Battery cell pouch

[dnmun]

there is no way to guess what the problem is without measuring the cell voltages.

you need to use the normal sequence and start with #1 at the bottom or others get confused.

you dimensions are off by about a factor 10 too. 1/4"=6mm. most pouches are 7-8 mm thick too.

you should be able to discharge the battery from the red and black wires coming from the BMS. but measure the cell voltages on the sense wire harness.

you can build a constant current discharger, but it would require extensive electronics experience. frodus sold one recently but it was more than your battery would cost new.

of course the current will change as the voltage changes so you have to make accurate regular measurements unless you have a wattmeter. then you can integrate the current over time to find the amount of charge delivered. you will need a wattmeter or cycle analyst anyway so this would be an opportunity to buy one.

 

[ambroseliao]

I need some information regarding the locating a vendor for one battery cell from my pack.

ZQPT 11140165
3.2v 15Ah
NT20100601-3784

Thanks. Regards JJ

Did you try Googling the company name?

http://www.zqpt.com/en/

:lol:

 

[SamTexas]

Milou: What do you really want to do?

1) Do you want to verify that cell #15 is the root cause if your current problem? If so, do the capacity test on that cell only as I suggested earlier. There is no need to maintain a constant current discharge. You can use a 12V, 50W lightbulb and connect it directly with clips to your pouch. That should give you a current of around 3A at the beginning and dropping to around 2A when the cell is down to 2.0V. If that process lasts 1 hour, then the capacity is roughly 2.5Ah ((3+2)/2).

2) Do you want to do a complete and accurate capacity check for the whole pack? If so, it would be more involved and more time consuming, but it can be done.

Why worry about finding a replacement cell now when you haven't determined the root problem? Worst case is you would end up with a 14 cells pack.

 

[docnjoj]

[Hi:
I have been reading about "how to battery-capacity-testing". A lot of unknown Mumbo-Jumbo. Given the battery voltage is not constant! When you attach the load, the battery voltage will slowly drop as the battery drains. Is there a way to use a constant-current load. Where such a load will remain constant regardless of the battery voltage (drawing a constant current)?

I assume I will put the load with clips to the cell pouch or battery pack? I bypass the BMS sensor. Else, how do I put the load to the three prongs from my battery pack (see attached PDF file)?

On another note: I already know my battery pack does not function as it should. Now I am suppose to find out why and where? When I find the problem with one of the cells, I will need to replace it. Given that the other good cells have been somewhat used, I would be putting a new cell with them. It appears there would be a balance issue again??? Not only the capacity but also the cell dimenssions (I have not yet found an identical replacement to the cells I have). Would it not be better off to change the whole battery pack as new?

Regards JJ

[/quote]

It's easy if you have a Wattmeter or TWM. Just hook a resistance (I use a food warmer tray) and measure the capacity of tha battery through the BMS. Then do as Sam and Dnmun have suggested when you find the capacity low. Do the same with cell 15. Keep an eye on the voltage but it is probably gunna go down fast. It is a lot cheaper to repair a battery than replace it!
otherDoc

edit: I looked up that company and they have a number of different cells. You may find one that matches your battery. E-mail and see if you can order the required number if there is more than 1 in parallel. They should send them for no charge but don't count on it! If all else fails buy a Ping battery. He would help with this kind of problem!

http://www.zqpt.com/en/

 

[dnmun]

you will see the low cell right away when discharging. the trick is to make sure you have fully charged that cell before you do the capacity test. so it has to get to 3.65V to be certain, but it may drop to 3.35V quickly. but once you know it was at the 3.65V level you can assume that it still has essentially all that full charge even at the 3.35V level. when thye are damaged, they don't hold the resting voltage.

but as soon as you start discharging, all the cells will be 3.3-3.2V depending on the load. later as the battery is used up it's charge the voltage will drop below 2.9, 2.7 then go down fast to 2.1V which is fully discharged and the BMS should shut off then.

if you are using a turnigy wattmeter, it will forget the last reading when the BMS shuts off at the 2.1V level so monitor it closely at the end. or you can use the 5V power supply for it that plugs into the side.

 

[docnjoj]

Yep! Good point dnmun! I use either a Wal wart at 5 v or a 9 volt battery plugged into the whattmeter. I have made enough of these mistakes so I now can make different ones! Hobby shops have the correct micro-servo plug, The meter will shut down otherwise when the BMS shuts down. For the single cell check stay awake and try not to drain it completely. Ideally you should have a second voltmeter just on cell 15 while you are doing the test.
otherDoc

 

[dnmun]

if you install the turnigy wattmeter in the black wire that connects the BMS to the battery negative, then you would be able to have it continue to display after the BMS had shut off. the wattmeter does consume more current than the BMS though, i think.


but if you wanted to do something like that then you could even put a switch in the red wire. you don't have to have current flowing in the big red wires to the wattmeter. just the voltage, so it can be a 26G wire even.

then if you have a switch in that small wire from the battery to the wattmeter, you could turn off the wattmeter when it is not used, and then when you use it and it shuts for LVC, it would still maintain the last reading up until the BMS cut off. that would be cool. you could take the shunt out like in the remoter wattmeter thread, take the shunt out and embed it in the black wire to the battery from the BMS, then run the two shunt leads to the wattmeter and you could take the voltage off of a 'fused' small wire on a switch from the battery plus. that could be 26G too, just like the shunt wires to the wattmer.

 

[docnjoj]

if you install the turnigy wattmeter in the black wire that connects the BMS to the battery negative, then you would be able to have it continue to display after the BMS had shut off. the wattmeter does consume more current than the BMS though, i think.


but if you wanted to do something like that then you could even put a switch in the red wire. you don't have to have current flowing in the big red wires to the wattmeter. just the voltage, so it can be a 26G wire even.

then if you have a switch in that small wire from the battery to the wattmeter, you could turn off the wattmeter when it is not used, and then when you use it and it shuts for LVC, it would still maintain the last reading up until the BMS cut off. that would be cool. you could take the shunt out like in the remoter wattmeter thread, take the shunt out and embed it in the black wire to the battery from the BMS, then run the two shunt leads to the wattmeter and you could take the voltage off of a 'fused' small wire on a switch from the battery plus. that could be 26G too, just like the shunt wires to the wattmer.

Now that is a cool idea! Thanks dnmun!
otherDoc

 

[Milou]

I need some information regarding the locating a vendor for one battery cell from my pack.

ZQPT 11140165
3.2v 15Ah
NT20100601-3784

Thanks. Regards JJ

Did you try Googling the company name?

http://www.zqpt.com/en/

:lol:

After my posting I did see the site, contacted them, and still have no response (~2 months). But thanks for the heads up.

Thanks for the reply to the battery pack replacement option. I was not aware you could use one less cell. I was thinking in the order of increasing the amperage on a new battery pack for more torque on the hilly area I live. Say 36V 20amps = 750W. I am not sure my motor rated at 500W 48V 15A can take other options? I imagine it all depends on the motor's winding and magnet levels? In any case, I will do the battery testing in a few days (my regular job is keeping me busy).

FYI, I saw this web page about "Battery Capacity Tester":

http://www.freeinfostuff.com/CapacityTester/New/NewCapacityTester.htm

You guys would know more about the feasibility of it but, seems interesting. Thanks again all you guys. Very helpful. Regards JJ

 

[Milou]

I have read and re-read your posts. Given what I understand from all your posts, I will be doing the capacity check soon and need confirmation on some details you gave me. The measuring instruments I will be using are two multimeters to keep track of the voltage/amps and do the calculation:

On a whole battery capacity check. The BMS will cutoff when the first cell from the pack reach 2.1V. How will I know the number (1st to 15th) cell it will be (without watt-meter)? And given the sense wires will be hooked to the BMS.

...you need to use the normal sequence and start with #1 at the bottom or others get confused. ...

Is the number 1 cell in a pack suppose to be the cell coming/going to/from the main negative, black cable (Where I named mine on the PDF file #15)?

...you should be able to discharge the battery from the red and black wires coming from the BMS. but measure the cell voltages on the sense wire harness. ...

If the sense wires are hooked to the BMS (for shut-off to function) how is one suppose to measure from them? I assume directly from the battery tabs???

Milou: What do you really want to do?

1) Do you want to verify that cell #15 is the root cause if your current problem? If so, do the capacity test on that cell only as I suggested earlier. There is no need to maintain a constant current discharge. You can use a 12V, 50W lightbulb and connect it directly with clips to your pouch. That should give you a current of around 3A at the beginning and dropping to around 2A when the cell is down to 2.0V. If that process lasts 1 hour, then the capacity is roughly 2.5Ah ((3+2)/2). ...

Where does the 3 (three) in the calculation ((3+2)/2) come from? One amp usage in one hour is one! I will most likely test the battery capacity one cell at a time. Easier for beginners.

 

[dnmun]

he meant to show how to calculate the average if it was two hours total, 3A at the start and 2A at the end.

using a wattmeter like the turnigy ($24) is more accurate and easy since you can discharge the battery through the wattmeter and it will record Ah directly over time as the pack discharges.

you can measure the voltage right on the top of the pouches if you can reach them. or you can use the sharp tips of the voltmeter and stick them into the plug on the end of the sense wires if it is accessible.

once you start measuring, it will be obvious if there is one cell that is less capable than the others. the voltage will drop from the 3.3V level by itself while the others remain at that level for a longer time. when it gets close to 2.1V you wanna keep track of the total Ah if using a wattmeter because it will lose the measurements when the BMS shuts off. keep track of which other cells also drop fast. when it gets down to 3.05V the cell is about 75% discharged, 2.9V 85%, 2.8V 90%, 2.7V 95% discharged

if you use the ammeter function of the voltmeter, you need to use the 10A scale. so the black probe of the voltmeter goes into the 10A spot on the meter.

you can use alligator clips to hold the meter probes onto the ends of the wires when discharging through the voltmeter. or you can buy some of the hsort jumpers with alligator clips on each end to make the connection.

 

[SamTexas]

Milou: What do you really want to do?

1) Do you want to verify that cell #15 is the root cause if your current problem? If so, do the capacity test on that cell only as I suggested earlier. There is no need to maintain a constant current discharge. You can use a 12V, 50W lightbulb and connect it directly with clips to your pouch. That should give you a current of around 3A at the beginning and dropping to around 2A when the cell is down to 2.0V. If that process lasts 1 hour, then the capacity is roughly 2.5Ah ((3+2)/2). ...

Where does the 3 (three) in the calculation ((3+2)/2) come from? One amp usage in one hour is one! I will most likely test the battery capacity one cell at a time. Easier for beginners.

The 3 is the current at the beginning of the discharge when the cell is still fully charged. As energy is being depleted, the cell voltage would gradually (very gradually for LiFePo4) drops along with the current. At the end of the discharge (when the cell voltage is around 2.0V) the current is 2A. The average current is 2.5A ([3.0A+2.0A]/2). Since the discharge process lasts ONE hour, the total capacity is 2.5Ah (2.5A * 1 hr).

Those are just guesstimated values to show how the capacity of the cell can be calculated without more sophisticated equipment. Your actual number will be different but should be close. Here's one more example:
Current at the beginning of the discharge (cell voltage at around 3.60V): 4.5A
Current at the end of the discharge (cell voltage at around 2.00V): 2.3A
Total time for cell voltage to drop from 3.60 to 2.00V: 45 mins (0.75hr)
Average current = (4.5 + 2.3)/2 = 3.4A
Capacity = 3.4A * 0.75hr = 2.55Ahr

Milou: Better tools make the job easier but can also overwhelm a new user with less experience. A watt meter can not monitor all the cells' voltage simultaneously. Keep things as simple as possible for now so you can finish your task. To ascertain that cell #15 is the root cause of your problem, you only need a few simple tools:
1) a 12V 50W lightbulb. You can also use a smaller lightbulb, 12V 20W or 12V 30W. But don't use anything larger than 12V 50W. Your multimeter might not be able to handle the higher current.
2) TWO multimeters. One to monitor the cell voltage and one to monitor the current. If you don't know how to monitor the current, ask.
3) A clock or a watch to monitor the time.
4) A few alligator clips to make the connections DIRECTLY to cell #15. The BMS is completely out of the picture in this test.

he meant to show how to calculate the average if it was two hours total, 3A at the start and 2A at the end.

Should read: he meant to show how to calculate the average if it was ONE hour total, 3A at the start and 2A at the end.

 

[Milou]

Thanks SamTexas. The word "average" was the key word missing in my mind. I am delaying the purchase of a Turnigy until later (Xmas dented my pocket book. Presents for others is presently more important, for now). I do have two multimeters and will take the time for testing one battery cell at a time. Thank you all of you for the help. Will keep you posted on the result (next year!). Regards JJ

 

[dnmun]

you do not test it by discharging one cell at a time. nonsense. not sure why you think you have to do that. not gonna explain how to do it again but that is just silly.

 

[Milou]

you do not test it by discharging one cell at a time. nonsense. not sure why you think you have to do that. not gonna explain how to do it again but that is just silly.

I am not understanding? One person says "yes it can be done" and another says "no it cannot"??? I do understand on your method of explanation and would do it. Personally, as a beginner, I feel more secure doing small steps with the tools I presently have available. I will look back over the details of all the posts to see what I am missing in all of this. Regards JJ

 

[SamTexas]

There is nothing wrong in testing every cell, one at the time. In fact that's how it's done by every reputable pack builders to ensure maximum capacity for the pack (a group of cells in series).

That said, you don't have to test all the cells in your pack because you're not building a new pack. Your goal is to identify and eliminate (or replace) the weakest or dying cell in your pack (presumably cell #15) so your can restore the overall pack capacity.

Background: Suppose you have 9.6V LiFePO4 pack. It consists of 3 cells in series. Cell #1 has a capacity of 15Ah, cell #2 has a capacity of 13Ah and cell #3 has a capacity of 5Ah. Your 9.6V pack has the capacity of 5Ah (48Wh [9.6*5] pack's total energy), the same amp-hour as that of the lowest cell.
1) If you eliminate cell #3, you'd end up a 6.4V pack with capacity of 13Ah (the same as that of the next lowest cell), 83Wh (pack, not cell)
2) If you replace cell #3 with a new 13Ah cell, you'd end up with a 9.6V pack with capacity of 13Ah (same as cell #2 capacity), 125Wh
3) If you replace cell #3 with a new 15Ah cell, you'd still end up with 9.6V pack with a capacity of 13Ah (same as cell #2 capacity), 125Wh
4) If you replace both cells #3 and #2 with new 15Ah cells, you'd end up with the maximum capacity of 15Ah or 144Wh.

Back to your situation: Your pack is rated at 15Ah but from your description the capacity is nowhere near it. I analyzed on the reasonable assumption (based on the info you provided since the beginning of this thread) that cell #15 is the culprit and that its capacity has drastically reduced (resurrection from 0.0V voltage). So you only need to test that cell. If the cell capacity is indeed low (7.5Ah or less) it must be eliminated or replaced with a new cell. Once eliminated or replaced, your pack capacity will be that of the next lowest cell capacity.

Don't despair, you are getting close to identifying the root cause of the problem.

 

[Milou]

Hi: I finally got time to test the single battery cell #15. As indicated I used a 12V, 50W bulb. Problem, I ended up with 0.4V, 0.00Amps after 8hrs 30min. It took a lot longer than what I though. Here are the results from the first 6hrs 30min:

1:26PM -- 3.6 V -- 2.016 Amps
7:56PM -- 3.2 V -- 1.906 Amps

It is the last two additional hours (@ 9:56PM), I got distracted and forgot to check in between. When I got there it was too late. Total discharged cell!!! My fault. I guess, now I know the cell needs replacement. I am not sure if the above numbers can tell me anything if it was a good cell or not? During the first six hours it seem to have remained steady. Thanks for feedback. Regards JJ

 

[dnmun]

@6 1/2 hrs you had used about 12.75Ah, almost 13Ah.

usually the BMS will turn off the discharge when the cell drops to 2.1V to protect it.

we never learned if your BMS would do that.

i had assumed your BMS would shut off for low voltage because this thread started when your BMS was shut off then.

did you immediately charge the cell up now that you have decided to use a single cell charger?

i'm sorry, this has happened to a lotta people who ask to get instructions here.

just don't overcharge it napping when recharging like the last guy did.

 

[docnjoj]

Those Voltphreaks single cell chargers are only 10 bucks apiece and will prevent overcharge of LiFePo4. Sounds like cheap insurance to me. I don't have to stay awake during the charge. Good thing 'cause I'm old amd fall asleep easily, expecially doing boring stuff like watching a DVM.
otherDoc

 

[Milou]

@6 1/2 hrs you had used about 12.75Ah, almost 13Ah.

usually the BMS will turn off the discharge when the cell drops to 2.1V to protect it.

we never learned if your BMS would do that.

i had assumed your BMS would shut off for low voltage because this thread started when your BMS was shut off then.

did you immediately charge the cell up now that you have decided to use a single cell charger?

i'm sorry, this has happened to a lotta people who ask to get instructions here.

just don't overcharge it napping when recharging like the last guy did.

Hi: The battery cell is rated at 3.2V 15Ah. Is the 13Ah good, bad, or ugly?

I already know my BMS is shutting off. It has happened several times on me while riding. What I do not know is who (battery cell) is causing it? And why? Any way I look at it, my pack is not good as 100% capacity.

Those Voltphreaks single cell chargers are only 10 bucks apiece and will prevent overcharge of LiFePo4. Sounds like cheap insurance to me. I don't have to stay awake during the charge. Good thing 'cause I'm old amd fall asleep easily, expecially doing boring stuff like watching a DVM. otherDoc

Over charging is one thing, over discharge is (I assume) another thing. I agree I need both.

Presently, my main problem is manual and/or automatic "cut-off" situation while testing. Given the #15 cell was already at zero once before, I recharged it, and again back at zero. I wonder, if it will go back up and test the capacity again (correctly this time)? I guess, I will go through this again. Regards JJ

 

[docnjoj]

[Presently, my main problem is manual and/or automatic "cut-off" situation while testing. Given the #15 cell was already at zero once before, I recharged it, and again back at zero. I wonder, if it will go back up and test the capacity again (correctly this time)? I guess, I will go through this again. Regards JJ

It might pay to start looking for at least 1 individual cell with similar specifications, even if you have to get it from Batteryspace. Then check how those cells are attached to each other. If soldered to a PCB this makes repair easier, but certainly not anywhere near as easy as a screw in attachment like agniusm, Headway or OSN. I'm making this repairability a prime requirement for my next battery. Even hobby lipo can be pretty modular so repairs can be fairly simple. These batteries must be made salvagable since they cost so damn much!
otherDoc

 

[SamTexas]

Milou: I'm about to give up! The data you provide do not match the actual test results. Here are the lastest info you provided:

- Your fully charged battery could only power your scooter 2 miles. When power was cut, you immediately measured each cell voltage and cell #15 was the lowest at 2.9V while all other cells were at 3.2V. That conclusively says cell #15 is the culprit. Since you were only able to travel 2 miles, you could not possibly consume more than 4Ah at the very worst.
- Your capacity test on cell #15 results in 12 to 13Ah, or at least 3 times more than expected. This is in direct contradiction of the above data.

I'm not sure how to proceed. I suggest you go back and review all your posts in this thread (skip everything that's related to your charger) and see if you can detect any info that might not be factual.

I can only think of one FAR FETCHED possibility: Although cell #15 still has 13Ah, it no longer has the ability to deliver high power. In other words, its voltage sags horribly at high current draw. Bad enough to trigger the BMS LVC. Here's how to test it. It should not take long.

- Recharge cell #15 to 3.65V.
- Do a high discharge capacity test. In the previous test you used a 12v, 50w bulb. Now you need 5 of them to get the current (amp) up to 10A. Don't use your multi meter to measure the current, you will ruin it.

Watch the voltage constantly. If the far fetched possibility is indeed true, the voltage would drop to below 2.5V in less than 30 minutes.

 

[Milou]

Milou: I'm about to give up! The data you provide do not match the actual test results. ...

Hi Sam: I'm the one who should "give-up". Although, it is not my motto. In any case, If you are stump by my results then I am certainly lost.

...- Your fully charged battery could only power your scooter 2 miles. When power was cut, you immediately measured each cell voltage and cell #15 was the lowest at 2.9V while all other cells were at 3.2V. That conclusively says cell #15 is the culprit. Since you were only able to travel 2 miles, you could not possibly consume more than 4Ah at the very worst.
- Your capacity test on cell #15 results in 12 to 13Ah, or at least 3 times more than expected. This is in direct contradiction of the above data.

I'm not sure how to proceed. I suggest you go back and review all your posts in this thread (skip everything that's related to your charger) and see if you can detect any info that might not be factual. ...

I was not sure if 13Ah was a good result but, you seem to confirm it is. I was also surprised the cell lasted this long (6.5hrs) with little amp drop.

Given all my test results, perhaps another cell is bad or maybe the BMS, controller??? I have gone back and forth on my postings as well as others posting many, many times. My familly is starting to worry about me!!!

...I can only think of one FAR FETCHED possibility: Although cell #15 still has 13Ah, it no longer has the ability to deliver high power. In other words, its voltage sags horribly at high current draw. Bad enough to trigger the BMS LVC. Here's how to test it. It should not take long.

- Recharge cell #15 to 3.65V.
- Do a high discharge capacity test. In the previous test you used a 12v, 50w bulb. Now you need 5 of them to get the current (amp) up to 10A. Don't use your multi meter to measure the current, you will ruin it.

Watch the voltage constantly. If the far fetched possibility is indeed true, the voltage would drop to below 2.5V in less than 30 minutes.

I am an agree with this statement. Personally, I think the battery as a whole is not "high power" for my needs (rolling hills, and steep climbs). Obviously, with meters attached all over I would get a better idea of who, what, how, when, where the battery gives up? This will be for another time for me. After buying several 12V 50W bulbs I would be better off buying a new cell. The most difficult battery testing process for me is the time from my work, family, and other pressing things. That is why I come back and forth so late on this. Thanks again. Regards JJ

 

[SamTexas]

You're welcome Milou.

Yes, the test data shows you have about 13Ah on cell #15 at around 2A rate. I agree, the heck with the battery, family is more important. And finally yes, there might be more problems with other cells and the BMS. Personally, I would have trashed the BMS long ago. It's totally useless (if not harmful).

Anyway, come back when and if you're ready to continue. PM me if you don't feel like posting here.