7 Best 21700 Battery Reviews – High Drain And Low Drain

Getting the best 21700 battery is not as easy as it seems. There are a lot of factors at play.

If you get a fake battery or you buy a battery that is not intended for your particular use case then you could experience serious problems.

Lithium-ion batteries are not a joke. Making a buying mistake could cost you more than just money and wasted time. The battery could explode or burst into flames at worse or you could get a battery that will not satisfy your device’s needs at best.

All of this can be avoided.

If you get a quality 21700 battery from a trusted brand that is meant for your use case you will experience all of the advantages the lithium ions have to offer.

That is why I made this guide to help you choose the best 21700 battery and to narrow down your choices to the reputable and respected brands in the battery community.

Now let’s go!

7 best 21700 battery Reviews

This review covers the batteries for low drain devices and the high drain 21700 batteries.

First I will review the best 21700 batteries for flashlights and similar low drain devices and then I will proceed with the top 21700s that are meant for high drain devices like vape mods, DIY battery banks, bike battery packs and similar.

Never use a low drain battery for a high drain device.

Never get a cheap knock off brand. This is most likely to end in tears or worse.

Always follow the instructions on using the lithium ion batteries.

Below the battery reviews, I wrote a buying guide to help you narrow down what you need. You should check that out if you are a beginner in the lithium-ion world. I assume you have the basic knowledge since 21700 batteries are usually not an entry level like 18650s for example.

Now let’s see which cells are great!

1. Olight 217C50

Last update on 2021-10-23 / Affiliate links / Images from Amazon Product Advertising API

Olight is a well known brand for their flashlights. They also make batteries that are specifically made for this use.

While it says on the battery wrap that it is for “high drain devices” I don’t think that you should take that at face value. They are meant for high drain flashlights and will serve that purpose perfectly but they can’t be used with other types of actually high draining devices.

This battery has a huge 5000mAh capacity and you will actually get that much as advertised. The Olight has good quality control in order to dish out any cells that fail to meet proper conditions.

It is a protected cell that has a protection board against overcharge, over-discharge and short circuit.

These are probably the best you can get for your flashlight. While they are costly, I think that it is justified. Still there are cheaper options.


image of the NITECORE NL2150HP 21700 battery

The Nitecore is one of my favorite brands. They sell their line of flashlights too but I love them the most for their battery chargers and batteries.

Their batteries are expensive and this 21700 battery is no exception. But just like with the Olight the additional price means that you will get the advertised capacity and the protections put in place will actually work as expected.

This is a 5000mAh battery that will work with loads under the 15A. Again, they say “high drain”. This only applies to high drain for flashlights. They should have specified that. You can’t use this 21700 to power some DIY project that needs 30A of current drain.

It has a built in PTC for surge protection, it has a pressure relief valve, overcharging, over-discharging and short circuit protections.

It is also built with high quality metals. The connectors are nickel-plated stainless steel and this helps with connectivity, rust resistance and impact endurance.

3. FENIX ARB-L21-5000


Fenix is a famous brand for its flashlights, headlamps, all kinds of lanterns and various every day carry equipment. They also sell their brand name 21700 battery cells that are known for their exceptional quality.

They are also on the expensive side and just like the two brands above, you are paying for great quality control and exceptional battery protection features.

This 21700 battery comes with the 5000mAh capacity and can be recharged up to 500 times.

It is protected with a protection circuit that prevents short circuits, over discharge and overcharge.

Fenix is a serious brand and if you decide to opt for their batteries it will cost a bit more but you will get a piece of mind in the long run as they are very reliable.

4. Molicel P42A 21700 4000mAh 45A Battery

image of molicel p42A

Now let’s move on to the high drain batteries. These are actually meant to withstand big loads.

Now we will see the best 21700 battery for the high drain use. The Molicel beats everyone out of the water left and right. No other 21700 on the market offers this mixture of high drain capability and capacity.

The Molicel P42A will endure 45A of maximum continuous discharge. That is insane and especially when coupled with the 4000 mAh capacity. How they do it is beyond me because this is almost impossible.

However, Molicel is a very trusted brand in the battery community and they are true to their specifications.

But there has to be a catch as with all things in life.. This high CDR rating and capacity come at a cost of charge/discharge cycles. If you actually push this battery all the time at its 45A rating then it will die sooner than if you keep it under 35A for example.

Still it is amazing that this battery can give you 4000mAh and actually endure constantly being under a 45A load.

5. Samsung 40T 21700 Battery

image of Samsung 40t

Samsung 40T 21700 lithium ion battery is a perfect example of a high CDR rated battery coupled with a big capacity. It will endure 30A of maximum continuous discharge which is very good for high draining devices.

The capacity is 4000mAh which is only one fifth less of the big brand names above but keep in mind that this battery doesn’t have any protections unlike them and is not specifically made for low drain devices.

Samsung is one of the top names in the li-ion battery world and this battery is one of their top 21700 choices. You get the capacity and CDR. What else could one want?

6. Samsung 30T 21700 Battery

image of Samsung 30t

Now for the next choice, again from Samsung, we have a very similar battery.

This battery has a higher CDR rating. It can endure 35A of maximum continuous discharge and even more when pulsed. This higher rating didn’t come without cost as it reduced the capacity of this battery to the 3000mAh which is still a lot so it is still a good deal.

You shouldn’t get this battery unless you really need that additional 5A of the current rating. The Samsung 40T is a much better choice if you will be using it in a sub 30A device.

This cell has almost no voltage sag making it one of the hardest hitting 21700 batteries on the market. An excellent choice for vape mods or similar highly demanding devices.

This battery comes in a flat top design as most of the 21700 on the market that are from the OEM (Original equipment manufacturers).

7. Molicel 21700 M50A

image of Molicel M50A 21700 battery

Now for the very end, I will review this Molicel cell that is meant for lower draining devices. It makes a perfect choice for flashlights and similar use where a lower CDR is accepted.

It can endure a load up to the 15A of continuous discharge while offering an amazing 5000mAh capacity and all with a much lower price than those brand names that I listed above like Fenix, Olight and Nightcore.

But this battery is a flat top battery unlike them and it doesn’t have any protections. So if your flashlight doesn’t have overdischarge protections you could overly deplete the battery and have its voltage drop under 3V and ruin the lifespan of your battery.

If you feel confident that you can take care of an unprotected battery then this is a great budget alternative to those protected brand 21700s.

21700 Battery Buying Guide

Now we will see what are some areas that you should think about if you are a total beginner in a lithium ion battery world.

I will talk about the brands, capacity vs CDR rating, flat top/button top, safety and a few other things.

Lets see the brands first.

What brands are trusted?

There are OEM brands and the rewrap brands on the market.

OEM brands are batteries like Samsung and Molicel above. They are originally produced by Samsung and Molicel and were sold in bulk to buyers overseas which are reselling them to you on a per cell basis.

The most trusted OEM brands are:

  • Sony
  • Sanyo
  • Panasonic
  • LG
  • Samsung
  • Molicel

Rewrap brands are brands like Nitecore and many others. They get the same OEM cells from the manufacturers like Sony, Samsung and etc. and then they do additional quality control to make sure that only the best cells come to you as a consumer.

Additionally they add PCB protection boards to secure the battery from overdischarge, overcharge, short circuits and similar issues.

Not every rewrap brand is good. Be very careful what you are buying. Fake batteries are flooding the market and they can be dangerous at worst or they can cheat you and sell you 500mAh battery at best.

Avoid any battery that claims bogus capacities like 10000mAh and especially if they claim high CDR with high capacities. Only a handful of brands can actually achieve good capacity with a high CDR ratio.

Capacity and CDR

What in the world was I talking about throughout the whole article when it comes to CDR and capacity?

Well if you are a total beginner this question could be in your mind.

Lets answer it.

Capacity is how much mAh your battery can store. That is its ability to store that many milliampere hours. Just like a bucket of water with a capacity of 10L for example.

CDR is the most important part. It represents the load your battery is rated for. CDR is short for Continuous discharge rating. The battery’s ability to be continuously discharged under a certain load.

The higher draining device the higher CDR you will need. For example, if your vape mod or any DIY device you are making will pull the current at the 20A load then you will want a battery that is rated for at least 20A of CDR.

Additionally, if you want to stay on the safe side you can use a battery with a higher CDR than you need but that will cost a bit more and you will have to sacrifice the capacity in turn.

That is because it is really hard to manufacture a battery that can have a high CDR rating and a high capacity at the same time while offering you a long life cycle of the battery.

NEVER use a battery with a lower CDR rating than what the device needs. If your device needs 30A but you are using a 10A rated battery chances are that your battery will vent fumes and if it is not from a quality brand explode. This is dangerous so just never do it. Always use the proper battery for a specific load.

Flat top or button top 21700 battery

Well, this entirely depends on the device you will be powering. If you will be doing some DIY battery work then you will most likely need a flat top battery.

Generally speaking, most 21700 from OEM manufacturers are found with a flat top variant on the market place. If you find OEM looking battery with a button top you should know that the button top was added by a third party. I am not aware of any OEMs making them with button top heads.

Rewraps are usually found with button tops as they are mostly marketed towards the flashlight community where a button top is often needed. However, many flashlights do not need a flat top and will work with both variants properly.

Typical flat top 21700 battery measures 21mm in diameter and 70mm in length. If the button top is added it will deviate in length by a little, if PCB is also added it will be even longer.

These are miniscule differences that don’t represent issues in most cases.

Taking care of your 21700 battery

Now let’s wrap this up with some safety talk and tips for extending the lifespan of your 21700 batteries. You should continue educating yourself about lithium-ion batteries as I can’t teach you all of it in one article.

Plus I assume you are already at least somewhat knowledgeable since the 21700 battery is usually used by people who already had some experience with 18650 batteries and they are pretty much the same except for the size and capacity differences.

  • Use A high-quality charger. You should never use some cheap random knock off as that will definitely reduce the lifespan of the battery if not outright start a fire. Not even the best of chargers are guaranteed to provide you with 100% safety let alone random cheap stuff. The quality chargers will have a lot of protections in place.
  • Charge your batteries under their rated charging current. That way you will extend their lifespan.
  • Store your batteries with 3.7V of charge. This is the best storing voltage. Good chargers will have the option to stop charging after your battery reaches 3.7v.
  • Be careful not to expose your batteries to humidity and condensation.

More important safety tips:

  • Never puncture your batteries or apply any physical force to them.
  • Do not use a battery that shows any weird signs. If a battery is leaking or it is deformed in any way it is not to be used anymore.
  • Never short circuit the battery.
  • You should always use the battery under their CDR rating.
  • Keep them away from the fire or heat sources.
  • Keep them away from liquids.

Are you also looking for Top 18650 battery?

If you need the best 18650 battery then you should read what I wrote about them. Since that article is much more devoted to beginners you will learn there much more than just the quality brands I recommend.

In that post, I wrote about the same things I wrote in here but in much more detail. I also covered some things like voltage and PCB protections that were skipped here.


I hope that I helped you choose the best 21700 battery for your needs. Remember to get a battery for the proper purpose. Low drain or high drain and if you need to use a high drain battery then always stay under the rated CDR amperage.

The Molicel P42A cell is your best bet at pushing the 21700 to the limit but at a cost at life cycle. Samsung 30T is a much more forgiving battery that can still take a ton of load.

1 thought on “7 Best 21700 Battery Reviews – High Drain And Low Drain”

  1. Thank you for this excellent battery guide. It is not easy for the newcomers in the lithium ions as no one really writes as if you are totally new. I also read your guide about 18650s which is more in depth and I particularly loved the CDR explanation.
    While I agree about the Nitecore and Fenix brands I think that they may be a bit over priced. But I am still a beginner. I will check them out if I get a chance. I am thinking of getting the Samsung 40T battery. It has incredible capacity and the CDR rating is just what I need. Do you think that if I stay under the limits of the battery that the battery will las longer? Like if I never drain the current under a bigger load than its CDR rating?


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