Solar charger v2 specs

Post test messages here

Moderators: adafruit_support_bill, adafruit

Please be positive and constructive with your questions and comments.
Locked
Spreng0r
 
Posts: 2
Joined: Sat Dec 07, 2013 4:15 pm

Solar charger v2 specs

Post by Spreng0r »

Hello adafruit forum.
I am interested in the "USB / DC / Solar Lithium Ion/Polymer charger - v2" but I didn't find all the information I need. What is the maximum current from a 6V solar panel the charger can handle? What is the maximum current and voltage I can get out of the LOAD output port? Regarding a high output current, how many Amps can I pull from one of your LiPos (e.g. the one with 2500mAh) savely?
Thank you very much.

Spreng0r

User avatar
adafruit_support_mike
 
Posts: 67446
Joined: Thu Feb 11, 2010 2:51 pm

Re: Solar charger v2 specs

Post by adafruit_support_mike »

As a general rule, you can safely discharge a LiPo's full energy storage in 1 hour. A 2500mAh cell can deliver up to 2.5A or be charged at up to 2.5A. That value is called 'C'. Some cells are designed to handle higher levels of current, so they're rated for 2C, 4C, etc.

Charging at the highest possible current tends to store less energy than a slower charge cycle, so chargers are usually specified for .5C or some such value.

The MCP73871 (the chip used in the charger) limits the battery charging current to 1A from a DC source (450mA from a USB connection). It can safely draw up to 2.5A, but normally limits its input current draw to 1.8A. It shares the input power between the battery and the load, giving priority to the load. It regulates the voltage charging the battery, but when sharing the supply, it passes the input voltage straight through to the load. Its pass-through resistance is about 200 milliohms, so you'll lose about 200mV per amp of current going to the load.

The board we sell comes configured for 500mA battery charging current. You can adjust that between 50mA and 1A by changing the programming resistor.

The datasheet for the MCP73871 is here: http://www.adafruit.com/datasheets/MCP73871.pdf

Spreng0r
 
Posts: 2
Joined: Sat Dec 07, 2013 4:15 pm

Re: Solar charger v2 specs

Post by Spreng0r »

Thanks for the fast answer.
So if I got this right there will be a maximum of 2.5A at aprox. 5.5V at the LOAD output at full load without charging (Solar panel delivers 6V)?
And while charging at 500mA this would decrease to 2A at 5.5V but only if I pull not more than 2A at the LOAD output?
I think if the chip most of the time only draws 1.8A this going to be even less and thus not powerful enough for my project :(.
Do you guys plan on making a more powerful solar charger with the ability to draw more amps or even use more LiPos in series(for example a 3 cell one with 11.1 V ?)?

Spreng0r

User avatar
adafruit_support_mike
 
Posts: 67446
Joined: Thu Feb 11, 2010 2:51 pm

Re: Solar charger v2 specs

Post by adafruit_support_mike »

The 2.5A value is an upper limit on what the chip can survive. The actual operating limit is 1.8A. If the battery is charging at 500mA, the load can only draw 1.3A.

Those limits are fairly important to the design of the charger: http://learn.adafruit.com/usb-dc-and-so ... sign-notes There are chargers that work at higher power levels, but they usually cost more.

Locked
Please be positive and constructive with your questions and comments.

Return to “Test Message Forum (closed)”