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Small Usb Chargers For Solar Panels Updated 2/5 In Red!

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The following small and inexpensive USB chargers are being used successfully with Solar Panels.

These are used because they don't have settings in the Firmware that have to be manually set before they will begin a charge.


A search on the web will turn up a few more with lot's of data to review. If you don't want to have to deal with PCB chargers, etc. this is a good way to go. The charger also doubles as the battery holder.


1. Beware what the maximum battery size battery is a charger will charge before purchasing!!

2. The USB chargers will discharge the battery some if it is left in them. The degree of discharge varies with the charger. Most discharge at a very small current, i.e. micro amps. PCB charger may also discharge the batteries if it is left connected to it. Check the specifications to be sure.



This one is the latest version of the Miller ML102 and takes only Unprotected cells due to a size restriction!!

Miller ML-102 (Latest is Version 8) Avoid Version 7!!



Xtar MC1


Xtar MC1 Plus


Xtar XP1






I prefer chargers that will restart charging if a cell is reinserted or power cycled, i.e. Solar Panel shaded, etc. This includes the Miller ML-102 and the Xtar XP1 and Xtar ANT MC1 Plus. The others will restart when the battery voltages drops to the recharge voltage set point in the charger. This also appears to work well, i.e. if some other device (camera, etc.) is using power from the battery while it charges.

Note: Please test your set up at home thoroughly before deploying it.

Voltage-terminated chargers may work, but can miss termination (if the termination voltage is too high) or fail to fully charge your cells (if the termination voltage is too low). Always test your system thoroughly. It doesn't matter if you're using a ready-made charger, assembling modules or building your circuit from scratch, you must make sure it charges your cells in a way that complies with the Li-Ion charging requirements.



NiMh Charging

From the web:

When it comes to charging NiMH cells, I strongly recommend that you use a buffer battery, because the -dV/dt algorithm used by NiMh smart chargers is not very tolerant of interruptions in power, especially when a NiMH cell is approaching full charge.


If a cloud passes in front of the sun, you don't have a buffer battery and the NiMH charger resets, it can lose track of the recorded voltage it needs to spot the -dV/dt endpoint. This can cause your cells to be overcharged, reducing their capacity and service life.


Good Luck to all,



Edited by ko4nrbs

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The XTAR XP1 does not support 18650 size batteries!!


Nitecore F1 can be added to the list for Solar Charging.


Note- It also has a stable 5.02v output at 1A from the USB port. Could be used for charging a phone, etc.!!

Solar Charging Field Test Example:





Edited by ko4nrbs

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