What is an MPPT Charge controller?
MPPT Charge controllers work differently to standard charge controllers. MPPT stands for Maximum power point tracking. All solar panels have a point when the power is at it's maximum so finding it and staying on that point can ensure that your solar power system receives the best output from the solar panels. The maximum power point of a solar panel changes with temperature/weather conditions.
Maximum power point tracking isn't always the best method and often standard, lower cost charge controllers will be just as good. Off grid solar panels for battery charging (not high voltage grid tie solar panels) are designed to produce maximum power in the sweet spot for charging off grid batteries. Using an MPPT charge controller is a waste of energy (MPPT controllers consume more power) and money. There are exceptions to this. One if these being when the distance between the solar panels and the batteries is considerable. Being able to string together several panels in series to obtain a higher voltage means less loss in the cables. In this case the controller acts like a tracker and a voltage converter. Another exception is being able to use grid tie/high voltage solar panels which are often cheaper than off grid solar panels.