Victron’s PowerAssist Function Explained

Victron's PowerAssist function operates discreetly in the background, allowing your Victron MultiPlus or Quattro inverter to adjust its charging current as needed. This ensures that the generator or shore power connection can continue to be used even when they are far too small to be utilized by traditional inverter charger systems. 

Put another way: PowerAssist means that when using a Victron Energy inverter/charger, you can adjust the input current to a level lower than the output power without affecting output power. The ability to utilize limited power sources enables a host of benefits. 

PowerAssist technology has changed how systems can be designed. However, many off-grid power systems are still specified with generators twice the size of the inverter. This approach compromises the generator's operational efficiency and significantly limits the system's potential. 

In this article, we'll explore how Victron's PowerAssist function works, its value to any power system, and practical scenarios where PowerAssist saves the day by offering an elegant solution for systems operating in the real world.

How does PowerAssist work?

When the input source is limited, but you still want to run your system normally, PowerAssist comes into play. If you're connected to the public grid or a two or 3X inverter-size generator, PowerAssist will probably not be a feature you will take advantage of. 

A typical scenario where PowerAssist saves the day is a 5000VA 48V Quattro inverter/charger. You are feeding it 13.5A, which is its minimum input limit. That would give you 1,620 watts of input power. Of course, that’s not enough to run all the loads you would expect to run with a 5000VA inverter. 

What happens when we need 2000 Watts or 4000 watts? Let's start with the 200-watt load on the system, and let's imagine it’s a Starlink. The power from our 1620W source can be sent directly to the batteries. Charging is at a ~30A at 53V. The max charge current for this inverter is 70A, and that's what we have it set to, but it will be automatically limited by the input current. 

As the loads build to over 1620 Watts, we need PowerAssist and we need to stop the battery charging current. PowerAssist has a minimum level at which it can operate based on the inverter type; for this particular inverter, it is 5.8A (or 670 Watts). The second we get to 1621 Watts of power, PowerAssist will stop charging entirely and assist with 670 watts of inverter power. This tends to confuse people because your input will drop by 670 watts in this case. Put another way, we can’t power assist with 1W, the minimum to play this game is 670W. At higher loads, for example, 4000 watts, the math is 1620 watts of input power + 2380 inverter power. 

If these loads persist higher than the input source, your batteries will be discharged as the inverter pulls power from them. If the loads are often on and off, the average power from the source is often sufficiently long-term. It's worth noting that when we introduce the word ‘average’ or look at things over time, the battery capacity significantly impacts what can be expected. 

Without PowerAssist

What would happen in this exact scenario without PowerAssist? You would have to disconnect from the input source and go back to operating off the inverter only. If you feed the inverter with, say, 3000 watts but you need 4,000 watts, well, you have to disconnect from the source, the generator, or the shore power connection. Your other option is to kill all the loads, such as the air conditioner, and charge those batteries. Without power assistance, you may also have to go into your charger settings and reduce the charge current so you're not overloading your small input source.  

In a system where you don’t have the ability to supply over twice the inverter size, you really can't charge the batteries and run the loads at the same time. You would end up doing things like backing off the charging current. PowerAssist is what allows you to bring in a smaller or right-sized energy source - or plug in where no one has plugged in before successfully - while maintaining total power output.

Adjustable current inputs

We touched on this, but it's worth hitting again. Adjusting your input current is not new to inverter chargers; what is new is the ability to do this without affecting output power. Victron's user-friendly interface makes these adjustments remarkably easy. Using a Digital Multi Control or the GX Touch Screen, you can easily increase or decrease this input current limit to match your available power source.

>>> Related Reading: Victron's Digital Multi Control: When & How to Use It

Right-sizing your generator

One of the most significant benefits of Victron’s PowerAssist is the ability to use more competitively-sized generators. Historically, in most off-grid or mobile applications—whether for a remote cabin or a wildland fire camp—you’ll find large generators in use. 

The PowerAssist option allows us to pair more fuel-efficient generators with our Victron power systems.

Generators can lose power as they age or when operating at high altitudes. With PowerAssist, you can identify the ideal operating conditions of almost any generator size and factor in its age and altitude to keep your system online.  

Let’s consider a few real-life examples where PowerAssist is critical to a system’s design: 

Scenario 1: Hybrid generator system

Conclusion