How We Charge Our Bus While Driving: A Guide to DC-AC Charging

Charging Our Bus While Driving

One of the greatest joys of life on the road is pulling into a free camp with 100% battery capacity and a full water tank. When you’re charged up, you have the freedom to choose the perfect camp spot — nestled among trees, with a beautiful view, or tucked away from everyone else — without worrying about where the sun hits for solar charging.

There are multiple ways to keep your battery system topped up while on the go, and I want to walk you through a couple of options we’ve used in our bus.

Option 1: Mictronix DC-DC Chargers

Mictronix DC-DC chargers are a reliable way to add charge to your system as you drive. Available in 10A or 20A versions (equivalent to 500W or 1000W of input at 48V), these units are straightforward to wire into your DC-DC busbar, feeding power back into your batteries every time the bus is on. They have built-in voltage sensing, so they automatically turn off when the engine stops, making them a set-and-forget solution.

The key to making these units perform well is to get the cable size right, ensuring efficient power transfer. If you need a bit more juice, you can even string multiple Mictronix chargers together for extra charging capacity.

Option 2: DC-AC Charging

For our bus, we use a different method: DC-AC charging with a 5 KVA Multiplus Inverter/Charger. This system not only generates 240V power but also charges from 240V sources like shore power, generators, or even an extension lead. With an impressive charging rate, the Multiplus can top off your battery bank quickly, as long as the power supply can handle it.

When our alternator died a while back, finding a genuine replacement part for our Hino bus was tough. After consulting with a supplier, we opted for a 175A Prestolite Alternator — a common and reliable choice found in many American trucks. These are easy to source if we ever need a replacement (though I don’t foresee needing one anytime soon with the amount of driving we do!).

After custom-mounting the new alternator, machining the pulley, and replacing the belts, we suddenly had a huge amount of power at our disposal. Under the bed, we installed a 24V 3000W inverter, wired through a Victron Battery Protect to ensure it turns off at a certain voltage when the bus stops charging. This inverter feeds power back to the Multiplus, which sees it as a ‘generator input.’

On our touchscreen, we set the Multiplus to draw 10A, providing around 2400W of charging power every time the bus is running. We pull about 100A from the alternator, which leaves plenty of power to run the bus’s electrical needs, like lights and charging devices.

This setup works perfectly for us because our alternator can handle the load, and we have the space to accommodate a 3000W inverter. Not every system has these luxuries, which is where the Mictronix DC-DC charger can be a better fit for some builds.

Here is what the system looks like:

Looking Ahead: What I’d Do Differently

If I were to redesign our system from scratch with what I know now, I’d choose a 5KVA Quattro Inverter/Charger over the Multiplus. The Quattro offers two charging inputs that can be programmed at different rates. One circuit could be dedicated to shore power, and the other to the DC-AC charging system onboard. This would eliminate the need for changeover switches or having to remember to plug in the DC-AC charger before driving off. It would create a seamless system that just works and keeps the batteries charged at every opportunity.