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PWM controller

PWM charge controllers (Pulse Width Modulation) charge your batteries by directly connecting panels to the battery bank via an electronic switch. A simple, reliable and affordable solution for small systems: motorhomes, garden sheds, leisure installations, emergency kits. Important: with PWM, your panel's Vmp voltage must be close to battery voltage (e.g. 18V panels for a 12V battery) — excess voltage energy is lost. For any system above 200W or using modern panels, MPPT is recommended (10 to 30% more energy). Available from SRNE.

MPPT Controllers (recommended)
AGM / GEL Batteries
LiFePO4 Lithium Batteries

Choose in 30 seconds

  • PWM or MPPT? PWM suits small systems ≤200W with panels whose Vmp is close to battery voltage (18V for 12V, 36V for 24V). For any other case — modern 30–40V panels, systems >200W, serious installations — choose an MPPT controller.
  • Battery voltage: check 12V or 24V according to your battery bank. Note: PWM controllers generally don't go up to 48V — another reason to switch to MPPT for larger systems.
  • Charge current (A): max current = PV power (W) ÷ battery voltage (V) + 20% margin. Example: 200W ÷ 12V = 16.7A → choose a 20A PWM minimum.
  • Options and monitoring: depending on the SRNE model, add an external display (MT50) or remote control (CU-ALL5) for monitoring from an accessible location.
MPPT Controllers
Off-Grid Solar Kits
Wiring Diagrams

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FAQ - PWM solar charge controller

1. What is a PWM solar charge controller used for? +
A PWM controller is used to charge batteries properly from solar panels by matching the battery bank voltage (e.g., 12V/24V) for durable solar energy use.
2. How do I choose between 12V and 24V? +
Choose based on your battery/battery bank voltage: pick a controller compatible with your system (12V or 24V).
3. How do I size current rating (10A, 20A, 30A)? +
Size in amps based on your panels and needs: higher charging current requires a controller with a suitable current rating (e.g., 10A or 30A).
4. Can I add a display or a remote control? +
Yes, depending on the model: you can add a display (e.g., MT50) or a remote (e.g., CU-ALL5) for easier monitoring/control.
5. Which batteries are these controllers used with? +
It depends on the system and charge settings. For storage options, see AGM / GEL batteries and lithium batteries (LiFePO4).

PWM solar charge controllers: complete guide to making the right choice



A PWM (Pulse Width Modulation) charge controller is the oldest and simplest solar regulation technology. It connects panels to the battery via a transistor that opens and closes thousands of times per second to maintain the desired battery voltage. Proven, reliable and affordable — but with important limitations to understand before buying.



How does a PWM controller work?



As the battery approaches full charge voltage, the PWM progressively reduces the connection between panels and battery (chopping) to prevent overcharging. Output voltage is brought down to battery voltage. Direct consequence: if your panel's Vmp voltage exceeds the battery charge voltage, the surplus voltage energy is lost — dissipated as heat in the controller.

Concrete example: a 30V Vmp panel connected to a 12V battery via PWM works at 14V (charge voltage). Energy corresponding to 30V-14V = 16V is wasted. Real efficiency can fall to 50-60% in this scenario.



When to use a PWM controller



  • Small installations ≤200W: leisure kits, garden sheds, small motorhome or boat installations with a single 12V panel.
  • Classic "12V" panels: older panels designed for 12V systems (Vmp ≈ 17-18V) work well with PWM on a 12V battery.
  • Very tight budget: a 20A PWM costs significantly less than a 20A MPPT. Valid for temporary or emergency installations.



When NOT to use a PWM controller



  • Modern 60-cell panels (30-40V Vmp): current residential panels have Vmp of 30 to 40V. On a 12V battery, PWM wastes half the energy.
  • Systems >200W: the MPPT's gain (10 to 30%) represents significant savings over time.
  • Series-connected panels: PWM cannot manage high-voltage strings — it generally only supports 18 to 50V input maximum.
  • LiFePO4 lithium batteries: lithium batteries require a precise charge profile. If your PWM doesn't have a configurable lithium profile, it may charge incorrectly and shorten battery life.



Parameters to check before buying



Battery voltage (12V or 24V)

Most PWM controllers support 12V and 24V (auto-detection or manual setting). Unlike MPPT, PWM rarely goes up to 48V.



Maximum charge current (A)

Formula: max current (A) = total panel power (W) ÷ battery voltage (V). Add 20% margin. Common ranges: 10A, 20A, 30A, 40A.



Maximum input voltage

A PWM controller has a maximum input voltage (often 25 to 50V). Never connect a panel whose Voc exceeds this value — risk of destruction.



SRNE at Wattuneed



SRNE is the reference manufacturer for entry and mid-range PWM and MPPT controllers. Their PWM controllers are valued for their robustness, integrated LCD display and compatibility with all battery technologies. Optional accessories (MT50 display, CU-ALL5 remote) allow remote monitoring away from the installation.