I wanted to share my recent (September 2022) disappointing experience buying prismatic cells to the forum. My plan was to buy a small group of prismatic cells (20 cells) and test them before committing to several larger purchases based on the results of the test.
I first did a bit of research on LiFePO4 cells and purchased some test equipment and went on a hunt for a supplier. To keep the total battery cost per Ah lower I planned to use cells in the 280-300 Ah range.
Based on nothing much more than comments in the forum, YouTube videos and email replies from some of the suppliers I decided to use Docan and worked with Jenny Wu. I will try to rank each part of the experience on a 1 to 10 scale.
- Jenny Wu was very quick to respond to all my initial questions about the cells they have in stock. I could send Jenny Wu a question and within a few hours I would receive a reply along with the “are you ready to order” at the bottom of the email. A mark of a good sales person who is always trying to close that sale. Jenny seemed knowledgeable about their products and answered “most” of my questions about the cells very quickly. Often within a few hours.
- After many emails describing the cell specifications, when they were manufactured, condition, capacity, shipping, and billing and what the supplier would do if there are problems with the cells (the replies to testing questions were rather vague) I decided on the EVE 280K cells. Then we discussed prices shipped from China vs shipped from Houston and I elected to pick them up at the Houston warehouse.
- New 280 Ah cells and I can get them within a few days of ordering the cells. The price is a bit higher than other suppliers but other than that this seems like a reasonable deal. Due to a few of Jenny Wu’s answers being vague there are a few points off. (8/10)
- The actual purchase of the cells went very smoothly. (10/10)
- Setting up the pickup time was just a simple phone call and the people working at the warehouse were very friendly and helpful when I picked up the cells. (9/10)
- The cells are packaged very well and it is doubtful even the most careless delivery driver could damage them in shipment. (10/10)
- Once I had them back home a quick visual inspection of the of the cells showed them to be in very good condition. No bloating and with just a few visual blemishes. Not pristine but very good. (9/10)
- In the next step the QR Codes were checked to validate the cells were made in December 2021. Some were and some in January 2022 and some in February 2022. Only a few of the cells were made on the same day and those were in different boxes. This was a concern since I expected new cells to all be from one batch so I ask Jenny Wu if it was normal to have so many different manufacturing dates and mentioned my concern. After numerous emails asking this question, I am still waiting for an answer. At this point I must assume Jenny Wu is not planning to answer.
- My thought is that cells made in the same batch are going to match each other much better than cells from random batches. So for mismatched cells and poor customer service. (2/10)
- The voltage and IR of the cells were checked. The voltage ranged from 3.2861-3.2951 V and the IR 0.18-0.20 mΩ. This seemed within specification from the EVE product specification sheet. (10/10)
- The cells were charged to full capacity using the specifications from EVE Power Product Specifications for LF280K cells. They specify a charge rate of 0.5C at a voltage of 3.65 volts and a cut off change rate of 0.05 C. I could only charge at 40 Ah but I did use 3.65 volts as the voltage maximum and stopped charging at 0.05 C or 14Ah. The room temperature is 23-24C.
- All of the cells required ~180 Ah to fully charge and were shipped at a 34-36% SOC. No dead cells and nothing with a high SOC and none of the cells showed any swelling when charged to 100% SOC so a (10/10).
- The test conditions in the Eve Product Specifications were used as much as possible. Temperature 23-24C. After charging the cells to 3.65 V they sit for 60-90 minutes before the discharge test begins. A ZKETECH battery tester is used at 35Ah (0.125C) until the cell voltage is 2.8 V. At approximately one hour into the test the terminal temperatures are checked (23-24C). After the discharge test I either recharge to about 35% SOC or fully recharge if I plan to do a second test.
- Since my early results were coming back low (263-275) I contacted Jenny Wu and other than one message claiming “The Battery Test Factory uses 30Ah” they never sent or said anything more. So, between the low test results and no response from the supplier. (1/10)
As a follow up to the 30Ah claim 3 cells were tested at 35Ah and then at 30Ah. The results of the test were all within a maximum 0.4 Ah of each other. I also retested 3 cells using a cut-off of 2.5V vs the 2.8V. Using 2.5V cut-off voltage resulted in 2.4- 2.8 extra Ah of capacity.
To be fair one cell did meet the 280Ah capacity test. It tested at 285.8Ah and a repeat test on that cell was nearly identical at 285.6Ah. Another interesting note is the few cells that were from the same batch all tested nearly identical capacities.
Overall… I am disappointed with the cells performance from Jenny Wu but more importantly I am disappointed in how the supplier handles problems. Before the cells were purchased we covered testing and performance. I did not expect a refund but did expect more than being ghosted by the supplier. So was I ripped off. Yes, I feel I was... My thought is even if it is a reasonable price if the supplier sells you 280Ah cells and you don’t get 280Ah cells then you were ripped off. It is just a question of how badly you were ripped off. As it is I can build a 263Ah battery from these cells and start looking for a new supplier.
