Nitecore UM10/UM20 Review

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Nitecore USB Battery Charger Review

The Nitecore UM10 and UM20 chargers are a USB management and charging system for Li-ion/IMR batteries which is made by illumination tools specialist Nitecore/Sysmax. The UM10 and UM20 USB management and charging systems featured in this review were provided by Nitecore for the purpose of this product preview.

Both the UM10 and UM20 chargers are packaged in Nitecore branded blister packs with their recognizable brand colors of black and yellow. The single bay UM10 charger retails for $9.99-13.99, and the 2 bay UM20 retails for $15.99-19.99 at various online retailers.

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Where to Buy a Nitecore UM10 or UM20:


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    • Type: USB charger for Li-on/IMR batteries
  • Input voltage: Micro USB DC 5V
  • Output voltage: 4.2V / 1% / 5V
  • Output current: 1000mA / 500mA
  • Compatible with:
  • Li-ion / IMR: 18650, 18490, 18350, 17670, 17500, 16340(RCR123), 14500, 10440
  • Dimensions: 100mm / 38mm / 35mm
  • Weight: 57 gram (without batteries or power cord)


  • High Definition LCD display screen
  • USB output charging
  • Priority mode for battery or usb charging
  • Enables data transfer via USB
  • Charge current selection based on battery chemistry
  • Reverse polarity protection


Like the I2/4 and D2/4 intelligent chargers, the UM10/20 USB management chargers are constructed from high quality ABS fire retardant materials. The UM10 USB charger shown below is a single bay charger, while the UM20 is a dual bay charger.

Both the UM10 And 20 feature a high definition LCD display screen, and include a micro USB charging cord with a built in cord winder at the base of the charger for storing the USB charge cord.

One of the things that I find to be most notable about the UM10/20 chargers is their compact size. Both chargers are smaller than the I2/4 and D2/4 series of intelligent chargers. The UM10 USB charger measures 3.94″x1.50″x1.38″ in size and 2.10oz in weight (no battery or cord). The UM20 USB charger measures 3.94″x2.20″x1.38″ in size, and 2.72oz in weight.

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The base of the UM10 and UM20 chargers are hinged, and flips open to reveal the USB port underneath the charger. The included charging cord is a micro USB which can be connected with a micro USB capable external device, or into the micro USB input port at the top of the UM10 and UM20 charger.

The UM10/20 chargers have a switch for selecting priority USB or battery charging while in use. I will cover this feature in more detail later in the review.

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Before I cover the functions and features of the UM10/UM20 chargers in detail, here is a look at Nitecore’s promotional video which is an overview of the features and capabilities of the UM10 and UM20 USB management and charging system.

It is important to note that the UM10/20 USB chargers are only compatible with 18xxx, 17xxx, 16430, 14500, and 10440 rechargeable Li-ion/IMR batteries, unlike the I2/4 and D2/4 intelligent charger which can charge several different battery chemistries. Being an intelligent charger, the UM10/20 chargers are capable of automatically detecting battery type and can adjust charging to the appropriate charge current according to the battery type detected. Larger batteries will charge at a rate of 1A, while smaller batteries will charge at .5A.

The UM10/20 chargers are also capable of activating over discharged protected Li-ion batteries. However, Nitecore does not recommend charging zero volt over discharged unprotected Li-on batteries with the UM10 and UM20 usb chargers. If the UM10/20 charger detects a damaged battery which cannot be charged, the error code “EE” will be displayed on the LCD screen.

The UM10 and UM20 chargers have standard and advanced charge modes, as well as the ability to select ‘priority’ charging for the battery, or an external USB device. To use the standard function of charging Li-on batteries, remove the USB cord from the base panel of the charger and install the micro USB end of the cable to the input port. Then install the other end of the USB into a power supply, either a computer USB port or USB wall adapter.

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When the UM10/20 is attached to a power supply the LCD display will illuminate and display an empty charge bracket and 0%. When a battery is installed in the charging bay the LCD display will indicate the batteries current charge level in percentage. The charge brackets on the left will also display a number of charge indicator bars which correspond to the current battery charge level shown in percentages. When charging is complete there will be 5 charge indicators bars and 100% displayed on the LCD display.

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When using the UM10 and UM20 chargers in the advanced charge mode to charge both a battery and an external USB device, you most use a high power supply in order to charge both the battery and the external device simultaneously.

In the case of low power supply, this is where the priority mode settings on the UM10/20 chargers come into play. As previously mentioned, you can set the charging priority mode of the charger for battery or USB. The priority mode selection will determine which device charges first. Once the selected priority device has completed charging, then the UM10/20 charger will complete the charge of the second device.

The UM10 and UM20 chargers are also capable of acting as a data transfer medium between an external USB device and a computer while the external USB device is connected to the UM10/20 charger.

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While the Nitecore UM10 andUM20 chargers have focused their marketing points around USB management alone, I honestly feel that the stronger selling point of the UM10 and UM20 is USB management charging system is their compact size and portability. The UM10 and UM20 chargers are considerably smaller than the Digicharger series and I feel that they are the perfect chargers for office or field work. Click here to check out our other recommended chargers.

Like all of the Nitecore branded charging systems, the UM10 and UM20 USB management chargers offer the same high quality, and accurate intelligent charging, which makes the UM10 and UM20 charger series easy to recommend.

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  • ​ABS fire retardant materials
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    ​High definition LCD display
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    Intelligent battery detection
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    USB compatible
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    Simultaneous battery and external device charging
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    Data transfer capabilities
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    Standard and advanced charging modes
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  • ​None that are a deal breaker!

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Where to Buy a Nitecore UM10 or UM20

15 thoughts on “Nitecore UM10/UM20 Review”

  1. Thanks Nicole , Nitecore makes quality stuff despite what some so called ” battery experts” often claim.

    To them only the most expensive charger on the market is worthwhile lol, these are affordable and work great.

    1. I agree, I have had a few Nitecore chargers and none of them have ever failed me. The Digicharger is still my favorite of course, but the UM10/20 is a nice middle point between the older i2/4 an the D2/4. Thank you for your comments. :)

  2. I’m happy with my Nitecore UM10 and 20, the passthrough is handy, and having one less cable type to deal with in the car is really handy. I have a 2a car charger connected to the UM10 tucked in the center console, and the UM10 connected to my phone. At home I run a UM20 off a 2a wall charger, and once again a cable from that to either top off my phone, bluetooth headset, tablet, and once in a great while a mod. :)

    It’s worthwhile to pick up both a 2a car and home charger to get the most out of the device..a UM10 with a 2a charger can and does charge a single 18650 and the connected device at the same time, and at a 1a rate (fast), no matter what the priority switch is set to. With a regular USB port or typical cellphone 0.5a charger it takes roughly twice as long to charge a battery, and can only charge the priority device.

    A 2a charger on the UM20 will throw 1a to each of the batteries once again for faster charging, but doesn’t have enough overhead to power an external device at the same time it’s charging both batteries, so the pass-through is less valuable on this unit (unless you’re just charging one battery, in which case it performs just like the UM10 above).

    And there’s the biggest quirk; When either the UM10 or 20 is showing 100% charge on a battery, removing and immediately reinserting the battery will show typically at 94% and it needs some time to really top off. Confirmed with a volt meter that 94% is roughly where it’s really at. This happens on both my chargers, on a variety of 18650s (LG, Samsung, Ewhattheheckmightbeinsidefest, etc), and using a variety of wall adaptors and my PC USB 3.0 ports.

    But for under $10 or $15, and considering the small size and flexibility, these are indeed nice little chargers.

  3. hate to say it but i had a bad experience with the um20 light always flashing reset or simply not reading batterys since day one sadly no recipt so 18 bucks down the drain. still a fan of nitecore but i agree the d4 is beastly and the um20 was nice for its compact design

    1. Hi Marvin .. well that sucks, but I guess defects can happen with the best quality device, even as I am a little surprised to hear about it with a Nitecore product. Thanks for your comment, and letting viewers know that it can happen.

  4. Same here, it worked for 2 weeks, now it just flashes on 0% and wont read or charge my batteries. Dont have a backup yet too…

  5. Mine doesn’t seem to be working right out of the package. I connect a cable by the battery/usb swithch and then connect to my wall charger and I’m just getting EE. Brand new 18650 battery. I can charge the battery thru my mod. Am I doing something wrong or is mine seem defective.

  6. Yea my UM20 says 100% but once i remove one battery (left or right doesnt matter) the remaining battery will drop back to 96%, when testing the batteries with my multimeter they read anywhere from 4.15v – 4.18v, this charger will not charge your batteries to a full 4.20V. overcharge isnt an issue until 4.23v – 4.25v…

    i find my self popping the batteries back in the charger to get them equally charged and keep my sets married… but they will never go over 4.18V on the multimeter.

    OK charger at best.. small size is good for travel and that is about it…

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