Can you run two DC DC chargers in parallel?

Two questions behind one

• Two chargers fed from the same vehicle input, both connected to the same auxiliary battery, to add their currents together.
• Two chargers fed from different sources, such as one from the alternator and one from a solar array, both charging the same battery bank.
• The first is a question about whether the units are designed to share a load. The second is a question about whether two independent sources can charge one bank, which is an arrangement we do publish for.

The alternator becomes the first limit

Doubling the chargers doubles what they will ask of the vehicle. The 12V range publishes a nominal input of 12V with an input window of 8V to 16V, and the output powers run from 250W to 750W depending on the model. Two units in parallel are asking for the sum of those figures from an alternator that was sized for the vehicle it was built into.

That is the constraint most often overlooked. It does not matter what the chargers are capable of together if the alternator cannot supply the pair of them and still run the vehicle. The alternator guide covers that side of the decision in detail.

Why a single larger unit is usually the answer

The reason to want two units is normally current, and the ranges already go a long way on their own. The 12V range runs to 60A and 750W. The DD range runs to a maximum charge current of 60A. If the aim is more charge current than one unit gives, the first question is whether a single larger model would do the same job with one installation, one set of cables and one fuse.

Two sources into one bank, done properly

Charging one battery bank from two sources at once is a normal thing to want, and it is the case our DD range is designed around. It publishes dual-input operation, drawing from the alternator and the solar array at the same time, with maximum power point tracking on the solar input at a published tracking efficiency above 99%.

• The PV input publishes a maximum PV open-circuit voltage of 80V and a maximum PV input current of 20A or 40A depending on the model.
• The generator side publishes a maximum generator input voltage of 80V across generator system voltages of 12V, 24V, 36V and 48V.
• Coordination between the two inputs happens inside one unit, which is a different proposition from two independent chargers meeting at the same battery terminals.

What we do not publish

We do not publish parallel-operation guidance, a current-sharing specification, or an instruction to connect two of our chargers to one battery. Where a manufacturer has not published that a configuration is supported, the honest answer is that it is not supported rather than that it probably works. If your installation genuinely needs more current than a single unit provides, take the alternator question to us before assuming two units is the way to get it.