Hi John, Current is not reduced "due to" the PWM or the MPPT process ass you described. Current is reduced as a function of the electro-chemical process causing the internal resistance to increase as the cells reach full absorption. The PWM regulation only controls voltage. MPPT is only converting voltage to current before PWM controls voltage.
Larry Crutcher Starlight Solar Power Systems On Aug 24, 2011, at 9:36 AM, John DeBoever wrote: > Darryl, > > Lead acid battery typically recommended bulk charge is 10-15% of C20 for the > flooded lead acid and 20 -25% of C20 for the sealed valve regulated lead > acid. Depending the application and the environment, these rates could be > optimized, on a case by case basis. As the battery voltage raise to the > absorption voltage (regulation voltage), the current automatically tappers > due to the PWM or MPPT regulation. > Off-grid standalone PV systems optimum designs feature 5-days autonomy at 80% > DOD at the worst month-average low temperature. Off-grid PV-genset hybrids > optimum designs typically feature 2 to 3 days autonomy at 80% DOD same > conditions. The purpose of the large battery bank is to take the best > advantage of the solar energy when it is available to store Ah in the battery > for a desired power supply system power availability level. So the maximum > current available from the PV array, after powering the load, is not wasted > and sent into the battery during bulk charge and then tapered in as the > voltage raise. > > Lithium-ion batteries charge mode have certain benefits in some well-defined > applications requiring fast charge with the requirement of a BMS. > > John
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