40A lithium DC–DC charger with solar input



  • In vehicle multi-stage DC-DC charger
  • Dual input MPPT solar/aux (alternator)
  • Multi battery chemistry selector
  • Suitable for modern smart alternators
  • IP66 rating – resistant to dust, water and shock damage
  • Maintains a 100% state of charge of auxiliary batteries
  • BMPRO signature durability and ease of use


Intelligent DC-DC chargers

BMPRO’s ProBoost40 is a DC-DC battery charger that allows you to charge a secondary battery using solar panels and/or a towing vehicle’s 12V electrical system.

The ProBoost40 blends both the solar and auxiliary inputs together, up to a maximum of 40A, to ensure there is always a consistent charge to your battery.

Compatible with both lead-acid and lithium LiFePO4 batteries, the high power density design of the ProBoost25 provides efficiency of up to 95%.

The ProBoost40 has an ultra-thin design, making it suitable for installation in small spaces, and is resilient to shaking, as well as wet, dusty or muddy environments.

A range of protective features built into the ProBoost40, such as overtemperature, overvoltage and undervoltage protection, will guard your caravan or camper trailer’s charging capacity.

Product Specifications

Input Voltage 9-18V DC
Solar Input Voltage 9-18V DC
Maximum Input Current 45A
Input Fuse Rating 60A
Continuous Output Current 40A
Output Fuse Rating 60A
Minimum Start Voltage (Lead-Acid) 4V
Minimum Start Voltage (LiFePO4)
Standby Current
Battery Chemistry
STD, Gel, AGM, Calcium, LiFePO4
Operating Temperature
-20°C to 80°C
IP Rating
Dimensions 183mm x 130mm x 43mm

Charge Type 3-Stage
Maximum Voltage (STD) 14.4V
Maximum Voltage (Gel) 14.1V
Maximum Voltage (AGM) 14.7V
Maximum Voltage (Calcium) 15.3V
Maximum Voltage (LiFePO4) 14.5V
Float Voltage (STD) 13.4V
Float Voltage (Gel) 13.5V
Float Voltage (AGM) 13.4V
Float Voltage (Calcium) 13.6V
Float Voltage (LiFePO4) 13.6V

Turn On Input (Standard Alternator) >13.1V
Turn On Input (Smart Alternator) >12.0V
Turn Off Input (Standard Alternator) <12.8V
Turn Off Input (Smart Alternator) <11.8V


Yes, the ProBoost40 will work with smart alternators.

We recommend using bolt down fuses, as they ensure a low resistance connection.

Blade type fuses are not recommended. These fuses can result in a high resistance connection which causes excess heat, which may damage the fuse holder and/or the wiring.

Self-resetting circuit breakers are not recommended. These may trip prematurely due to the heat generated by the current flowing through the wires.

To set the battery type of the ProBoost40, press the Mode button on the front of the ProBoost40 until the LED is lit for the correct battery.

The supported battery types are:

  • STD: standard lead-acid batteries.
  • GEL: gel lead-acid batteries.
  • AGM: absorbent glass mat lead-acid batteries.
  • CAL: calcium lead-acid batteries.
  • LiFePO4: lithium iron phosphate batteries.

Yes, you can use the ProBoost40 inside your engine cabin. The ProBoost40 is designed to be installed in a variety of environments, including the chassis rail, engine cabin and driver cabin.