The ultimate multipurpose 27100 Lithium-Ion battery

Feb 21 2022 - 5 min read

Armytek LED Wizard Pro XHP50 (18650) vs Armytek Wizard C2 PRO MAX (27100)

Armytek Wizard C2 PRO MAX with one 18650 adapter

I try as much as possible to standardize my mobile power sources at home or for outdoor activities. After a long period of using the AA battery format, I switched a few years ago to the 18650 Lithium-Ion battery. The great thing about 18650 batteries is the capacity, charge retention over time, durability and versatility. I just recently switched to the new 21700 standard and I’ll explain why. The 21700 battery is ideal for self-sufficient nature activities or high consumption needs at home. We’ll see that the choice of models can be critical to making your batteries work in all your equipment.

Difference between a 18650 and 21700 battery

The difference between a battery 18650 and 21700 will be first of all in its dimensions. The 21700 will have a larger diameter and length, the model indicates the dimensions of the battery: 21700 = 21 x 70 mm.

Battery	Diameter	Length
18650	18mm	65mm
21700	21mm	70mm

The 18650 format Li-ion cells can be compared to the new 21700 format in terms of their electrochemical, thermal and geometric properties. The 21700 battery has a nominal voltage of 3.6V to 3.7V just like the 18650, so you can use your 18650 batteries in equipment designed for the 21700. You will need a plastic adapter to extend it a bit and avoid side play.

The 21700 batteries were initially developed as a new generation of cells for electric vehicles. The 21700 battery was quickly used for vaping. When the 21700 battery is used as a cell, the power gains can be significant. Studies done on commercial batteries [1], show that the energy content per cell can be 50% higher for the 21700 than the 18650.

Discharge current

Discharge current is measured in Amperes (A). Each battery will have two discharge current indicators:

Continuous Discharge Current: shows what the battery can deliver continuously.
Max Continuous Discharge Current: shows what the battery can deliver at a given time in peak.

The Continuous Discharge Current must be lower than the Continuous Discharge Current.

The 21700 battery will also have a higher discharge current than the 18650. In use, this means that a higher power can be drawn in peak. For example the Samsung 21700 30T battery has a discharge current of 35A.

Protection circuit board

The 21700 batteries can be protected or not. Protected 21700 batteries have a protective PCB (Printed Circuit Board) and an overheating protection. Care should be taken as protected batteries can be longer. Most chargers will have a statement indicating whether they charge protected batteries or not, those that support protected batteries will have more room to accommodate the battery. Some 21700 batteries come in a flat version, while others are in a button version.

Capacity of the 21700

Because the battery can hold more active material, 21700 cells have a higher capacity compared to 18650 cells. The increase in cell size allows for a better ratio of energy storage materials to non-energy storage materials. This available energy is measured in mAh.

Battery	mAh min	mAh max
18650	2000	3700
21700	3000	5000

You can find batteries advertised on Chinese websites at 19900 mAh, these batteries do not deliver the capacity, these specifications are misleading, you should not buy these batteries.

This additional energy allows to deliver more power. If we take the Bosch 18V tool batteries, the battery based on 18650 cells will be able to deliver 800W while the ProCORE 18V battery using 21700 cells can deliver 1440W.

Bosch ProCORE 18V 5.5 Ah based on 21700 cells

21700 compatible equipments

As the 21700 battery is newer and less used than the 18650 there are less compatible devices. The 21700 is more used as a cell in bikes or cars.

My favorite equipments for these high capacity batteries are flashlights.

I have several Armytek, here is the difference between a 18650 model and a 21700 model

Armytek LED Wizard Pro xhp50 using an 18650
Armytek Wizard C2 PRO MAX 3720 Lumens using a 21700

The lamp only accepts 21700 without PCB, the PCB batteries will not fit in diameter or length.

Note that a plastic adapter can be used to use its 18650 in the Armytek Wizard C2 PRO MAX:

Even though the lamp can light a soccer field with its 3720 Lumens, in low light mode, the lamp will fully exploit the 21700 by being able to light for 2 months continuously:

Moonlight 1: 0.33 Lumen ANSI (2 months)
Moonlight 2 : 4.2 Lumen ANSI (14 days)

Powerbank

I have several powerful powerbanks. In mobility, I prefer the 21700 battery chargers that make powerbank. The interest is the versatility, the batteries can be used as powerbank, flashlight or tool battery. You can easily modulate the amount of energy on the move from a few units for a WE to a larger stock for a three week raid. By being off-grid, the management of its energy is facilitated, one can charge the batteries with solar panels. In case of failure of a cell we have the redundancy of each battery which is autonomous. It is necessary to have several chargers to be also redundant.

I’m using two powerbanks using one 21700 battery :

Ledlenser Powerbank Flex 5 | 4500 mAh

Nitecore f21i

Input: USB-C：5V⎓2A / 9V⎓2A
Output: Battery:4.2V⎓4A (MAX) USB-C:5V⎓2.4A / 9V⎓2A / 12V⎓1.5A

Choice of the battery brand

It is necessary to choose well its mark, the famous manufacturers are Samsung, LG or Panasonic.

I tested these batteries:

Keepower 21700 5000mAh Too big for my Armytek Wizard C2 pro max
Ledlenser 27100 1S1P 4500 mAh Too big for my Armytek Wizard C2 pro max
Nitecore NL2150HPi I don’t recommend the particular connectivity that forces to use only Nitecore battery.
Samsung 21700 INR21700-33J (beige) I prefer to buy only 5000 mAh, 3270 mAh is a bit light.
Samsung INR21700-50E 4900mAh - 9.8A (blue) Recommended