DC to DC Charger: The Ultimate Guide

If you enjoy taking long drives in your campervan then you know a stable power supply is important because it runs the lights, heating system, fridge, water pumps, and switchboards as well as all outlets.

Therefore, in order to always ensure your battery is always charged you’ll need a DC to DC charger.

What’s a DC to DC Charger?

While you’re driving the alternator creates electricity that charges the battery.

If you have a van the same alternator is used to charge the house batteries that charge features such as lights.

Often the battery is an AGM or Lithium battery.

The alternator is automatically set to determine when your battery is fully charged and the amount of power it requires to put it out.

However, it isn’t designed to automatically know the conversion going on at the back of your campervan.

Hence the need for a DC to DC battery charger.

Why Should You Get a DC to DC Charger?

You should get a DC-DC charger because most probably you have a lithium battery and your alternator is only designed for charging a lithium battery.

However, your housing battery is different and requires a different charging form to charge the battery.

Therefore, the DC-DC charger notifies the alternator regarding the following:

  1. The house battery type you have
  2. All charging requirements

Simply put, the charger tells the alternator the way to correctly charge your house battery to full power.

DC (Direct Current) Explained

Direct current commonly referred to as DC is popular for its continuous voltage flow, unlike alternating current (AC) whose voltage flow is always changing.

Although house appliances still use AC, direct current is highly efficient and is commonly used in boats, vans, and cars.

With the application of solar energy in vehicles growing by the day the DC to DC chargers have become important players.

DC to DC Charger: Campervan Equipped With Solar Panels

Caption: Campervan Equipped With Solar Panels

Below are the various ways the DC varies from AC.

  1. Normally a system of batteries or one battery is used to keep the converted power.
  2. DC to DC charger converts the output from the main battery and proceeds to charge the secondary battery via optimal charging.
  3. The auxiliary batteries powered by the DC to DC charger can be used to charge cell phones or even run the fridge.

How Do DC to DC Chargers Work?

DC to DC battery chargers uses the alternator to convert any available power.

Then it converts the power to an increased voltage to charge your secondary batteries.

Below is a three-step process of how chargers charge a battery.

  1. Bulk – the DC to DC charger changes the power from your alternator filling in the auxiliary battery to almost full charge.
  2. Absorption – now the power levels off and proceeds to stabilize to prevent the battery from overcharging.
  3. Float – it occurs once the battery reaches 100% and has reached optimal capacity.

Benefits of Using a DC to DC Charger?

Using a DC to DC charger has a number of benefits including;

Overcoming Issues Accompanied by Smart Alternators

Today vans are equipped with state of the art smart alternators made to reduce power output meaning they can’t charge an auxiliary battery via their load restriction.

The DC to DC converter cancels the issue by separating the primary battery from your alternator. 

Increases Primary Battery Charge

Another advantage is maximizing the primary battery charge.

The charger converts as little as 9V to about 13.5V to charge your battery more efficiently and quickly.

With an excellent day of driving you can charge your battery up to 100%.

Works With Solar Power

If you travel around areas that aren’t exposed to sunlight a DC to DC charger might come in handy.

With a DC to DC charger, you don’t have to worry about solar power or other power backup options because you can charge the auxiliary battery.

Adapts to a Variety of Batteries

An added benefit is its adaptability to different types of batteries, which will save on the cost of having to buy a new charger each time you need to replace the battery.

Also, depending on the battery use a DC to DC charger can adjust the power to minimize the chances of overcharging the battery which could cause damage.

Can You Use DC to DC Chargers With Lithium Batteries?

The answer to your question is yes. A DC to DC charger can be used with lithium batteries because it optimizes your battery’s life.

Below is how it compares.

  • DC to DC chargers effectively manage the power output in lithium batteries ensuring it doesn’t heat up when overcharged.
  • A lithium battery will absorb the max amount of energy available, which could cause complications, especially if you’re charging your battery directly from the alternator. The reason behind this is that the alternator already has a heavy load and adding the lithium battery load will burn out the alternator.
  • Lithium batteries have particular battery chemistry and different restart processes making them harder to charge via the alternator.

What Size of DC to DC Charger Should Opt For?

Often batteries with a 200Ah rating require a DC to DC charger rated around 25Ah.

If the battery exceeds an Ah rating of over 200 then you’ll need a 40Ah DC to DC charger.

If the alternator is rated 200Ah, take that amount and divide it by two and that will be the charged power.

It’s best to run your alternator at 50% because if it runs at maximum output it is tough for it and will therefore wear out quicker.

To choose the best size DC to DC charger consider the following;

  • Battery Type –  chargers rated 20% of your battery amperage will work for lead acid and AGM batteries. However, with lithium batteries, you can opt for higher, up to 30% of the battery amperage.
  • Usage – energy usage plays a role in choosing the size of your DC to DC charger. If your secondary battery powers a number of appliances then you’ll need a bigger charger.
  • Alternator Size – alternators typically range from 60Ah to 150Ah while DC chargers vary between 6Ah to 40Ah. You’ll need a bigger charger for optimal use if your alternator has a higher capacity.
  • Voltage – it’s advisable to match your charger and van electrical system. For instance, if your system is 12V it’s best to get a 12V charger.

The Best DC to DC Charger Picks Today

Below are our top picks for DC to DC chargers.

Red Arc

  • Functions well with a variety of battery types such as lithium, AGM, and gel.
  • It includes solar radiation to allow you to prioritize charging options from several power supplies(battery vs solar).
  • It’s reliable and can withstand extreme climates and temperatures.
  • Works with both 24V and 12V systems.
  • It has a price tag of about $410.


  • It has three variations; 120 A, 70 A, and 40 A with the 12V option, hence catering to a wide variety of users.
  • Functions perfectly with smart alternators with inbuilt vibration sense mode.
  • It is compatible with lithium and features a low-temperature trip for lithium-ion batteries.
  • It costs around $350.


  • Works with lead acid and lithium batteries as well as a 24V and 12V system.
  • It features Bluetooth therefore, you can control it from an app on your phone.
  • It’s durable and adapts to high temperatures.
  • It has a price tag of about $230.


  • It has a flexible design that improves usability and enhances safety.
  • It offers reverse polarity protection and overvoltage to prevent overcharging the battery.
  • It’s compatible with AGM, lithium, and lead-acid batteries.
  • It costs about $160.


Having discussed the various aspects of DC to DC chargers you can now make a more informed decision on what type of chargers to get.

For all your DC to DC chargers needs feel free to contact Cloom Tech.