CottonPickers Dual 4.2V-4.35V



CottonPickers has been making chargers for a long time, mostly he sells them on cpfmarketplace, but you can also sometimes find them in webshops. This model here is for some special LiIon batteries (LG 18650 D1 3000mAh (Pink) and Sanyo UR18650ZTA 3000mAh (Magenta)), but can also charge normal LiIon batteries, depending on a switch setting.



I got the charger in a nice box.



The charger is delivered with two sets of wires, one with alligator clips and magnets and one set with magnets only. A car charger was included and a instruction sheet was also included, it contained warnings about the 4.35 volt mode (It must never be used on a 4.2 volt LiIon cell).
Together with the charger I also got a battery tray (This must be ordered seperatly).




The charger is usb powered and need a usb port that can supply 1A when charging 4.35 volt cells. The switch is used to select between 4.2 volt and 4.35 volt and as an extra warning the symbol for 4.35 volt is a skull and crossed bone. The voltmeter is 3 large red digits.



There is a red led behing the bump it will be brightly lit when charging to 4.2 volt and weakly lit up to 4.35 volt.
Without a battery connected it will be lit.



The charging leads or the tray is connected to the small connector.



I used the tray for my tests. It can fit any 18650 between 65 and 70 mm in length.
When a battery is put into the tray the red led on the tray will be lit.





With the magnets the charger can be used for many LiIon battery sizes.



Measurements

The charger is basically two 0.5A chargers in parallel, one 4.2 volt and one 4.35 volt, the switch will enable or disable the 4.35 volt charger.

• When charging there is a voltage drop in the wires, this means that the voltmeter will show to high a voltage (I have seen 0.2V diffence).
• When not charging the meter is within 0.01 volt
• Without power connected, the meter is powered from the battery, this means up to 20mA current draw from the battery.
• With power connected and charging terminated, the meter is powered from the battery, this means up to 20mA current draw from the battery.
• Below 2.86 volt the charge current is 100mA (50mA for 4.2 volt), above it will charge at full current.
• The meter works from around 2.7 volt.
• The meter works above 4.4 volt (I did not test higher), but only shows 2 digits from 4.4 volt.
• In 4.35 volt mode the charge will restart at 4.22 volt.
• In 4.20 volt mode the charge will restart at 4.06 volt.
• Charge led is week between 4.2 and 4.35 volt.
• Battery reinsertion will not restart charging when voltage is above restart limit.
• Power cycling will restart charging when voltage is above restart limit.

The first curve shows the reason to get this charger (4.35 volt charge). The current trace look at bit special between 150 and 175 minutes, it is when it reaches 4.2 volt and only the 4.35 volt charger is left. The termination is around 30mA.
Generally I will call it a CC/CV curve, but with a slow change from CC to CV, it means longer charge time, but will have no ill effects on the battery.



A normal 4.2 volt charge does also use CC/CV and 50mA termination









Even my old IMR16340 is handled perfectly.



Conclusion

The charger is a good 4.35 volt charger and does also work well 4.20 volt. I will only recommend the charger if there is a need for 4.35 volt charging (A wrong switch position for a 4.20 volt battery is not good).



Notes

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