The difference between PWM and MPPT?

When you installs solar panels i boat, motorhome or off-grid-system is it not just of the panel size and placement that plays roll. A crucial component is solar charge controller – the unit that steers how the current from the panel chargers the battery. Here exists two main types: PWM (Pulse Width Modulation) and MPPT (Maximum Power Point Tracking).

It exists a whole part misunderstanding around of these, so here clarifies we out the differences, the functions, the advantages – and when you should choose what.

Voltage make a solar charge controller?

A solar charge controller sits between solar panel and battery. This most important task is to protect the battery from overcharging and to optimize the charging process.

Without regulator should solar panel be able to charge the battery with for high voltage, which quickly can damage or destroy the battery. The regulator regulates therefore both voltage and current from the panel so to the battery charged correct - based on type, capacity and charging status.

PWM - a basic solution

So works it:
The PWM-regulator works by quickly turning the power on and off (pulse modulation) to regulate the voltage to the battery's level. When the battery is full, the PWM-regulator simply turns off the charging or lowers it to a maintenance mode.

Typical use case:
A smaller system where the solar panel's nominal voltage is very close to the battery's (e.g. 12V panel to 12V battery). PWM is best suited for simpler installations with short cables and low energy consumption.

Advantages with PWM:

• Cheap and easily accessible

• Simple technology

• Low self-consumption

• Fits for small, simple 12V-system

Disadvantages:

• Very energy goes lost, especially when solar panel produces more voltage than the battery need

• Can not adapt the charging to prevailing solar conditions

• Requires exact voltage matching between panel and battery

• Limited possibility to connect in series panels

MPPT – the intelligent and effective the solution

So works it:
The MPPT-regulator works with something called "maximum power point tracking", which means that it constantly searches for the point where the panel delivers maximum power (Watt = Volt x Ampere). If the solar panel produces e.g. 18V and the battery is at 12V, then the MPPT-regulator converts the excess voltage to extra current – not just voltage.

This make to you can get up to 30–40 % more charging power, especially i call climate (there of the panel voltage often is higher) or at cloudy weather.

Advantages with MPPT:

• High efficiency, often 98 % or more

• Works excellent also at longer cable installations

• Handles higher tensions – you can to use panels i series connection

• Automatic optimization after solar radiation and temperature

• Possibility to combine different panel configurations

Disadvantages:

• Higher purchase price

• Some more advanced technology (but Victron's models is very user-friendly)

Example on difference i practice

Voltage says Victron?

Victron Energy is leading within both the technicians, but almost all their new installations today uses MPPT. They have a broad range av MPPT-controllers (t.e.g. SmartSolar and BlueSolar) with built-in Bluetooth, clear status lights and possibility to monitoring via app (VictronConnect).

Victron's PWM-models is used primarily i simpler, cost-effective system with low load and there panel and battery is well matched i voltage.

When will you choose what?

Conclusion

Want you get out it most av your solar panel and charge the batteries so effectively that possible – choose MPPT. Sure is the investment somewhat higher, but the difference i performance make it often more than worth it.

We on Thermo products have long experience av Victron's regulators and helps you gladly to size right system – regardless about you builds for boat, motorhome or cabin. Contact us or talk with someone av our dealer for advice and products that holds high quality.