LIPOnano



This charger is made by a German guy and sold on Tindie, it uses usb power and can charge a LiIon battery. The charger is based on a MCP73831 chip.



I received the charger in a envelope, without any extra stuff.



The charger is only a circuit board, without any box or protection. Click on pictures for larger version.
On the circuit board is mounted a green and red led to show the charge state.
Red: Charging
Green: Finished
Red+green: No battery




When mounted in a usb port, most of it is hidden.



The charger can charge with either 500mA or 100mA, when delivered it is programmed for 500mA, removing a solder blob will change it to 100mA.



I did not have a connector that fit the charger, instead I uses the provided holes to solder a couple of wires.





The charger can handle nearly any size LiIon, but for larger sizes it will take a long time to charge.
For connection to the batteries it is possible to use leads with magnets, but nothing is supplied.



Measurements

• Below 2.8 volt the charger will charge with about 9mA in 0.1A configuration.
• Above 2.8 volt the charger is applying regular charge current (See curve below).
• When charger is disconnected from power, but with a battery in, it will draw below 1uA from the battery.
• When the charge current goes below the termination current the charging is stopped and it will charge with around 9 uA.
• The charger will restart charging when the cell drops to 4.0 volt.
• The charger will not restart after a power loss or battery insertion, except if the battery voltage is below 4.0 volt.

First test is with a 3400mAh battery, it takes nearly 10 hours to charge. The charger drops to 300mA charge current very fast, this is because the chip gets hot and it then reduces charge current to surview.
Termination current is 50mA.





This battery has higher charge voltage and because of that the charge current will be higher.





Reducing the charge current to 0.1A (100mA) allows the chip to charge at full current without getting hot. Notice that the termination current is reduced to 10mA, this makes this charger very good for small batteries.



The charger has no problem with old 16340 cell.



Conclusion

As expected the LiIon charger chip does a good job, but some better cooling on the chip would have improved the 500mA charge rate.
The size of the charger makes it a very good travel charger if you are carring some usb power supply, but some work is required before batteries can be connected.



Notes

Any charger using the MCP73831 chip will have identical performance except for charge current.

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