What is load balancing?

Load balancing is the heart of Easee's advantage. It means easier, efficient, and most importantly optimal charging.

But that is not a true explanation of what is happening when loads are balanced.

A more simple explanation

When several charging robots are connected to the same fuse, the total current will be divided automatically and dynamically between what is using the power. In the case of the Easee chargers, the fuse determines how much power the chargers can use among all of them. The total load of the chargers will therefore never exceed the limits of the fuse.

All connected cars can be charged simultaneously and the available charge-current is automatically shared between them, provided that there is enough power available on the supply. If there is not enough power available, the cars will be put in the queue.

For example, Easee requires a minimum of 6 Amps (A) to charge a car. If the fuse is 15 A (a very low fuse value, but this is only an example), and there are two cars charging, each car can charge at 7.5 A. If a third car connects, that would require a minimum of 18 A (3 cars, 6 A each - a car requires at least 6 A to charge). Since the fuse is limited to 15 A, the third car will be kept in a queue until enough power is available to charge it. In this case, this will happen if one of the other cars stops charging.

Easee Equalizer accomplishes the same thing but between the fuse controlling the Easee Chargers and the rest of the house's available power. If more power is required in the house in a particular moment, for example the washing machine and air conditioner are both running, then the Equalizer will prevent the chargers from taking too much power from the house. Similarly, the Equalizer will ensure that as the power fluctuates, the most power possible is sent to the car or cars to complete their charge effectively.

A more mathematical explanation

We have three wires. A B and V. Each wire carries the charge. Now you think "But if three wires are carrying the full amperage, then why isn't that three times the amperage?" That is because their waveforms cancel out.

If you look at the drawing, think of A as the black wire, B as the red wire, and V is the blue wire. Each moves from -1 to 1 in a sine wave, where 1 is the most power possible. But the waves are 120 degrees separated, which means the sum is zero. If you look at the point where A (black) crosses B (red), they are both drawing power at 0.5. That adds up to 1, of course. But look where the current of the V (blue) wire is at that point. It's at -1. So combining to power in A, B and V, you get zero. And in an ideally balanced system, it will always add up to zero.

And that's where the Easee charger comes in. Given the power sent to it, it is able to determine the value on each wire and, in essence, shift the waveforms so they are as balanced as possible. Balance means there are no gaps in the power, and no power lost to overload on one wire over the other two.

Why is load balancing important?

The balancing is important for a few reasons. In a simple system, it makes sure that the charging is working as efficiently as possible. No drops in charge, no overloads that cost you money for power that never reaches your vehicle.

The balancing becomes an even more efficient tool when used across multiple chargers.

Consider we have a car that can only charge on one phase, and a car that charges on all three.

With the 1-phase car, it will have to take all of its charge from one of the wires. Using the example above, we'll say that the 1-phase car is charging from wire A. The 3-phase car can take power from all three wires. But when they are put on the system together, in order to balance off the first wire, the 3-phase car must take a smaller charge.

We'll say the fuse controlling our two Easee chargers is a more realistic 32A. If the single phase car charges by itself, then the maximum amperage would look like this:

All 32 amps are on the single phase, and because the car is single phase, the other two wires carry no charge.

The three-phase car would look like this:

Because it can take the 32 A on each wire, and the amperage is balanced. However, if they are together, they have to share the power on the one phase the single-phase car uses, and in order to do that, the three-phase car must have its power limited.

The maximum available is 32 A, and since 32 A is delivered on the first wire, it must alternate the 8 A for the 3-phase car across all the wires so that it never goes above 32 A. The B and V wires cannot take 32 A while the first wire takes 8 A, because that - 8 32 32 - is obviously not balanced. The 1-phase car is always drawing 24 A regardless of which phase the other car is getting, which leaves only 8 A for the 3-phase car, though it can use it across all three wires.

But there is another solution, which the Easee chargers would accomplish:

Both of the cars get maximal current. The Easee chargers have realized that the first phase will be maximally used by the 1-phase car, thus it will then charge the 3-phase car as if it were a 1-phase car. It does mean that it is not maximally efficient, since the B wire goes unused. However, this method delivers the maximal efficiency without removing equality.

Optimal distribution means "make sure current power is equally distributed as needed" and not "maximize power and make the charge fit regardless of where it ends up." Because if optimal distribution were used that way, then all of the power would go to the 3-phase car at 32 A per phase, and the 1-phase car would get none. We don't want that. We want our cars charged so we can use them.