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Battery Autopsy

LewTwo

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Joined
Apr 8, 2014
Messages
2,119
Location
Houston, Texas
Well I was warned ( markz, https://endless-sphere.com/forums/viewtopic.php?t=110214 ) but I did it anyway. I purchased a “Open Box” battery off EBAY. It was an “imotorbattery” branded LiFePO4 48 volt 15 amp hour battery. The Ebay listing indicated that it had been tested. Turns out the vendor (name omitted to protect the guilty) had no clue how to test a Lithium-Ion battery. Yep it was defective. I could charge it to 58 volts but once the charger was removed it dropped down to 54 volts in mere moments. Two capacity tests (2 Amps) shut down after 3 hours with a measured capacity of about 7 Amp Hours. I believe the technical term for this condition is “Tango Uniform”.
imotor pouch battery capacity test 01 failure(600).jpg

So I contacted the vendor and informed him of problems. It took several days before he acknowledged that there might be a problem and that I had 30 days to return it. How says I. The battery is rated at 720 watt hours and weighs 17 pounds. It exceeds the 300 watt hour limits for a consumer to ship a lithium ion battery (UN3480) via FedEx, UPS and/or DHL. He instructed me to open a Ebay return case and that he would take care of it. For my trouble I got a USPS return label. USPS limits are even lower than the common carriers (100 watt hours). It seems that this vendor is “willfully ignorant” of any regulations for shipping Lithium-Ion batteries. I should note at this point that the vendor shipped the battery to me via UPS ground without any lithium warning labels. If I can not legally return the Ebay Sale item then the vendor is under no obligation to issue a refund (I am still contesting that). I used the USPS label to send him printed copies of various UPS, Fedex, USPS and Fed regulations regarding Class 9 Hazardous Cargo.

I reluctantly accepted that I was likely going to have to eat my loses. I had done a number of layouts for cylindrical cells (18650, 26650, 32650) but had not found a good match for the battery dimensions. Eventually I cut into the battery to see if I could discover the problem. Some very fine surgical slicing and dicing with a sharp utility blade managed to reveal the first big surprise: this is a pouch (polymer envelope) battery … a huge, glorified RC battery encased with cardboard and shrink wrap. A bit more careful cutting, so as not to accidentally nick one of the pouches, allowed me to fold back the upper third of the case (not much of a case). It appeared that someone in manufacturing neglected to fully seat the 16 pin balance connector to the BMS board. The last cells in series had a intermittent connections.
imotor pouch battery autopsy(1024).jpg

So next I broke out the multimeter and checked the voltage levels for each cell:
imotor pouch battery cell structure(1024).jpg

Note the values for cells 13, 14, 15 and 16. I decided to use my variable 30 volt 5 amp bench power supply to manually balance the individual cells followed by bulk charging the battery. Of course charging a 60 volt battery with a 30 volt supply is a bit of a challenge. I used my solder gun to add a new 16 AWG wire to the junction between cells 8 and 9. Then I charged each individual low voltage cell to bring them close to same voltage. Next I charged that block of four cell to bring them up to the voltage of the other four cell blocks (13.16 volts). Lastly I needed to charge the two banks of 8 cells to 29.2 volts … or I planned to. Turns out the little bench supply did not have sufficient mojo for the task. After setting it to 29.5 volts and 3 amps it showed 0 Amps being delivered when the output was turned on. The multimeter showed no volts and 12 milliamps from the power supply terminals :-( Tacklife is shipping a replacement Power supply :) I am going to derate that replacement PS to 24 volts and hope it does not fail.

Moving on to Plan “B”: All the previous stuff was done with the BMS out of circuit. I wired the BMS back in being certain to fully seat the balance lead connector. Then I connected up the original 58 volt charger and plugged it into house current (110 VAC). Now to wait for the green LED. I have no love for watching grass grow, paint dry or electrons moving about in the ether. A watched pot never boils and a watched charger does so excruciatingly slowly.

13:30 hours … time to take a nap … 16:30 hours


Well the Green LED is lit but the balancer leds keep flashing on and I am only seeing 56.3 volts from end to end. One LED in the middle is ALWAYS lit and the last four (which correspond to the problem children) never light up … h’mmm, I need to take out the trash and watch a youtube video

This is signalland BMS. Not much found in the way of documentation but I did find a video:
https://youtu.be/6i8i6h1LkBw

17:30 hours ….
imotor pouch battery BMS blinking(1024).jpg

Well the LED’s have stopped blinking. The first 12 LEDs are on and the last four are off. So I wait for all the LED’s to turn off and then check the cells again. The first 12 are sitting between 3.164 and 3.121. The last four are siting at 2.925 to 2.920. I rechecked the first cell and the voltage had dropped while I was testing from 3.163 to 3.144. Either the cells are self discharging or the BMS is draining the battery.
imotor pouch battery cell voltages(1024).jpg
That last column is after the battery was bulk charged with the BMS. Those voltages are actually lower than the starting voltages.

I unplugged the BMS again. My suspicion is I either have a defective BMS or 4 defective cells or both. I am going to place my bet on the BMS and cut it out. That should allow me to directly charge the battery from the charger (I hope) …. after I manually balance the cells again. Oops, I can not do that as the power supply is now Tango Uniform as well. Well the cells are fairly close (about 0.15 volts). H’mmmmmm …. my low voltage problems all went away after I got rid of the BMS. The OEM charger was happy to pump some power into the battery without the BMS sitting in the middle.

Time for capacity test. I am using a low voltage cutoff module between the battery and the capacity tester. That is set to shutdown at 40 volts. So it is off and running. Did I mention something about watching paint dry ….

After 5 hours and 18 minutes the pack voltage was down to 46.5 volts having drawn 11.24 Amp Hours (578 wHr). Unfortunately the last four cells were down to 2.1 volts while the 8 front cells were sitting around 3.2. Boys and girls THIS is why you have a BMS.
imotor pouch battery capacity test 03 failure(600).jpg

The Autopsy conclusion is Dead On Arrival caused by critical organ failure.

Replacement LiFePO4 poly cells in this size run about $40 each (plus shipping and tax).

https://www.batteryspace.com/High-Power-LFP-Polymer-Cell-3.2V-15Ah-87122200-2C-48Wh-30A-rate.aspx

I am dead in the water until I have a working variable voltage power supply. I did order a new Daly 16S LifePO4 25 Amp BMS (common port for charge/discharge) via EBAY and a slow boat from China. I will likely try one more time to resurrect this battery when I get it … however the prognosis is NOT promising. At that point I can salvage 12 cells and call it a 36 Volt 15 Ahr battery or put the 12 cells in a 4S3P configuration to call it a 12 Volt 45 Ahr battery. Either way it will weight about 13 pounds.



Now where did I put those layouts for 16S headway 8 AHr cells ….. :?:
Lets see … two banks of 16 cells and ………………. :oops: :arrow: :confused:
 
serious_sam said:
I think we're witnessing the creation of an ebike addict here :lol:
LOL --- I built my first E-Bike around 2006. This was the end result (notice the three lead acid batteries).
end result.jpg
I hit a pothole at speed :oops:
Went over the handle bars and made a full face landing.

My e-bikes are currently my ONLY mode of transportation(have been since 2011).
 
IIRC, those Signalab BMSs were "famous" for killing the first four (four most negative***) cells in various Ping brand packs years back. That BMS is powered off the first four cells, so they are drained continously whether you are using the pack or not. This pack probably sat on a shelf for a long time without being charged before you got it, causing the result you see.

It is possible that it had actually sat so long at some point that the first four cells were overdischarged and damaged, then manually brougth back up to a chargeable state, and then left that way again.

***It looks like you are numbering your cells from the most positive end of the pack, assuming the red wire on the balance connector is the most positive end...if so, that's backwards from the way I'm used to seeing them counted, so wherever you see me talk about first or last or whatever, I'm counting from the most negative end of the pack. :)

The channel that never goes out could be either a cell that just has more capacity (or resistance) than the ohters so it's voltage is alwyas high enough to trigger the channel. Or it can be the channel is stuck on. (but if that was the case then that cell should also show really low voltage, or be totally dead).

Some threads mentioning Signalab in the title (not all of which have useful info, but I have not read any of them in years, not enough time ATM for me to poke thru for relevancy, but thought you might want the info anyway)
https://endless-sphere.com/forums/search.php?keywords=signalab&terms=all&author=&sc=1&sf=titleonly&sr=topics&sk=t&sd=d&st=0&ch=300&t=0&submit=Search
and a spelling variant
https://endless-sphere.com/forums/search.php?keywords=signallab&terms=all&author=&sc=1&sf=titleonly&sr=topics&sk=t&sd=d&st=0&ch=300&t=0&submit=Search

Some threads on Ping packs that may (or may not) have info on this problem:
https://endless-sphere.com/forums/search.php?keywords=ping+&terms=all&author=&sc=1&sf=titleonly&sr=topics&sk=t&sd=d&st=0&ch=300&t=0&submit=Search

just Ping BMS (way less threads to look thru)
https://endless-sphere.com/forums/search.php?keywords=ping+bms&terms=all&author=&sc=1&sf=titleonly&sr=topics&sk=t&sd=d&st=0&ch=300&t=0&submit=Search


If manually charging up all the cells to the same 3.65v, then letting them all sit for a day without anything connected to the balance or pack main leads, doesn't result in cells that are at least similar in voltage, then you have some damaged cells (usually the ones that have dropped most in voltage).


Another problem with the pack, probably unrelated to the balance issue, could be the interconnect method. It looks as if they just folded over the tabs onto each other for the series connections. Is that the case? Or is there some form of weld between them?

If there *are* interconnect issues, you may be able to fix those using some of the various methods in the assorted A123 20Ah pouch cell build threads.
 
amberwolf said:
....

***It looks like you are numbering your cells from the most positive end of the pack, assuming the red wire on the balance connector is the most positive end...if so, that's backwards from the way I'm used to seeing them counted, so wherever you see me talk about first or last or whatever, I'm counting from the most negative end of the pack. :)

Yep, I started counting at the front (positive) ... as the BMS has no labels it seemed logical at the time :|
It is the first pouch battery I have ever seen.
One of my first thoughts was how does one even draw a representation of that?

amberwolf said:
If manually charging up all the cells to the same 3.65v, then letting them all sit for a day without anything connected to the balance or pack main leads, doesn't result in cells that are at least similar in voltage, then you have some damaged cells (usually the ones that have dropped most in voltage).

Well I will not being doing that until I have a working power supply ...
I have the pieces parts for a Riden RD6006 but I want to change the cooling to a single 60mm x 25mm 12 volt noctua fan running from the switching power supply. I have to mod the case for the 60mm fan. Also I accidentally ordered the wrong fan .... 5 volts :oops:

"Self balancing" ... I have heard of that but not observed it actually happening. I just took careful readings on the rear five cells (one to five by your method). I will check tomorrow and see if there is any change. If it makes any difference the BMS is removed.

I saw a note where the BMS is "supposed" to scavenge power from the first four cells. However traces on the circuit board are not consistent with that. Perhaps this is a different version.

amberwolf said:
Another problem with the pack, probably unrelated to the balance issue, could be the interconnect method. It looks as if they just folded over the tabs onto each other for the series connections. Is that the case? Or is there some form of weld between them?

The tabs are folded over and soldered together. I am hoping that those four cells are just a bit ahead on the discharge curve than the other 8. That voltage falls rapidly as it approaches full discharge.

imotor pouch battery terminals(1024).jpg
 
Ah, the classic signalab BMS that drains it's power from 4 cells and eventually kills those.

Must be a ping battery or an offshoot.
Wonder how old it is..

With extensive balancing, you'll find out if it's worth keeping or not. It would need to be on a charger for days to accomplish that.

I'd return it by any means possible if the 4 cells cause the battery to hit LVC very early in real world riding.
 
neptronix said:
I'd return it by any means possible if the 4 cells cause the battery to hit LVC very early in real world riding.

Not possible to return it .. at least not legally unless I rent a vehicle and drive to Utah myself.

At this point, the worst case scenario is I salvage the 12 good cells.
 
SO I plan to through and charge each cell to 3.50 volts or at least what the power supply thinks is 3.50 volts. There can be a significant difference between the voltage at the power supply terminals and that read across an individual cell .... especially during charging. This picture is the "Start" and "End" of charging cell number two.
cell charge.jpg
This is one of the problem children. I have not yet set the calendar date and time but one can still derive the delta between the start and end: six hours twenty minutes. It could take a while to get through all 16 cells. Hopefully when I get through the four cells at the lower end the process make take a tad less time. The other thing to note is the number of amp hours pumped into the cell: 13.68. Immediately after charging this cell the voltage was 3.44 volts across the cell terminals. This Power Supply has sufficient "Mojo" to bulk charge the entire pack. I will use that to bring the pack up to 58.0 volts.

Edit Update:
Número tres gotas como una roca. It is already down to 2.6 volts :cry:

What about a nominal 48 Volt 15S1P LiFePO4 battery ?
 
LewTwo said:
Edit Update: Número tres gotas como una roca. It is already down to 2.6 volts :cry:

What about a nominal 48 Volt 15S1P LiFePO4 battery ?

I'm sorry to hear you learned a hard lesson about buying used batteries.
I don't even sell my used batteries. Too much of a PITA shipping them or worry about what happens to them in transit.

Those cells are 2C max, 1C sustained. So... 8-20A constant, depending on the ping cell.

Given that the pack is probably significantly aged, it may perform more like a 0.5C cell now. So your continuous current expectations need to be really low.
 
neptronix said:
LewTwo said:
Edit Update: Número tres gotas como una roca. It is already down to 2.6 volts :cry:

What about a nominal 48 Volt 15S1P LiFePO4 battery ?

I'm sorry to hear you learned a hard lesson about buying used batteries.
I don't even sell my used batteries. Too much of a PITA shipping them or worry about what happens to them in transit.

Those cells are 2C max, 1C sustained. So... 8-20A constant, depending on the ping cell.

Given that the pack is probably significantly aged, it may perform more like a 0.5C cell now. So your continuous current expectations need to be really low.

Everyone keeps referring to these as PING cells. Forgive my ignorance but I thought "Ping" was a brand name. This pack is branded as "Imotorbattery" which appears to the same chinese manufacturer as "BTR Battery" which are both selling current LiFEPO4 pouch batteries rated at 5C.

It has also been a very enlightening and educational experience. I have learned a lot more about lithium batteries and I finally got the 'round to it' required to assemble my Riden RD6006 power supply.
 
Well yes, this is ping battery's design, both the cell layout, the choice of bms, how things seem to be wired, etc.. so i call it a ping battery.. or more technically, a ping battery clone.

Hey, glad you learned. That's what this place is all about. :)
 
amberwolf said:
If manually charging up all the cells to the same 3.65v, then letting them all sit for a day without anything connected to the balance or pack main leads, doesn't result in cells that are at least similar in voltage, then you have some damaged cells (usually the ones that have dropped most in voltage).

You do realize that took me the better part of a week?

The first run took 4 days so some the cells had rested anywhere from 4 hours to 4 days.
(not to mention that the big dummy somehow managed to skip cell number 4 on the first run)

It took 3 runs charging to 3.50 volts to get them to a common level.
Then I bulk charged the pack up to 58 volts.
After 'resting' for 24 hours all the cells measure between 3.35 and 3.45 volts.
At least they are fairly consistent even if a bit on the weak side.

Assuming that they are NOT glued together ...I think that I will likely break these up into four 12 volt packs with 4mm bullet connectors and external balance leads. Then I can charge them separately with my ISDT Q8. The bullet connectors will allow me to configure them from 12 to 48 volts. Then I can use them power remote WiFi video cameras, run a small inverter, power an arduino project or supplement my e-bike packs for trips that might otherwise exhaust the on board battery.
LiFePO4 Watt hours (1024).jpg
 
LewTwo said:
You do realize that took me the better part of a week?
Sorry, didn't mean to waste your time on stuff...just that this is one of the best ways to find problem cells in the situation you have. (I think I spent a month or something like that working out the problems with my first non-nickel commercial battery pack, the *first* time, and probably taht again later on when it got worse).
 
amberwolf said:
Sorry, didn't mean to waste your time on stuff.....
Definitely NOT a waste of time. I learned a lot. Thank you for the advice.
I also have a new power supply/charger as well as a capacity tester.

I was also able to diagnose the problem on my Shark 52 volt MCA battery pack and will be installing a new Daly BMS.
Down the road a bit I intend to run a capacity test on my Golden Motor 36 volt pack (it is just over 6 years old).
 
Let us know how the Daly BMS works out, and which version you use. I don't know if this will work for Daly (is meant for JBD/XiaoXang) but if you have the time and desire, you might want to try out the OS monitoring software over here: https://endless-sphere.com/forums/viewtopic.php?f=14&t=110621 .


I have been considering using something as a BT-capable monitoring device for a while now, mostly for testing / curiosity rather than necessity, as I have been running with no BMS for years on the EIG cell packs, and have never had a really good way to monitor all the cells during a ride for test purposes. (I have a celllog-based monitor system on the way now, and it may do everything I need without having to be connected except when using it...but I'd still like to see more detail on the Daly and similar BMSs).
 
amberwolf said:
Let us know how the Daly BMS works out, and which version you use. I don't know if this will work for Daly (is meant for JBD/XiaoXang) but if you have the time and desire, you might want to try out the OS monitoring software over here: https://endless-sphere.com/forums/viewtopic.php?f=14&t=110621 .

thank thee :)
I will have to take a closer look at that when I get the Daly in and can ID the chips used. I have done some python programing in the past so I should be able to follow the code.
 
amberwolf said:
Let us know how the Daly BMS works out, and which version you use. I don't know if this will work for Daly (is meant for JBD/XiaoXang) but if you have the time and desire, you might want to try out the OS monitoring software over here: https://endless-sphere.com/forums/viewtopic.php?f=14&t=110621 .

I now have two of the DALY BMS units in front of me. These are the dirt simple common port version. The BMS you referred to in the other thread has other features with include a communications port. I also have a third "Electronic -Mall" BMS purchased by mistake (Max discharge 15 Amps).

The one thing all three of these have in common is that the balance lead connectors use 2.0mm pin spacing as opposed to 2.54mm. Just something to be aware of. Yet another series of connectors to start filling my box with.
 
Well this is what I wound up with. Not sure what I going to do with this 17 pound beasty. It may just become bench top power supply. With a buck converter it should be able to run an Arduino Nano for several hours.

So I just closed the case up with some fiberglass strapping tape. Note that the BMS (15 Amp max discharge) is now OUTSIDE the battery assembly and it also has 4mm bullet connectors. Lastly I put the female half of an Amass XT90 Anti spark connector on the wires.

Question: When does a AntiSpark connector fail?
Answer: When you have a direct short.

I ran too much current through my Peacemark capacity tester. The next time I tried to plug it in the AntiSpark Connector SPARKED! Smoked the built in resistor. The light bulb you seen in this picture is my new load tester :oops:

X1(900).JPG
 
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