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LiIon LiFePO4 MPPT Solar Charger

Voltaic Systems has partnered with Young Circuit Designs to develop their own lithium-ion / lithium-polymer and LiFePO4 MPPT solar charge controller. In the same vein as Sparkfun’s Sunny Buddy and Adafruit’s Solar Lipoly Charger, it has the ability to efficiently charge a single-cell lithium polymer battery from a solar panel (in addition to other battery configurations and chemistries). At its core is the TI bq24650 chip, which gives it more flexibility in its input MPP voltage range, as well as its battery compatibility.


Get started with Voltaic’s LiPo / LiFePO4 Solar Charger

To get started you’ll need a solar panel with an output voltage greater than that of the battery, so for Voltaic’s standard panels which run at 6V, you can charge a single-cell LiPo or LiFePO4. With our 18V panels, such as the 9W or 17W, you can charge a 1S, 2S, and 3S LiPo, or 1S, 2S, and 4S LiFePO4, or even a 12V lead acid.

After getting the panel and battery, turn the left and right knobs to the appropriate positions for the solar panel and battery.

A quick example setup is a 6 Watt Solar Panel, plus one of the 3.5x1.1 to 5.5x2.1 adapters, which connects directly into the barrel jack at the top left of the board. To match this panel, the left knob should be turned to 5.9V MPP. With a 1S 2000mAh LiPo cell from Adafruit, we turn the right knob to 4.2V for 1S LiPo. Connecting both the panel and the battery to the board and putting it out into the sun will start the charging cycle. The red LED will remain on while it charges and turn green when it is done charging.

Unlike other solar charger boards on the market, ours is compatible with a multiple cells in series as well as lead acid and LiFePO4. Another possible configuration is our 17W panel (left knob turned to 17.7V), paired with a 12V lead acid battery or a 4S LiFePO4 (knob turned to 14.4V). Maximum charge current is 2A into the battery (so a 17W, 18V panel will deliver 2A to a 1S LiIon battery for ~7.4W charging, but can deliver the same 2A into a 2S LiIon battery for ~14.8W charging).

To use the battery simultaneously, you have the option of using it directly from the cells, or through a Pololu regulator, for which we’ve included the header at the top of the board.

Download User Guides

• Minimum voltage in: 4.8V

• Maximum voltage in: 28V

• Maximum current: 2A into the battery

• Temperature range: -40°C to 60°C

• Default MPP voltages:

• 5.9V
• 11.8V
• 17.7V
• 24V
• 4.8V USB
• Custom

• Default Battery options:

• Lithium-Ion / Lithium-polymer

▪ 1S 4.2V
▪ 2S 8.4V
▪ 3S 12.6V

• Lithium iron phosphate (LiFePO4)

▪ 1S 3.6V
▪ 2S 7.2V
▪ 4S 14.4 V

• 12V lead acid

▪ Equivalent to 4S LiFePO4 14.4V

• Input connections:

• microUSB
• 3.5mm solder pads (compatible with these screw terminals, not included)
• 5.5x2.1mm barrel jack

• Output connections:

• 2mm JST
• 3.5mm solder pads (compatible with these screw terminals, not included)
• 3.5mm screw terminal (if using regulator, included)

Download User Guides

Any solar panel with an open circuit voltage less than 28V, and multiple battery cell chemistries: lithium-ion, lithium-polymer, lithium iron phosphate, and lead acid. Please see user guide for more information.

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