NiteCore UM2 vs UMS2

I noticed the UMS2 cost nearly double the price of the UM2. So, what are the differences and is the UMS2 worth the extra cost and why?

I have several chargers (all from XTAR) but now I'm looking for a charger to connect to a foldable solar panel to charge my lithium and NiMh batteries. All thoughts and ideas of what to buy are very welcome.


Try checking the in-depth reviews by HKJ. (search for the model name).

The most basic characteristics of these 2 chargers are listed in the table here (clicking the name goes to the review of each charger)

Thanks for the link!

My UMS2 carked it recently, one of the few chargers that fits longer protected 21700 cells.
Got the Vapcell S4 arriving tomorrow.
It was a little over 2 years old.

Following this thread as I’ve got a UM2 because I didn’t realise there was a ?newer version.

Possibly a difference in the charging algorithm? HJK and others said the termination voltage for Li-ion was 4.25v for the UM2.

OP updated.

I bought UMS2 a few days ago. LiIon termination voltage is 4.13V. It seems to me… not so good. What do you think?

I don’t know why I bought this charger, it does not have a power bank option. I think I will get something for single cell with usb output.

I have the UMS2 as well, fits the longest 21700 cells I have with easy. Most chargers don't.

That's the main reason I bought it.

That is more or less in line with HKJ's observation in his review. Mine leaves topped up batteries at resting voltages around 4.14 - 4.16V. Not great, not terrible.

If you are looking for a charger that clocks in at 4.20V check for Miboxer C4 or C4-12. All my Miboxer chargers settle very exactly at 4.20V (+/- 0.01V). It seems they have a much lower termination current (10mA or less) in the final CV phase. I have a Vapcell S4+ charger incoming. I hope this one will charge close to 4.20V, too.

I’m going to bump this thread given the thread here about UM2 cooking NiMh cells…

Does anyone actually know the difference between the UM2 and UMS2?

HKJ’s comprehensive technical reviews for:

Nitecore UM2:

Nitecore UMS2:

very quick summary on charge current (with regards to Li-Ion batteries):
a) UM2, the earlier model has selectable charge current from 0.1A to 1.5A (in 0.1A steps), assuming USB-QC power supply

b) UMS2, the later model has selectable charge current from 0.3A to 3.0A (in 0.1A steps), assuming USB-QC power supply
UMS2 also has battery internal resistance reading, while the UM2 does not.

Regarding the UM2 ‘cooking’ NiMh, I doubt the UM2 is really doing that, as it seems the battery used are old (too high resistance) and probably problematic for many chargers as well.

It depends when you measure the OCV. Couple of minutes off-the-charger, the voltage typically should read 4.18-4.19 V, but it depends on the cell and the charging (end of charge current). Also, is your DMM calibrated?
It is best to measure the voltage during the CV-phase of the charge, it should read as close as possible to 4.200 V. Make sure that you use a trusty DMM, preferably with a 5000 count display (or more), so you can read voltage to 1 mV.
I may run some tests tonight on a calibrated (to within 2-3 mV) SkyRC MC3000 and report.

Here are the promised test results on a calibrated MC3000.

Cell: Samsung 50E
Charge current= 2.5 A (approx. c/2)
End of charge current= 250 mA (1/10 of charge current)

Voltage during CV phase of the charge =4.196 V
Voltage at 1 min. after end of charge =4.182 V
Voltage at 2 min. after end of charge = 4.180 V
Voltage at 5 min. after end of charge = 4.176 V
Voltage at 45 min. after end of charge = 4.165 V

All measurements done with a UNI-T UT139C. The DMM was checked against 5.0000 V reference source and found to be 2-3 counts out, i.e. the precision of the above measurements is 3 mV.

I need more examples of voltage termination for both charges.
Here I found:
NITECORE UM2 обзор зарядного устройства - YouTube at 10:40
NITECORE UMS2 обзор зарядного устройства - YouTube at 16:00

I had the UMS4 for a short time and now the UM2.

There are differences, and I don´t mean the slot-quantity or the max. charging current.

The UM2 need a longer button-push after selecting the charging current.

UM2 seems to stop NiMH at 1,48V, UMS4 at 1,52-1,56V

After the charging is finished the UMS4 show “full” and voltage, the UM2 switches between the different values like at the chargetime

The UMS4 also increase the display the display brightness after a cell is finished.

UMS4 decrease the charging current some minutes before end of charging, UM2 doesn´t

I´m not sure if Nitecore is a real charger manufacturer or just a orderer?

After testing the UM2 with NiMH I´m not so satisfied with it.

While the UMS4 was very reliable, except with some very problematic cells, the UM2 terminates to early. Not only because it stopps at 1,48V with NiMH, also because it terminates much to early, especially with AAA-cells. This happens not so often like with Xtar VC4SL, VC4 or ISDT C4 EVO, but it happens

My ums2 i have to plug it into the outlet a bunch of times trying different configurations before it will work and charge. If i just plug it in and try to charge a battery, it will turn the screen on show the Good charging indication display 66 resistance, but never actually charge. So i take the plug out of the wall flip it around or try different outlet until it shows a different resistance and that’s when it will start charging. Hella annoying. But it does charge quick when it finally works.

1 Thank

Strange, never had this problem with my UM2 or UMS4.

And I tried different power supplies with both