To understand the basics, we recommend reading our Dynamic Load Balancing article first. We will assume you understand this, and in this article we will only focus on the impact this has for multiple chargers at one location.
How does Dynamic Power Sharing work?
There are 2 goals you are probably looking for:
To prevent using too much power and to optimally share the available power between all chargers.
To prevent wasting surplus solar power and only charge your cars on green energy.
Power Sharing simply takes the above two goals, already realised by Dynamic Load Balancing and Dynamic Solar Balancing, but shares the power between multiple chargers.
Basics of Power Sharing
Static Power Sharing
Imagine two chargers. They can use a maximum of 40A together. One charger is being used, it gets 40A (although the car probably only uses 32A maximum).
The moment a second car is being charged, both chargers only get 20A.
Dynamic Power Sharing
If the building as a whole can only use 40A, we can install a meter at the main fuse to take into account the usage of other devices. Imagine all other devices combined are using 10A, we can now only give 30A to the two chargers, each getting 15A.
Read Dynamic Load Balancing for more information.
And with this meter, you can also enable the two chargers to charge on solar power only. For example, if the usage of all devices combined is -20A (so a surplus of 20A caused by solar panels), each charger will get 10A to charge so your net usage is 0.
Read Dynamic Solar Balancing for more information.
Real-time adjustments based on car
Volt Time's Power Sharing is extremely advanced and we keep track of what the cars are doing to optimise the power distribution.
Because the charger does not know what car is connected, we will start by offering this car the maximum power. After a few minutes, we will detect that this car doesn't need that much power, and we will scale back so other chargers in the group can charge faster.
Here is how that looks:
Slower car
Let's go back to our two chargers, each using 20A. If the second car is only using 16A, we will detect this after a few minutes, and start limiting the charger to 16A instead of 20A. This means the first charger now gets 24A.
If the second car suddenly wants more, we will also detect this, and we go back to giving each charger 20A.
Full car
The above works exactly the same if the second car is using 0A. We will give the first charger 40A, and check back in with the second charger periodically to see if it still doesn't want to charge.
1-phase and 2-phase cars
We start by giving each car power on all 3 phases, but if the car is only pulling on 1 or 2 phases, we will detect this and give this power to the other phases of each charger.
Multi-level charger groups
Basic multi-level charger groups
At home, we only have to protect your main fuse. But in larger installations, you may find sub-fuses. For example:
Building's main fuse: 100A
Charger group A, with 2 chargers, with a fuse: 30A
We simply have a maximum of 30A to share between the two chargers, so we do not go past the fuse of Group #1. However, we must also take into account the main fuse of 100A, and because other devices in the building are also using power, we must place a meter at the main fuse to monitor what's being consumed:
You can also have multiple groups under one main fuse, of course:
You can create as many groups under the main fuse as you want, and you can even create as many groups under existing groups, if things get very complex:
Charger groups with multiple dynamic metering points
Now imagine Group #2 doesn't have that sub-group #3, but there are some other devices connected that are not chargers. The lighting in the garage, or the garage door, for instance. We must know what these devices are using, to prevent using more than group #2's maximum power of 45A.
With Volt Time Power Sharing, you can add as many metering points as you want. You should do this for every charger group that also has other devices connected to it, so that we can get a full picture of the situation:
Inter-group phase balancing
With Power Sharing, we are monitoring every phase. This works in all directions:
Downstream: If a device on phase #1 of the Main Fuse is using more power, all the charger groups below it will get a little bit less power on phase #1.
Lateral: If Group #2 suddenly has a 1-phase car using extra power on phase #1, the parallel Group #1 will get less power on that phase.
Upstream: in the previous example, if group #3 would start using more on that phase, both the groups #1 and #2 above it would be restricted.
Here's a screenshot of the real Power Sharing user interface where you can see what's happening per phase in real-time:
Meter, Available, Requested, Allocated: Explained
You may come across these labels and wonder what they mean exactly.
Meter (only if a meter is installed at this point): What the meter is detecting. A positive number is usage, a negative number is a surplus of (solar) energy.
Available: How much power is left to charge the cars with
Requested: How much power the car wants to charge with. If this is unknown, this will be displayed as the maximum power the charger can pull.
Allocated: How much power we are really giving to the charger.
Usage or Import: How much power the charger is using at the moment.
These values are only shown if there is an active transaction. If there is no transaction, all values in the whole Site will be displayed as "- A".
Graphs
The live view per phase can also be viewed as a live graph. There are two types of graphs:
Group-level graph: This displays the meter, how much power is available and how much power is being used in total by all devices and sub-groups underneath.
Connector-level graph: This displays only one connector of a single charger. This useful because it tells you exactly what this single charger is doing.
Because there are so many data points, we split everything into one graph per phase. So for one connector, you have three graphs.
To see these graphs, go to Locations > View > Load Management > Technical Details, then hit "View History" on the desired level.
Data is only stored in graphs for 48 hours. If there are no data points, for instance because there is no active transaction, there will be a blank space.
Example of a group-level graph (phase 3):
Example of a connector-level graph (phase 1):
Import is the same as Usage.
Smart Charging in Power Sharing Groups
If you want to enjoy "Smart Charging", so charging based on real-time energy prices, this is entirely possible. The entire group of chargers will be set in the same Smart Charging mode.
To learn more about Smart Charging, check out this article.
How to configure Dynamic Power Sharing
Go to Locations>View>Load Management>Power Sharing.
You must set the following:
Create a group, you can create multiple groups. You usually only need one.
Set Group fuse, this is the maximum power this group may use.
Select a meter, if you only have chargers on this group connected to Power Sharing, this is not necessary.
Add chargers
Set Phase Rotation, this is how the phases of the chargers are connected to phase 1, 2 and 3 of the building respectively. So if you do "RST (L1,L2,L3)", it means phase 1 of the charger is connected to phase 1 of the building, etc.
Maximum current is how much power this charger, so all of its connectors combined, may use.
Connector maximum current is how much each connector of the charger may use. For instance, a charger with 2 connectors can be installed as a 32A charger but each connector only gets 16A.
