This is my first review here and (you guessed it) I received the charger free of charge from Miboxer for review. I have no other ties to Miboxer and I will do my best to do a honest review. Please let me know if I made any mistakes or there is something that I left out. Unfortunately I am not able to delve into the more technical details that many of the excellent reviewers here do; but I will try to answer any questions as best as I can. OK on to the review.
Miboxer C4 Smart Charger Review.
The C4 Charger: this is a 4 bay charger designed to independently charge 10340-26650 size Li-ion IMR, INR, ICR and LiFePO4 cells at 4.35, 4.20 and 3.6 Volts plus 1.2 Volt AAAA, AAA, AA and C NiMH/NiCAD at a nominal 1.48 Volts charge current. Cell lengths accepted by the C4 is up to about 72 mm.
In the box: The C4 charger came with a US style AC power cord (90-260V/ 50-60 hrtz/4 Amp max.), small instruction booklet (in English and Chinese) and plastic adapter to hold 2 AAA or AAAA size cells in the proper position while charging (which I found to work well).
I like the simple power cord and I am glad that Miboxer didn't make the C4 a USB powered charger since many USB power sources don't supply enough Volts/Amps to fully power a 4 bay charger.
There is also a jack for a 12V car charger, which is not included (apparently sold separately?).
The C4 appears to be well constructed with smooth working sliders and is said to be made from flame retardant materials.
Display: the vivid blue back lit 47x76 mm (1.85x3 inch) LCD screen displays real time Voltage, nominal charge current and charge time. A SLOT button is provided to switch between the 4 charge slots. And a MODE button for selecting charge functions. The back light shuts itself off after about 3 minutes and can be reactivated by pressing the SLOT button.
Basic charging: The C4 will automatically detect a cell's voltage when it is installed in a charging slot (designated C1-C4 from left to right) and will select the default charge settings. The default is 1.48 Volts for NiMH's and 4.20 for Li-Ions. The default charge rate is the "high" charge rate of 300 mAh for NiMH (and NiCads) and 800 mAh for Li-Ion. This is quick and easy enough for the common most cells. There is also a low charging current mode and 3.6 Volt and 4.35 Voltage settings which need to be selected manually.
Setting charge current: To change to the "low" charge rate of 150 mAh for NiMH cells (recommended for NiMH's with under 500 mAh capacity) or 350 mAh for Li-ion6's (recommended for Li-ion's with under 1200 mAh capacity), press the SLOT button to toggle to the slot with the cell you want to set the charge current for, Press the MODE button and "CUR" should start flashing, pressing and holding the MODE button again will toggle between High and Low current on the screen and another quick press locks in your selection.
Personally, I would like a lower Low for Li-ions, maybe 250 mA and a higher High, maybe 2 Amps if possible and a 500 mA medium charge rate. For the NiMH's I would really like a similar 2 amp mode added with a medium mode of around 400 mA and maybe a 200 mA low. While I didn't have any problems with missed charging terminations, the C4's charge currents are too low in my opinion for larger cells (such as AA/C NIMH and 26650 Li ion). The 350 mA Li-Ion Low maybe a little too high for some of the smaller cells.
Setting charge Voltage: Setting the voltage is similar to setting the current; press the MODE button until "BAT:" blinks on the display then you can toggle from 4.20 V to 4.35V to LiFePO4 (3.6 V). I found getting to the LiFePO4 setting to a bit tricky, as it seems to be slow to switch from the 4.35V setting and sometimes took me a couple of tries to get it to into LiFEPO4 mode.
I like that the C4 charging bays are completely independent so that you can charge different cell chemistry, Voltages and charge rates in each slot.
Internal Resistance Measurement: The C4 is designed to measure the internal resistance of cells in slot 4 only. All that is needed is to place the cell in slot 4 and about 8 seconds later the internal resistance in milli-Ohms is displayed for about 6 sec. before changing to the charge milli-Amp reading. I found this to be inconsistent when the same cells were tested multiple times. This may be do to inconsistent contacts with slider, rails and cell contact points. While it may not be completely accurate, I think this may be useful feature for weeding out cells that have developed high internal resistance if you are willing to test each cell several times and go by the lowest reading.
Charge/Discharge Capacity Test: The C4 can charge/discharge a battery (in slot 4 only) to test capacity. The cell is first charged, than discharged, while recording the capacity in real time, then the cell is recharged and the total capacity is retained on the display. The discharge rate is 400 mA when set on the high charge rate or 200 mA when set on low. As you can see, this will take some time to charge/discharge and recharge any cell with half way decent capacity. Since this function only works in slot 4, If you have a lot of cells it's going to be awhile before you get your data!
I tested the capacity of several AAA and AA NiMH's and the C4 seemed to work well, when the cell is discharged to 0.90 Volts, it starts recharging while the cell's capacity remains on the screen.
Lithium battery restoration: This is a feature that works automatically in slot 4 to gently restore a over discharged cell. I didn't have such a cell available, so I didn't get to try this feature.
Reverse polarity protection: If a battery is put in backwards, the C4 will detect it, stop charging and give an "ERR" message. Although I did not test it, the C4 is designed to do the same with a short circuit/damaged cell.
I found that the C4 will not detect alkaline cells and will attempt to charge them - you need to be careful that you only try to charge proper rechargeable cells!
I tried some old no-name NiMH AA's that have high internal resistance that won't charge in a BQ 17 Panasonic Eneloop smart charger and they charged up with no problem in the C4, though these cells are overdue for the recycle bin.
Warranty: 15 day replacement through the dealer if DOA, 3 year/ 36 month free repair through Miboxer; beyond that only labor is covered, exclusive of any parts needed for repair.
Bottom line: The C4 does what was intended to do – charge a wide variety of 4.20-4.35 Volt Li ion, 3.6 Volt LiFePo4 and 1.2 Volt NiMH/NiCD cells, though the charge currents are lower than they should be for larger capacity cells and the accuracy of the internal resistance test function needs to be improved.
Would I recommend the C4 charger? Only for someone who is not interested in charging anything larger than AA standard capacity NiMH or 18110650 Li-Ions, who does not need a fast charger and who does not need to do a lot of capacity testing. If Miboxer could increase the charge current, fix the internal resistance test feature and allow capacity testing in all 4 bays - I would recommend this charger without reservation.
Suggested Improvements: Aside from increasing the charge current as already mentioned, I would like to have the width of the charge slots increased to accept D cells. There are not many good smart multi bay chargers that can deliver the current required by the higher capacity D cell NIMH's currently on the market. If the C4 were upgraded with higher charge currents and the capability to charge high capacity NiMH D cells, it would be the only charger I would need.
Along with fixing the inconsistent internal resistance issue would be real nice as would something to prevent charging of alkalines. Some sort of charging indicator light that signals when charging is complete might be nice as well. Lastly, a instruction booklet with larger/bolder print and bigger illustrations would be nice for us old people who have trouble reading fine print.
Thanks to everyone who read through another review of this charger and thanks to Miboxer for providing it for review.
Miboxer C4 Smart Charger Review.
The C4 Charger: this is a 4 bay charger designed to independently charge 10340-26650 size Li-ion IMR, INR, ICR and LiFePO4 cells at 4.35, 4.20 and 3.6 Volts plus 1.2 Volt AAAA, AAA, AA and C NiMH/NiCAD at a nominal 1.48 Volts charge current. Cell lengths accepted by the C4 is up to about 72 mm.
In the box: The C4 charger came with a US style AC power cord (90-260V/ 50-60 hrtz/4 Amp max.), small instruction booklet (in English and Chinese) and plastic adapter to hold 2 AAA or AAAA size cells in the proper position while charging (which I found to work well).
I like the simple power cord and I am glad that Miboxer didn't make the C4 a USB powered charger since many USB power sources don't supply enough Volts/Amps to fully power a 4 bay charger.
There is also a jack for a 12V car charger, which is not included (apparently sold separately?).
The C4 appears to be well constructed with smooth working sliders and is said to be made from flame retardant materials.
Display: the vivid blue back lit 47x76 mm (1.85x3 inch) LCD screen displays real time Voltage, nominal charge current and charge time. A SLOT button is provided to switch between the 4 charge slots. And a MODE button for selecting charge functions. The back light shuts itself off after about 3 minutes and can be reactivated by pressing the SLOT button.
Basic charging: The C4 will automatically detect a cell's voltage when it is installed in a charging slot (designated C1-C4 from left to right) and will select the default charge settings. The default is 1.48 Volts for NiMH's and 4.20 for Li-Ions. The default charge rate is the "high" charge rate of 300 mAh for NiMH (and NiCads) and 800 mAh for Li-Ion. This is quick and easy enough for the common most cells. There is also a low charging current mode and 3.6 Volt and 4.35 Voltage settings which need to be selected manually.
Setting charge current: To change to the "low" charge rate of 150 mAh for NiMH cells (recommended for NiMH's with under 500 mAh capacity) or 350 mAh for Li-ion6's (recommended for Li-ion's with under 1200 mAh capacity), press the SLOT button to toggle to the slot with the cell you want to set the charge current for, Press the MODE button and "CUR" should start flashing, pressing and holding the MODE button again will toggle between High and Low current on the screen and another quick press locks in your selection.
Personally, I would like a lower Low for Li-ions, maybe 250 mA and a higher High, maybe 2 Amps if possible and a 500 mA medium charge rate. For the NiMH's I would really like a similar 2 amp mode added with a medium mode of around 400 mA and maybe a 200 mA low. While I didn't have any problems with missed charging terminations, the C4's charge currents are too low in my opinion for larger cells (such as AA/C NIMH and 26650 Li ion). The 350 mA Li-Ion Low maybe a little too high for some of the smaller cells.
Setting charge Voltage: Setting the voltage is similar to setting the current; press the MODE button until "BAT:" blinks on the display then you can toggle from 4.20 V to 4.35V to LiFePO4 (3.6 V). I found getting to the LiFePO4 setting to a bit tricky, as it seems to be slow to switch from the 4.35V setting and sometimes took me a couple of tries to get it to into LiFEPO4 mode.
I like that the C4 charging bays are completely independent so that you can charge different cell chemistry, Voltages and charge rates in each slot.
Internal Resistance Measurement: The C4 is designed to measure the internal resistance of cells in slot 4 only. All that is needed is to place the cell in slot 4 and about 8 seconds later the internal resistance in milli-Ohms is displayed for about 6 sec. before changing to the charge milli-Amp reading. I found this to be inconsistent when the same cells were tested multiple times. This may be do to inconsistent contacts with slider, rails and cell contact points. While it may not be completely accurate, I think this may be useful feature for weeding out cells that have developed high internal resistance if you are willing to test each cell several times and go by the lowest reading.
Charge/Discharge Capacity Test: The C4 can charge/discharge a battery (in slot 4 only) to test capacity. The cell is first charged, than discharged, while recording the capacity in real time, then the cell is recharged and the total capacity is retained on the display. The discharge rate is 400 mA when set on the high charge rate or 200 mA when set on low. As you can see, this will take some time to charge/discharge and recharge any cell with half way decent capacity. Since this function only works in slot 4, If you have a lot of cells it's going to be awhile before you get your data!
I tested the capacity of several AAA and AA NiMH's and the C4 seemed to work well, when the cell is discharged to 0.90 Volts, it starts recharging while the cell's capacity remains on the screen.
Lithium battery restoration: This is a feature that works automatically in slot 4 to gently restore a over discharged cell. I didn't have such a cell available, so I didn't get to try this feature.
Reverse polarity protection: If a battery is put in backwards, the C4 will detect it, stop charging and give an "ERR" message. Although I did not test it, the C4 is designed to do the same with a short circuit/damaged cell.
I found that the C4 will not detect alkaline cells and will attempt to charge them - you need to be careful that you only try to charge proper rechargeable cells!
I tried some old no-name NiMH AA's that have high internal resistance that won't charge in a BQ 17 Panasonic Eneloop smart charger and they charged up with no problem in the C4, though these cells are overdue for the recycle bin.
Warranty: 15 day replacement through the dealer if DOA, 3 year/ 36 month free repair through Miboxer; beyond that only labor is covered, exclusive of any parts needed for repair.
Bottom line: The C4 does what was intended to do – charge a wide variety of 4.20-4.35 Volt Li ion, 3.6 Volt LiFePo4 and 1.2 Volt NiMH/NiCD cells, though the charge currents are lower than they should be for larger capacity cells and the accuracy of the internal resistance test function needs to be improved.
Would I recommend the C4 charger? Only for someone who is not interested in charging anything larger than AA standard capacity NiMH or 18110650 Li-Ions, who does not need a fast charger and who does not need to do a lot of capacity testing. If Miboxer could increase the charge current, fix the internal resistance test feature and allow capacity testing in all 4 bays - I would recommend this charger without reservation.
Suggested Improvements: Aside from increasing the charge current as already mentioned, I would like to have the width of the charge slots increased to accept D cells. There are not many good smart multi bay chargers that can deliver the current required by the higher capacity D cell NIMH's currently on the market. If the C4 were upgraded with higher charge currents and the capability to charge high capacity NiMH D cells, it would be the only charger I would need.
Along with fixing the inconsistent internal resistance issue would be real nice as would something to prevent charging of alkalines. Some sort of charging indicator light that signals when charging is complete might be nice as well. Lastly, a instruction booklet with larger/bolder print and bigger illustrations would be nice for us old people who have trouble reading fine print.
Thanks to everyone who read through another review of this charger and thanks to Miboxer for providing it for review.
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