Bench Test Results: Samsung 40T 35A 4000mAh 21700 Production Cells...same performance as before

These tests below only note the estimated ratings for these batteries at the time I tested them. Any battery that is not a genuine Samsung, Sony, LG, Panasonic, or Sanyo can change at any time! This is one of the hazards of using “rewrapped” or batteries from other manufacturers so carefully research any battery you are considering using before purchasing.

Misusing or mishandling lithium-ion batteries can pose a SERIOUS RISK of personal injury or property damage. They are not meant to be used outside of a protected battery pack. Never exceed the battery’s current rating and keep the plastic wrap and top insulating ring in perfect condition.

Testing batteries at their limits is dangerous and should never, ever, be attempted by anyone who has not thoroughly studied the dangers involved, understands the risks, has the proper equipment, and takes all appropriate safety precautions.

If the battery has only one current rating number, or if it only says "max", then I have to assume the battery is rated at that current level for any type of discharge, including continuous.




Bottom Line
Batch/date code 2IA3 is a production version of the 40T and it performs the same as the preproduction version I tested in July 2018 until you are below 3.2V. The production version then performs a bit better.

The 40T is a fantastic cell, especially for regulated mods at under 25A/75W or so. The datasheet rates it at 35A continuous and 45A if you keep it below 80°C (it’s “temperature-limited” rating). In my opinion it is not a true 35A battery though as it runs up around 87°C at that current level and that’s too hot for decent cycle life.

At above 25A/75W or so the Samsung 30T is the better performer anyway. The 40T is best at moderate power levels where it can be the most efficient. The 40T is still an amazing 30A battery though!

If you are running your mod at around 75W per battery you will have to try both the 30T and 40T to see which performs better for the way you vape. It’s just not possible to predict.

The two cells I tested delivered 4126mAh and 4135mAh at 0.8A (0.2C) down to 2.5V. This is fantastic consistency and typical of the cells from the big manufacturers.

I am estimating the ratings of batch 2IA3 and later of the production version of the 40T to be 30A with a temperature-limited rating of 40A (if kept below 80°C) and 4000mAh. Earlier versions are still being rated at 25A/35A.

Two cells were donated for the purposes of testing by EnerCig (ENERdan GmbH – briniging positive energy!). Thank you!


Continuous Current Discharge Graphs



Ratings Graphic



Performance Specs
- DC Internal Resistance = 14.1mOhms (milliohms) average for the two cells.
- Total energy delivered down to 3.2V at 10A continuous = 11.4Wh (Watt-hours) average
- Total energy delivered down to 3.2V at 20A continuous = 10.0Wh (Watt-hours) average
- Total energy delivered down to 3.2V at 30A continuous = 8.3Wh (Watt-hours) average

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To see how other cells have tested check out this link: List of Battery Tests | E-Cigarette Forum

 

That’s just a different batch or assembly code if that is the second line under the wrap. Only the second character of the first line, or the entire first line of it’s N40T, under the wrap matters for identifying the battery

 

Earlier batch, assume 25A current rating.
The datasheet lists a “standard”charge rate of 2A with a max rate of 6A. Slower might, maybe, perhaps extend overall life a little bit.