The maximum amount of power a PV array can produce varies with solar intensity, solar cell temperature, and module design. With these factors constant, the actual power that the module delivers varies with the voltage at which it is allowed to operate. A PV module is a constant current type device. As shown on a typical curve of PV module voltage vs. current, current remains relatively constant over a wide range of voltage. A typical 75 watt module is specified to deliver 4.45 amps at 17 volts with a cell temperature of 25°C.
A traditional PV controller connects the PV array directly to the battery when the battery is not fully charged. (The only time it actually processes the power is when it must be reduced to prevent overcharge.) When this 75 watt module is connected directly to a battery charging at 12 volts, it still provides about the same current. But, because PV voltage is now reduced to 12 volts by the battery rather than 17 volts, it can only deliver 53 watts to the battery. This wastes 22 watts of available power.
The patent pending MPPT technology used in the Solar Boost line of charge controllers operates in a very different fashion. Under these conditions Solar Boost calculates the maximum power voltage (VMP) at which the PV module delivers maximum power, in this case 17 volts. It then operates the PV module at 17 volts, which extracts the maximum available power. Solar Boost continually recalculates the maximum power voltage as operating conditions change. Input power, in this case 75 watts, feeds a power converter which reduces the 17 volt input down to the battery voltage at the output, and correspondingly boosts the current. The full 75 watts which is being delivered at 12 volts would produce a charge current of 6.25 amps. A charge current increase of 1.8 amps or 40% is achieved by converting the 22 watts that would have been wasted into useable current. In reality, current increase will be somewhat less as a bit of power is lost in the conversion process.
For a particular installation, the actual charge current increase will vary with PV temperature and battery voltage. Lower PV temperature increases VMP and thus the potential current boost. Lower battery voltage also increases the boost. In cool but comfortable temperatures with typical 75W modules, current increase normally varies between 10 to 25%, with up to 30% or more achieved in cold temperatures with a discharged battery. These controllers work quite well with higher voltage BP Solar 85W modules since a large portion of their power increase is due to higher VMP which traditional controllers can't make use of. In hot weather, when PV voltage is lower and current boosting may not be possible, Solar Boost will pass current through with a very low voltage drop.
Solar Boost also features 3-stage charge control (bulk, absorption and finish). This type of charging assures the most rapid charging but it reduces water loss and battery damage during long periods of excess energy. It has a manual equalize setting for periodic battery maintenance. It is adjustable to the amp-hour size of the battery bank, to optimize both energy transfer and battery life. You can also connect it to an external shunt so that its decision to drop to finish charge is based on the net current flow measured right at the battery. A temperature compensation probe is additional.
Solar Boost controllers are rated for their maximum OUTPUT capacity in amps. In general, the PV array capacity can be as much as 80% of that, but no more. This is because the controller will boost the current! Since the boost effect tends to be greatest when sunlight is weak (cell temperature low), that much margin is normally sufficient. In very cold climates, 75% array size should be the maximum, since large increases in charge current can occur during peak charging conditions. If conditions are sufficient to cause output current to exceed the rating of the controller, current limiting will prevent controller overload without shutting it down.
The 48V Solar Boost can use a 48V PV array to charge a 24V system. Similarly, the 24V model can use a 24V array to charge a 12V system. This way the long wiring from the array to the control center can be reduced not to half, but to ONE QUARTER! This is a major cost-saver if an array is far from the batteries, or if an array is to be enlarged but the installed wiring is not sufficiently large to carry the increased current. To determine the array capacity of the controller, observe "Array Capacity vs. Controller Rating" above, then cut the result in half. The output current will be doubled AND boosted!
Wellsee WS-MPPT Solar energy controller (also known as WELLSEE intelligent solar charge controller, solar charge controller, PV controller) can intelligently regulate the working voltage of solar panels, letting the solar panels always work at Maximum Power Point of V-A curve. Compared with standard solar controller, this MPPT controller can increase the efficiency of PV modules by 10%-30%. WELLSEE WS-MPPT solar controllers 10A--60A include 12V series, 24V series and 48V series, welcome to contact!