Charger CottonPickers DM + 4 settings



Cottonpickers makes a line of small single cell USB LiIon chargers. This is the largest model with a voltmeter and 4 current settings.



The charger is supplied in a plastic bag with a simple instruction sheet and two sets of charge leds, one set with magnets and one set with alligator clips and magnets. There is no cradle for batteries.



With magnetic leads it is possible to connect the charger to any size cell.



Here is the two types of charge leds can be seen. The magnetic connection will also work on batteries with a protection circuit, the magnet is strong enough to hold onto the metal on the real battery bottom on the other side of the protection circuit.





The charger is not build into any kind of box, just sealed with silicon and adhesive rubber tape. This makes it a very compact charger, but the design is not exactly good looking. The charger has printed specification on the side of the led display.
The charger has a led sealed into the silicon, this will make the silicon opposite the usb connector glow red when charging.



With the multiple current settings and use of magnets for connection the charger can handle just about any size cell directly.



Measurements

The charger starts charging from 0 volt with 300 mA (Except on 90mA setting, where it is 90 mA).
Depending on setting it will stop charging at a specified current: 90: 7 mA, 300: 27 mA, 500: 47 mA, 700: 75 mA
The charger restarts charging at 4.05 volt
When the battery goes above 4.2 volt or the charge current stops, the charger will discharge with 15mA because the voltmeter is powered from the battery.
When charger is disconnected from power, but with a battery in, it will draw about 15 mA from the battery, again due to the voltmeter.



The first test is with a 2200 mAh cell on the 700 mA setting, with the highest current setting it takes 4 hours to charge the cell. The charger does not use a true CC/CV charge profile, some of the reason might be because the charger reduces the current due to heat.



When reducing the charge current to 500 mA a constant current (CC) phase can be seen, there is also a constant voltage (CV) phase, but between them there is something that is neither CC nor CV. This is no problem, it just means that the charging will take slightly longer than with only CC/CV.



The 300 mA works the same way as 500 mA.



The 90 mA setting is again the same. This setting is low enough to charge small batteries like 10280 and 10180.


Conclusion

The charger is close to a CC/CV charging profile and supports nearly any cell size. It also has a build in voltmeter, making checking of LiIon cells easy. This makes it a very good charger for LiIon, it can both be used to verify the cells with the voltmeter and to charge the cell. The lack of a real box and the high charge current with empty batteries is a disadvantage for this charger.
With small cells it is important to remove the batteries when the charger is finished or it will discharge the cell (But not to lower than 4.05 volt). The reason for this is the voltmeter that takes power from the battery.



Notes

Here is an explanation on how I did the above charge curves: How do I test a charger

The charger is sold on cpf marketplace.