Test/Review of Charger Klarus Smart Charge C2

Charger Klarus Smart Charge C2

This is a simple dual channel charger from Klarus with support for both NiMH and LiIon. It can also be used as a power bank.

I got the charger in a retail cardboard box from a gearbest. The box has the specifications printed on the back.

The box contained the charger, a mains cable and a instruction sheet.

The charger has both a mains power input socket and a 12V DC input barrel socket.

The charger can works as a power bank. With one LiIon battery it is rated for 1A and with two LiIon batteries it is rated for 2A.

The charger do not have much user interface, only 3 yellow leds for each battery. When charging one of the leds for each battery will flash and the number of lit leds will show the actual charge status. When finished all 3 led will be steady lit.

The charge uses the typical slider construction with a metal rail and works from about 30mm to 69.3mm, i.e. the charger cannot handle the longest protected 18650 and 26650 cell.

The charger can handle 69.3 mm long batteries, including flat top cells.
The minimum charge current is 0.5A, this is on the high side for 10440 cells.


  • Power consumption when idle is 0.42 watt.
  • Below 0.7 volt the charger will flash all 3 leds and charge with 4mA.
  • Between 0.7 volt and 2.0 volt the charger assumes NiMH
  • Above 2.0 volt the charger assumes LiIon
  • The charger will not restart if battery voltage drops.
  • Charge will restart charging after power loss, or battery insertion.
  • When LiIon battery is fully charger the charger will charge with 0.6mA
  • When not connected to power it will drain about 14mA from a LiIon and 0.2mA from a NiMH battery.

Charging LiIon

This is a nice simulated CC/CV charge curve with 7mA termination.

Second slots looks the same as the first.

No problem with different capacity.

This older cell is also handled fine.

The smaller cells is also handled fine.

Two cells is charged with about the same speed as one cell.

The current consumption is only about 0.5A on 12V.

M1: 34,6°C, M2: 34,9°C, M3: 51,6°C, M4: 42,6°C, M5: 43,4°C, HS1: 54,4°C
Batteries are fairly cool during charge.

M1: 33,8°C, M2: 33,9°C, M3: 49,6°C, HS1: 55,6°C

The charger needs about 4 seconds to start and measures voltage with the current turned off.

Charging NiMH

The charger is terminating on voltage and probably slightly before the cell is full (Temperature has not started to increase).

It works the same way on the second channel.

The Pro and XX cells works the same way.

But on the powerex the temperature has started to increase, i.e. the cell is full.

Again a slightly premature termination.

Detecting a full cell is fairly fast with voltage detection.

Two cells is charged with about the same speed as one cell.

The power consumption from a 12V supply is fairly low when charging NiMH.

M1: 35,2°C, M2: 36,5°C, M3: 48,3°C, M4: 41,9°C, M5: 42,4°C, HS1: 51,0°C
Also NiMH stays fairly cool during charging.

M1: 33,5°C, M2: 33,6°C, M3: 38,7°C, M4: 47,0°C, HS1: 50,6°C

The charger needs about 4 seconds to start and measures voltage with the current turned off.

Charging LiIon and NiMH at the same time

It is possible to charge one LiIon and one NiMH battery in the charger at the same time.

In this curve I recorded the NiMH battery, it looks the same as above.

The LiIon also looks the same as above, the power consumption drops when the NiMH battery is finished.

USB output

  • USB output is turned off when mains is connected.
  • Batteries are drained to 2.8 volt
  • When nothing is connected to usb output it will drain about 14mA from a battery
  • USB output is coded as Apple 1A

With one cell supplying the usb output it can deliver just above 1A, before output starts to drop. There is no real overload protection.

With two cells the current is double up, but again no overload protection.

With 0.5A load and one 18650 cell the usb output can run for about 3½ hours. The output will not turn completely off when the battery is empty, but keeps the battery voltage at termination voltage.

When the load is increased to 1A with one cell the output voltage cannot be maintained at low battery voltages. It looks like the maximum battery current is limited to about 1.8A.

There is a slight voltage difference between the two batteries.

When running with two batteries the voltage difference it obvious, at about 120 minutes the first battery is empty and the second battery takes over.
Note: The efficiency calculations are wrong, because I only measure on one cell.

Running at the full current (2A) works, but again the output voltage sages when the batteries are low on voltage.
Note: The efficiency calculations are wrong, because I only measure on one cell.

Output has very low noise with 5mV rms and 45mVpp

Increasing the load will increase the noise, but it is still very low 9mV rms and 70mVpp

Even at full current the noise is low with 35mV rms and 280mVpp

Testing the mains transformer with 2500 volt and 5000 volt between mains and low volt side, did not show any safety problems.


This is a simple charger to use and it is good at charging both LiIon and NiMH batteries.
The usb output works fairly well. The output voltage will sag before the batteries are empty and it drains the batteries to 2.8 volt, instead of turning usb output completely off when the batteries reaches 2.8 volt. The always on power bank function does also mean that it is a bad idea to leave batteries in the charger when not powered (A few days is ok, but the battery will need charging).

The final verdict must be that it is a good charger.


The charger was supplied by Gearbest for a review.

Here is an explanation on how I did the above charge curves: How do I test a charger
Read more about how I test USB power supplies/charger

That is so much better than our classic i2. Thanks for HKJ for your depth review. Will be stocking them up very soon. By the way, does C4 has similar performance? different breed.

Looks like a good field charger and the powerbank function is very handy. Does the price give it good value compared to other options on the market?

Looks a good simple universal charger. Thanks for the review HKJ, I always enjoy reading your in depth reviews of products.

With the code on my website the price looks good (I do not know if its the best offer around, I usual do not follow prices in detail).

Before anybody complains: The link on my website is not a affiliate link, but supplied by gearbest.

I know this is a bit old thread, but i need to solve a doubt:

Is this charger completely silent? or does it make any kind of noise?

I have just adquired one and it makes quite electrical noise, continuously whitout battery inserted, and intermittently while charging.

Have i got a faulty one?

No, that is something most modern electronic may do, due to the way the power supply in the charger works. Only if it is fairly loud is there reason for complains.

Thanks HJK for the reply,

I am afraid that “fairly loud” is a too subjective term, but it is good to know that that noise is part of correct operation.

BTW, great review!

The problem is that nearly all electronic makes noise, sometimes it is outside hearing range, sometimes not, sometimes is is barly audible, sometimes load enough that everybody within a few meters can hear it (In the last case it is often possible to get the product replaced).
One example on a loud product was on EEVBlog recently, a guy got a DMM where the backlight was fairly loud, resoldering a capacitor fixed the sound. By accident the way the capacitor originally was placed on that meter amplified the sound significantly, other meters from the same batch did not have nearly as much audible noise.

Not that much at all. Now, at night, can be hear from a pair of meters, is like having a wall clock :-/ .

Yes, i am familiarized with whining coils and capacitors on computers, but i didn’t expect noise from a battery charger, i don’t know why.

I may disassemble it to see, as you say, if a capacitor was not sitting on PCB and therefore making the noise, but first i want to use it a bit :smiley:

I found on google :
‘’Indicator: The light will turn green after fully charged ’’

But on my charger it is orange light and as far as I can see it wont turn into green, is this normal ?

Also I notice that it wont to charge low quality 14500 batteries, I empty battery capacity almost to the end, and then put it on C2 then very fast ( in couple of minutes ) I get all 3 orange lights.

But when I put it on ordinary Chinese charger, that charger charge a bettery 2 hours untill its fully charged.

Not everything on google is correct, this charger has 3 single color leds for each slot, they will never change color.

It usual depends on charge current and termination. I sounds like the 14500 you tested with is very bad.
You can see here what I say about that Chinese charger: Review of Charger Bowei HC-103W

Yeah, I know that chinese charger is really bad, but he will charge that 14500 and klarus obviously not, since after couple of minutes show all 3 led steady. But never mind it is low quality battery and it is not so important.

Tomorrow I will get my Convoy L6, and today I put 2x 26650 ( 5200 mAh ) on C2 to charge them first time… when I put them one led was steady and second was blinking, and it took 6 hours that third led starts to blink :cry: , during that time charger was really hot and I can manage to hold it, but USB port was so hot that I can’t hold my hand on it more than 5 seconds. When third led starts to blink all heat was gone and charger was cold, it took 1 hour more that third led stop to blink.

So to 2 steady leds 6 hours and charger extremely hot on USB port, to 3 steady leds 1 hour and charger cold.