Gipfel EDS Ltd was commissioned by Solar Capture Technologies to develop a 30W Solar powered SLA battery charger. The challenge was to develop a cost effective, efficient, and configurable battery charging controller which maximises the energy captured by the solar panel.
Solar Charger – first prototype
The solar charger needed to be able to deliver charge to the battery with a solar input voltage range from 3.5V up to 30VDC, whilst controlling the battery charging current and final voltage. This means that the charger needs to be able to both boost and buck the input voltage when necessary.
Maximum Power Point Tracking algorithms, (Perturb and Observe), were employed along with battery management control functions so that as little energy is wasted as possible.
Below are some of the Solar Charger features:
- Battery voltage selection switch: 6V, 12V, or 24V sealed lead-acid battery.
- Battery final voltage temperature compensation.
- Low quiescent current consumption.
- Load high-side switch with current limiting and switchable depending on daylight conditions and battery voltage.
- User selectable battery charging current limits.
- Status LED
A Siemens SN-29500 life-time prediction analysis was performed on the design as Solar Capture Technologies wanted to ensure that the controller would be reliable.
Also, an EMC pre-compliance test and report was carried out to ensure that the product passes EMC testing first time. Differential and common mode emissions were measured using a current clamp and LISN, and the results documented.
A special power supply was built to emulate the V/I output characteristics of a solar panel. A standard bench supply couldn’t be used due to it’s sharp current limiting function.
