Hello,
I am developing a solar battery system to power actuators in remote areas.
I have investigated both MPPT (SmartSolar) and PWM (BlueSolar) charge controllers for this application. I have a few questions concerning exactly how these work and what settings are possible. My objective is to determine how long it will take to charge my chosen batteries with my chosen solar panels.
It is my understanding that the most common effective method for recharging lead acid batteries is to use 3 phases – bulk, absorption and float. In the bulk phase, the maximum amount of current available from the panels is supplied to the batteries. In the absorption phase, a constant voltage is maintained whilst the current is progressively stepped down. Finally, in the float phase, a small current is supplied at a constant voltage to overcome self-discharge. An MPPT charge controller uses a DC-DC converter to match the batteries voltage during the bulk phase, increasing the current to ensure all the power available from the panels is supplied to the batteries. It then uses pulse width modulation to step down the current progressively during the absorption phase. A PWM charge controller supplies the maximum current from the panels during the bulk phase and, like the MPPT charge controller, uses pulse width modulation during the absorption phase. The charge controller switches from the bulk phase to the absorption phase at ~80% fully charged and sets a timer for the absorption phase based on the initial voltage of the battery before charging began. Is this explanation correct?
For lithium ion batteries, it is my understanding that the absorption phase is not required and that they can be charged entirely within the bulk phase with charging ceasing at a set voltage limit. Is this correct?
Finally, in direct reference to the SmartSolar and BlueSolar products, can an output current limit be set? This may be useful in a situation where the recommended charging current of a battery is less than the output current from the solar panel.
Thank you in advance for your advice