Efest – Has anything changed?

Earlier this year i was sent a box of Efest cells to test by a long term and well respected customer in the vaping industry who was keen to get an understanding of the product they were supplying. An admirable move by a business in an industry that preaches battery safety but doesn’t always have the means/knowledge to show what is and isn’t safe and i was pleased they reached out for assistance.

Heres what happened…

Unboxing – The packaging I have to admit is good. Packed in pairs and/or individually cased (albeit more for display than protection) the packaging meets basic requirements for air or ground shipping in terms of security and isolation of cells. It’s nice to see a decent list of warnings on their use on the side in legible English. As a product you can take out of a box and put straight on a store shelf, so far so good…

Wraps, insulators and general appearance – Overall the cells are visually appealing. (I have no shame in admitting that my favourite colour is actually purple, which they all are). Warnings are repeated on the cell wraps which is great and it also includes almost all of the information required to be compliant with EU/UK battery legislation (missing the Li-ion marker). They appear to replace all of the insulators with their own matte black plastic ones. Not sure why but its no issue.

So now the juicy bit. How did they perform? 

Efest 18500 1000mAh 15A

Picture of Efest 18500 1000mAh 15A Discharge Test

Efest 18500 1000mAh 15A Discharge Test

Test 1 carried out with Cell “1” – Capacity Test @ 5Amps

  • Start Voltage 4.190v
  • Ambient Temperature 23’C
  • End Temperature 38.9’C
  • End Voltage 2.81v
  • Capacity Delivered 996mAh

*This test is solely for capacity, to ensure the cell delivers the amount of energy it promises on the wrap. 996mAh is a good result for a 1000mAh rated cell, especially at a third of its maximum discharge rating.

Test 2 carried out with Cell “2” – Discharge Test @ 10Amps

  • Start Voltage 4.194v
  • Ambient Temperature 23.2’C
  • End Temperature 51.6’C
  • End Voltage 2.80v
  • Capacity Delivered 984mAh

Test 3 carried out with Cell “1” – Discharge Test @ 15Amps

  • Start Voltage 4.196v
  • Ambient Temperature 24.1’C
  • End Temperature 73.4’C
  • End Voltage 2.83v
  • Capacity Delivered 1030mAh

Interestingly Cell 1 delivered a very slightly better capacity on the second charge and discharge but only by fraction. I would rate this cell at 1000mAh with a 12A CDR (constant discharge rate) based on its performance and temperature. The maximum continuous rating of 10A is perhaps slightly conservative but as there is currently no international/common standard for pulsed discharge rating, I think this one can be ignored and it is perfectly safe to accept Efest’s own 10A rating. Given the final temperature of the cell during testing at 15amps, no further tests were carried out. They would only serve to damage the internal chemistry of the cell and would be above the widely accepted maximum operating temperature of 80’C for lithium-ion cells. I’m not able to ascertain what cell is used under the wrap of this one.

Efest 18650 3500mAh 20A

Picture of Efest 18650 3500mAh 20A Discharge Test

Efest 18650 3500mAh 20A Discharge Test

Test 1 carried out with Cell “1” – Capacity Test @ 5Amps

  • Start Voltage 4.196v
  • Ambient Temperature 21.1’C
  • End Temperature 37.9’C
  • End Voltage 2.82v
  • Capacity Delivered 3115mAh

*This test is solely for capacity, to ensure the cell delivers the amount of energy it promises on the wrap. 3117mAh is a good result for a 3500mAh rated cell being tested at 5A. While the graph shows it as a failure, I set the bar at 90% and discharged to 2.8V and it still achieved 89.1%.

Test 2 carried out with Cell “2” – Discharge Test @ 10Amps

  • Start Voltage 4.198v
  • Ambient Temperature 21.6’C
  • End Temperature 71.1’C
  • End Voltage 2.81v
  • Capacity Delivered 2854mAh

The above is a good piece of data for a cell operating comfortably at its limit.

Test 3 carried out with Cell “2” – Discharge Test @ 15Amps

  • Start Voltage 4.196v
  • Ambient Temperature 24.1’C
  • End Temperature 89.3’C
  • End Voltage 2.83v
  • Capacity Delivered 1878mAh

This is a strong cell in terms of energy density, but overrated on discharge ability. While the graphs shows a failure for capacity, it was a reasonable effort for a 10A rated cell discharged at 5A down to 2.8V. Factory capacity tests are carried out at 0.2c (0.2c of 3500mAh equals 0.7A) down to 2.5V. I am 99% certain this is an LG cell, most likely a MH1 or MJ1. Im leaning towards the MJ1 given Efest’s 3500mAh capacity rating. Perfect for mouth to lung set ups at low wattage (under 30w) or in a low wattage dual battery device. The 20A “pulse” discharge is useless because there are no set standards for testing this and putting it as the larger number on the cell is a bit of a daft move by Efest in my opinion. Although it states in smaller text that it is only 10A constant, because more prominent text shows 20A, I ran testing past 10Amps. As you can see, at only 15A the initial voltage sag was extreme and the cell temperature reached 89’3C. This was pushing the cell beyond its limit and no further tests need be carried out. Irreparable damage will have almost certainly been caused to this cell’s internal chemistry and capacity by this test.

Efest 18650 2600mAh 40A

Picture of Efest 18650 2600mAh 40A Discharge Test

Efest 18650 2600mAh 40A Discharge Test

Test 1 carried out with Cell “1” – Capacity Test @ 5Amps

  • Start Voltage 4.189v
  • Ambient Temperature 17.7’C
  • End Temperature 32.1’C
  • End Voltage 2.80v
  • Capacity Delivered 2345mAh

*This test is solely for capacity, to ensure the cell delivers the amount of energy it promises on the wrap. 2345mAh is a good result for a 2600mAh rated cell down to 2.8V.

Test 2 carried out with Cell “1” – Discharge Test @ 15Amps

  • Start Voltage 4.188v
  • Ambient Temperature 20.2’C
  • End Temperature 70.2’C
  • End Voltage 2.80v
  • Capacity Delivered 2435mAh

Test 2 carried out with Cell “2” – Discharge Test @ 25Amps

  • Start Voltage 4.188v
  • Ambient Temperature 20.2’C
  • End Temperature 100.4’C
  • End Voltage 2.80v
  • Capacity Delivered 2295mAh

This is a very bad result. I only allowed this test to continue above 90’C on the basis that the final 10’C increase happened as it was rapidly approaching 2.8V and I wanted to see if it would actually make it.

No further tests will be conducted on this cell. It runs far too hot at 25A for this to be its actual maximum discharge rating and certainly can’t be used at the 40A printed in bold/larger text. On initial inspection and from the ratings given I had quickly assumed that this might be a re-wrap of the Sony VTC5A however the above test shows this isn’t the case. On further inspection, it has a vent perforation design under the positive cap that I haven’t seen before and doesn’t match any Sony cells we have tested previously. The capacity of the two cells also appears to be wildly different. Given the temperature at 15A and 25A, I would estimate this cells true CDR to be around 17-19A.

Efest 18650 3000mAh 35A

Picture of Efest 18650 3000mAh 35A - Discharge Test

Efest 18650 3000mAh 35A – Discharge Test

Test 1 carried out with Cell “1” – Capacity Test @ 5Amps

  • Start Voltage 4.196v
  • Ambient Temperature 19.8’C
  • End Temperature 30.4’C
  • End Voltage 2.80v
  • Capacity Delivered 2755mAh

*This test is solely for capacity, to ensure the cell delivers the amount of energy it promises on the wrap. 2755mAh is a good result for a 3000mAh rated cell down to 2.8V. It likely would have hit 3000mAh. More on that below.

Test 2 carried out with Cell “2” – Discharge Test @ 20Amps

  • Start Voltage 4.199v
  • Ambient Temperature 20.3’C
  • End Temperature 74.8’C
  • End Voltage 2.803v
  • Capacity Delivered 2478mAh

Another good result for a cell operating at its limit comfortably. (Ignore the first Pass mark/red vertical line on the graph for this discharge. Capacity pass/fail was left on at 80% by mistake.)

Test 3 carried out with Cell “2” – Discharge Test @ 25Amps

  • Start Voltage 4.189v
  • Ambient Temperature 21.8’C
  • End Temperature 100.1’C
  • End Voltage 2.83v
  • Capacity Delivered 2260mAh

This cell performed well at the CDR given by Efest of 20A, however given the largest number on the wrap is 35A, I was keen to see how close it would get. At just 5Amps more than the CDR, it hit over 100’C right at the end of the test. I had a feeling this might be the case, because the cell under the wrap is a Samsung 30Q. Samsung rate the cell at 15A on their datasheet but they are well known to be 20A capable, proven above. Although it only delivered 2755mAh in capacity testing, Samsung’s test parameters for reaching the full 3000mAh is a discharge from full (4.2V) at 1.5A, down to 2.5v. I have every confidence it would make that. In short this is a good, well known cell in different clothes, wearing an unfortunate rating. If they had put the CDR in bold instead of a useless pulse discharge rating, this would be a perfect cell.

Efest 20700 3100mAh 30A

Picture of Efest 20700 3100mAh(30A) - Discharge Test

Efest 20700 3100mAh(30A) – Discharge Test

Test 1 carried out with Cell “1” – Capacity Test @ 5Amps

  • Start Voltage 4.173v
  • Ambient Temperature 20.8’C
  • End Temperature 28.9’C
  • End Voltage 2.80v
  • Capacity Delivered 2749mAh

*This test is solely for capacity, to ensure the cell delivers the amount of energy it promises on the wrap. 2749mAh is a reasonable result for a 3100mAh rated cell down to 2.8V. A deeper discharge (to 2.5V) would have seen a better result but a 5A drain on a 3100mAh 30A rated cell should have seen closer to 3000 really. I would estimate its true capacity being around 2900mAh and likely 20A discharge

Test 2 carried out with Cell “2” – Discharge Test @ 15Amps

  • Start Voltage 4.199v
  • Ambient Temperature 21.’C
  • End Temperature 59.1’C
  • End Voltage 2.80v
  • Capacity Delivered 2785mAh

At 59.1’C, we’re already approaching this cells maximum constant discharge rate. On that basis, the capacity no longer looks so much of a poor effort.

Test 3 carried out with Cell “1” – Discharge Test @ 20 Amps

  • Start Voltage 4.196v
  • Ambient Temperature 20.4’C
  • End Temperature 74.3’C
  • End Voltage 2.801v
  • Capacity Delivered 2708mAh

I considered going straight for the cells maximum discharge rate on this test, but given the previous test having got to 59’C at half of 30A, I decided to do an intermediate. This was also on the basis that Mooch has also tested this cell and found its true limit to be 20A. Based on the above, I have to agree. 74’3C is a nice, safe working CDR for this cell.

Test 4 carried out with Cell “2” – Discharge Test @ 30 Amps

  • Start Voltage 4.196v
  • Ambient Temperature 20.4’C
  • End Temperature 91.8’C
  • End Voltage 2.801v
  • Capacity Delivered 2587mAh

As expected, the 4th test carried out at the only figure provided on the wrap ran hotter than it should, indicating that both my previous thoughts and Mooch’s testing tally up. This is an overrated 20A cell and 30A is asking too much of it. I believe I have actually seen this cell elsewhere, from a Chinese battery manufacturer rather than one of the big OEMs (Samsung, Sony etc) Unfortunately and annoyingly I have forgotten which one.

Efest 21700 3700mAh 35A

Picture of Efest 21700 3700mAh 35A - Discharge Test

Efest 21700 3700mAh 35A – Discharge Test

Test 1 carried out with Cell “1” – Capacity Test @ 5Amps

  • Start Voltage 4.173v
  • Ambient Temperature 20.8’C
  • End Temperature 29.1’C
  • End Voltage 2.80v
  • Capacity Delivered 3404mAh

*This test is solely for capacity, to ensure the cell delivers the amount of energy it promises on the wrap. 3404mAh is a reasonable result for a 3700mAh rated cell down to 2.8V.

Test 2 carried out with Cell “2” – Discharge Test @ 20Amps

  • Start Voltage 4.186v
  • Ambient Temperature 22.3’C
  • End Temperature 68.7’C
  • End Voltage 2.80v
  • Capacity Delivered 3342mAh

Test 3 carried out with Cell “1” – Discharge Test @ 30Amps

  • Start Voltage 4.196v
  • Ambient Temperature 17.4’C
  • End Temperature 81.6’C
  • End Voltage 2.83v
  • Capacity Delivered 2987mAh

Another good cell, with a slightly over-zealous rating. I suspect the full capacity would have been reached with a 0.2C discharge down to 2.5v so we can probably agree this is a 3700mAh cell but given the 81’C temperature at 30A, we’re at the top end of this battery’s ability and I rate it no further than this. A further unlisted test at 35A reached 96.4C. Again, this mirrors testing done on the same cell by Mooch.

So, what do we think? – Visually appealing products, very well packaged for the retail market but they’re still showing some marketing immaturity in their continued use of ratings alone to sell batteries where Vapcell have gone in the right direction and made their name selling accurately rated but “first to market” and/or (initially at least) hard to find cells (VTC5D, VTC6A, 20S etc). Some of the cells tested here are good cells. They dont need a trumped up rating to sell if the price point is right but i can 100% see why they do it and its motivation lies in profit. How do you make a Samsung 30Q which can be purchased almost anywhere for circa £4-5 these days, worth £8? You slap a shiny purple wrap on it and give it a 35A rating. That’s how. Like with almost all companies re-wrapping cells, they are selling you a product you can buy elsewhere for less money and to do that, you need to add value. The problem here lies between actual value, and perceived value. You think you are getting more value because outwardly, it appears to perform better but look above. Look at the actual ratings, look at the price of that cell, then compare it to an OEM cell from Samsung, Sony, LG.  Chances are, you can get the same cell or better, at a better price.

Do you have any thoughts? Is there some value in these products that i’ve missed? Let us know in the comments below

Ben – Sales Director

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