Test/review of Samsung INR21700-40T 4000mAh (Cyan)

Batteries and Chargers Rechargeable Batteries
1

Samsung INR21700-40T 4000mAh (Cyan)







Official specifications:

  • Rated discharge capacity: 3900mAh

  • Standard discharge capacity: 4000mAh

  • Nominal voltage: 3.6V

  • Standard charge: CCCV, 2A, 4.20V, 200mA cut-off

  • Rated charge: CCCV, 6A, 4.20V, 100mA cut-off

  • Max. continuous discharge: 35A with temperature cut.

  • Max. continuous discharge: 45A with 80°C temperature cut.

  • Discharge cut-off voltage: 2.5V

  • Cycle life: 250 cycles to 60% at 6A charge and 35A discharge.



This is a high current with good capacity in the new 21700 format.










The two cells tracks very well and capacity drops slowly with higher current. I had a slight problem with the B cell, my connection in the battery holder was not good enough and it got hot at 30A.





















Conclusion

It is a very good high current and capacity cell and looks to be one of the best at the current time in this size.



Notes and links

How is the test done and how to read the charts
How is a protected LiIon battery constructed
More about button top and flat top batteries
Compare to 18650 and other batteries
2

Yeah, this is what we were looking for in 21700 cells. Hopefully now we can get manufacturers to start making more flashlights in this size.

3

Thank you for this review.
Looks like the 30T by Samsung is now obsolete (if we forget about the price-tag for this moment).

4

Obsolete? It’s point of existence in the flashlight world was that it could drive lights harder than any other tested cell.
After 40T is tested, 30T still can drive lights harder than anything else.

So this is a very good cell, but I don’t see how it would make 30T obsolete.

5

No, no. The 30T, 40T and 48G are all brand new cells. They each have their advantages and disadvantages.

30T - 30A continous 3000mah
40T - 20A continous 4000mah
48G - 9A continous 4800mah

So they have a cell for every need. :+1:

6

The 48G is obsolete, its production was stopped by Samsung SDI and replaced by the 50G (5000mAh), stores that still sell 48G are just lucky not to have sold everything, but once their stock is exhausted it will not replenished. And the 40T is not a cell having a nominal discharge of 20A but 35 continuous amperes (this is the official datasheet that says it, not me) or 45 amperes continuous if the cell is kept below 80 ° C (see official datasheet). And for the 30T, it’s the same as the 40T, 35 continuous amps and 45 amps continuous if kept below 80 ° c. Always check your info before publishing, otherwise you mislead other people and this without wanting.

7

this is what i expect from 21700, higher discharge and capacity than 18650

8

And check the OP :slight_smile:

Is the 50T still 9A continuous? A bit more would be nice.

9

Just a thought here. I do not put 100% merit in the specs and data sheets that manufacturers list.

I have seen countless batteries reviewed by HKJ and other notable sources, where these specs were over rated and blown up.

I do not know what the real specs are for the aforementioned battery[ies].

I would believe an independent test before I would take the manufacturers number as if they are “Written in Stone”.

10

The battery is rated for 6A rapid charge too although it may shorten useable life.

All I need now is a reasonbly price 21700 light.

11

@wolfdog, actually, their ratings are not false most of the time, if done by the original manufacturer

Let’s not forget manufacturers test capacity down to 2,5V, or even lower, while HKJ tests them down to 2,8V, and in a controlled environment with specific charge parameters.

I’m not saying HKJ is wrong. His testing method is more realistic and takes into account uncertainties. However, the manufacturers are not lying about their capacity at 0,2C down to 2,5V, most of the time of course.

12

Thank you for the nice review.

13

I think it’s you who may have been mislead by the manufacturers. You seem to be mixing up the measurements.

There is continous output, like HKJ and Mooch measure, and then there is a different measurement which the manufacturers use and is misleading if you don’t read the fine print.

Continous discharge means you apply a load and it can go from fully charged to empty without exceeding “safe” temperature limits. HKJ will need to say what that is. I think 60°C to 70°C?

The manufacturers use a higher discharge rating that will exceed their own safe operating parameters, meaning it goes over 80°C. Just look at the tests above. Who is going to be monitoring their battery temperatures to know when to turn down the current? No one. So don’t be fooled by them.

Just like with every battery, of course you can exceed their continous output ratings, you just have to remember that it can only do this for a short amount of time.

Some wrappers are even flaunting “35A continous discharge” and putting “up to 80°C” in fine print. Please don’t be fooled by this. Some people already posted that Efest Orbtronic was superior because the wrapper said it was 35A continous. Again, don’t be fooled or mislead.

Mooch has given the 40T a slightly higher continous rating of 25A.

14

@BlueSwordM.

This is what I meant. Jason was more detailed and factual than I was.

15

Yeah the manufacturers also take their specs to the limit, and are slightly misleading in terms of power ratings.

They usually don’t lie about capacity by their testing methods.

But yeah, they could be better.

16

This is interesting news. I had not heard about it, nor have I ever heard about the new 50G. Thanks for the update.

Some batteries stay in production many years before being replaced. You can buy Panasonic NCR18650B 3400mah everywhere, but that battery came out in mid 2014, if not earlier. So at least 4 years.

I think the 40T came out in late 2017, so only 1 year old and it’s already replaced. Hmmm.

I couldn’t find any info on the 50G, maybe you meant the 50E? It seems they are just coming out onto the market. None of the US stores I use carry them yet. I only see them for sale on ebay. I guess in the next few months they will start becoming more common.

17

Given that every last cylindrical LiIon cell is specified and sold for use in some sort of managed application, like a battery pack, it is absolutely realistic and honest that their testing and specifications include caveats like temperature limits.

We’re the ones using cells outside their intended application. Don’t be fooled into thinking otherwise.

HJK and Mooches tests are invaluable not because they show the manufacturers up, but because they fill in the blanks between the manufactuers specs and what we need to know for our applications.

That the people wrapping/package and selling these cells are misrepresenting manufacturers specs is a separate issue. The blame for that falls on the wrappers/sellers, not the cell manufacturers.

18

This is common as well. There are different charge rates for every battery depending on whether you want max life or not. The capacity is going to slowly be reduced everytime you recharge it anyway, some charge rates reduce it a bit quicker than others.

21700 flashlights are slowly coming out. Most are pretty expensive though. I just bought the Sofirn C8F 21700 for $36 shipped including a 4000mah battery and a simple charger. I think this is the cheapest 21700 light I’ve seen so far.

19

To clarify, I was refering to flashlight users such as all of us here. We don’t monitor battery temps in flashlights (unless we need to).

I’m sure these new higher ratings the manufacturers are using are more for vehicle use where they are water cooled and monitored closely. Or tool use or vacuum use etc… where temperatures can at least be monitored.

We are just low-tech bums. We have to take the battery out of our flashlight and measure the temperature by hand and go “Ewww boy, that sure feels hot!”. Lol

20

HERE is the:

Samsung INR21700-50E Rechargeable 10a High Drain Battery 5000mAh flat top.

“IF” those specs are right it is Only 10A Not 20/25A like the 40T.