PWM vs MPPT solar charge Controller

MPPT vs PWM Solar Controllers

Which is the best solar controller for my system?

 MPPT or PWM?

We have compiled a small amount of information that will hopefully help you to
understandbetter what the difference is, and why you should choose an MPPT or
a PWM type Solar Controller for your system.

A solar charge controller is needed in virtually all solar power systems that 
utilise batteries. The job of the solar charge controller is to regulate the power 
going from the solar panels to the batteries. Overcharging batteries will at the 
least significantly reduce battery life and at worst damage the batteries to the 
point that they are unusable.

The most basic charge controller simply monitors the battery voltage and opens
the circuit,stopping the charging, when the battery voltage rises to a certain level.
Older charge controllers used a mechanical relay to open or close the circuit,
 stopping or starting power going to the batteries.

More modern charge controllers use Pulse Width Modulation (PWM) to slowly
 lower the amountof power applied to the batteries as the batteries get closer and
 closer to fully charged. This type of controller allows the batteries to be more fully
charged with less stress on the battery, extending battery life. It can also keep
batteries in a fully charged state (called “float”) indefinitely.
 PWM is more complex, but does not have any mechanical connections to break.

The most recent and best type of solar charge controller is called
Maximum Power Point Tracking or MPPT.
MPPT controllers are basically able to convert excess voltage into amperage.
This has advantages in a couple of different areas.

Most solar power systems use 12 volt batteries, like you find in cars.
(Some use other voltages and the same advantages apply to these systems as well.)
Solar panels can deliver far more voltage than is required to charge the batteries.
By, in essence, converting the excess voltage into amps, the charge voltage
can be kept at an optimal level while the time required to fully charge the batteries
 is reduced. This allows the solar power system to operate optimally at all times.

Another area that is enhanced by an MPPT charge controller is power loss.
Lower voltage in the wires running from the solar panels to the charge controller results
in higher energy loss in the wires than higher voltage. With a PWM charge controller
 used with 12v batteries, the voltage from the solar panel to the charge controller
typically has to be 18v. Using an MPPT controller allows much higher voltages in the
cables from the panels to the solar charge controller. The MPPT controller then converts
the excess voltage into additional amps. By running higher voltage in the cables from the
 solar panels to the charge controller, power loss in the cable is reduced significantly.

When using high voltage “Grid Connect” panels with VOC voltages above 35v to charge a
12v battery bank, the only controller option is an MPPT charge controller.

The final function of modern solar charge controllers is preventing reverse-current flow.
At night, when solar panels are not generating electricity, electricity can actually flow
backwards from the batteries through the solar panels, draining the batteries.
 You’ve worked hard all day using solar power to charge the batteries;
 you don’t want to waste all that power! The charge controller can detect when no
 energy is coming from the solar panels and open the circuit,
disconnecting the solar panels from the batteries and stopping reverse current flow.

When assessing which type of solar charge controller to purchase, you need to know
 about their functionality and features but it’s also helpful to see a straightforward
comparison of your options. To that end, we’ve put together a comprehensive look at the
 pros and cons of both PWM Type Solar
Controllers and MPPT Solar Charge Controllers for your convenience!

PWM Type Solar Controllers	MPPT Solar Controllers
PROS
– PWM controllers are built on a time tested technology. They have been used for years in Solar systems, and are well established – These controllers are inexpensive, usually selling for less than $350 – PWM controllers are available in sizes up to 60 Amps – PWM controllers are durable, most with passive heat sink style cooling – These controllers are available in many sizes for a variety of applications	– MPPT controllers offer a potential  increase in charging  efficiency up to 30% – These controllers also offer  the potential ability to have an  array with higher input voltage  than the battery bank – You can get sizes up to 80 Amps – MPPT controller warranties  are typically longer than PWM  units – MPPT offer great flexibility  for system growth – MPPT is the only way to regulate grid connect modules  for battery charging
CONS
– The Solar input nominal voltage must match the battery bank nominal voltage if you’re going to use PWM – There is no single controller sized over 60 amps DC as of yet – Many smaller PWM controller units are not UL listed – Many smaller PWM controller units come without fittings for conduit – PWM controllers have limited capacity for system growth – Can’t be used on higher voltage grid connect modules	– MPPT controllers are more expensive, sometimes  costing twice as much as a  PWM controller – MPPT units are generally  larger in physical size – Sizing an appropriate Solar array can be challenging  without MPPT  controller manufacturer guides – Using an MPPT controller  forces the Solar array to be  comprised of like photovoltaic  modules in like strings