Update: Efest is investigating this issue. They are saying that our tests do not match up with theirs and that it's possible these batteries were simply defective while other ones that look like this may be good. This is a possibility. They will send more test data. We'll update on this issue as more info comes in. Until then please take these results with a "grain of salt" knowing that since we only have two batteries in the 4 post style it's possible they're not representative of all others.
Those of you that follow Mooch might have seen his report that the 3000mAh Efest has been possibly changed to use a much worse battery under the wrapper, likely an LG MH1. It seems some legitimate authentic Efest 3000mAh's were found in the wild that tested just like the MH1, which is significantly worse at high discharge currents than the cell being used before (Which seemed like the Samsung INR18650-30Q).
Our current stock of the Efest 18650 3000mAh 35A as of 12/19 all arrived on 12/8 direct from Efest. It was checked and we tested lots of random samples from each box and it was determined that our cells are all the good version. Discharge tests show the same battery as before, which we think of as a great 20A 3000mAh battery. I want to stress again, this battery is really good.
However, we did have very isolated complaints, about 1/600 batteries, of poor performance. In these circumstances we exchanged good batteries for the poor ones. After getting them back we looked at them in detail. They are definitely a different cell than the usual battery. Here's a picture:
As you can see, the good ones have 3 connection points on the top cap, identical to most Samsung high drain batteries (if you have a Samsung 25R or Samsung 30Q to compare to, it should look the same). These bad ones have a top cap that looks more like many LG batteries.
Unwrapping them also shows some rust around the separator...it is very possible that in addition to not being the right battery, these might be used/recycled or low bin batteries. In our experience Efest usually uses A bin batteries.
No other markings are on the bare tube under the wrapper.
It should also be noted that there is another variant of the incorrect battery under a 3000mAh wrapper, which is likely a LG MH1. These do have 3 connection points on the top cap and are a little bit harder to tell the difference, but you can definitely tell. We have never found any of these in our inventory but others report finding them from other sellers. See Mooch's blog for more info on these.
So let's test them (click for bigger 3000mAh Efest test chart).
First, compare the green line to the red line, which is a 20A continuous test. You can see an enormous difference. The good ones show great performance, right alongside the absolutely awesome Samsung INR18650-30Q (I am near certain these are rewrapped A bin Samsung INR18650-30Q normally). You can see very little voltage sag, with them getting warm but not hot.
The bad ones are a different story. The voltage immediately breaks down on the bad ones. I only get around 400 mAh before going below 3V. And the battery starts heating up fast. I cut off the test early because of how obvious the difference was.
The other lines are all the bad batteries. You can see a 5A continuous test, and a 1A continuous test. Even at 5A there is quite a bit of sag from internal resistance. Based on the internal resistance level and performance shown, I'd say these are probably 2900mAh or 3000mAh 8A or 10A batteries. It's not one we otherwise carry though so I cannot say exactly what it is. This is similar to the performance level Mooch has shown from the other incorrect version based on the LG MH1, which is a 3200mAh 10A battery.
The good news is the internal resistance is such that if you tried to run these at high amps, what happens in the graph is what will happen...they'll fall on their face and not put out power and the device will shut off. This is much better than some very low quality batteries out there (ahem...ultrafire, trustfire, etc...) that could actually be dangerous. This is just the type of thing where you try the battery, don't get the performance you expect, and return it. Still very bad for Efest's reputation, but not as bad as it could be.
I would recommend being careful who you buy this battery from. We are aware of the issue and continually making sure our stock is good which requires battery testing which as you know most vendors do not do.
If you receive one from us that you believe to be the inferior version, please contact us and we'll exchange it for you. We'll continue to monitor new shipments and make sure this battery doesn't change.