Test/review of Charger NiteCore UM4

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HKJ's picture
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Location: Copenhagen, Denmark
Test/review of Charger NiteCore UM4

Charger NiteCore UM4
This is a USB QC powered 4 cell universal charger with adjustable current.
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The cardboard box lists lot of specifications, battery types and features.
The box contains the charger, a USB cable, manual and a warranty card.
The charger has the USB connection on the back together with a plastic heat sink.
The charger has two switches:
C: A short press will change slot and longer press will enter the charge and battery menu.
V: Step between displayed values and change settings in menu.
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When charging it will show chemistry (Li-ion), algorithm (CV), charged capacity, internal resistance, current, voltage and time.
The “Quick Charge” is present when the charger is power from a QC charger.
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The charger supports 4.30V, this will undercharge 4.35V batteries slightly. LiFePO4 is shown as 3.7V and NiMH is shown as NiMH/NiCd with -dv/dt algorithm.
The yellow label has the important specifications and is easy to read.
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The slots uses the usual construction and works well. They can handle batteries from 30mm to 79.8 mm long, the new 21700 with protection will fit in the charger.
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The charger can handle 79.8 mm long batteries, inclusive flat top cells.

  • Discharges LiIon with 0.3mA and NiMH with 0.06mA when not connected to power
  • Below 0.8 volt the charger will show EE and charge with about 1mA.
  • At 0.8 volt the charger will assume NiMH and start charging.
  • The charger will assume NiMH below 1.8 volt and LiIon above 2.0 volt.
  • Will not restart if battery voltage drops.
  • Charges with 0.05mA when LiIon battery is full.
  • Voltmeter readout freezes when charging is finished
  • Voltmeter is within 0.02 volt.
  • Change between 0.5A and 1A is around 56mm long batteries.
  • Charger uses 9V in QC mode and up to 2A current.
  • Charge will restart charging after power loss or battery insertion.
  • Slot #1 and #3 share a charge circuit.
  • Slot #2 and #4 share a charge circuit.
  • Power consumption from USB when idle without batteries is 35mA

LiIon charging
Current can be adjusted from 0.3A to 1.5A in 0.1A step. Default is 1A with long batteries and 0.5A with short batteries.
This is a nice CC/CV charge curve with about 150mA termination current.
Display shows 2820mAh, 3:38, 232mOhm
The 3 other slots are similar, but there is a minor voltage difference.
Display shows 2907mAh, 3:44, 210mOhm for #2
Display shows 2815mAh, 3:54, 110mOhm for #3
Display shows 2847mAh, 3:51, 202mOhm for #4
The two other capacities are also charged fine.
Display shows 2350mAh, 2:58, 163mOhm and 2610mAh, 3:25, 152mOhm
This old cell is handled fine.
Display shows 1794mAh, 3:44, 500mOhm
Increasing charge current to 1.5A works without problems.
Display shows 2628mAh, 2:17, 176mOhm for AP18650
Display shows 3076mAh, 2:57, 161mOhm for SA18650
Display shows 2918mAh, 2:15, 112mOhm for SA20700
A lower current also works fine, but with the same termination current.
Display shows 2778mAh, 6:05, 258mOhm
This old and worn down cell I charged at lowest setting., the charger works fine, but a lower termination current would have worked better.
Display shows 116mAh, 0:32, 375mOhm
A 14500 with 0.5A charge current works, but again a lower termination current would have been better. The termination is also at the minimum voltage.
Display shows 604mAh, 1:39, 500mOhm
Boosting input voltage to the charger with QC do not make single cell charging faster.
Display shows 2640mAh, 2:08, 157mOhm
With four cells in the charger the current is reduced to 0.5A for each cell.
Display shows 2966mAh, 6:56, 126mOhm for #1
Display shows 2880mAh, 6:38, 117mOhm for #2
Display shows 2896mAh, 6:55, 128mOhm for #3
Display shows 3003mAh, 6:47, 94mOhm for #4
With QC power the charge speed is faster, in this case around 1½ hour is saved.
Display shows 3101mAh, 5:31, 164mOhm for #1
Display shows 3016mAh, 5:13, 111mOhm for #2
Display shows 3038mAh, 5:29, 120mOhm for #3
Display shows 3028mAh, 5:13, 167mOhm for #4
Using a 0.5ohm resistor in series with 5V power to simulate a weak charger or long cable makes the charger real slow, but it will charge the batteries.
Display shows 2712mAh, 19:22, 223mOhm on #1
Display shows 2672mAh, 18:02, 146mOhm on #1
Display shows 2581mAh, 19:23, 229mOhm on #1
Display shows 2704mAh, 17:46, 123mOhm on #1
M1: 41.5°C, M2: 43.1°C, M3: 42.9°C, M4: 42.1°C, M5: 45.8°C, HS1: 51.9°C
M1: 48.4°C, HS1: 52.9°C
The charger need some time to start a charge. The charger measured voltage with current off.
Using QC do not change much, the charger is a bit faster to start, probably because the QC request is answered.
The charger will timeshare the charging circuit when multiple slots are used, this means average charge current is halved.
When entering the current change menu the current is turned off and first resumed when leaving the menu.
The charger has a small problem with a unstable power supply.
4.30V LiIon charging
The charger charges fine to 3.0V, but most “high voltage” batteries are 4.35V and they will be undercharged slightly.
Display shows 2564mAh, 3:10, 236mOhm
IFR (LiFePO4) charging
Display shows 439mAh, 1:05, 560mOhm
LiFePO4 is charged fine.
Display shows 1104mAh, 1:25, 185mOhm
NiMH charging
Current can be adjusted from 0.1A to 1A in 0.1A step both with USB and QC power supplies. Default is 0.5A
This is a nice -dv/dt charge curve with a very short top-off at the end (Only a few minutes).
Display shows 1706mAh, 1:47, 480mOhm
The 3 other channels looks similar.
Display shows 1986mAh, 1:52, 423mOhm on #2
Display shows 1748mAh, 1:49, 500mOhm on #3
Display shows 1740mAh, 1:49, 263mOhm on #4
The two high capacity cells are also handled nicely.
Display shows 2506mAh, 2:36, 500mOhm for Pro
Display shows 2581mAh, 2:41, 142mOhm for Leise
Termination works fine at 0.5A charge current on AA.
Display shows 1748mAh, 3:38, 464mOhm
This makes it easy to charge a AAA battery.
Display shows 714mAh, 1:30, 500mOhm
A full cell is detected in about 10 minutes, this is fairly fast for a -dv/dt charger.
Display shows 139mAh, 0:10, 197mOhm
The 1.5A charging also wors fine.
Display shows 1898mAh, 1:19, 223mOhm
With four batteries I may select 1.5A, but the actual current will be around 0.75A
Display shows 1923mAh, 2:43, 480mOhm on #1
Display shows 1815mAh, 2:34, 266mOhm on #2
Display shows 1932mAh, 2:43, 187mOhm on #3
Display shows 1965mAh, 2:39, 204mOhm on #4
There is no bonus for using a QC power supply here.
Display shows 1798mAh, 2:32, 313mOhm
Display shows 1898mAh, 2:40, 177mOhm
Display shows 1956mAh, 2:39, 208mOhm
Display shows 1940mAh, 2:42, 209mOhm
M1: 46.2°C, M2: 48.2°C, M3: 48.3°C, M4: 47.2°C, M5: 50.8°C, HS1: 66.2°C
HS1: 63.9°C
The charger needs some seconds to initialize before it will start charging.
Using QC do not change it.
The charger will timeshare the charging circuit when multiple slots are used, this means average charge current is halved.
Charging is turned off while adjusting current.
Unstable power supply do not work perfectly with NiMH either.
Internal resistance
The internal resistance measurement is not very impressive on this charger.
This is for LiIon
And NiMH.
Some of the readings are probably correct, but there are to many sporadic readings.
The charger works well with good default LiIon currents, it is possible to select a lower or higher current with some button presses. There is also the detail about time sharing, this means with 3 or 4 batteries in the charger the current is halved.
The internal resistance measurement do not work very well.
I will rate the charger as good.
The charger was supplied by a Nitecore for review.
Here is an explanation on how I did the above charge curves: How do I test a charger

My website with reviews of many chargers and batteries (More than 1000): https://lygte-info.dk/

DavidEF's picture
Last seen: 1 day 6 hours ago
Joined: 06/05/2014 - 06:00
Posts: 7699
Location: Salisbury, North Carolina, USA

Thanks for the test. Looks like just another decent charger (not an amazing one). It’s good that it can support multiple chemistries, including LiFePO4. But it doesn’t support very small cells, like 14250 or 10180. I know those are very unpopular, so it makes sense to not make any extra effort to support them. But then, how much could it cost really to make the slot size range a little more?

The bigger deal is the current sharing. I don’t buy four-slot chargers to get effectively 2-slot charging rate. That’s unreasonable from a so-called premium manufacturer like Nitecore.

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Last seen: 18 hours 7 min ago
Joined: 12/04/2017 - 06:33
Posts: 684
Location: United Kingdom

I just acquired one of these chargers cheap, and the biggest advantage of it, for me, is that it charges the huge Rofis and Manker protected 21700 and 26650 I have got. It can fit the biggest cells Smile It does QC 2.0 so is not too slow.

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Last seen: 1 day 1 hour ago
Joined: 08/04/2017 - 23:58
Posts: 2519
Location: Manila, Philippines

The display looks quite similar to the Nitecore SC4 and apparently has the same slot time-sharing issue common to several other Nitecore chargers, but this uses a USB/QC2-9v input.

Although has several fixes/updates:
- mentioned battery length of 79mm is really long to accommodate basically any protected 21700 (and maybe other longer battery types in the near future)
- high capacity NiMh will now get more or less fully charge (SC4 won’t fully charge 2500mAh NiMh)
- capacity display is at least more or less correct when multiple batteries being charged? (SC4 display will sometimes show very incorrect “charged capacity” when multiple slots are being used)

- I wonder why Nitecore still couldn’t properly fix the IR measurements (even if not calibrated, at least make the slots more consistent across IR measurements, even if not comparable to other chargers IR measurement).

Last seen: 1 year 7 months ago
Joined: 02/15/2020 - 13:42
Posts: 1

the display on the UM4 never sleeps? I just got mine and as near as I can tell the display never shuts off like the D4 does. I don’t like that.

Last seen: 1 year 1 month ago
Joined: 08/15/2020 - 01:42
Posts: 1
Location: Hungary

I just bought this charger, but I’m really displeased with it.
The time sharing charging was a bad surprise, but there are worse things
The charger overcharged a 4 pack nimh batteries of mine when I left it for overnight.
The batteries always charged fine with Nitecore D2, but this charger never terminated the charging of the 2500mah batteries and pumped 7500ma into them, causing them to overheat.
The charging status was not even in the last segment.
Im considering to never use this charger anymore, but it keeps me wondering, what could have caused this.
Do you think the timesharing? I suspect it’s harder to detect a full battery, when they are charged in 5 second pulses.