4.2 Battery Charging Information
Four Charging Stages
The MPPT40CC has a 4-stage battery-charging algorithm for rapid, efficient, and
safe battery charging.
Figure 4-2 MPPT40CC MPPT charging algorithm
Bulk Charge
In this stage, the battery voltage has not yet reached boost voltage and 100% of
available solar power is used to recharge the battery.
Boost Charge
When the battery has recharged to the Boost voltage set point, constant-voltage
regulation is used to prevent heating and excessive battery gassing. The Boost
stage remains 120 minutes and then goes to Float Charge. Each time when the
controller is powered on, it checks if the battery is over-discharged or
overvoltage. If none of these conditions are encountered, the controller will enter
into boost charging stage.
Float Charge
After the Boost voltage stage, MPPT40CC will reduce the battery voltage to float
voltage set point. When the battery is fully recharged, there will be no more
chemical reactions and all the charge current transforms into heat and gas at this
point. The controller reduces the voltage to the floating stage, charging with a
smaller voltage and current. It will reduce the temperature of battery and prevent
gassing, but charging the battery slightly at the same time. The purpose of Float
stage is to offset the power consumption caused by self-consumption and small
loads in the whole system, while maintaining full battery storage capacity.
In Float stage, loads can continue to draw power from the battery. In the event
that the system load(s) exceed the solar charge current, the controller will no
longer be able to maintain the battery at the Float set point. Should the battery
voltage remains below the boost reconnect charging voltage, the controller will
exit Float stage and return to Bulk charging.
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