If you are looking for the best DC to DC charger money can buy, Enderdrives ePOWER EN3DC40 12v/40a DC to DC Battery Charger is our top pick. This Enerdrive ePOWER 40a/12v EN3DC40 DC to DC charger truly stands out from its competitors. Engineered to perfection and manufactured to the highest possible quality, it's easy to see why Enerdrive is quickly overtaking the market. The Enerdrive ePOWER 40a/12v EN3DC40 DC to DC charger is a fully automatic multistage, multi-input battery charger that has the capacity to charge from solar power using the integrated Maximum Power Point Tracking (MPPT) Solar Controller or from an alternator connected to a battery. The main/house battery can be charged from any of the two accessible inputs: the engine when moving, or the solar panels. Both functions are managed internally by the device itself without the use of external relays, making it completely automatic to select between the engine or the solar power.
Features

• Two totally independent DC Inputs for both engine and solar regulation charging one house battery bank output
• DC M6 screw terminals that will allow for large battery cable connection between all sources
• A dedicated Maximum Power Point (MPPT) solar regulator
• The same battery algorithms as included in our AC mains ePOWER battery charger. GEL, AGM, Flooded, Lithium and the ability to create a full custom profile
• Vehicle input allows for either 12 or 24v and a maximum solar input of 45V/800W
• 40A output up to 40 °C with thermo controlled fan cooling
• Fully programmable LCD display to show which source is charging the battery along with charger status, voltage and amperage
• Temperature sensor included with charger for more accurate battery charging