AliExpress Order 1 of 4 cells bad

hpd611

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May 19, 2021
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7
Thanks for any feedback you have. I ordered and just received 4 120ah 3.2v LiFePo4 cells and a Daly BMS.

The short question is this: 1 of the cells is bad and tested .2 volts lower upon receipt, but only put out 77.4ah dropping off way sooner than the others. I have 15 total days to open a dispute on AliExpress. I've sent the seller a message. I'm wondering what to expect and if it's best to open a dispute right away or to wait? And if they say they will send another and they don't or it is bad, will AliExpress still help at all? I'll provide more info and photos below. Thanks a bunch for your time and for the knowledge shared here!

(I'm new to LiFePo4 in practice, but have done tons of research and have a strong background in electronics down to the component level.)
After charging and upon testing these cells as a battery, I was only able to get 77.4ah. At this time the BMS cutoff on the bad cell at 2.5 the pic shows my order info and the BMS as well as the shunt meter reading. I believe the cell is bad, just wondering what to expect from an AliExpress seller as far as a replacement goes?
 

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hpd611

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May 19, 2021
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I did NOT. Wasn't aware of that step but researched after reading your comment. I'll get to work with my fingers crossed! Thanks so much for your time. I'll let you know how it goes!
 

rickst29

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Mar 27, 2021
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After you re-test with top balancing (and if you find it still lacking in capacity), then I recommend that you DO open the formal complaint on time. Ali-Express will advise the seller to resolve it with you privately, and the private messaging process can proceed as you have now started. The seller will probably prefer to do a partial refund, rather than ship only one replacement cell. If you can find a comparable single cell from a USA supplier, that becomes your starting point in negotiating a refund amount.

You state that replacement cost as the price to make to 'make it right', they come back with a much lower figure, and you should meet somewhere in the middle. You can advise then advise the Ali-Express Guarantee 'Process' that a refund agreement has been reached, using the online response mechanism.

(As you've already guessed, I have executed a similar process on a similar problem - although that process was executed with a DhGate Seller, rather than Ali-Express.
 

hpd611

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May 19, 2021
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Doing the top balancing was clearly better for the cells, unfortunately the one is still bad. While the others were holding between 3.12 and 3.14, the bad one dropped out to the cutoff at 2.5. I did get 84.5ah this time vs 77.4ah previously.

I would like to test the individual cells, but I don't have anything that can draw a load of more than 2amps. Any common suggestions of tools or things around the house or RV for a higher amp load at the voltage of one cell? I need to get a good bench supply and load tester.

Thanks to both of you for your time! I will be practicing and preaching top balancing from now on! I'll also get my complaint opened with AliExpress.

Thanks again. This is the most useful forum experience I've had in a long time!
 

FrankS

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Aug 1, 2021
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Doing the top balancing was clearly better for the cells, unfortunately the one is still bad. While the others were holding between 3.12 and 3.14, the bad one dropped out to the cutoff at 2.5. I did get 84.5ah this time vs 77.4ah previously.

I would like to test the individual cells, but I don't have anything that can draw a load of more than 2amps. Any common suggestions of tools or things around the house or RV for a higher amp load at the voltage of one cell? I need to get a good bench supply and load tester.

Thanks to both of you for your time! I will be practicing and preaching top balancing from now on! I'll also get my complaint opened with AliExpress.

Thanks again. This is the most useful forum experience I've had in a long time!
after a few month have past - can you give us an update what happened?
 

GR6627

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Apr 17, 2021
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Location
SF Bay Area
Doing the top balancing was clearly better for the cells, unfortunately the one is still bad. While the others were holding between 3.12 and 3.14, the bad one dropped out to the cutoff at 2.5. I did get 84.5ah this time vs 77.4ah previously.

I would like to test the individual cells, but I don't have anything that can draw a load of more than 2amps. Any common suggestions of tools or things around the house or RV for a higher amp load at the voltage of one cell? I need to get a good bench supply and load tester.

Thanks to both of you for your time! I will be practicing and preaching top balancing from now on! I'll also get my complaint opened with AliExpress.

Thanks again. This is the most useful forum experience I've had in a long time!
Maybe try again as it sounds like you were in a hurry, and 3.14 is not full charge. At 3.14 you are on the middle/downward curve of the SOC.

Try charging to 3.6 in parallel, I let the charger go to zero Amps @ 3.6V (actually 100mA or less works fine). Let stand for 24-48 hrs. Then reconnect in Series with a BMS and run the discharge test.

With Top balancing patience sometimes pay off. ;)
 

hpd611

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May 19, 2021
Messages
7
after a few month have past - can you give us an update what happened?
Thanks for the inquiry. I ended up purchasing another 120ah battery with the same specs off of ebay. I did a parallel top charge to 3.6v and it seems to be working great now. The one cell was just not cutting it and I believe it was bad. I can also tell you that going into this I has believed that the balance charging by the BMS would be much more impactful and active than it is. Balance charging by the BMS takes many charges to have much impact on a single cell, so good top charging is a must.

I purchased these cells and an 80amp Daly BMS on Aliexpress. They were terrible to deal with trying to get a refund for the amount of the 1 bad cell. The company selling refused to respond at all to any of my messages asking for assistance, and then when I filed the dispute it was very clear that Aliexpress is loyal to their sellers, not their buyers. I had provided photos of all readings and the information that I had. It was more than enough to prove what I was saying. I was super nice and not one of those raging angry customers that some people are, but they still didn't care. They insisted that I hadn't proven to them that the cell was bad. So I had to make a video. I put together a several hour video showing that the cell would not maintain during the discharge. This was a pain in the rear as I had to find a phone that I could keep the screen on and stay connected to the BMS via the app, then make sure that I showed the load and battery cells along with the readable display all in the same frame. This was silly as I had already given them the photos and the video didn't show anything different. I finally had to threaten to dispute the charge with my credit card company before they finally agreed to a small refund. The amount was less than 25% of the purchase, but I had my fill of dealing with them so I just eventually accepted it. It was clear their policy doesn't protect the customer the way they claim and I'll be very cautious of any purchase in the future from them, if I buy from them at all.

I would also suggest buying the Overkill BMS recommended by William on this forum. The support documents for the Daly BMS leave much to be expected and I had no idea that the max charging current was only 40amps until much later in the process. There are cheaper options, but for safety, quality, and care of the cells, the Overkill is probably worth it. It's also well worth having a good power supply to do the top balancing with. Parallel charging 4 120ah cells (total of 480ah) at 3.6 volts and 10amps max, but more like an average of 6amps, takes several days. You can turn up the voltage a bit while you're monitoring the cell voltage, but be ready as these cells fill and the voltage climbs on a very short curve.

Thanks again to everyone that took the time to help me, and if I can share any tips from my build, feel free to ask!
 

GR6627

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Apr 17, 2021
Messages
9
Location
SF Bay Area
Glad it worked out. For future reference you can hook the cells up in their 12V configuration WITH THE BMS for initial charge for top balancing, Typically this is much quicker as chargers are generally 20 Amps or more. Then reconfigure the cells in parallel for top balance/charge. Generally you will only need a few amps from your 10 amp (variable) bench supply. Typically this cuts you time in half, or less.

I've been using JBD 100A BMS's. You will notice that they are very similar to Overkill (i.e. probably Overkill's source), with the same features for about $70 with Blue tooth dongle. The difference is documentation, Overkill does a great job here where JBD is very basic.

If you watch Wills tutorials, and postings, as well as the members here, you will gain a lot of knowledge on LiFePo4 cells, and their applications.
 
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