Headway/Signalab 2.5 build saga begins (poorly).

C

chvidgov.bc.ca

10 kW
Joined
Apr 24, 2008
Messages
812
Location
Victoria, British Columbia
My headway build begins...planning to build a 48V 10Ahr unit. 31802S cells (16S).

--------EDIT - Retrospective/conclusion/bottom line-----------

At first, I had some issues with the first Signalab 2.5 BMS I installed, blew it up, but the replacement Signalab 2.5 is now installed. It works ok, but some manual balancing may be required over time, sporadically, as it doesn't equalize the cells particularly well after all the LED lights come on, around 57.6 volts out of 58.4 that the charger is set to...my whole experience with the Signalab is outlined here, with much help from DNMUN, the saga ends happily. I learned a lot about balancing the Headways on the Signalab and constructing the packs. The bottom line is that..."After all the LEDs are lit up, and the charger is quiescent but still connected, if you drain one cell with a resister, the overall pack voltage will be maintained at close to 58.4, so energy is going into the other cells, which is improving the balance beyond the "All LEDs are on" point - that point doesn't truly reflect perfect balance. Further manual balancing beyond the "all LEDs are on" point is necessary, now and then. Which isn't difficult.

------------------------------------------------

...the REST of the story........

Ordered from BMSBattery.com. All cells arrived in Victoria, British Columbia in about 6 days. With interconnects and orange plastic blocks. Planning on using Signalab 2.5. All cells were 3.32 on arrival. No complaints on service.

Soldered sense wires to interconnects (not on battery at time) by drilling tiny hole in interconnect and putting sense wires through them, and soldering. Taped over centres of buss interconnects and sense wires to protect solder junction from flex and shorting from screw to can.

Assembled pack in orange blocks. Snug fit, no removal of outside blue material necessary. No cracking of blocks. No condoms.

Attached buss interconnects/sense wires, in correct order, by drilling small holes in middle of interconnects, and soldering sense wires into holes. Total voltage of pack 53.2. All sense wires in order, and checked for incremental voltages at the white plug (all increased by 3.2 volts, up toward 53.2). Definitely in the right order..

Attached Signalab 2.5 bms as per Ping diagram. Probed white plastic connector at each sense wire. Each one went up by 3.2 volts as required, to total voltage of 53.2-3, on last wire, so all sense wires operating correctly.

Started charging, with Ping charger (61volts according to multimeter). I should have used a cooler charger, maybe 59.2 volts - even though I thought I should do this - I was too eager, and I thought the cells were balanced already (my bad).

9 LEDS go on, after a bunch of on/off cycles of the charger. Everything looks ok, except pack voltage is now over 60...

Checked all cell voltages as pack voltage - WTF - one cell is at 4.2!

I hear a loudish pop. Don't know whether it was the BMS dying, or a cell going down. 9 Leds on BMS still on, but no output. BMS LVC? One cell is down (zero volts). Others range from 3.3 to 3.75 (also too high).

My original plan was to charge with one single cell charger, to 3.65, with all cells connected in parallel, then connect the bms, too impatient.

So, I am ordering a replacement cell, and I'm going to try the "new" bmsbattery bms. http://www.bmsbattery.com/5-bmspcm , after balancing at 3.65 all the cells.

--------------

I drained all of the high cells down to 3.65 for storage over the next week.

I will single cell charge all of them in parallel to 3.65 to bring up the low cells, and get closer to balance...

I will then find a charger that puts out only about 3.7 per cell (59.2), and hook that up.

I will try the Signalab 1.0 I have, or maybe the bmsbattery "new" bms http://www.bmsbattery.com/5-bmspcm (which is what BMSBattery provides in pre-assembled pack).

Hopefully I haven't damaged too much the other high cells which were over 3.7

-------------
Question - did I really kill the BMS? If the LEDs are still on?

Why didn't the BMS prevent HV condition on the high cell? I thought it would cut in at 3.9?

Maybe the Signalab V1 could "bleed" more current preventing HV state on high cell? Compared to the v2.5 version.

How to adjust down the voltage of the el-cheapo Ping 2 amp charger. 61.4 is awefully high?

What BMS should I use, and where can I get one. I'm not competent to build a GoodrumFechter type.


--------------

HELP?/Comments welcome. I'd prefer plug and play as I have a low attention span when it comes to these batteries...
 
Yes how does it work the charger stops at 61.3v. The bms leds come on at 3.7v 3.8v ? I had a cell go to 4.2v for 30sec. no problem. But if one cell lags at 3.6v or 3.5v and all others at 3.8v except a runaway at 4.2v. Where's the hvc on the signalab bms ? I mean this has happen to me. Or the signalab just bleed after 3.7v and that's it hvc till the charger shuts at 61.3v ? Where is the protection per cell for hvc ? Or does it realy on all cell being balanced to start with to start to charge ? Answer one answer all. No skippes. Thank.
 
All of the below assumes the new Signalab BMS are intended to work the same as the old Signalab V1 BMS in basic function. I haven't played with his new BMSs.

The CV mode of the charger needs to be set higher than 60.3V for these BMSs to work properly. 60.8 to 61.5 is good for 16 cells. Because of the way the balancing algorithm works, if you charger is set to anything less than 60.3, your weakest cell or cells will never finish charging. They will self-discharge over time and eventually get so far out of balance as to make your pack useless.

A more detailed explanation is here:
http://www.endless-sphere.com/forums/viewtopic.php?f=14&t=24290&hilit=ping&start=15#p359032

The fact that you had one cell over 3.9 suggests a bad connection on that cell's balance lead, or some hardware malfunction in the BMS. I have the old V1 BMSs, and when I charge my headways with them, no cell ever goes over 3.9V.
 
I can assure you that every balance lead was connected. I tested the voltage on each line, and was quite careful to solder them on securely, and put them in the right order. Also, as I recall, that one cell had its LED come on much earlier than the others, and yet it continued to climb to its demise. Unless that loud pop I heard was the "defecting" of the BMS, which then allowed the cell to skyrocket. I definitely heard a pop. That couldn't have been a cell surely. It must have been the smoking of the BMS. I think I will try the V1 I have, next, before the bmsbattery bms, after pre-balancing at maybe 3.7
 
did the charging mosfet blow up on your BMS? if it shorted then the cell could have pushed up to 4.2.

so then the pop would not have been the cell, but is the charging mosfet that blew. i don't think 4.2V would cause the headway cell to blow up. so my money is on the mosfet.
 
Hmmm...I examined the board in detail and couldn't see any physical damage. Not sure how to test that. The thread that julesa mentioned seemed to indicate that it might not be possible to reach a balanced state at all, unless all the cells (when balanced) total up to the charger voltage - that there is no "bleeding" per se, other than capping at 3.8 of some of the cells. So, it could be that it is a very good idea to bring all the cells as close as possible to 59.2/16 = 3.7 (optimal state according to Headway specs) before charging, and use a charger set to that level. And then now and then reequalize them to that level. If the charger were at 61, then they would all have to be at 3.81 to be balanced at that level, which is rather high. So it kinda makes you wonder if the balancing that this bms does is really rather lame, and only works to keep a balanced pack more or less balanced, and doesn't work very well on an unbalanced pack. Sounds like I need a different (or no BMS), or prebalance then keep an eye on the balance thereafter with periodic single cell recharging of lower cells.

In other words, if a few cells are at 3.8 and a lot of the cells are lower, but the sum of the cells is at that time the same as the charger voltage, no further charging will occur.

I suspect the sound came from the BMS, so I think that failure was what allowed the cell to get over the 3.8 that it was clamped at (at that point the LED was on - I think, for that cell only). Could have been the charging mosfet.

On the other hand, my Pings are balanced, as far as I know and seem to keep on working without examining the individual cell voltages.

Thanks everyone for their thoughts. On the brighter side, I still have two Ping packs, and I'm getting in some nice spring e-triking...
 
chvidgov.bc.ca said:
Hmmm...I examined the board in detail and couldn't see any physical damage. Not sure how to test that. The thread that julesa mentioned seemed to indicate that it might not be possible to reach a balanced state at all, unless all the cells (when balanced) total up to the charger voltage - that there is no "bleeding" per se, other than capping at 3.8 of some of the cells. So, it could be that it is a very good idea to bring all the cells as close as possible to 59.2/3 = 3.7 (optimal state according to Headway specs) before charging, and use a charger set to that level. And then now and then reequalize them to that level. If the charger were at 61, then they would all have to be at 3.81 to be balanced at that level, which is rather high. So it kinda makes you wonder if the balancing that this bms does is really rather lame, and only works to keep a balanced pack more or less balanced, and doesn't work very well on an unbalanced pack. Sounds like I need a different (or no BMS), or prebalance then keep an eye on the balance thereafter with periodic single cell recharging of lower cells.
Click to expand...

You definitely want to balance your cells before you build them into a pack. Yeah, the cheapo BMS algorithm is pretty lame, but IMHO it beats doing it manually. There is "bleeding." It's just that it's happening at about 100mA = ten hours of balancing time per amp-hour of imbalance. Sloooooooow. :)

Still, if you're charging your battery more than a couple times a week, you shouldn't have to leave it balancing very long per charge. Cells shouldn't go out of balance that fast.

If I had to charge a 16S Headway pack without monitoring at the cell level (which I probably wouldn't ever do), yes, the first step would be to manually take every cell to the same charged voltage, ~3.7V. After that, I would set my charger far more conservatively than 59V (55 or 56V to start, at most), and I would still watch it like a hawk for the first few weeks while charging, standing at the pack while it charges and measuring cell voltages until I had some idea of how long I could safely go between balancing sessions. And manually balancing would get old really fast, even if you could get away with only doing it once a month.

If you're not careful, after you run the pack for a while without balancing, you might end up with just a few cells that fill up before the rest of the pack does. They stay right at 3.3V until they're almost full, and then once they're full, the voltage climbs very quickly, so if you're charging at 59V you might get 13 cells at 3.3v (still charging) and 3 cells over 5V.
 
Any thoughts on whether the bms that bmsbattery includes on their pre-bundled pack might do a better job? The Signalab is becoming rather less appealing, and I was suckered by some of the positive reports I read, I guess. Or just unlucky, with a hardware problem in the BMS.
 
Thanks for your input. Any thoughts on whether the bms that bmsbattery includes on their pre-bundled pack might do a better job? The Signalab is becoming rather less appealing, and I was suckered by some of the positive reports I read, I guess. Or just unlucky, with a hardware problem in the BMS.
 
I've had good luck with the V1 Signalabs, personally. I bought two cheap BMS from BMSbattery before I got the Signalabs, and both of those fried on day 1. Luckily I only lost one cell. But I don't think BMSbattery is still selling the type of BMS I bought from them, I know a lot of people had problems with that board. I have no experience with the BMSs they are selling now. They might be great. For $45 I'd just buy one and call it an experiment.
 
Charge management is easy, just use single cell chargers, or their equivalent. They are pretty close to being foolproof and will prevent the vast majority of cell problems (which are almost always charge, rather than discharge, related).
Click to expand...

I was reading this in another thread about not using a BMS because of their reliability, and the fact that you are trusting your pack to them. It sounded like there was a way to avoid this balancing BMS problem. I didn't quite understand it can any one explain how you would do it with a headyway 16S pack.

Thanks
 
ok. I have a nice single cell charger which can charge all of the cells at once in parallel. I will do that first, bringing them to 3.65

Now...I have a new BMS (and a new charger set to 58.4). This is the same stuff that bmsbattery uses in their pre-assembled packs.

This is the BMS discussed here...

http://endless-sphere.com/forums/viewtopic.php?f=14&t=26674 (Smartec BMS)

http://www.bmsbattery.com/322-433-thickbox/17s26s-24a-max-discharge-current-bms.jpg

How to wire it?

There is no charger minus (C-). Does this mean that the output pair of plus/minus connectors will also be the charger connectors.

Two P- and two B- means that the wires are doubled up for higher current, I assume, why two P-?

I guess I need a wiring diagram (not included).

Bump
 
Well, this seems better. I got a different charger set to 58.4 (3 amp charger) from bmsbattery.com which is set 2 volts or so below the PING.

Also, last night I parallel charged all the cells to 3.65. Although they were a bit out of balance today due to the time taken and the self-discharge which occurred.

I decided to try another Signalab 2.5, rather than the Smartec BMS, as I confirmed that when connected to a Ping battery, the charger set to 58.4 was still able to bring all the LEDs to light, ie. balancing the pack (which was already very close to balanced) at the level 58.4 (3.65 per cell) on the ping. So, I'm not sure why Pings chargers are set so high.

I'm using another Signalab 2.5 on the Headways, this time at the lower 58.4 voltage, after witnessing the 2.5 on the ping with the new charger.

So far, after about 20 short cycles, the number of LEDs has gone from 6 to 8, and the minimum pack voltage on each cycle of the charger has been slowly increasing. Now, with 8 lights on, the pack minimum on the latest cycle is around 57 volts, and the max voltage on each cycle has been increasing to just under 58.5, as observed with a Turnigy watt meter. So, if this goes on all night, it should take about 50 cycles to fully balance the pack, given that pattern of incremental voltage increase per cycle on the whole pack.

I think I may have done it. I will know tomorrow morning. Each cycle takes about a minute, as the total pack voltage declines, and then the charger starts up for maybe 8 seconds. The last LED which started to stay on stays on just a bit longer on each cycle, until it stays fully on, and the next LED starts to go on, etc.

This is all new to me, so it is interesting to watch. The LEDs are definitely a major clue that something good is happening, and the pattern makes sense.

Hopefully in the morning, all the lights will be on.
 
you can drain charge off the high cell that shuts down the charger.

i have some big 25 watt ceramic encased power resistors i use. two in parallel at 10 ohms each so equivalent 5ohms. it drains 780mA off the high cell as long as it stays there.

the old power resistors were just scrap parts from an old tv set i scrapped out for the components a long time ago.

anyway, when the high cell is drained down a little, it allows the charger to stay on and that charges up the lower cells faster. the BMS shut off the charge when that cell climbs up to 3.9V. draining the charge off drops the voltage faster than the shunt resistor.
 
Would this be equivalent to connecting a watt-meter, which must consume some energy to light up the LEDs? I guess that would drain all the cells simultaneously though, through the P minus. Do you hook up the resistors to the plus and minus of the identified high cell? I didn't notice if the "high cell" is always the same cell, as the cycling has progressed. Is the last LED which lit up always the high cell, which at first is lit up then disappears again until the next cycle when the same LED comes on, eventually staying on. Wouldn't then the next LED to go on/off by cycle be the high cell, at that point in time? I guess what I'm asking is how to identify the high cell (at some point in time? or is it always the same cell?)

I imagine I should do a few shallow discharge cycles, maybe just doing a few miles to get some bagels tomorrow.
 
you can find the high cell with your voltmeter. it will be oscillating from 3.9V down to 3.8V when the charger turns back on again.

just connect the resistor across that high cell and the charger will remain on until the next high cell shuts it down, so then you can drain that cell, so it just speeds up the balancing when the pack is far out of balance, and the high cells don't have to be constantly jammed up to 3.9V. you can use what ever resistor you want, try to find the smallest value in the largest resistor, maybe 22 ohms in a 2 watt would be enuff, that would quadruple the rate of balancing of the v 2.5 signalab.
 
Or put a resistor in series with the charger to limit the maximum current to whatever the BMS can shunt long term, probably 100 ma. Then the charger will stop cycling and that high cell won't get stressed going to 3.9 volts every seven seconds. I combine 10 ohm 1 watt resistors in series and parallel for my 36 volt packs. I have been balancing one for two days through 25 ohms at 100 ma, using a power supply set to 48.4 volts. Note the higher the supply voltage and resistance, the less change in current as the pack comes up to voltage.
 
Thanks for the help guys. All of the 12 bms LEDs now stay on, with a total pack voltage of 58.28 which is close to the designated 58.4. Does "all LEDs on" mean "is balanced?" I note that the cells now range from 3.63 to 3.71 - or is this just "balanced enough" from the BMSs perspective/algorithm?
 
I found that if I left the charger connected, although all the lLED lights would stay on continuously throughout the following... if I then drained the high cells to a level of around 3.59, below the others, the charger wouldn't come on, they would spring back up to a level just below where they were before (still higher than the others), but the aggregate energy in the other cells would at that moment be higher than before the draining operation, so the overall balance had improved. I've gotten the range to be from 3.62 to 3.66 now, which is better. I don't think that without this by-hand intervention the Signalab 2.5 will ever perfectly balance these. The single cell charger I bought unfortunately doesn't work on single cells below 9 ahr, so I've got a couple of single cell chargers from Voltfreaks on the way. A bit more hand balancing, after a few rides, will be required. I hooked up the pack to a bike and it ran fine, so that's great. I'm going to keep the depth of discharge fairly shallow for a while. This is a small pack just for close-in commuter apps, so I'm not worried by any weak cells at LVC for now.
 
Brother, You are doing find. Be cause you didn't pre balance it will take more time, but you are going forward. How many led lit ? Rember to answer all question for true help. I think the headway cells like a lower voltage than the Ping pouch cells like, listening to Dumn. I guess the bms is set to turn the leds at 3.8v ea. or 60.3v on the signalab.
 
they all like the same voltage, anything around 3.61-3.65 is essentially fully charged, and i think the leds turn on around 3.6V.

i think you will find that the balancing with the signalab is not as close as it is with the headway BMS, because they actually are able to adjust the shunt balancing resistor divider bridge at final test on the headway BMS so it is always right at the 3.65V.

the signalab is made by reflow of fixed parts so some variations of these resistors in the resistor bridge that controls the input to the shunt transistor will give some small variations in the final balanced voltage of each cell. that voltage should always be the same though, so the leds would always light up in about the same order. worry if that changes, not before.
 
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