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| Solar Charge Controllers might well be the most complicated part of the whole solar electric system, even more so then the inverter. To start with there is MPPT (Maximum Power Point Tracking) and PWM (Pulse Width Modulation), Diversion loads, Equalizing charging, Bulk charge, Float charge and many more terms. |
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| MPPT is the top of the line charge controller in the market. It is able to track or trace the input power from your solar array and the voltage from your battery bank. It then re-adjust the voltage for the highest amp output to the battery bank. Mppt is capable of taking a higher voltage and down converting to a lower voltage. In my testing of the MPPT I have found about a 10% to 12% loss of power from the input side of the charge controller to the output side which is about the best you can expect. Charge controllers use power to do their job. Keeping things simple lets use a 24 volt solar array and a 12 volt battery bank. If the solar panels have an output of 24 volts and 5 amps and your battery bank is at 12 volts. The Mppt will down convert the voltage from 24 volts to 12 and while doing this it will double the amps to 10 amps. So you would have 12 volts and 10 amps to the batteries. One other great trick Mppt is capable of is it adjust with cloud cover or edge of cloud brightness. With my 810 watts in panels I have seen output to the battery bank of as much as 1048 watts. I am sure this was edge of cloud performance. The non mppt controllers would have suppressed this spike and the extra boost would be lost. A standard charge controller without MPPT when charging hooks the panels direct to the battery bank. It makes no adjustments for the higher output of the panels. If your battery bank is at 12 volts and your panels are putting out 24 volts at 5 amps. The PWM controller will allow the battery bank to pull the panels down to the 12 volts. There is no down converting. So a simple way to look at it is you loose half the volts and half the amps. Most solar panels are in the 16 to 19 volt range. So mppt is a plus to have. Just to let you know, Mppt controllers use PWM as well. PWM charging allows the battery to reach full charge by pulse charging, The PWM pulses slower, gradually tapering off the charge as the battery fills with amps. Pulsing is good for the batteries because it mixes the electrolyte cleaning the lead plates and preventing sulphation (is that a real word?). This technology is used in most all charge controllers. |
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05-25-08
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Charge Controllers with MPPT and PWM charging are used on Solar |