Victron Energy Inverter/Charger Buyer Checklist

Cover photo by Vanna Adventure Vans

The rumors are true; Victron Energy makes the best off-grid inverter chargers on the market. 

As the cornerstone of your system, the inverter charger serves three functions:

1. It is a robust battery charger with built-in algorithms for different battery chemistries.
2. It is a powerful inverter that provides clean, reliable, continuous power.
   
3. It offers a transfer switch to enable the generator to provide power to your loads while the batteries are charging.

Choosing the right one for your mobile or off-grid power system is, of course, really important. This article addresses the main questions we ask our customers to consider before purchasing a Victron inverter/charger:

1. Do you need two AC inputs, or is one OK?

Victron makes two main inverter/chargers: the Multiplus and the Quattro. The primary difference between these two units is the number of AC inputs. The Multiplus, our more compact option, has a single AC input - while the Quattro has two independent AC inputs.

While there are options for managing multiple AC sources on a single input, the Quattro has some advantages when dealing with a pair of independent inputs.

Let's take, for example, a grid connection and a generator feeding the two AC inputs on a Quattro. A grid connection (or, in the case of a mobile setup like an RV or boat, your shore power input) on your first AC input would be your primary source of power, both to charge a connected battery bank and to power the loads on your home (or RV, boat, or other system). If, or when, that primary connection fails or is disconnected, the Quattro can automatically switch to the secondary AC input and even be able to trigger your generator to start via a low-voltage relay.

The Multiplus, with its single AC input, is an equally capable but slimmed-down system. We see these primarily in mobile power systems where there is no generator, such as; a van conversion that mainly needs to top up its battery banks via shore power, a small RV without any onboard generator, a tiny home that wants to provide some short-term battery backup, but is not concerned with having a backup generator. The main advantage of the Multiplus is its footprint; this unit is a more compact and lightweight option when size or cost are important factors in designing your power system.

It's important to point out that all of our Inverter/Chargers have two simultaneous AC outputs. While you can modify the function of the second output somewhat, its default, and most common use, is to provide an AC output to your "non-critical" loads or those loads which you do not want to power when operating exclusively on your DC battery backup.

In an off-grid system, you'd keep your primary and most important AC loads connected on AC Out 1 - things like; heat, fridge/freezer, lights, etc. The output for AC 2 might be connected to less critical but high-usage appliances like your dishwasher, washer/dryer, living room outlets, etc.

In a mobile setup, your AC Output 1 would power any system you want to use while entirely off-grid, whereas your AC Output 2 might be reserved for systems you would only use in a shore power-connected situation, like your roof-mounted air conditioner.

2. Have you looked at comparable models (same voltage, same power)?

Let's look at two "equal" units in terms of power: the MultiPlus-II 48/5000/70-50 230V and the Quattro 48/5000/70-100/100 230V. Both units are 48V DC-based systems with a total throughput of 5000VA.

Besides the two independent inputs of the Quattro, the differences begin to show themselves when we look beyond the first two primary digits in the model name: 48/5000/70-50 230V

The first number indicates the DC voltage this model is designed to work with. In the case of both the Multiplus and Quattro, that is 48V.

The second number is the VA capacity of the DC-AC conversion. For both units, that is 5000VA or around 4000W.

The third number indicates that both units can provide up to 70A, at 48V, of charge to your DC battery storage.

After the hyphen, we begin to see some differences. In the case of the Mutiplus, the "50" indicates that it can provide up to 50A of AC power at 230V through its AC input. Meanwhile, the Quattro (100/100 230V) can provide up to 100A of AC power at 230V on both independent AC inputs. This difference in the amount of power it can pass through from an outside AC source is where the added power of the Quattro model really shines.

There is also a difference in the physical sizes of these two otherwise comparable Inverter/Chargers. The Quattro and Multiplus weigh nearly the same. While the Quattro is shorter from top to bottom by 6 inches, the Multiplus is under 6" deep, making it a great option for a tight space in a mobile application like a van conversion or RV. Even the most powerful of the Multiplus II are under 9" deep. In general, the Multiplus will be lighter and taller but less deep - while the Quattro will be heavier and a bit deeper from front to back. That said, none of these units take up a huge amount of physical space; our largest, the Multiplus II 48/15,000, is 32" tall x 16" wide x 8.5" deep.

Both units are wired in by removing a front panel on the lower portion of the Inverter/Charger, with all data and power connections protected behind this cover. The Multiplus, in particular, keeps the cables close to the wall side of the unit, though both provide direct routing out the base of the unit. Mounting is also very flexible, the main rule being that it can't be mounted on its head due to venting and airflow considerations. It may, however, be mounted sideways, back down, or even mounted to a ceiling facedown (or the underside of a floor, as might be seen in mobile setups).

3. Do you understand the 2x 120 for 50 Amp service on a motorhome?

The MultiPlus II 2x120 unit is an ideal solution for RVs and coach buses with a 50 amp service. The 2x120 allows full 50 amp pass-through with two 120V lines in and two 120V lines out. When connecting to a single-phase 120V supply, the L1 input of the MultiPlus-II 2x120V will accept incoming power for charging and passthrough while combining the L1 and L2 outputs for single-phase 120V on each line.

Now, let’s say you plug into a 30-amp service with your RV, and you want to run appliances that draw more than 30 amps. The 2x120 will bridge L1 and L2 to compensate for the lack of power coming from shore power. What if you are boondocking away from a shore power source? The MultiPlus will switch to inverter operation, and it will internally connect both lines L1 and L2 together to provide 120VAC to loads on either output. Therefore, in all connection circumstances, both sides of a distribution panel will be supplied with 120V.

4. Do you need an Autotransformer?

If you're buying a 240 Volt inverter, you likely need an Autotransformer to function in the US. The only reason why you wouldn't include an Autotransformer is if you're installing your Inverter/Charger in a vehicle with European power needs or you are powering exclusively 240V loads.

That said, combining a Victron Inverter/Charger with a Victron Autotransformer allows for some powerful additional functionality:

• Many Victron Inverter/Chargers may be set up to run in parallel to provide additional power; adding an Autotransformer can very effectively combine the outputs of paralleled units to keep the power draw on your system balanced. 

• Convert 120V to 240V, or 240V to 120V. Some of our larger Multiplus and Quattro Inverter/Chargers are only available in a European 230V. With an Autotransformer, however, they can be effectively used with US 120V loads, providing multiple options for applying the Victron line of equipment. 

• Split phase output balancing to provide full power on each leg of your split phase setup.
  

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The Victron Autotransformer is a uniquely powerful device. Its features may also be applied to other brands of inverters as its capabilities are not specifically tied to Victron gear - though matching blues are a nice touch. There are a few considerations for grounding and how to manage bypass breakers. Get in touch with us directly if you have questions about this potent option.

5. Do you have what you need to program the inverter?

The internal settings of the Victron Inverter/Chargers offer some detailed control over your power system. The primary method to manage these settings is through use of the MK3-USB Interface and the VE Configuration application with a PC. Among the numerous settings you have access to are: input and output current limits, setting up ESS management, setup features for parallel/split phase/three phase systems, DC charge parameters, and a whole swath of other options. Generally speaking, this is something you set and then never have to touch again as most of the day-to-day details can be managed through VRM or locally over Bluetooth. Still, in your initial setup phase, this can be a crucial tool for accessing the advanced functionality of your Victron inverter charger.

Need product advice or design support? Send us a message. We're happy to learn about your system and help answer any questions you might have.