Eizfan NC2 USB Charger
This is a very simple dual slot USB powered LiIon charger.
It arrived in a nice box with specifications on.
The pack contained the charger a usb cable and a instruction sheet.
The charger is powered from micro usb.
On the top is a led for each slot (One led, the 4 part is only design), it is blue while charging and green at other times. If a battery with very low voltage is put into the charger the led will turn off.
Not much easy readable information on the back of the charger, the specifications are embossed in the black plastic.
The charger uses the typical slider construction, it can handle batteries from 32mm to 74mm.
The charger can handle 74mm long batteries, inclusive flat top cells, this means just about all protected cells, even 21700.
The charge current is too high for small batteries.
Measurements charger
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LiIon Batteries will be discharged with less than 0.01mA when power is off.
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Charges full LiIon batteries with a few mA when connected to power.
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Charger reports full at 4.20V
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When battery is below 1 volt the charger will charge with 100mA and the led will be off.
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Between 1V and 2.8V the led will be blue and the current will be 0.1A
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Above 2.8 volt full charge current will be used.
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Charger will restart if battery voltage drops.
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Charger will restart charging after power loss, or battery insertion.
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Charger uses about 6mA from USB when idle with no batteries.
The charger uses 1A charge current until the battery is close to 4.2V, then the current starts dropping, it will never turn off.
The second slot is the same.
The other batteries looks similar.
With this old battery the missing termination means the battery will be filled completely.
With a smaller cell the initial voltage increase is higher, this helps to reduce the charger current, but the current is too high for the first 40 minutes, this will add extra wear to the battery.
With two batteries the current drops a bit at the start, probably due to heat in the linear circuit, current will increase to 1A when the internal voltage drop is lower.
Adding a resistor in series with the usb power supply to simulate a long cable or weak supply did not prevent the charger from charging the batteries, but it did slow it down.
M1: 36.2°C, M2: 35.9°C, M3: 46.2°C, M4: 45.8°C, HS1: 60.8°C
The batteries are fairly cool, but the circuit is a bit warm.
HS1: 68.8°C
The charger is very simple and do not need any starting time.
Being a simple charger it works fine with unstable supply.
Conclusion
The charger will charge one or two batteries with 1A, but it misses a real termination. As long as the batteries are removed within a few hours after the charger report full the extra wear on the batteries will be limited. Because it maintains the 1A current fairly close to 4.2V the charger is on the fast side for a 1A charger. Being a simple charger it is not very critical about the input power.
I will only call it acceptable due to the missing termination.
Notes
The charger was supplied by Eizfan (Efan) for 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