MiBoxer C2-4000 Smart Charger Review

Batteries and Chargers Chargers
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MiBoxer C2-4000 Smart Charger Review

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Hey folks today we will be reviewing the MiBoxer C2-4000 battery charger. The C2-4000 was sent to me by MiBoxer for review I will leave a link to there amazon store here. None affiliate link!
Miboxer sent me 3 chargers at the same time so its a bit of rush to get them all done.

Also one more disclaimer I am no charger expert but I do own around 10+ so I have seen many different kinds of chargers.

The C2-4000 is the sister charger to the MiBoxer C2-3000 which I reviewed earlier in the year. Think of this as an upgraded C2-3000 features wise. Keep in mind that edition of the C2-3000 was the first one per-release so no manual control selection.

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What is included in the box?

  • MiBoxer C2-4000 charger
  • Instruction manual
  • AC Adapter multi voltage 100-240v

Design
Design wise the C2-4000 looks fairly different to the C2-3000 it is a bit beefier and chunkier and has lots more curves? How important is that? Well these curves are in all the right places like dips on the side wall of the battery compartment making it easier to place and remove your cells. The screen on both the C2-3000/4000 are the same size and they are both very well lite and easy to read. The C2-4000 like the C2-3000 has easy to read digits which is important to me the digital are of adequate size.

Build quality
Build quality is what you would expect from MiBoxer the C2-4000 is built great and is very well finished. It looks a tad more premium compared to my Liitokala engineer 500. The slide rails work well and the contact point are set up well to handle larger and smaller cells. The spacing in the bays is awesome and works well with any size cell you throw at it.

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UI
The UI is okay the C2-4000 only has 2 buttons so not many option of keys to push. Changing current is easy to do and cycling between the different function and outputs like Ohm reading is easy. I did find it hard to navigate to the cell capacity testing it took more then a few tries of reading thru the manual to get it. I am not the best at finding obscure settings lol. Now i have done a few times it is much easier you only push 2 buttons and its on!

On the screen you will find a few different functions.

  • Battery percentage for the first channel/bay
  • First channel/bay
  • Battery type
  • Second channel/bay
  • Battery percentage for the second channel/bay
  • Remaining time/Charge time/ total charge and discharge time
  • MAH (battery capacity)
  • Charge/ discharge symbol
  • Internal resistance/Current/Voltage

Charging amperage displayed on the screen
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Charged voltage displayed on the screen
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Internal resistance displayed on the screen
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Features

  • Compatible with batteries of Li-on (4.2/ 4.35v) lifePO4 (3.6v), Ni-MH/Ni-Cd 1.48v (All standard sized cells)
  • Charges all types of cylindrical batteries Li-on and Ni-MH (10340-26650)
  • Maximum charge current of 1.5amps per channel (3amp total max charge current)
  • Manually set up charge and discharge current at your own discrepancy (Great for smaller cells like 10440 charge current can be set at 100 milliamps) (large cells current can be set at 1.5amps)
  • High precision calibration source
  • Reverse polarity protection and short circuit protection built in
  • Intelligent temperature control function (Has an inbuilt fan for use with the discharge Mah test cycle)
  • Automatically detects the battery and displays the state of charge
  • Automatically measures battery internal resistance
  • Measure the battery capacity during charge cycle
  • Can measure actual capacity of a battery through charge-discharge-charge cycle
  • Two fully independent slots (Can charge different range of cells at the same time)
  • Supports small capacity battery charging (Min charge rate of 100 milliamps)
  • Supports Li-on battery repair function (For cells with safety functions)
  • Supports DC12v input (Able to use in the car)
  • Made of PC fire retardant material
  • Excellent heat dissipation and circuit design
  • 3 year warranty

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Performance
The MiBoxer C2-4000 is awesome performance wise. The C2-4000 can charge almost any cells you can throw at it. With the manual select letting you choose a wide variety of current options. The options are endless I will specify the current outputs below.
Current outputs

  • 100ma
  • 200ma
  • 300ma
  • 500ma
  • 800ma
  • 1000ma
  • 1500ma

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The MiBoxer C2-4000 utilizes the correct charging current for cells of all sorts. The C2-4000 uses Constant current and constant voltage CC/CV for all Li-on cells. This is the correct way to charge lithium cells and is much safer than pulse charging in some circumstances like charging smaller cells.
The C2-4000 does use pulse charging for Ni-MH which is the correct way to charge Ni-MH this way of charging is best to fully utilize a Ni-MH.

Cells types

  • Li-on (4.2/4.35v)
  • lifePO4 (3.6v)
  • Ni-MH/Ni-Cd 1.48v

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The MiBoxer C2-4000 charges and ends the cells cycle well from what I can tell. It stopped all my tested cells at the correct 4.20v and it did slowly lower the charging current as the cycles ends.
The Ohms read out on the C2-4000 are as good as any other battery charger it works okay. They should be used for general guidance and be all.

I will leave some tested Ohms here

  • LG HG2: 60 milliohms
  • Samsung 25r: 35 milliohms
  • Sony VTC5: 43 milliohms
  • Liitokala 26650: 35 milliohms

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Capacity tester
The capacity tester works well and is fairly accurate it charges then discharges then charges a final time to find out overall capacity. It does save the data at the end of cycle in case you are not at the charger to read it. You should never leave lithium batteries alone while charging. The fan does only activate while in discharge mode to keep the charger cool I discharged 2 cells at 1.5amp each and the charger read 44 degrees Celsius. Discharge cuts of at 3v from what I can tell. After this 3v mark there is hardly no capacity left in a Li-on cell.

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Tested capacity

  • Samsung 25r: 2726ma
  • Imalent 18650 (2600mah rated): 2554ma

Auto charging
Auto charging works good it charges according to the resistance of the cell in the slot. Generally a smaller cell will have higher resistance I am not sure how that works. Charged my Samsung 25r and they charged at 1.5amps which is fine for a high drain 18650 they read at @35 milliohms.
I tried my Soshine 10440 a fairly hard cell to charge because of its size many chargers are not suited to charging such low current. Auto charge selected 300ma charging current which is okay but still a tad high I would rather charge at 150-200ma. I have charged these cells many times at 300ma because my Liitokala engineer 500 smallest charge select is 300ma.

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These Soshine 10440 read at 200 milliohms I would expect the resistance to be even higher then the reading. The major flaw in this auto charge is the fact that it uses resistance to select charge current. If you insert any protected 18650 it will charge fairly slow by default because the protection circuit adds extra resistance. This is why manual select is the way to go once you chose a current on manual mode the charger will stick to that current and not change unless you input a new charge current.
Last but not least I tested the C2-4000 with a Trustfire 14500 IMR cell its rated at about 600mah. The auto charged selected 450mah and gave me an Ohms reading of 155 Ohms. This charge current is acceptable.
Generally speaking you charge cells at half or less of there capacity. 300Mah cell go for 150mah or less charge current those Soshines have a max charge rate of 350mah. If charging 3 Amp 18650 go for 1.5 amps or less generally 1amp unless you are fast charging. Slower charging and or lower current may help with the longevity of the cell. This is also dependent on the batteries chemistry.

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The MiBoxer C2-4000 is a great all around charger and incorporates some really useful features in a small and compact design. Although its only a 2 bay charger with the 1.5amp fast charge it can make up for the lesser overall slots by charger each cell faster.

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Let me start by saying I like this charger and I wish there were more 2 slot chargers with this feature set.

However, you would be remiss not to mention how LOUD the fan is. It only turns on during the discharge portion of the capacity test (GOOD) and keeps the unit quite cool (GOOD) but I literally cannot be in the same room as this charger while it is doing the discharge test.

Also, it took me several attempts to figure out what the manual meant when describing how to start the capacity test. You hold SLOT till the 4 digit capacity starts blinking then press mode once. I was expecting the 3 arrows to come up after step 1 but they only actually appear once you get it into the correct mode.

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Lol i think the fan sounds cool like a little jet engine lol. I dont mind it i have a louder fan in the room where i charge cells so its not to bad. I should say for me personally. I will pull this apart and see if we need the fan when i get a chance.
Maybe we can replace it.

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What termination current you see, when charge Li-Ion 18650 ?
I see on my C2-4000 termination current <0.01A, and final part of charging require additional 30-60mins, with currents of 0.05-0.01A, but this part adds <0.5% of capacity.

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My 6000 takes forever to complete top off.

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The C2-4000 has become my every-day charger. I like it very much. My only complaint is that its too easy to forget when its in the charging mode. Once the display dims down after a couple minutes,it kinda disappears on my desktop. Wish it had even a single led to indicate that its in operation.

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Great review EveryDaySurvivalGear.

Ditto most of the comments as well. The fan’s noise startled me at first until I realized it was only during the optional drain cycle which I seldom use so it doesn’t really disturb me.

The taper charge at the end does take a while but when I’m in a hurry I just pull off the cells at 98% to save time, but mostly I just drop cells in and forget.

The wallwart’s large but I think it’s helpful in transferring some of the heat away from the body of the charger itself.

I am really liking my C2-4000 and even prefer it over my 4-slot Nitecore.

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What cells? Are they older cells? Older cells always take longer to terminate.

I should say cells that have aged bad my LG HG2 are not that old but have been driven hard there whole life and take longer to charge then my other cells.

A termination current of under 100ma is good for a 18650 some where around 30-50ma termination is what you are aiming for.

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Mine are brand new ncr18650 b and ga protected. I think the protection circuit is tricking the charger .

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I’ve found that my C-2 4000 charges all button top batteries at a very low rate when on auto. Probably because it also reads all button tops as having high internal resistance—even new batteries. I’m assuming it’s because—unlike flat tops—the button tops only make contact with one of the little dimples on the C-2’s positive post. That’s my theory anyway.

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Even if I manually step the charge rate up , at the end it goes into a very low rate .

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Be thankful if it ends at a “very low rate “ , probably at 10% of the charging rate, for it means it’s doing what a proper cc/cv procedure charger should do.

Once the charger shows 4.20v, (the cc stage), the cv stage takes over, the 4.20v stays, but the current tapers down to 10% of the rate used in the cv until its terminated, then displays “full”.

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Yes, termination current of 50ma is good , but I think, that
termination current 5-10ma is crasy,
it’s simply additional 30mins for <0.5% capacity.

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I did a little experimenting last night with a new ncr18650ga . I first put it in slot 1. It first read very high resistance so I put it in slot 2 and the resistance went down to 110mohm,92,4.2v,.56amp. I tried it back in slot 1. The resistance read 124 mohm,95,4.2v and .09 amp. It took over 2 hours to complete charging. Does that seem like a long time or is that normal?

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Are you saying it took 2 hours with the battery having 95% capacity and started charging at .09 amps in slot one?

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Yes . Seems long,right? Always get high resistance readings /low auto charge currents. Re inserting them helps reduce resistance reading usually.I think I have to override the auto select feature to get shorter times. I wish I had some unprotected cells to test.

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Very long. Battery is practically charged anyway. Just use it as is all you will gain is a few mah anyway.
How long does it take if the battery is fully depleted?

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When they came from Liion Wholesale, they read about 3v. Can’t remember for sure , but they took about 8 hours.

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Sounds like the charger is trying to squeeze every last electron it can in to the cell.
“Table 2: Typical charge characteristics of lithium-ion. Adding full saturation at the set voltage boosts the capacity by about 10 percent but adds stress due to high voltage.”
Might be better for the cell if it was pulled a little earlier in the CV stage.

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Thanks for the tip.