The Flexcharge Charging Algorithm Explained
The Flexcharge Energy State Taper Charge Process monitors the battery for the full charged resting
voltage of the batteries cells. There are tremendous advantages to this charge method.The Flexcharge method greatly reduces the need for temperature compensation. This occurs because the plate voltage is not constantly held at the critical plate saturation point. Tapering is controlled by the battery's level of charge rather than with timers, or fixed voltages as in PWM and other constant voltage charge methods. The battery takes exactly what it needs rather than being forced to take a set voltage. With the Flexcharge method you can charge your battery bank indefinitely and overcharging will not occur. The batteries will last longer, require less watering maintenance, and hold a better charge.
As charging begins the controller allows full charging current to pass directly to the battery. When the battery voltage rises slightly above the plate saturation point, the controller opens the charging circuit. Much like a sponge will continue to absorb water towards its center after it has taken it all into its surface, the chemical charging process continues after the charging current has been removed. As the charge is absorbed the battery's voltage will fall. When the battery voltage has floated down to approximately 13.5V to 13.8V on a 12 V system, it is ready to accept another charge pulse. This charge regulation method is actually controlled by the battery's ability to accept and absorb energy. When the battery needs more energy indicated by plate voltage, the controller applies it. Mid way in the charging cycle the controller will cycle ON and then OFF sending full charge current pulses into the plates. A process which charges with very low gassing, and equalizes the plates with each full charge. As the battery reaches a higher level of charge the amount of time the controller spends in charge is reduced, and the time in rest is increased. At full charge the controller will apply short duration pulses to maintain the battery at an average voltage of about 13.75 volts. This keeps gassing to a minimum while effectively trickle charging, and equalizing at the same time.
There has been allot of discussion over which
charge process is better, PWM, or this method. To add fuel to the fire, each company
making "ON-OFF" controllers has chosen different voltages to set the disconnect
and reconnect points. We have seen controllers using a version of this method where
the reconnect voltage on a 12V system was set at 12.6V @ 70°F. On this system the
batteries would never see more than 80% charge, and likely much less. The PWM type
controllers will obviously regulate the charging your batteries, and with proper
temperature compensation, heat sinks, and the correct Bulk-Regulate-Float (3 stage)
algorithm will do a pretty good job of it, but why settle when you can get so much more in
a charge regulator. Instead of three stages with PWM you get an infinitely variable
charge process which will supply the battery with exactly what it needs and only when it
needs it. You get less plate saturation gassing, non destructive equalization and
Zero EMI as well.
