Managed AC Charging for Buildings, Fleets and Networks

Two operating models, with four managed control strategies

A site is either unmanaged or managed. Within the managed model, the control strategies differ in what they measure and how quickly they respond. Each adds capability and a failure mode worth understanding before committing.

Phase balance

Single-phase chargers on a three-phase supply load one phase each. Distributed carelessly, a site can hit a per-phase limit while two phases sit idle. Allocation that is aware of phase assignment recovers capacity that a simple total-current budget leaves unused.

Prioritisation is an operations decision

Once capacity is scarce, someone charges slower. Whether that is the visitor rather than the tenant, the short-dwell rather than the overnight vehicle, or the low-duty rather than the first-out fleet unit, is a business rule. The system should implement your rule rather than impose one.

What RIOD provides

Per-charger current limiting is in shipping firmware. Site-wide dynamic load management ships through the RIOD CMS. Integration with a third-party load management system is possible as custom work.

What actually happens in apartments

Apartments show the highest utilisation of any AC site we operate, and it concentrates overnight. That is the awkward part: the building is least able to take the load at exactly the hour every resident wants to plug in.

The usual answer is to upgrade the supply. The cheaper answer is usually to move the load. Our chargers hold a schedule, so charging can be kept out of a defined evening peak, run at reduced current through it, and complete across the hours afterwards. A resident who plugs in at seven and leaves at seven does not care which of those twelve hours the energy arrived in.

The second constraint in apartments is connectivity. Basement and podium parking is where mobile coverage is unreliable, and a charger that needs a backend to authorise a session stops working there. Ours run in a community mode that keeps charging and access control working locally with no internet at all, and reconciles when the connection returns.

What the failure rate means for a managed service

Managing chargers on an operator's behalf means committing to availability, so we are precise about what actually breaks.

Unit failures across our deployed AC fleet run at roughly 0.5 percent, about one in two hundred. That is the number that sizes the spares pool.

It is not the number that sizes the service, because most of what arrives as a charger fault is not the charger.

• The supply: a tripped protective device upstream, or a site that has run out of headroom at the hour everyone plugs in
• The installation: earthing, cable termination, or a protective device selected for the wrong duty
• The vehicle: an onboard charger that negotiates badly, or a driver expectation that was never achievable

Each still needs diagnosing before it can be handed to whoever owns it. Managing a site well is mostly about telling them apart quickly, remotely, and before anyone is dispatched.

Managed and unmanaged, which is the whole choice

There are two arrangements, not five, and the difference is whether anything is deciding how much each charger may draw.

Unmanaged is correct where the supply genuinely covers every point at once. Everywhere else it is buying capacity you use for an hour a day.

What the controller actually does

Managed charging is a central controller with load management, watching the building's own consumption and any third-party loads on the same supply, and adjusting the chargers to fit inside what is left.

• Adjusting charging levels continuously as other load rises and falls
• A per-charger cap, so no single point can take more than its share
• Allocating across active bays, so capacity follows the vehicles that are actually there
• Rotational allocation: a vehicle that has already taken a lot can be reduced so one that has just arrived gets a useful rate
• Phase-aware allocation, so the arrangement does not unbalance a three-phase supply

Which of these applies is a site decision. A depot with known departure times and an apartment basement want different behaviour from the same equipment.

Install for phase balance from the start

On a three-phase supply the limit applies per phase, not to the total. A site with 100 A per phase does not have 300 A to share out.

Single-phase charge points each load one phase, so how they are distributed across the three at installation decides how much of the connection is usable. Getting that right when the points go in costs nothing. Correcting it afterwards means rewiring. This is worth insisting on with whoever does the electrical work, and it is the first thing we look at on a site that is tripping one phase while the others sit idle.

What managed charging cannot promise

Worth saying plainly, because the expectation otherwise is unreasonable.

Managed charging shares a fixed amount of capacity between however many vehicles are present. When the bays are full it will take longer than it would have on an unmanaged site with an enormous connection. That uncertainty is real and it is the trade you are making: more points, a smaller connection, and a charging time that varies with how busy the site is.

For overnight and long-dwell sites that trade is almost always worth taking, because twelve hours absorbs the variation. For short-dwell sites it needs thinking about.