An Overview: DC to DC Battery Chargers

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Your camper van would need a stable supply of electricity and is vital for long trips.

Your electricity supply lights up your van, powers up your switchboards and sockets, activates your heating system and even your fridge and your water pumps.

One component that raises a lot of questions is the DC to DC Battery Chargers Toowoomba. What is a DC-DC battery charger and why do we need it?

DC-DC Battery Charger

Your vehicle’s alternator creates the electricity and charges the vehicle battery while you’re driving. When you have a campervan, that same alternator is used to charge your house batteries.

There are several ways to charge your campervan batteries. The main ones are the alternator (DC-DC), solar, and shore power (plugging it in). This one would require you to have an inverter/charger.

The first alternative is the solar panels on the van’s roof rack.

In lithium versus batteries, you have your alternator set up to know when your vehicle battery is charged and how much power the alternator needs to put out. It’s not designed to know about the campervan conversion you have going on in the back.

DC-DC Charger

You would need a DC to DC charger because most of the time your vehicle battery is a lead acid, and your alternator is designed to charge a lead acid battery. The charging profile to charge your house battery is different.

The DC to DC charger tells your alternator what type of house battery do you have and what are the charging requirements. it actually acts as the brain that tells your alternator how to properly charge your house batteries.

Direct Current

Direct current (more commonly known as DC) is known for its constant voltage flow. In contrast, AC (alternating current) has a changing flow of voltage.

Whereas most of our home appliances still work on alternating current,direct current is more efficient and popular in small cars, boats, and vans.

With the soaring popularity of solar power in vans, DC and DC-DC battery chargers have emerged as important players.

Some comparison

Your DC-DC charger (also known as a battery to battery charger) converts the output from your primary battery and charges your secondary battery using optimal charging.

Typically, a single battery or a system of batteries is used to store the converted power.You can use the secondary batteries powered by a DC-DC charger for minor purposes (charging cellphones) and running major appliances like your fridge.

(If you are an on-the-go van lifer travelling miles on the road, you can charge your secondary battery via the DC-DC converter quite efficiently.)

DC-DC charger work

The DC-DC battery charger actually uses your van’s alternator (an electrical generator) to convert the available power. That power is then converted to a higher voltage (Ah) for your secondary battery (i.e. your house battery).

3-step charging process

The DC-DC charger uses a 3-step process to charge your battery optimally.

By bulk, the DC-DC battery charger converts the current from the alternator and fills in the secondary battery almost to the maximum.

Through absorption, the power levels off and stabilizes so the battery doesn’t ‘overcharge’. in float, this happens when the battery is fully charged with its optimal capacity reached.

DC-DC Charger benefits

The first one is overcoming the issues with smart alternators. Most vans these days come with smart alternators designed to minimize power output.

This means they cannot charge a secondary battery with their load restriction. A DC-DC converter takes care of this problem by isolating the main battery from the alternator.

The second benefit is maximizing the main battery charge is its ability to maximize the charge of the main battery. The charger can convert an amperage of as low as 9 volts up to 13.5 volts to charge the main battery quickly and efficiently.

You can get close to 100% charge on your main battery with a good day of driving.

Thirdly, the charger works without solar power. These DC-DC chargers are also a blessing in disguise if you mainly travel in areas without a lot of sunlight.

More benefits

DC-DC chargers can help charge the auxiliary battery to power your gadgets without worrying about solar power or other energy backup options.

Finally, the charger’s adaptability is one of the most important benefits in that it adjusts for different battery types. This is useful as it can save you the time and cost of buying a different charger every time you replace your battery.

A DC-DC charger also adjusts the power based on what the battery is used for, minimizing damage to the battery through overcharging. 

Working with lithium batteries

A DC-DC charger with lithium batteries can optimize your battery life. A DC-DC charger can also extend your lithium battery life.

Lithium batteries absorb the maximum amount of power available. (This is an issue if you are charging directly from an alternator.)

The reason is that if the alternator already has a significant load, the lithium battery will add to this load, causing the alternator to burn out.A DC-DC charger effectively manages the power input in a lithium battery, making sure it doesn’t heat up when overcharged.

Also, these batteries also have a different restart process and specific battery chemistry, making it difficult to charge them through alternative means such as an alternator. 

DC-DC Charger size

Batteries up to 200Ah typically require a DC-DC battery charger of around 25Ah. For ampere-hours exceeding 200, a 40-ampere DC-DC battery charger will work better.

If your alternator has a 200-amp rating, you would want to take that number, and cut it in half and that would be the charged power.

The reason it’s recommended to run it at 50% is that you never want your alternator to be running at its maximum output loadbecause it’s really hard on the alternator and it wears them out.

Selection notes

When selecting the best size for your DC-DC charger, the following can be your guide.

Alternator Size

Typically, alternators range between 60 to 150Ah while DC-DC chargers vary between 6 to 40Ah. Get a larger charger for optimal usage if you have a high-powered alternator with more capacity.

Battery Type

A DC-DC charger rated 20% of your battery’s amperage would work fine for conventional batteries such as AGM and lead-acid batteries. With a lithium battery, you can go higher, to almost 30% of your battery’s rated amperage.


You need to match your charger with your van’s electrical system. For example, if you have a 12-volt system (which is most common), you should go for a 12-volt DC-DC charger.


Your energy usage also plays a part in determining your DC-DC charger size. If you use several appliances with your auxiliary battery, you will need a DC-DC charger.

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