage and feeling the BMS. What does yours do?

[reagle]

I am shamed to admit, but my pack is still not built yet. I am sitting on cells, a bunch of variations of BMS and the charger that just arrived. When I plug in it goes red, but I am yet to check what it actually does. I plan on connecting Meduza Research's meter in series to track voltage/current/charge, plus my BMS will be gas gauging board built on TI chipset, so that will report all these things as well.

[jmygann]

I have the headway cells ... how do you get a hold of Victoria ?

[dnmun]

jg, this is the address i have for victoria: chcj55@gmail.com

travis is gonna keep importing large batches of cells i think to support his evcomponents business so he may be able to help you too.

[frodus]

travis is gonna keep importing large batches of cells i think to support his evcomponents business so he may be able to help you too.

We're importing them and will continue to do so.... boat is on its way with 2500 loose cells + packs + chargers + hardware + BMS's and I'll let everyone know when its landed. If there are any questions, come to me and ask travis@evcomponents.com and I'll get the info you need as quickly as I can.

[patrickza]

Have I got a runt cell?

I was going for a long ride today and the BMS cut out. Pack voltage was still 76.8 so I really wasn't expecting the cutout. Got back and checked the cells, and the first cell in the pack (the most negative cell) is reading 2.5v, all the rest are 3.2v.

Charged it up again, waited for it to balance and a little after taking the cells off the charger all cells read 3.5v except for the first which is on 3.3v this time. I just think it's a little unusual for it to be the very first cell, could it be something else causing this?

I do have 2 spare cells so I could swap it out, it is a fairly large amount of work though so I'm not keen. Any ideas on what could cause this, or other tests I could do?

Cheers,

Patrick

[frodus]

I'd check if that cell is even being balanced. It could be that the balance circuit on cell 1 is bad. Put it in another place and see if the problem follows the cell, or stays in cell group 1.

[patrickza]

I'd check if that cell is even being balanced. It could be that the balance circuit on cell 1 is bad. Put it in another place and see if the problem follows the cell, or stays in cell group 1.

I think you might be right, more likely the BMS than the cell. I'll most likely swap it out tomorrow and see what happens. I've mailed Victoria to see if they've had similar problems with the BMS before but no reply yet. I do have a fetcher/goodrum BMS on the way, it'll hopefully be here next week sometime so if I don't find time tomorrow I'll swap the BMS out and see if the problem persists.

I did leave the charger running with the cycle analyst on last night, and it never stopped bumping the voltage up to 87.6. Usually I turn the cycle analyst off, and cut the positive line to the controller (not the positive charge line) while charging and it stops balancing after a while. That shouldn't influence the BMS though should it? I'm imagining the draw from the cycle analyst was enough for the charger to think it needed more balancing time. It didn't have any effect on cell 1 though. When the charger pulsed the voltage up by a volt the first cell would climb half a volt then settle back to 3.32v. The same happened with the other cells but they settle back to 3.6v or so.

[dnmun]

can you just exchange the one low cell #1, with a high cell? and see what happens on #1 after.

[patrickza]

can you just exchange the one low cell #1, with a high cell? and see what happens on #1 after.

Ok I swapped out the first cell with one of my spares and still the same problem. All the others charge to +-3.65v but the first cell only gets to 3.32v.

I'll send Victoria another mail, let's see how good the customer service is.

[Sacman]

can you just exchange the one low cell #1, with a high cell? and see what happens on #1 after.

Ok I swapped out the first cell with one of my spares and still the same problem. All the others charge to +-3.65v but the first cell only gets to 3.32v.

I'll send Victoria another mail, let's see how good the customer service is.

I recall Nicky1961 had similar problem with voltage drop in 1st cell caused by resistance in long (-) wire. You might take a look at his excellent post and see if it can help you. viewtopic.php?f=14&t=6034&start=90#p96455

[dnmun]

i went and read through the jimmy wu thread, i was so dufus then, didn't really have clue, so sorry if i led anyone astray. i was convinced the headway yahoo group buy was the deal and got bob to buy in on it and i think he ended up getting shorted on that one too. i really do feel bad about it. so sorry.

anyway, i don't see how the long lead from the BMS to the battery can cause the BMS to not balance the first cell. plus the headway has a separate lead from the BMS to the pack at the bottom.

if patrickza was here in the states, i would trade my new 72V BMS for his to see if that fixes his problem and see if i could figure out what happened to that one.

is there enuff voltage from the charger to charge the low cell if all the others are full? i wonder if you could tell if there is current in the shunt resistor for #1 before there is current in the other shunts? that would imply that the shunt transistor is turning on at too low a voltage, and the charge then bypasses that cell. seems like the only way to account for #1 not charging.

maybe a test would be to discharge the pack enuff to initiate charging, then put your finger on the shunt resistor to see if it gets hot first, before the others and measure the voltage too.

the BMS is such a simple circuit, i find it hard to believe they could be defective from manufacture. maybe it will behave differently if it has a few more cycles on it and tries to balance that #1 cell yet.

or even a little higher charging voltage if that is leaving the #1 cell short at the end.

[patrickza]

can you just exchange the one low cell #1, with a high cell? and see what happens on #1 after.

Ok I swapped out the first cell with one of my spares and still the same problem. All the others charge to +-3.65v but the first cell only gets to 3.32v.

I'll send Victoria another mail, let's see how good the customer service is.

I recall Nicky1961 had similar problem with voltage drop in 1st cell caused by resistance in long (-) wire. You might take a look at his excellent post and see if it can help you. viewtopic.php?f=14&t=6034&start=90#p96455

Thanks for that Nicky, it was a good read, but I think the situation here is different. The Headway BMS has a sense wire for the first cell which is used in conjunction with the negative battery lead. I'm also using 8 guage wire on my battery leads. Also he was getting a low cell indication under load while I have the low cell reading under no-load.

What I'm wondering is if the BMS is picking up the readings for all the cells voltage using the sense wires, but picking up the reading for the 1st cell using the sense and negative lead, obviously with much lower resistance, is it picking up the voltage as being higher than the other cells, or doesn't it matter as the second sense wire is of the same resistance as the other cells. Could that be causing an inconsistency?

It also seems to adjust to exactly 3.32v after balancing, as if it thinks the 3.32 is actually 3.65.

[dnmun]

3.3V is where they generally stay when charged and self discharge just a little down to the 3.3.

when they are really packed and don't leak down too fast, they will hold the 3.65V for awhile.

yes the nikky stuff has nothing to do for you, can you devise a way to measure the current from your charger into the pack? it may still be trying to charge up the #1 cell, but that cell had already reached 3.65V when it was in another spot so to be dragged down to 3.3V when you put it at #1 is significant. imo.

[patrickza]

3.3V is where they generally stay when charged and self discharge just a little down to the 3.3.

when they are really packed and don't leak down too fast, they will hold the 3.65V for awhile.

yes the nikky stuff has nothing to do for you, can you devise a way to measure the current from your charger into the pack?

I thought that might have been the case, but then when I was testing the range of the pack, the first cell dropped to 2.5v while the others were still at 3.2 so it definitely wasn't fully charged. After charging the other cells drop slowly to 3.5 then 3.4 and settle there for quite some time. When I was watching the pack on trickle charge all the other cells bump up and then settle, the first is always lower than the rest.

When I left the pack on trickle for a whole night by leaving the controller on, all the cells were at 3.65 by morning and the first 3.32, it was still trickling (which it seems to do continuosly if the controller is on, with it off it stops after a while) so it definitely hads enough time to get the current it needed.

I'll try go buy some extra multimeter leads and chop off the ends and fit andersons onto them. Then I can connect it in series and watch the charge amperage. Won't be able to get the leads until friday though.