LetEl EV Charging Platform: Custom Charger Development, Mobile Apps and Multi-Vendor Management

Finding a charger is only the beginning of an electric vehicle charging journey. Drivers also need to know whether it is available, what it costs, how to reserve it and whether charging actually started after they tapped the button.

Adequate Infosoft developed the LetEl solution for SoftControl around these connected requirements. The project combined React Native mobile applications, an ASP.NET Core backend, PostgreSQL and Microsoft Azure with vendor management and custom charger development.

Drivers can figure out where to charge, book supported stations, start and finish sessions, pay for charging and receive billing invoices. Vendors can sign up to the offered service, manage locations and prices on charging offered at available parking.

The information in this account has been based on project information provided by development and publicly available LetEl data. The MCU, protocol versions and some Azure services discussed below are just suggestions in the absence of the deployment records.

A shared charging service has three different views of the same event. The driver sees a booking and a price. The owner sees a parking space, electricity consumption and revenue. The charger sees a cable connection, electrical conditions and permission to supply energy.

LetEl needed to connect these views without treating them as interchangeable. A booking does not prove a vehicle has arrived. A successful payment does not prove electricity is flowing. A charger appearing online does not necessarily mean its connector is available.

The project therefore extended beyond a map application into a complete charging and commercial management workflow.

The React Native app provides a common mobile codebase for Android and iOS. Drivers may locate charging stations, check their locations and identify the available stations from the busy ones owing to green and red indicators.

For the purpose of accessible design, text explaining the status should be provided wherever colour is used. Special treatment should be provided to unknown, offline and faulty connectors instead of showing them as available which is only due to the absence of a session.

Drivers can select a supported station, review its energy and parking prices, reserve it and navigate to the location. LetEl's public description confirms reservations, owner-defined tariffs and parking charges associated with the booking period.

A reliable reservation workflow must prevent overlapping bookings and explain cancellation, expiry and arrival conditions. A reservation also needs to identify the relevant charging connector, not merely the address of a site containing several chargers.

Once reaching the desired destination, the operator of the car initiates the charging process via his or her mobile device. The system registers this particular transaction from the user's side, booking and a specific charging solution. While the charging process is on-going, the driver of the car can monitor how much energy and money has been consumed during the service.

At the end of the process, the driver has to enter the command to stop the session, wait for it to be completed by the hardware, and remove the plug of the charging system from the car, having received final instructions from the charging point.

The engineering distinction is between requesting an action and confirming its execution. The interface should show "starting" until charger feedback confirms charging, and "stopping" until completion is acknowledged. A delayed network response must not encourage repeated payments or duplicate sessions.

Parking charges may continue under the disclosed tariff even after energy delivery ends; those timelines need separate handling.

The vendor part of the application allows several managers to register and run their charging enterprises on the platform.

Vendors are allowed to enter the location of the stations, place markers on the map, set up the availability of the stations, prices for electricity and parking as well as discounts. Vendors can also check the payments made for their stations.

This allows for different models of operation from one individual trying to provide appropriate parking space solutions to companies controlling several charging points.

The project brief's "station pin" is treated here as a map location. If a charger also uses a private activation PIN, that credential needs a separate protected workflow.

Tenant isolation is essential: one vendor must not gain access to another vendor's customers, pricing or financial records. Permissions must be enforced by backend checks, not simply by hiding screens in the portal.

ASP.NET Core supplies the backend of the application, while PostgreSQL serves as the repository for business information. The key information model is formed by the connections between users, providers, locations, chargers, plugs, bookings, charge activities, tariffs, transactions invoicing.

In this information model, significance is associated with transactional and uniqueness mechanisms, which will allow avoiding a situation in which there will be conflicts between reservations and repeating of transactions.

It is critical to ensure keeping the versions of tariffs. This avoids a situation in which a new price of a vendor would interfere with the conditions of the already done bookings.

Charging records also need stable identifiers across the mobile app, charger connection and payment provider. These references help support teams investigate an interrupted session without relying on screenshots or matching records by approximate time.

Recommended background processing includes reservation expiry, session reconciliation and invoice generation, with retry rules that preserve transaction identity.

Drivers can add or remove supported payment methods, pay for charging and retrieve invoices. Vendors can review the corresponding payment activity. SoftControl's public LetEl material identifies MobilePay and card payments as supported options.

The financial design should distinguish payment authorisation, capture, refund and vendor settlement. Seeing a payment in a dashboard does not necessarily mean the vendor has received a payout.

Saved payment methods should use provider-issued tokens rather than raw card details. Server-side payment confirmation should determine financial status, while repeated callbacks must not generate duplicate invoices.

An invoice should explain energy consumption, applicable parking time, discounts, taxes and the final amount. Removing a saved payment method must not erase records required for accounting or dispute resolution.

The cloud environment of this solution is hosted by Microsoft Azure. An appropriate service layout can place ASP.NET Core application on either Azure App Service or Containers Apps with the relational storage taken care of by Azure Database for PostgreSQL.

Options for asynchronous tasks include Azure Service Bus, Azure Key Vault for storing secrets, Azure Blob Storage for documents, and Application Insights for operational monitoring. Note that the services mentioned above are simply recommendations but not a comprehensive list of LetEl's resources in use.

Capacity planning should consider persistent charger connections, telemetry volume and peak booking activity separately. Database backups, restore testing and controlled releases remain necessary regardless of the selected hosting service.

The project's scope includes a personalized charger that vendors can buy and utilize to set up charging sites for specific purposes. The publicly available LetEl material also talks about stationary CleverHouse charging devices, but the controlling MCU is not revealed.

A suitable candidate for an AC charging controller that needs to connect with the network and expand is the STM32H753ZI.

ST describes it as running a Cortex-M7 microprocessor working at a speed of 480 MHz, along with 2MB Flash and 1MB RAM capability, Ethernet MAC, CAN FD, and hardware acceleration features.

These capabilities make it worth evaluating for charging-state control, metering interfaces, connectivity and authenticated updates. It is not universally the best or lowest-cost option; selection depends on firmware size, interfaces, thermal constraints and production cost.

An Ethernet PHY and any Wi-Fi or cellular connectivity would require additional hardware. This recommendation must not be presented as the MCU actually shipped in LetEl without checking the production bill of materials.

The plan for controller design would clearly differentiate low voltage logic from circuitry related to the mains. It would also include suitable interfaces for various purposes, including control-pilot signalling, locking of connectors, receiving feedback from the contactor, as well as sensing temperature and using an approved energy meter.

The firmware would be written in C/C++ along with RTOS such that both time-critical charging control and network communication would be segregated. Local protective action can be taken without relying on the cloud being available.

The design requires qualified electrical engineering, suitable protective devices, EMC assessment and applicable conformity testing. An MCU recommendation is not evidence of charger certification.

Turning a parking space into a charging location also requires permission, adequate electrical capacity, professional installation and a commissioned connection to the platform.

For new charger development, OCPP 2.0.1 over secure WebSockets is a sensible charger-to-management-system target. Legacy equipment may require OCPP 1.6-J support. The versions are not directly compatible, so interoperability needs explicit implementation and testing.

Vehicle-side AC charging control is a different responsibility from OCPP. Likewise, a local meter may use Modbus RTU over RS-485, while the mobile app communicates with backend services over HTTPS.

These are recommended architecture choices; the project's deployed protocol versions require confirmation. Implementing OCPP alone does not establish ISO 15118 Plug & Charge support, which involves additional vehicle communication and credential infrastructure.

SoftControl explicitly associates LetEl chargers with Hubject roaming. It should be described as a roaming platform connecting operators, not as one company owning every charger displayed in the app.

Hubject publishes the Open InterCharge Protocol, or OICP. Its documentation is the relevant starting point for assessing a direct integration; the project's actual connector and version still require confirmation.

External station discovery and the ability to start or pay for a session are separate capabilities. Each depends on data access, commercial agreements and supported operations. The app should not promise LetEl-style reservations at every roaming location.

The acceptance testing should involve testing the overlapping reservation process, checking for the (non)availability of the charging stations, testing the disconnections, preventing the double charge notifications, testing whether or not the stop requests are filled up, look for the presence of changes in pricing policies, and complete vendor access limits check.

With respect to the above, please note that this is only to suggest different test scenarios available, not to say that one has obtained information on a specific test report.

The description of the proposed project includes the applications for drivers, vendor management, payment, and charging machines. The provided listing of LetEl's applications allows discovering the stations and making payments.

The project illustrates Adequate Infosoft's work across mobile software, backend development and connected charging systems. Its value is the joined-up workflow: drivers can manage charging, while owners can configure and operate participating locations. No unverified revenue, uptime or charging-volume figures are claimed.

LetEl, the EV charging platform is a genuine production system in operation for over five years. The platform integrates mobile applications, backend services, connected EV chargers, payment processing, reservation functions, and the vendor management process into a complete EV charging system.

Take a look at the functioning LetEl platform as a case study of our success in the EV charging platform development.