Folomov Key Charger



This is a combined charger and power bank in the size of a car key.



It arrived in a transparent plastic box, the box contained the charger and a instruction sheet.






The charger has a usb lead stored around it, this connector on this lead fits a normal usb power supply and is used to power the charger.



The user interface is four leds that shows the charge status of the battery.





The charger uses a flying lead for connection to battery minus, when charger is not used it is stored inside the charger. It can fairly easy pop out.
The charger fits 18xxx to 21xxx flat top cells, button top are not stable.




The usb connector in the charger is both use for storing the usb input lead and for output when using the charger as power bank.








The charger can handle up to 70mm long batteries,



Measurements

• Power consumption from usb when idle with no batteries is about 8mA
• Will discharge a battery with about 9mA when not powered
• Below 2.8V the charger will charge with 300mA
• Above 2.8V the charger will use full current.
• Will restart charging if voltage drops below 4.12V.
• Will restart charging if battery is inserted or power cycled.

Charging



The charger curve is some sort of CC/CV, but with a termination current around 300mA, this means it is best for batteries with not too high internal resistance.



This battery is a bit old and has some internal resistance, this means a significant voltage drop when using a 300mA termination and the charger will restart many times.



This battery is not as old, but has the same problem.



Using a high current 20700 battery works much better.



A 0.5ohm resistor in series with the usb power to simulate a long cable or weak supply will reduce the charger rate significantly and also the termination current a bit.



M1: 37.6°C, M2: 42.8°C, HS1: 55.6°C



Being a fairly simple charger I could draw the current profile.



The charger is fast to start.



Power bank

• Will discharge a battery with about 9mA when not powered due to the leds.
• Will discharge with less than 0.04mA below 2.75V
• Usb output is coded as usb charger (DCP)
• Output turns on when loaded, it is very sensitive.
• Cannot be used as UPS, there may be a short power break when input voltage is removed.

The charger can deliver about 1.8A with a full battery.



When powered from usb it will pass the current straight through.



Also with a battery in the charger it will (Sometimes) pass the current straight through when powered from usb.



The output voltage is a bit low for a usb charger, this means devices will usual select a low charge rate.
The power bank function discharges batteries to 2.75V and then stops (Good)



With a 1A current the voltage starts dropping shortly before the battery is completely empty and the termination do not work perfectly, it will resume when the battery voltage increases due to no load.



At 0.5A the noise is 31mV rms and 180mVpp



At 1A the noise is 5mV rms and 35mVpp



Power consumption from LiIon battery when idle, the led gauge need some current and some of the variation in current is due to the number of leds turned on.



Conclusion

I like the size and the nice way to store the input lead, it is also a very easy to use power gauge it has. It is very nice that it support both 18650 and 21700 batteries. The power bank has very low noise and uses the best coding for a 1A power bank.
I do not like the high termination current, it limits how well it chargers older batteries, I would have like more output voltage and a better termination when the battery voltage is low.

I will rate it as fairly good, both for charger and power bank functionality.



Notes

The charger was supplied by Lumin Industrial Ltd for review.

Here is an explanation on how I did the above charge curves: How do I test a charger
How do i test usb charger and power banks