SIGNALAB (Ping) BMS Schematic

Batteries, Chargers, and Battery Management Systems.

SIGNALAB (Ping) BMS Schematic

Postby Niky1961 » Tue Feb 24, 2009 3:49 pm

Hey All,

I am going to investigate my SIGNALAB BMS since it looks like it's cutting off prematurely at cold weather.
I couldn't find any complete information on-line, so I decided to make a schematic and identify all the components myself.
I was not trying to identify FETs - there are plenty of different types available and it's not critical.
Here is my result.

Enjoy,
Niky1961
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Re: SIGNALAB BMS Schematic

Postby silicium » Tue Feb 24, 2009 4:18 pm

Very good job :D

This seems identical to a BMS signalab lying on my table ...
This will be very useful when it is down!
There is also the balancing circuit is very light ... :roll:
RH205, A123 4P12S with BMS http://vae-tech.forumactif.org/t8-un-bms-home-made (in french)
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Re: SIGNALAB BMS Schematic

Postby swbluto » Wed Feb 25, 2009 12:29 am

So... did you identify what the DIP chip was? Was it the NAND gates in your schematic?
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Re: SIGNALAB BMS Schematic

Postby fechter » Wed Feb 25, 2009 12:45 am

Thanks for posting! That's interesting.

The overcurrent protection circuit is tricky.
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Re: SIGNALAB BMS Schematic

Postby Niky1961 » Wed Feb 25, 2009 7:51 am

To swbluto:
Somebody on this forum mentioned CD4011, I checked and it functionally and electrically fits. I believe, it can be almost any CMOS 2-input NAND gate.

To fechter:
No, it’s not. It’s using first cell NCP800 chip over current protection circuit to protect the whole battery. The threshold is ~200mV, so in my case with current sense resistor of 40mOhm the maximum current is ~50A. See NCP800 Datasheet: http://www.onsemi.com/pub_link/Collateral/NCP800-D.PDF

Any questions – just ask.

Thanks,
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Re: SIGNALAB BMS Schematic

Postby swbluto » Wed Feb 25, 2009 10:33 pm

fechter wrote:The overcurrent protection circuit is tricky.


And rather sucky in my opinion if shorting allowed my battery's BMS to be killed.

And, yes, thank you VERY MUCH for posting this! If only I had seen this about, oh, 2 weeks ago, I might've made an attempt to repair my battery's BMS instead of replacing it. And I think I have a 4011 NAND chip from my childhood 101-in-1 radio shack electronics kit too! Haha.

For the next time I short the BMS! :lol:

(Why do some of these smilies look like aliens all of a sudden? :shock: Can't forget the little green men! :mrgreen: )
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Re: SIGNALAB BMS Schematic

Postby swbluto » Tue Mar 17, 2009 2:56 pm

And to those who don't know, Ping's original batteries uses the Signalab BMS. I think another vendor also used this BMS, but I don't know who.
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Re: SIGNALAB BMS Schematic

Postby monster » Wed Mar 18, 2009 8:26 am

my BMS in the version 2 pack (just got it before the V2.5 started) was signalab but it didn't have any of the big resistors like i have seen in pictures posted on here. it was all surcace mount technology and looked very high tech with LED's for each cell group that indicated something to do with balancing (discharging?). the LED's flashed possibly to indicate sensing or charging and then turn on when the cell is full. during balancing the LED's gradually all switch on, one at a time, and when the charger switches off they gradually all switch off, one at a time. it didn't get too hot (~40*C)
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Crystalyte X503, 48v ping 24ah, 40amp controller (with variable current limit mod and soldered shunt to 93 Amps), hacked watts up meter, disc brakes front and back.
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Re: SIGNALAB (Ping) BMS Schematic

Postby dnmun » Wed Mar 18, 2009 11:21 am

we haven't seen the new BMS. do you have pictures yet? no need to take everything apart, but if you already have it out, both sides with the plug off.thanks, dm
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Re: SIGNALAB (Ping) BMS Schematic

Postby swbluto » Wed Mar 18, 2009 2:55 pm

Yes, some pictures would be nice. It's also interesting that he's using a different schematic already before announcing an "officially" different battery, but it could just be minor changes/enhancements. Anyways, leds for each parallel cell group sounds nice! Are those Surface Mount LEDs, by the way? He should start packaging operating instructions so we can understand what the blinking means. :lol:
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Re: SIGNALAB (Ping) BMS Schematic

Postby GGoodrum » Wed Mar 18, 2009 6:05 pm

Yes, interesting, indeed. This doesn't appear to have any sort of shunt-based balancing, or am I missing something? It just looks like once a cell voltage reaches 4.3V, it cuts off the charge current. Can't see how that would ever let a low cell catch up.

Also, I've never understood why these imported BMS boards do discharge current protection at all. Since all the current has to go through all the cells, all the time, current limiting can be done at the pack level, like in the controller. I guess it is because the packs these are used with need absolute protection from trying to pull too much current.

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Re: SIGNALAB (Ping) BMS Schematic

Postby swbluto » Wed Mar 18, 2009 6:23 pm

I haven't looked at the schematic in that much detail, but my experience with the charger is that it cuts-off when one of the cells reaches the high voltage threshold and then I assume the cells lower in voltage by some mechanisms(Perhaps its selectively draining the ones that aren't low? Or perhaps the voltage naturally lowers more on the high voltage cells?) and then it resumes charging once "it" goes below a certain threshold. I don't know what "it" is and how it's determined, but it must decide to resume charging based on something. It then goes through this cycle and this is what I presumed was "balancing". I don't, however, think this balancing, if it is balancing, is very effective for large SOC differences as it seemed like it'd never balance the faulty low-capacity parallel cell group I had.
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Re: SIGNALAB (Ping) BMS Schematic

Postby GGoodrum » Wed Mar 18, 2009 7:27 pm

It is really not balancing at all. If you watch what happens when cells start to get full, there is a sudden change in the rate of voltage increase, once a LiFePO4 cell gets to the 3.65-3.70V point. At that point, if unchecked, it will rise very quickly up over 4V. The current will be next to nothing. What a proper charger does is to hold the voltage at that 3.65-3.70V point, which will cause the cell to start reducing the amount of current it can accept. This "CV" mode is how you get the last 10-15% capacity into the cell. Cutting off the charge current will let the high cell's voltage drop below the cutoff, but it will very quickly rise up to the cutoff again. With perfectly matched cells, this might work okay, although it would take forever for the cells to get completely full. With some low cells, only the high cell might get close to being full.

What most BMS designs do is to include a shunt circuit in each channel that in effect, performs the CV mode. Basically, it is like a very efficient zener diode. It will hold the cell's voltage at the 3.65-3.70V point, and will bypass any current the cell can't accept anymore, up to a limit. For most imported BMS designs I've seen, this bypass current is usually somewhere between 75-200mA. What this does is let each cell have at least some current to finish charging. If the shunt current is fairly high (our BMS board allows about 500mA of bypass current...), that will shorten the time it takes to balance a pack.

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Re: SIGNALAB (Ping) BMS Schematic

Postby swbluto » Wed Mar 18, 2009 7:56 pm

I think you're right.

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Re: SIGNALAB (Ping) BMS Schematic

Postby monster » Thu Mar 19, 2009 12:48 pm

damn it! i'm trying to upload pictures but my home internet connection is broken and thats where the pictures are!
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Re: SIGNALAB (Ping) BMS Schematic

Postby monster » Thu Mar 19, 2009 12:54 pm

the LED's are surface mount. i *think* it has balanced my pack because dogman said it was well out of balance and after a 24 hour charge it seams good -no more BMS cut outs. i'll have to check the cell voltages again sometime but im having too much fun atm.
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Re: SIGNALAB (Ping) BMS Schematic

Postby lawsonuw » Fri Mar 20, 2009 10:38 pm

The AP431 looks to be doing the balancing on this BMS. It bypasses some current through the 33ohm resistor whenever the cell voltage goes high enough. Stringing together a bunch of single cell BMS chips to make a multi-cell BMS is clever. Unfortunately the NCP800 look to be a LiCO part with an over-voltage threshold of 4.35volts, less than ideal for LiFePO4. Under-voltage threshold listed on the datasheet is fine at 2.5v.

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Re: SIGNALAB (Ping) BMS Schematic

Postby fechter » Sat Mar 21, 2009 6:54 pm

OK, I just got a slightly fried one from nicobie, so I'll get some better pics when I get a chance.
I'll be curious to see what it does when I hook it up. Thanks nicobie!
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Re: SIGNALAB (Ping) BMS Schematic

Postby rkosiorek » Sun Mar 22, 2009 6:36 pm

just a thought really. it should be possible to add a 10K resistor to the gate of Q2 and Q3 (where R23 is connected). the other end of this resistor could then be wired to a small switch to allow it to be shorted to ground. this way the pack could be turned off and on using a small switch. the pack would be turned off when the resistor is connected to ground.

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Re: SIGNALAB (Ping) BMS Schematic

Postby fechter » Mon Mar 23, 2009 8:31 am

rkosiorek wrote:just a thought really. it should be possible to add a 10K resistor to the gate of Q2 and Q3 (where R23 is connected). the other end of this resistor could then be wired to a small switch to allow it to be shorted to ground. this way the pack could be turned off and on using a small switch. the pack would be turned off when the resistor is connected to ground.

rick


Yes, this would be a good idea. It would be like a solid state contactor relay. I don't know why they didn't do something like that. What happens when you switch on against a big bank of capacitors in the controller? No contacts to weld, but the surge might be rough on the FETs. Would you still need a precharging resistor? I suppose if you could make the FETs turn on sort of slow, but still turn off quickly, you could soften the startup.
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Re: SIGNALAB (Ping) BMS Schematic

Postby monster » Mon Mar 23, 2009 12:38 pm

pictures at last
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Re: SIGNALAB (Ping) BMS Schematic

Postby monster » Mon Mar 23, 2009 12:40 pm

more
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Re: SIGNALAB (Ping) BMS Schematic

Postby fechter » Tue Mar 24, 2009 9:14 am

Interesting. The sample I have appears to be an older model.
Here's the top side: You can see there is an obvious problem here.
Signalab top side.jpg
Signalab top side.jpg (95.3 KiB) Viewed 8045 times

Here's a closeup of the regulator chip:
regulator chip.jpg
regulator chip.jpg (104.85 KiB) Viewed 7952 times

Here's the shunt transistor.
shunt transistors.jpg
shunt transistors.jpg (87.25 KiB) Viewed 7942 times

These are the optocouplers:
optocoulplers.jpg
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Re: SIGNALAB (Ping) BMS Schematic

Postby nicobie » Tue Mar 24, 2009 12:28 pm

Hi Fetcher,

I see you got the cooked BMS. It is from a Ping V2 split 48 volt pack that is about 4 months old. I wanted to add a plug in the balance wires so I could more easily remove the pack. Well, it appears that I lost track of the wires because when I connected everything up, I let the smoke out of the resistor.

Nick
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Re: SIGNALAB (Ping) BMS Schematic

Postby monster » Tue Mar 24, 2009 3:35 pm

i have split my 48v pack in the same way nicombe. what caused the smoke in your case do you think? i know that without half the balance wires the pack voltage goes down which i found weird. i dont really know how BMS work but if you try and charge or discharge out of this lowered voltage condition then its probably not good.

check my build in the ping battery box thread http://www.endless-sphere.com/forums/viewtopic.php?f=14&t=8659&start=15
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