Universal Lipo Charger - USB / DC / Solar - BQ24074

Universal USB / DC / Solar Lithium Ion/Polymer charger connected to a solar panel

This charger can be used to keeps your Lithium Polymer (LiPoly) or Lithium Ion (LiIon) battery charged at the top.
This universal charger can work from various power source like USB, DC Power, Solar power to charge the Lithium Ion/Polymer battery. The input voltage range can vary from 5V to 10V DC!

Thanks to the smart charger chip, the charging current will be reduced when the input current drop under 4.5V. This situation can happens with solar panel since charging depends on sunlight illumination. Reducing the current draw makes the charger working alike a MPPT solar charger allowing the charger to work with a large range of solar panel.

Even if designed for solar charging, this charger board can also gets the power input from plain USB or DC power (you can use 5V or 9V chargers). The high charge rate is great for quickly charging large battery packs!

This universal charger had nice advantages compare to a basic Lipo charger:

• USB Type C port - great for modern charger / computer.
• Charging rate up to 1.5 Amps
• Input DC voltage up to 10V (28V protected)
• "Load" output is regulated to never be over 4.4V.
  It can be used with 3.3V regulators or 5V boost converters
• No need for stabilization capacitor.
• "Load" output is shared between battery and DC/USB/Solar.
  Power delivery on "load" output prioritize the DC/USB/Solar usage and only uses battery when no other power source is available.
  That's avoids battery discharge cycle (better to increase battery life time)
• Power Good LED : indicates when the charger is working

However, there is some restriction...

• The load current is limited to 1.5A
• No 'Charging Done' LED!
  The CHG LED turns off when charging is complete.

This charger is a great option for solar project and will perfectly work with 3.7V to 4.2V LiIon batteries. A 6V Solar panel will be a good selection for this charger.

How to use:

• Plug the battery into the BATT port (JST PH 2 pin cable) cable
• Plug the solar panel into the DC jack (2.1mm adapter cable)
• Connect your project on the LOAD output (voltage will never get higher than 4.4V).

To start charging, the Solar panel must be placed outside. the battery must be kept cool, so protect it from the sun.

The bq24074 linear battery charger used in this design will automatically draw the most current from the solar panel in any light condition.
The bq24074 is not a MPPT (max power point tracker) but will offer similar performance without the need of a buck-converter (which save cost).

This product can only be used with Lipoly/LiIon batteries! Other batteries may have different voltage, chemistry, polarity or pinout.

Content

For each order, you will receive a fully assembled and tested charger board.
Lipoly battery or solar panel are not included but are available on the shop.

Technical Details

• 3.7V/4.2V Lithium Ion or Lithium Polymer battery charger
• Charge with
  * 5-10V DC,
  * USB
  * 6-10V solar panel
• Can have both USB and DC plugged in at the same time, higher voltage source will be used.
• Solar panel: Automatic charging current tracking for high efficiency.
• Use with any wattage solar panel
• Use any 6-10V solar panel the charging circuit is linear, not switching, so any voltage above 6V is 'lost as heat'
  * 6-7V panels are perfect.
  * 5V panels will droop too much (given not good experience).
• Two color indicator LEDs - Power good and Charging
• Configured for 1000mA max charge rate.
  Current can be adjusted to 500mA or 1.5A with solder jumper
• Battery charging:
  * Will always draw the most current possible from a solar cell
  * Will limit the charging current to selected max rate!
• Smart load Output
  * Will used power available from Solar panel / USB before the battery.
  * Keeps battery from constantly charging/discharging
  * up to 1.5A draw.
  * Load output is regulated to no-more-than 4.4V
• Optional Temperature monitoring of battery by soldering in a 10K NTC thermistor (not included)
• suggested for outdoor projects where the battery may get hot (50°C) or cold (0°C).