Victron Energy BlueSolar PWM-LCD&USB 12/24V-20A20A 12/24V PWM solar charge controller with LCD and USB

Overview

The BlueSolar PWM-LCD&USB 12/24V-20A carries 20A of charge and load current, enough for up to 240W of 36-cell panels on 12V or 480W of 72-cell panels on 24V, as stated by Victron. The load output can run dusk to dawn or on a 1–23 hour timer for lighting, with low-voltage disconnect protecting the battery. It uses the compact 0.15kg housing with 6mm² terminals.

• 12/24V models from 5A to 30A with automatic voltage detection
• 48V models at 10A, 20A and 30A, up to 100V PV
• Presets for AGM, gel, flooded and LiFePO4 with internal BMS
• Load output with low-voltage disconnect, dusk-to-dawn and timer modes
• Two 5V USB outputs, 2A combined
• Common-positive grounding, IP20, indoor wall mounting

How it works

The BlueSolar PWM-LCD&USB regulates charging by pulse width modulation: the panel is connected to the battery and switched on and off to hold the target voltage, in three stages (bulk, absorption, float). Because the panel works close to battery voltage, the array must match the system: 36-cell panels for 12V, 72-cell panels for 24V, and two 72-cell or four 36-cell panels in series for 48V.

After the absorption voltage has been reached the controller drops to float two hours later. A new charge cycle starts when the battery falls below 13V on a 12V system. On 12/24V models the system voltage is recognised automatically when the battery is connected, and the boot screen confirms the model and the detected voltage.

Key features

The LCD and three buttons show battery voltage and state of charge, PV voltage, charge and load current, USB voltage and internal temperature. Five battery presets are available: AGM, gel and flooded lead-acid, plus 12V and 24V LiFePO4 for batteries with an integrated BMS; the LiFePO4 presets are not offered on 48V models. Low-voltage disconnect and reconnect levels are adjustable in 0.1V steps.

The load output can be switched manually, run dusk to dawn, stay on for 1 to 23 hours after sunset, or remain permanently on (factory setting). Night is detected from the panel voltage, with an adjustable trigger level and a 10-second confirmation delay. Two USB-A ports supply 5V with 2A shared between them.

Installation and compatibility

Always connect the battery first, then the solar array, then the load, and disconnect in reverse order; a wrong sequence can damage the controller. Keep battery cables short. Only solar panels may be connected as a charging source. The controller has no remote on/off input, so lithium batteries must have their own internal BMS. Mount it vertically on a wall, indoors, with free air for natural convection.

Grounding is common positive: connecting panel or load negative to battery negative is reported as a wiring error. Terminals take 6mm² cable on the 5A, 10A and 20A units and 16mm² on the 30A and 48V units. Inverters are best wired directly to the battery, with their remote switch on the load output; Phoenix VE.Direct inverters can be controlled this way.

Protection

Above 85°C internal temperature the controller reduces PV current; above 90°C it stops charging and switches off the load, resuming below 82°C. The load output shuts down after 60 seconds at 110–130% load, after 5 seconds at 130–160% and immediately on short circuit, retrying after 30 seconds. Short-circuit protection can be disabled for loads with high inrush current.

Questions and answers