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MPPT vs PWM Solar Charge Controller


Max Power Point Tracking - Pulse Width Modulation.

Wind and solar charge controllers, are the device used to regulate the flow of volts and amps being pushed into a battery or battery bank from a solar panel, windmill, Or other source of electrical energy generation.

Xantrex C Series with PWM load and diversion - solar charge controllerMPPT (maximum power point tracking)

The MPPT Charge Controller is known for the ability to down convert voltage while up increasing the amps to give you as much as 30% more power from a solar array that is normally lost when using a common or non MPPT controller.

Example: A module with a 17.2 volt Vmp would be pulled down to the battery voltage If the battery was at 11.7 volts using a common non MPPT charge controller. A loss of 5.5 volts or 32%. This means, if you have 1000 watts in panels, you just lost 320 watts. That would pay for an MPPT controller with money left over.

PWM (pulse width modulation)

Helps to remove buildup on the plates in a battery extending a battery’s life.

All three of the above types of charging are used at the same time to charge faster and clean the plates. When the battery is low on charge, PWM will pulse longer with at a higher modulation. As the battery fills up it will pulse shorter with a lower out power level

Solar charge controllers are engineered to keep you from damaging your batteries by controlling the charging limits. And should be used in every setup no matter how large or small the system. This is done by adjusting the power from the charging source based on how much power is required to bring the batteries up to full charge. This is done in three stages. Equalize, Bulk, Absorb and Float charge, and not in any written in stone order. Charge controllers can and do change directly from float charge to bulk or equalize as needed.

Bulk Charge,
Is normally the first step. In wet cell lead acid batteries it will allow enough / max power through the controller to bring the voltage up to a set voltage. This will keep the acid water mix bubbling and hold at this level for a set amount of time which is called the absorb stage.
Absorb Charge,
Is a tapered charge which the controller will slowly taper down the amps as the battery reaches full charge not allowing the battery charge to go over the bulk voltage limits.
Float Charge,
The charge controller will auto switch to the float charge, which is a lower voltage closer to the nominal battery voltage. During this stage as you use more power from the batteries the unit will adjust the input amps up and down to hold this float voltage.
EQ Charge (Equalize)
Is only used on wet cell batteries and is normally 1 volt higher then the bulk charge voltage. Read your battery and charge controller instructions before EQing your battery.

A good brand charge controller may cost a little more, but well worth the extra cost. To get the same power output using PWM or a non MPPT charge controller., You will need extra modules which will take up more space on your roof and cost more.

Here are some good MPPT solar charge controllers from our webstore.

Apollo Solar charge controller

Blue Sky Solar Boost

Midnite Solar charge controller

MorningStar MPPT 45 and 60 solar charge controllers

OutBack FM60 and FM80

Schneider Electric MPPT60 and MPPT80

Some PWM solar charge controllers from our webstore

MorningStar TS-45

MorningStar TS-60

MorningStar ProStar

Xantrex C Series