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Instructions and description of controllers with overcharge and over
discharge protection, gasing regulation and temperature compensation.
In photovoltaic solar systems lead batteries are often used for storing solar
current. These batteries have to be protected against overcharging and over
discharging. The Solar charge controller SCG0606 / SCG0808 / SCG1010
/ SCG1515 fulfill both tasks in one device. They can be used for 12 and 24 V
systems.
1. Overcharge Protection
When the battery exceeds the final charge voltage, it starts to gas. As this
process is temperature dependent, the final charge voltage is adapted
automatically to the ambient temperature by built-in sensor. Strong gassing
leads an electrolyte loss and finally the destruction of the battery. The battery
is however not charged completely when the final charge voltage is reached, so
that the current flow should not be interrupted. The charge controller therefore
reduces the current flow into the battery just as much as that the final charge
voltage is not exceeded. This procedure is called "IU-charging" which is
considered to be especially fast and gentle. The reduction of the current flow is
effected by very quick, temporary short-circuiting (pulse width modulation) of
the solar generator.
2. Gassing Regulation
The final charge voltage is changed in dependence with the discharge level.
When a lead battery is operated without gas development for a longer time,
there is the danger of a harmful acid layering. This acid layering can be avoided
by limited, controlled gassing; this function is fulfilled by the gassing regulation.
The gassing regulation switches off the overcharge protection until the so-called
final gassing voltage is reached. Further more the gassing regulation increases
the final charge voltage during high cyclization. By this temperature dependent
function, the battery capacity is better used.
3. Over discharge protection
The batteries have to be protected from over discharge, as it would be
destroyed otherwise. Therefore the charge controller protects the battery from
over discharge by disconnecting the loads when the voltage falls below the final
charge voltage. After the battery has been recharged by the solar generator and
the reconnection voltage is reached, the users are again reconnected.
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