Specifications

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tolerances. This also applies to wind turbines, and applications where wind turbines and
PV panels are applied simultaneously. The most efficient way to correct this it to employ
an MPPT charge controller on each and every solar panel and wind turbine in the
system. However, the most common method is to simply apply one MPP charge
controller on the entire solar array and one on the wind generator array.
4.1.3 Charging Circuitry
In our research, it was required of us to look into the charging process of the several
different batteries that we had to choose from. Lead acid, nickel-metal hydride, and
lithium ion batteries all needed to be looked at to determine how each battery
chemically charged and discharged. With each battery acting differently in this respect,
the charging circuitry of each battery would need to be closely considered before we
made our final decision on which battery to use.
Figure 6 – Lead Acid Battery Charger Circuit
Permission Pending
Above is an example of a lead acid battery charger. The lead acid batteries were found
to be the most sluggish of all the batteries when it came to charging. To fully charge a
sealed lead acid battery it could take as long as 12-16 hours. This time could be
reduced, however, to fewer than 10 hours if higher charge currents and multi-stage
charge methods were utilized. During the charging process there would be three
distinct stages: constant-current charge, topping charge, and float charge.
Constant-current charge would take up about half of the total charge time and would
perform the bulk of the battery‟s charging. During this stage, the battery is charged to
about 70% of its maximum capacity. This process can last between five through eight
hours depending on the charge voltage that is applied to the battery cells.