Live: Review of "smart" charger Miboxer C2-3000 (updated step by step)

[CuriousOne]

Hello.

As charger review is a lengthy process, I decided to do it live - while text is being posted, measurements are conducted, so if you have any opinions on what to test, you are welcome.

This charger was provided by Miboxer for review. MSRP: $24.99 Official link: http://www.miboxer.com/eng/p2.html

Key features:

Charging currents and voltages are adjusted on the fly, based on actual battery measurement, to achieve optimal results and fastest charge time possible.
Dual slot charger, with up to 1.5A charging current per slot.
Supports cell sizes from CR123 to "D", without any additional support needed.
Can be operated from USB charger, Car cigarette lighter socket (adapter included), AC Mains (adapter not included)

Minor disadvantages:

No AC adapter included
No dedicated USB socket, requires special USB<>barrel cable

So far, so good, let's see what you will get:

The box (nicely made, solid carton) includes the charger itself, car adapter and usb<>barrel head cable and manual.

Charger is very solid, made from high grade plastic, and feels like a tank. It is quite large too, especially for 2 slot charger, but do not forget, that it supports cell sizes up to "D", so a lot of space is definitely needed. On the picture below, you can see it next to LaCrosse BC-700:

Car charging adapter is very special, it can provide either 5 volts or 12 volts of output. Initially, I thought that it was Quallcomm Quick Charge protocol compatible, but it is not. Looks like it uses different method to tell charger what to do. Unfortunately, it is very solidly built, so I can't take it apart, to see the internals:

Let's plug it in (I will be using 5V USB charger for todays tests. Will do 12V adapter tests later) , and see what happens. Screen comes on, charger model is displayed, and backlight is on:

 

[CuriousOne]

For initial testing, I will be using two 18650 cells, one - "bad" Samsung ICR-18650-22FU, which measures below 2.8 volts and "good" Feilong 18650 cell, which measures 3.7 volts. After insertion of the battery, charger displays charge level for each slot, and with the press of the "slot" button, you can toggle additional display, which will show remaining time, capacity already charged and last segment will alternate between voltage, current and internal resistance of the selected cell:

As I can guess from the screen data update, charger checks voltage, current and internal resistance each 2 second, and based on that, adjusts charging current and voltages respectively. For example, the discharged Samsung cell had internal resistance of 488 ohms at beginning, so it started charging with 0.1A current. As voltage increased, resistance dropped, so now it measures as 113 milliohms, and current went to 0.85A.

Feilong cell had higher starting voltage, and lower internal resistance, less than 90 ohms, so while it was also started with 0.1A current, it went to next setting - 0.3A, just under one minute, and reached 1.5A in about 15 minutes. Now cell measures 93 milliohms and 4.20 volts, and charging current is 0.31A and is going down. Will post next post, after charge of the cell will be finished.

 

[CuriousOne]

OK, charge of Feilong cell was completed. Charger reading was 4.20V and actual voltage, measured by precise DMM was 4.1998 volts, which indeed is very good. Now, after charge completion, voltage is slowly dropping, and already at 4.18 volts. This means, that charger disconnected charging circuitry from the battery, so no trickle charging, as it was with C4 charger. The middle section of the display toggles between the "FULL" text and mAh measurement:

 

[CuriousOne]

After basic LiIon tests, I've decided to continue with NiMH cells, but I encountered a problem - I don't have any discharged NiMH cells lying around. After careful checking, I've found one Sony CycleEnergy 2100mAh LSD cell from 2012, which was measuring 1.2V, while others - 1.3, so I put it into charger. It started with 0.1A, but in maybe minute or so, went to 0.15A and still charging.

 

[CuriousOne]

NiMH charging current settled on 0.25A and continues. Samsung cell charging was completed and it now measures 4.2013 volts. Now I will go a bit different way - I have low capacity, rechargeable CR123A cells, which I use in my studio strobe remote triggers. Will insert it and watch the current closely. These cells have fairly high impedance, so it is interesting, how far charger will go.

 

[CuriousOne]

Rechargeable CR123A charging current quickly went from 0.1A to 0.4A, despite it's high measured internal resistance - 488 milliohms. I have metal bucket with wet sand inside ready nearby - just in case...

 

[CuriousOne]

Rechargeable CR123A charge completed, as charger says, 904mAh went into battery. Considering the fact, that at 0.5A discharge, this cell delivers around 458mAh, I think, 904mAh is a bit inflated reading. Meanwhile I got another 18650, also made by Feilong, which was reading at 2.29V. Put it into charger, and surprisingly, it instantly started charging with 0.2A current. After reaching 3 volts, it ramped current to 0.45A and after reaching 3.2 volt, current is set on 0.6A.

 

[CuriousOne]

That "bad" Feilong cell charging is going in quite interesting way: Capacity is at 80%, Current is at 1.15A, remaining time shows 0:48, but mAh reading does not increase and sits on 2220mAh !

 

[CuriousOne]

While user manual states that it is prohibited to charge Alkalines in this charger, and it might lead to explosion, I decided give it a try, I just put discharged Zi5 Alkaline cell into charger, and while charger charged it only with 100mA current for 18 minutes, battery became swollen, as you can see on the pictures. It's negative pin inflated, and now looks almost as positive pin. So this is good illustration, that Alkalines should not be put into this charger.

 

[CuriousOne]

Did some tests with IMR cells. As charger "sees" lower internal resistance, it quickly goes to max. current of 1.5A and finishes charge faster. This gives excellent charge speed for Li-Ion, but nothing spectacular for NiMH - C4 appears to be faster than C2 on NiMH. But all those were just charging tests. Tomorrow, all these charged cells will be discharged, to measure what energy charger put into them. Stay tuned!

 

[KITROBASKIN]

Interesting, Thanks

 

[CuriousOne]

Did discharge test on LiIon cells, that were charged using this charger. Discharged capacity was equal to what should be expected from the capacity of the batteries, so I assume, that it properly charges this chemistry. Since discharge tests took long time, had no time today to check with scope for curves, will do that tomorrow.

 

[magellan]

Great review, thanks!

 

[magellan]

Rechargeable CR123A charge completed, as charger says, 904mAh went into battery. Considering the fact, that at 0.5A discharge, this cell delivers around 458mAh, I think, 904mAh is a bit inflated reading. Meanwhile I got another 18650, also made by Feilong, which was reading at 2.29V. Put it into charger, and surprisingly, it instantly started charging with 0.2A current. After reaching 3 volts, it ramped current to 0.45A and after reaching 3.2 volt, current is set on 0.6A.

Interesting, the 904 mAh is a little high for a CR123A battery, as even new ones are usually 100 mAh or 200 mAh less. But one of the EE guys here explained once that is common with older batteries with higher resistance since it takes more time and energy to get the battery back to its full state. That was when I realized for the first time that as a cell ages it doesn't just have lower capacity, it takes more energy to get it to that lower capacity than when new.

In other words, say a cell only has 85% of its former capacity, originally rated at 700 mAh. It could take 900 mAh on the charger just to get it back to 85% or about 600 mAh.

I think I'm remembering this right. But if not any of the EE's out there can feel free to correct me.

 

[miboxer]

Hello CuriousOne

This is Leo from Miboxer, thank you for your nice review and your hard work, I will forward your feedback to our engineers

Thanks again

 

[magellan]

It's pretty cool they noticed your review and will let their engineers know about it.

 

[brighterthanthesun]

They are very responsive to reviewer/user feedback. I am testing this charger right now and I commented right away that they needed to include an AC power source with the charger that will allow us to charge two cells at 1.5 amp each. They responded the next day that production models will be shipped with an AC power source.

 

[CuriousOne]

I have done more detailed testing, including current measurements, thermal conditions and some other data. Will post them tomorrow. Overall, this is indeed a great charger, but I would suggest two improvements:

1. Add standard Micro USB port for charging.
2. Add QC 2.0 support, so users will benefit from faster charge, without need of standalone 12V adapter.

In short words, take a look at Wismec Avatar smart charger - it has some great functions, that will be even great, if realized in your charger, and release 4 slot version asap

 

[CuriousOne]

2 weeks passed, used this charger heavily these days, along with the C4. Some additional conclusions can be made:

C4 is a bit faster at charging NiMH, and since it has 4 slots, and I need to recharge 4 AA cells at same time (used in camera flash), I used it more often. Also, unlike Lacrosse BC-700, which can't detect heavily discharged NiMH, and needs "kick" for such battery, C4 had no problems with that.

For the lithium cells, both chargers (C2 and C4), show equal performance in terms of charging speed and amount of charge delivered to battery. Both were far superior to LiitoKala Li-260, which charges cells longer and heats them more, than C2 or C4. Since I use wild number of LiIon cells (from RCR123A to 26650), automatic current capabilities of C2 are really handy.

So, both chargers are in use, C4 replaced BC-700, and C2 replaced Li-260 at my "charging desk", getting faster charges and cooler batteries. Thanks Miboxer!

 

[xxo]

C4 is a bit faster at charging NiMH, and since it has 4 slots, and I need to recharge 4 AA cells at same time (used in camera flash), I used it more often.

One of the things I liked about the C2 is that it charges NiMH's at up to 1 Amp compared to only 300 mA (600 for the last few min. of charge) for the C4, so it is a good bit faster, though of course you are limited to 2 slots vs 4 of the C4.