PING BMS light stuck on

[outbackhack]

About to email Ping about this issue, but wanted to throw it out here to the forum to see what people think.

Halfway through my 2nd test ride today with my new PING 48v20ah pack I noticed that one of the LEDs on the BMS was lit up. My first thought (based on my limited understanding of BMS's) was that a cell had reached a lower voltage than the others and that it had cut that one out of the loop. So I opted to pedal myself home without power-assist, using regen on the downhills to try and pump some power back into the cells. I was only 6.5ah into the 20ah pack at the time, and the numbers I found when I got home to my multimeter suggest that the pack is well balanced, so that's not the issue. Also when I got home I hooked up the 2amp charger to the pack to see if that would make the LED go away, but after 10-15 minutes I unhooked it not wanting to cause any damage since it didn't seem to resolve the issue right away. Can anyone give me a hint on what's going on here?

Here's what I found hooking my multimeter up to the balance wires. I think the BMS is altering the reading on the last cell, not sure how to measure it since I can't access a direct line to that group of cells without un-shrinkwrapping the BMS I think. I don't see any signs of scorched components on the BMS as other have posted, but again I haven't removed the shrinkwrap which is obscuring half the BMS.

A Pack (w/ BMS)
03.33 3.33
06.62 3.29
09.94 3.32
13.26 3.32
16.58 3.32
19.91 3.33
23.22 3.31
20.50 -2.72
B Pack
03.32 3.32
06.63 3.31
09.94 3.31
13.26 3.32
16.58 3.32
19.89 3.31
23.21 3.32
26.52 3.31

 

[outbackhack]

Forgot to mention, I've unplugged all the wires for now to prevent the BMS from draining the battery till I can resolve this.

 

[amberwolf]

The A) pack reading doesn't make sense at the end. I don't see how it could go backwards, unless wires are swapped between two cells (and I am not sure, but I expect that might cause obvious failures). Are you sure the readings aren't written down backwards for those last two cells?

I don't remember if that LED is for overcharge of a cell and balancing current flowing, or if it is for undercharge of a cell and LVC.

But if it is the undercharge, and if it's a new pack, you might wanna just leave it on the charger so it can balance it out. I could take a long time, since the resistors on that BMS can't deal with all that much voltage difference.

 

[Caliban]

In Ping's Guide to his V2.5 packs (downloadable from his site) he writes ...

"Caution: If any of the LEDs on the BMS light up permanently (charger is not connected) and never go off, the BMS should have problem. Please disconnect the black multi-pin connectors immediately (in this way, the problematic LED will be turn off) and then send email to pingping227@hotmail.com."

So, wait and see what his response is.

 

[outbackhack]

I figured out how to get what I think is a correct reading out of the last cell in the pack by subtracting all the other measured individual cell voltages from the total pack output and got 3.33v. Since that's exactly what the others were all outputting I'm inclined to be believe that it's correct and all the cells are balanced.

From what I've been able to gather, the light being on indicates that the BMS thinks that cell is fully charged, and it will not allow the charger to put any more juice into it. So if I were to try to charge the pack now it would result in the pack getting unbalanced. So the only way I could continue using the pack at the moment would be to bypass the BMS to charge the pack, which I'm not going to do to a brand new pack.

I emailed Ping last night, and he's been pretty responsive so far, so hopefully he can get back to me soon with either steps to fix it or a replacement BMS. I was Just throwing this information out there in case someone else had had the same issue and knew of a quick fix.

 

[dogman dan]

Sounds more like a wonky bms than a wonky cell. You can walk both leads of the voltmeter down the row to get readings of the cells without the addition of voltage as you go.

 

[outbackhack]

Just heard back from Ping, he confirmed it was a BMS issue and said that the likely cause was the wire that joins the split battery pack worked loose. When I inspected it the wire was still connected, but not seated all the way, it could have been loose enough to cause an intermittent cutout in the pack. So I won't blame the Ping's hardware completely for failing in this case, but I would have appreciated a stronger worded warning if this is a well known cause of failure and it's so easy for it to happen.

Anyways, he's offered to replace the BMS, but also given me some information on how to repair it. I would prefer to try and repair it if possible first and the replace it only if it can't be repaired. He named a MOSFET si2333 and capacitor 0603 104 as the components to replace. Since these are tiny surface mount components and too small for me to solder, I'm not sure how successfully they can be replaced, but it might be worth a shot if I can find someone with the right tools.

 

[dnmun]

i agree with ping, sounds like the connection between the two packs ends up leaving that cell high.

your assumption that the led means the cell is full may not be correct. they all appear to be about the same voltage, but you have to measure while on the charger, not off.

 

[DAND214]

Get the new BMS and save the battery. As said if left connected that cell will be discharged and ruined. I have about 3 of those boards do that. And they weren't loose connections.

Get the new one.

Dan

 

[999zip999]

Yes this has been a problem with the signalab bms. It can be draining the one cell always when the led is on, it shows draining of a high cell. Get the new bms from ping and shrink wrap ect. as the new one for the pack. Easy to replace, a plug and three wires to solder. I would first look very careful at the plug and the pin conections. The pins are held in place but a very small flat sheet metal tab that can back out of one of the plugs. 48 pins conections or more with the same small tabs. I lightly hot glued the wires runnig into the plugs after all was right.

 

[fechter]

If the connection between two sections of pack goes open, it could put full reverse pack voltage on one of the BMS sections, destroying it. This can happen with any setup. The cell interconnections have to be rock solid.

Does this pack have two separate sections? If so, are they detachable?
It would be important to completely disconnect the BMS board before separating the pack sections.

 

[999zip999]

The cells should be ok just don't let the one over drain. Just unplug the sense wires from the bms so it stop draining ( If it is draining ) Those pins back out easy. Two differane problems. Plus buy a single cell charger from ping with the new bms. I think it charges to 3.8v ? as I broke mine. And voltfreaks stops at 3.65v.

 

[outbackhack]

Yes, the pack is divided into 2 sub-packs. Ping supplied the pack with an XT150 connector (which has no retention clips to keep it together) on the wires joining the packs. In retrospect I remember a sentence buried in the instructions about making sure this wire didn't disconnect while in use, but it didn't say that it would fry the BMS if that happened. In the future I will just remove this connector plug and fuse the wires together so they cannot come apart again.

I replied to Ping requesting a replacement BMS. I'd like to fix this one, but looking at those tiny components I'd say my odds of success are less than 50%.

 

[999zip999]

What motor and controller ( amps ) are you running ? If needed you can upgrade to a 10 fet signalab BMS, But is a 5 fet and more wider and you plug will just plug in. If needed it. Or limted your draw to 23amps. Ask ping to send you the parts to fix it for a spare.

 

[Rassy]

Jason wrote:

These ping packs keep having problems.

Not a fair comment IMHO.

I've had a total of 5 LiFePO4 packs, 3 Pings and 2 others. The two others are long gone, and in the meantime did have a couple of small problems.

The Pings have never had a problem, except user error when my son didn't keep one charged properly, and that was corrected by a little charging attention. One of the Pings is almost 3 years old, and the other two are almost two years old.

Also, when folks do have the occaisinal problem Ping jumps right in to help resolve the issue.

 

[999zip999]

Ping is a good man. With fast email return. Is Ping the same as signalab or does he just use then ?

 

[fechter]

Ping IS Signalab. He has an excellent reputation here.

 

[dnmun]

these split packs always have a problem with the connection between the two sections. the biggest is the onset of LVC because of the large voltage drop on the connection link between the sections. this is gonna be the big problem for your pack too.

also because of the way that ping attaches the heavy wire lead directly to the end pouch tabs puts a large strain on the tabs of those end pouches and they flex and break first because of that. on a normal pack there are only two cells at each end subject to this failure, but with the split packs this is doubled to 4 cells which can die prematurely from tab failure.

it would be nice if someone who has this problem would actually prove that the led stays on long enuff to drain the cell to zero. after all the requests i made, only one person ever said they measured, and they said the voltage was 3.61V on the cell that was being damaged. but no pictures or real evidence that this is happening, just that the led remains on.

 

[999zip999]

Yes Dnmun my ping 48v20ah split pack. Had this problem no pic's can't download on my comp. The cell keep draining for over a hour after all were level. It was lit and wasn't acting normal. Didn't want to kill the cell or while to bring it up. Alway's best to keep balance. Run without a bms for 3 weeks and it keep great balance. Was happy to put the 10 fet signalab bms. Was running at to high a amps. The cells were on the broader at those amps on a bmc 600. Plus other's have post same thing.

 

[outbackhack]

Just to post a follow up. Ping was just as helpful as people have reported here, and I had a new BMS in my mailbox in just over a week. Wired it up and put it though a couple cycles now and looks like the new one is working fine. I've since soldered the two wires together that join the split packs so that it will be more difficult for them to separate. Also reinforced the areas where the wires exit the packs, so hopefully that will cut down on flexing/stress on the battery tabs.

 

[fechter]

I'd love to get the old one.

 

[999zip999]

The other problem I had was the sense wires pulling out of the 8 plug on the split pack used a spot of hot glue to keep them in place after it was working right. Just a drop on the wires going into the plug. Glad to hear it work out.

 

[heathyoung]

The problem is, yes, I can confirm that one with a 'stuck led' will drain a cell down to zero volts. That LED is across a resistor, which (due to a shorted device) is across the cell. The LED will extinguish once the voltage across the resistor drops past its Vf, but the resistor will continue to drain the cell to 0.00 volts.

 

[outbackhack]

I'd love to get the old one.

Unfortunately (but understandably), Ping asked me to send the damaged one back to him. I would have kept it and tried to repair it, but given how tiny the components are I didn't think my odds of success with the tools I have were that high, so I took Ping up on the offer of a replacement.