Relay questions, answered.

Relay is a middleware solution that allows any OCPP-compliant EV charger to connect with one or more CMS simultaneously. Instead of being limited to a single CMS, Relay enables multi-CMS connectivity — increasing charger visibility across multiple networks and mobile apps.

Normally, a charger connects directly to one CMS via an OCPP URL provided by that CMS.

With Relay, you configure a Relay URL in the charger. The charger connects to Relay, which in turn connects to multiple CMSs.

Relay acts as a bridge between your charger and all desired CMS platforms.

Yes. Relay is protocol-agnostic and supports all OCPP-compliant chargers, whether AC or DC, and works seamlessly with OCPP 1.6J and OCPP 2.0.1.

No. Relay uses the standard OCPP configuration. You simply replace the CMS URL in the charger with a Relay-generated URL. No firmware or hardware changes are needed.

Yes. Relay can be integrated without any downtime. The onboarding process involves replacing the existing CMS URL in the charger with the Relay URL — a quick configuration that usually takes just a few minutes.

Once configured, Relay bridges your charger to one or multiple CMS platforms. You will need the CMS URLs from the respective CMS providers to complete the setup.

Although Relay sits between the charger and CMSs (adding one additional network hop), everything happens in a blink of an eye. Relay uses optimized message routing, making latency negligible and ensuring smooth transaction flow and real-time responsiveness.

Technically, there’s no limit. Relay has been successfully tested in our staging environment by connecting several chargers with up to 10 different CMS platforms simultaneously.

In production, most chargers are connected with 3–4 CMS platforms, providing increased visibility, utilization and revenue.

Relay is OCPP compliant and supports both ws and wss secure connections at the network layer. It also supports basic authentication at the application layer for additional protection.

Yes. Relay isolates connections between CMSs, so if one CMS is offline or unreachable, other CMS connections remain unaffected.

No. Relay doesn’t replace your CMS — it enhances it. Relay acts as a middleware bridge between chargers and multiple CMS platforms, allowing a single charger to communicate with more than one CMS simultaneously.

In an OCPP-based EV charging setup, each charger is identified using a Charge Box ID (also called Charge Point ID).

How Charge Box ID Works in a Typical CMS Setup

• A CMS generates an OCPP URL that is configured in the charger.
• The last part of the OCPP URL usually represents the Charge Box ID.
• This ID uniquely identifies the charger within the CMS.

The same Charge Box ID is:

• Displayed in the CMS dashboard
• Shown in the mobile app (map or list view)
• Sometimes printed or physically labeled on the charger

This helps EV users match the charger shown in the app with the actual charger on-site, especially when multiple chargers exist at the same location.

Challenge When Multiple CMS Platforms Are Involved

When a charger connects to multiple CMS platforms, each CMS may generate its own Charge Box ID. This creates a problem because:

• A charger can display or label only one physical Charge Box ID.
• Different IDs across CMS platforms can confuse operators and end users.
• The charger’s identity may not match consistently across apps and dashboards.

Best Practice When Using Relay

When using Relay with multiple CMS platforms, it is recommended to:

• Use the same Charge Box ID across Relay and all connected CMS platforms.
• Maintain a single, consistent charger identity irrespective of the CMS.
• Ensure the Charge Box ID shown in mobile apps, dashboards, and physical labels all match.

This approach simplifies:

• Charger identification
• User experience at sites with multiple chargers
• Operations, monitoring, and troubleshooting across CMS platforms

• Better visibility: Your charger appears in multiple apps.
• Higher utilization: Broader exposure drives more charging sessions.
• Business continuity: If one CMS goes down, others remain active.
• Scalable growth: No dependency on a single CMS network.

There’s no fixed number. Consider:

• Network size (user base and market strength)
• Local vs. national presence (regional popularity vs. pan-India reach)
• City vs. highway focus (urban vs. intercity usage patterns)
• User persona (different CMSs may attract different charging habits)

Analyzing these factors helps maximize utilization and ROI.

No. Each CMS can independently display and manage the charger under its own brand and user interface without changing the charger’s core connection. This means a single charger can simultaneously appear under multiple branded CMS networks.

Each CMS manages its own payment collection process from EV users through its respective app or platform. Relay does not handle or process end-user payments — it simply facilitates the connectivity between the charger and multiple CMS platforms.

Each CMS carries out settlements directly with the charger owner according to the agreed terms — daily, weekly, or monthly. Relay does not interfere in the financial flow; it only enables and manages the technical connectivity across multiple CMSs.

Relay follows a pure utilization-based model — no setup or subscription fees. You pay INR 1 per kWh of energy delivered, regardless of the number of CMS connections.

Example: If a charger delivers 5,000 kWh in a month (spread across 5 CMSs), you’ll be billed ₹5,000 total. You will make the payment at the start of the next month, and this information will be visible in the Relay dashboard for easy tracking.

Not significantly. If your tariff is ₹20/kWh, ₹1/unit is just 5%, while you gain more traffic and utilization through multiple CMSs — resulting in higher net revenue.

Even well-utilized chargers can benefit from broader reach. A charger is rarely used 24/7, so every extra hour of charging improves ROI. Multi-CMS connectivity ensures consistent traffic and reduces downtime dependency.

CMSs may charge in different ways:

• Subscription model: Fixed cost per charger (₹2,000–₹8,000 annually).
• Revenue-sharing model: 5–10% of transaction value or ₹0.50–₹2.00 per kWh.
• Hybrid model: Combination of both.

If you plan multi-CMS connections, a transaction-based model is more cost-efficient.

Most CMS providers set a fixed model, and you may not have a choice. If you plan to connect with multiple CMSs, a transaction-based model is usually more cost-efficient:

• Subscription fees can add up across multiple CMSs, even if utilization is low.
• By explaining the multi-CMS scenario to CMS providers via Relay, they may offer a transaction-based model, so you only pay service charges when the CMS actually drives traffic to your charger.

Yes. Plugzmart collaborates with several CMSs across India who are already familiar with Relay. We can help connect you with the right partners for faster integration and go-live.

No. Relay is designed for commercial or publicly accessible chargers. Connecting a private or personal charger would not provide any additional visibility, utilization, or revenue benefits.

No — integrating with Relay does not affect your brand identity. Your chargers will continue to appear under your existing branding and configuration. The only difference is that your chargers will also become visible and accessible through multiple other CMS platforms.

This means users from different CMS mobile apps can discover your chargers, navigate to your locations, and start charging — leading to higher visibility, utilization, and revenue for your network.

Relay provides a single, consolidated monthly bill summarizing your usage across all CMSs, including per-CMS session counts and usage (kWh).

No. Relay does not have access to tariff or pricing information, as such data is not exchanged between the charger and CMS through OCPP messages. Relay provides insights based only on operational data such as energy delivered, session count, and duration — helping you assess utilization, not revenue.

No. The charger simply connects to the Relay URL. Relay handles the connections to multiple CMSs behind the scenes, so the charger is unaware of how many CMSs it is connected to.

No. Each CMS only sees its own connection to the charger. The CMS perceives the connection as directly from a charger (though it actually comes through Relay).

No. Each CMS only sees its own authorized sessions and data. While certain generic charger information — such as heartbeat, status updates, and availability — is broadcast to all connected CMSs, charging session data is CMS-specific:

• A CMS receives only its own sessions and related information.
• It does not see sessions that happen on another CMS.

This ensures data isolation and privacy between CMSs, even when connected through Relay.

All messages sent or received between the charger and CMS pass through Relay, giving it access to OCPP messages. Relay stores only essential operational data and does not receive or store any personal or user-identifiable information, as the OCPP protocol itself does not include such data.

Relay stores the following:

• OCPP messages
• Charger availability status
• Health metrics (voltage, current, etc.)
• Charging session details (energy delivered, duration, timestamps)

This data is used only to provide:

• Charger health and utilization insights
• Debugging and monitoring via the Relay dashboard

EV Roaming allows a charger from one CMS to be shared with other CMS networks, giving EV users better access and more charging options.

OCPI (Open Charge Point Interface) is the standard protocol that enables EV roaming between CMSs. It allows different CMS providers to share their chargers securely with other networks, ensuring interoperability and expanding the reach of each charger.

Both enable charger sharing but work at different layers:

• Relay: Operates at the charger-to-CMS layer, allowing a single charger to connect to multiple CMSs.
• OCPI (EV Roaming): Operates at the CMS-to-CMS layer, allowing networks to share chargers among themselves.

Relay empowers charger owners or local CPOs, while OCPI empowers CMS providers and larger CPO networks.

Absolutely. Relay connects your charger to multiple CMSs. Each of those CMSs can then use EV Roaming/OCPI to share chargers further — offering multi-level visibility across national networks.

Because:

• Not all CMSs are OCPI-enabled, so some popular networks cannot be accessed via OCPI. Relay lets you leverage these networks.
• OCPI partnerships are selective. Even OCPI-enabled CMSs may not connect with all others.
• Relay ensures you can still connect directly to any CMS, maximizing your charger’s presence.

Yes. The Relay dashboard allows you to:

• Monitor charger connectivity and health.
• Track CMS connection status.
• Analyze utilization across CMSs.
• View which CMS is driving the most traffic to your charger.

Not necessarily.

• If the CMS uses a subscription model and the subscription fee isn’t covered by the profit generated, you can choose to disassociate.
• If the CMS uses a transaction-based model, there’s no upfront cost. Even if the utilization is low, any revenue you earn is pure profit, so disassociating is not required.

Yes. You can pause or disable CMS connections without disconnecting the charger or affecting others.

EV users can start charging through a mobile app in two common ways:

• QR Code Scan – Users scan the QR code displayed on the charger (or one pasted around the charger) to view charger details and start the session.
• App Selection – Users select the charger from the map or list view and press Start Charging to initiate the session.

When a charger is connected to multiple CMSs, the QR code on the charger might belong to one CMS provider’s format. If another CMS’s app scans that QR, it may not recognize it.

To solve this, it’s best to display multiple QR codes (one per CMS) on or near the charger — each with the respective CMS’s branding or color theme.

For RFID-based sessions, there’s no change in user experience.

As long as the RFID card or tag is authorized by the CMS handling that specific session, the charging process works seamlessly — just as it normally would.

It may or may not be different. Even though a charger is connected to multiple CMS platforms, the charger owner remains the same.

We recommend that the charger owner maintain consistent pricing across all CMSs to avoid confusion among EV users and ensure a uniform experience across apps.

No. A charging session must be started and stopped from the same CMS app that initiated it.

Each CMS manages its own session authentication and control. Since CMS platforms are not aware of one another’s sessions, cross-app session control is not possible.

Users can view their session history only in the CMS app where the session was initiated. Relay enables multi-CMS connectivity at the charger level but does not synchronize user accounts or session data across different platforms. Since each CMS operates independently and is not aware of the others, cross-app session visibility or control is not possible.

Yes. Generic charger information such as availability, status, and health is broadcast to all connected CMSs. This ensures that users across different apps always see up-to-date charger status.

No. Only one charging session can be active per connector at any given time.

Once a session has started, all other apps will show the connector as in use until it becomes available again.

If multiple CMSs or apps send Start Charging requests for the same charger simultaneously, the charger will accept only the first valid request and reject all subsequent ones.

This first-come, first-serve rule applies across different CMSs as well as within the same app.

Possibly, yes. The same physical charger may appear in multiple apps if those apps are connected to different CMSs that list the same charger. This is expected — and actually the purpose of Relay — to enable the same charger to be visible and accessible through multiple CMS networks simultaneously.

No. OCPP reservation does not work reliably in a multi-CMS setup.

OCPP reservation operates at the charger level and is designed for a single controlling CMS. It is not a slot-based or time-booking feature. When one CMS creates a reservation, the charger enforces it locally, but other CMS platforms are not aware of this reservation.

As a result, users coming from another CMS may see the charger as available in the app but find it reserved when they reach the site, leading to a poor user experience.

No. CMS-based reservation is typically implemented as slot or time-based booking within a single CMS. When a charger is connected to multiple CMS platforms:

• A booking created in one CMS is not visible to others
• Other CMS platforms may allow users to book or navigate to the same charger for the same time slot

This again results in double bookings and user confusion.