This is a Lithium Ion / Lithium Polymer chemistry battery (4.2V) solar charger.
The goals are
- To allow the use of a wider range of PV panels
- Ampere-level charging current (currently max. 1A, goal is around 3A)
- To provide a regulated voltage output (3.3v or 5v) at >2A (currently 3.125A)
- To provide an unregulated output
- To provide an USB port output (micro usb) - might change to USB-C in the future
This is done by
- Allowing the use of a larger range of PV solar panels voltages (3.6-18V)
- Bigger charging current capabilities with a goal of around 3A (currently 1100mA)
- Bigger input current.
The goal of this small circuit is not necessarily to be the most efficient. The primary goal is to be able to support a large variety of panels, while also being able to provide >2A of 5V to the device to power.
The supported panels just have to be within the support of the main IC, the BQ25185. Therefore supported PV panels MUST provide BETWEEN 3.6 AND 18V at a MINIMUM of 500mA.
Then, depending on your PV panel current capabilities, you HAVE to solder ONE AND ONLY ONE of the solder jumpers (on the back of the circuit)
- If your solar panel provides 500mA < solar panel current < 1100mA, you HAVE TO solder the 500mA jumper. This will limit the input current from the panel to the circuit to 500mA.
- Else, if your panel is able to provide >1100mA, you can still solder the 500mA jumper (this will limit the current). If you wish for more current, you can solder the 1100mA jumper.
This circuit is designed to work with single cell Li-Po batteries ONLY This means cells with charge a nominal charging voltage of 4.2V. For the LiPo chemistry, this ONLY works with 1SXP configurations.
A later version will allow a 4.1V charge option to improve cell life at the expense of capacity.
This circuit provides 500mA or 1000mA (default) charging current capabilities. Please double check your cells current charging capabilities.
Your cells MUST be able to sustain a continuous 1A or 500mA charging current. The charging current is set to 1000mA by default. To set the charging current to 500mA, cut the JP1 solder jumper on the front right of the board.
Maybe we should use a BQ24074 instead ? This allows for 1.5A charge current What about MAX77787 ?