Three Points of the Compass has found it difficult to happily integrate Nitecore’s 21700 Intelligent Battery System into a backpacking system. However I was intrigued enough to purchase this kit if only to gain a better understanding of the ‘new’ 21700 batteries that appear set to become the standard in rechargeables.
Three Points of the Compass has used 18650 batteries quite extensively on backpacking trips of many weeks duration. I wrote of a lightweight power set up that I have used here. But I left that system behind me a while back as more convenient and lighter alternatives came onto the market, not least the terrific Nitecore NB10000 power bank.
21700 series batteries were developed around 2015 for use in electric bikes and Tesla adopted them in 2017 for use in their Tesla Model 3. The ‘old’ 18650 batteries are good batteries. They can pack a lot of power capacity into them, however it is pretty obvious that if you up the size of the battery, then they can hold more power.
While my Nitecore NL1834 18650 series batteries can each hold 3400mAh and weigh 48g individually, the Nitecore NL2150HPi is a 21700 series rechargeable battery that holds 5000mAh and weighs 76g. The 21700 batteries can hold up to 42% more power than the 18650 batteries. Some of the battery classification is pretty easy to get your head round. An 18650 battery is 18mm diameter and 65mm long (we shall ignore the fact that Nitecore builds in some additional circuitry in the cap of their batteries that increases their length just a little!). The 21700 batteries are 21mm diameter and 70mm long (yep, those from Nitecore are a little longer-76mm).
Nitecore 21700 Intelligent Battery System
The Nitecore 21700 Intelligent Battery System is a bit of an odd name. It is simply the bringing together of a battery, a light wand and a nifty little input/output charge cap, what Nitecore call a power bank, which it isn’t. I cannot quite get a full charge of my Samsung Galaxy S20+ phone with this system, but it will substantially top it up. Typically, from 21% charge to 88%, and from 7% charge to 81%.
The battery is a high energy density 21700 i series battery. This 75.5g NL2150HPi battery has a 5000mAh capacity. Nitecore have refined this ‘i series’ battery so that both positive and negative polarities are found at one end.
The second item included in this kit is the ML21 magnetic light. This little 12.8g wand, or lantern light, attaches to the end of the 21700 battery magnetically (the MPB21 has to be removed first). This provides a diffused 80 lumen pool of light at 4000-4500K. From a fully charged 5000 mAh battery up to 19 hours runtime of the light can be expected.
The third accessory included is the MPB21 ‘Magnetic Power Bank’ which attaches to the end of the battery. This little cap is just 22mm x 23.5mm and weighs 11.7g. The cap has a 5v/2A micro USB input to enable the battery to be charged. This takes up to five hours due to the maximum charging rate of 2A. It also has a USB-A output to enable the battery to act as a small 4.2v output power bank. It can be charged and act as a power bank at the same time (through charging). The output ceases when the voltage is below 3v. The MPB21 has to be attached to the battery first, before connecting it to an external device.
The MPB21 has both advantages and disadvantages. The biggest advantage is the incredibly light weight and small size. These make it suitable for a lightweight backpacking kit list. However the magnetic attachment is pretty weak and it seperates easily from the battery. The slow charge rate makes it difficult to charge on brief halts near a mains power port. I also find it difficult to gauge remaining charge in the battery. The size, weight and simplicity of this kit may work for some, but Three Points of the Compass could do with a firmer grip being maintained when charging with the battery while stowed in the pack. Another issue for me is that the charging cap input is not USB-C (unlike my phone) so requires another charge lead or adapter. Finally, do I really need another light in my multi-day gear? This little kit may suit some but at present it is not meeting many of my needs that I can identify, other than a small and neat top-up facility for my phone on day hikes, hotel/hostel/bunkhouse stays and weekenders.
It does look as though Nitecore have listened to my and other’s gripes and will soon release what may be a solution. A charger for an ‘i series’ battery that is held firmly in place while charging and also has a USB-C charging port that, wait for it, permits 18W fast charge. Which means I can use it with the same charge lead that my Samsung S20+ uses and with the Samsung Quick Charge 18W plug. I will be looking at the portable Nitecore F21i 18W Fast Charger in another blog.
Care has to be taken when purchasing batteries for specific purposes as there are a great many subtle differences in classification and not every battery can be used for every purpose. Sometimes a battery simply will not perform optimally, other times an incorrect battery can be downright dangerous. The MPB21 in this little kit should only be used with HPi batteries such as the included NL2150HPi. On manufacturer advice, it is not safe to use with the similarly sized Nitecore NL2150HPR, NL2150R or NL2150i batteries.
The three items come in a 24g plastic box and are kept segregated with an additional 2g of foam. There is no need to keep the three component items in this box, but it does store them well in a compact package. Even if for just throwing into a kitchen drawer or glove box. The question is if these items have a place on trail? That I am still unsure about. The battery is handy but 5000mAh is a little small for me for much of the time.
There is nothing wrong with the 18650 batteries I have used previously and I shall continue to use these, but now more in a home or car setting than on trail. One of these batteries now fills a Nitecore MT25 flashlight (a torch to anyone else). This is part of their Multi-Task Series that has a small but adequate number of modes, such as strobe. I keep a small orange wand and spare 18650 batteries with this in the car for use in the event of breakdown or similar. Advances in technology does not necessarily mean everything ‘old’ has to be binned, simply repurpose it.
Three Points of the Compass 
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