Module 4: Attendant Training (Battery Swap)¶

Audience: Station Attendants Prerequisite: Module 1 (Getting Started)

Learning Objectives¶

By the end of this module, trainees will be able to:

Log in with employee credentials
Complete the full 6-step battery swap flow
Identify customers by scanning subscription QR codes
Scan and read batteries via Bluetooth (ATT and DTA services)
Understand the cost calculation formula
Collect payment when required
Generate and review swap receipts

Flow Diagram¶

The complete 6-step Attendant Battery Swap workflow:

flowchart TD
    A[Open OvApp] --> B[Select Attendant Role]
    B --> C[Login with Employee Credentials]
    C --> D[Attendant Dashboard]

    D --> S1["Step 1: Customer Identification"]
    S1 --> S1a{Scan QR or Enter ID}
    S1a -->|Scan QR Code| S1b[Camera Scans Customer QR]
    S1a -->|Manual Entry| S1c[Type Subscription ID]
    S1b --> S1d[Customer Details Retrieved<br>Name, Plan, Quota, Rate]
    S1c --> S1d

    S1d --> S2["Step 2: Return Old Battery"]
    S2 --> S2a[Scan Old Battery QR Code]
    S2a --> S2b[BLE Connects to Battery]
    S2b --> S2c["Read ATT Service → Battery ID"]
    S2c --> S2d["Read DTA Service → Remaining Energy (kWh)"]
    S2d --> S2e[Old Battery Recorded]

    S2e --> S3["Step 3: New Battery Assignment"]
    S3 --> S3a[Scan New Battery QR Code]
    S3a --> S3b[BLE Connects to Battery]
    S3b --> S3c[Read ATT → Battery ID]
    S3c --> S3d[Read DTA → Energy Level]
    S3d --> S3e["Calculate Cost:<br>energy_diff = new - old<br>net = diff - quota<br>cost = net × rate"]

    S3e --> S4["Step 4: Review"]
    S4 --> S4a{Quota Covers Cost?}
    S4a -->|Yes| S6["Step 6: Done"]
    S4a -->|No| S5["Step 5: Payment"]

    S5 --> S5a[Collect Payment]
    S5a --> S5b{Payment Method}
    S5b -->|QR Scan| S5c[Scan Payment QR]
    S5b -->|Manual| S5d[Enter Receipt Code]
    S5c --> S5e[Payment Confirmed via MQTT]
    S5d --> S5e

    S5e --> S6
    S6 --> S6a["Receipt Generated:<br>Subscription, Batteries, Energy,<br>Amount, Timestamp"]
    S6a --> S6b[Hand New Battery to Customer]
    S6b --> S6c[Tap New Swap → Return to Step 1]

    style A fill:#4CAF50,color:#fff
    style S1 fill:#2196F3,color:#fff
    style S2 fill:#2196F3,color:#fff
    style S3 fill:#2196F3,color:#fff
    style S4 fill:#2196F3,color:#fff
    style S5 fill:#FF9800,color:#fff
    style S6 fill:#4CAF50,color:#fff

Visual Reference¶

Attendant Dashboard & Swap Start¶

Dashboard	Start Swap

Main attendant dashboard after login	Beginning the swap process

Customer Identification¶

Customer Identification

Scanning the customer's subscription QR code to retrieve their details.

Key Points¶

Attendants log in with employee credentials (username and password)
The swap flow has 6 steps: Customer > Return > New > Review > Pay > Done
A progress indicator at the top shows the current step

Hands-On Exercise¶

Open OvApp and select the Attendant role
Log in with your employee credentials
Observe the 6-step progress bar at the top

Lesson 4.2 -- Step 1: Customer Identification (10 min)¶

Key Points¶

Identify the customer by scanning their subscription QR code (primary) or entering the subscription ID manually (fallback)
The app retrieves from the backend: customer name, subscription plan, energy quota remaining, swap count, and rate per kWh

Hands-On Exercise¶

Ask the customer to show their QR code
Scan it using the in-app camera
Verify the customer details shown on screen (name, plan, quota)
Try the manual entry method: tap Enter ID and type a subscription ID

Common Issues¶

Issue	Solution
QR code won't scan	Clean the screen; try manual entry
Customer not found	Verify the subscription ID with the customer
Camera permission denied	Enable camera access in device settings

Lesson 4.3 -- Step 2: Return Old Battery (10 min)¶

Key Points¶

Scan the QR code on the customer's old (depleted) battery
The app connects via Bluetooth and reads:
- ATT service -- battery ID
- DTA service -- remaining energy (kWh)
The old battery's ID and energy are recorded

Hands-On Exercise¶

Scan the QR code on the demo battery
Wait for the Bluetooth connection to establish
Verify the battery ID and remaining energy are displayed
Confirm the reading

Common Issues¶

Issue	Solution
BLE connection fails	Ensure Bluetooth is on; move closer to the battery
Energy reading times out	Retry; re-scan the battery if needed

Lesson 4.4 -- Step 3: New Battery Assignment (10 min)¶

Key Points¶

Same process as Step 2 but for the fresh replacement battery
The app reads the new battery's ID and energy level
Cost is calculated automatically:

energy_difference = floor(new_energy - old_energy, 2)
net_energy        = energy_difference - quota_remaining
cost              = net_energy x rate_per_kWh

If quota covers the full cost, payment is skipped

Hands-On Exercise¶

Scan the QR code on the new (charged) battery
Wait for BLE connection and energy reading
Observe the calculated energy difference and cost
Note whether the customer's quota covers the cost

Lesson 4.5 -- Steps 4-6: Review, Pay, Done (10 min)¶

Key Points¶

Step 4 -- Review:

Full breakdown: old/new battery IDs, energies, energy difference, gross cost, quota credit, net amount due
If quota covers full cost: skip to Done

Step 5 -- Payment:

Collect payment via QR scan or manual receipt entry
Payment and service events are reported to the backend via MQTT

Step 6 -- Done:

Receipt shows: subscription ID, returned battery, issued battery, energy difference, amount due, amount paid, timestamp
Hand the new battery to the customer
Tap New Swap to start the next transaction

Hands-On Exercise¶

Review the swap summary -- verify all details are correct
If payment is needed: scan the payment QR or enter the receipt code
Review the final receipt
Tap New Swap to return to Step 1

Use Cases¶

Use Case 1: Standard Battery Swap (Payment Required)

Scenario: A rider arrives at the station with a depleted battery. Their energy quota is exhausted, so payment is required.

Steps:

Attendant scans the rider's subscription QR code → customer details load
Scans the old battery QR → BLE reads ATT (ID) and DTA (0.3 kWh remaining)
Scans the new battery QR → BLE reads ATT (ID) and DTA (1.8 kWh)
App calculates: energy difference = 1.50 kWh, quota = 0, cost = 1.50 × rate
Review screen shows breakdown → attendant confirms
Rider pays → attendant scans QR or enters receipt
Done screen shows receipt → attendant hands over the new battery

Expected Outcome: Swap is recorded, payment is confirmed, and both battery events are reported via MQTT.

Use Case 2: Swap Covered by Quota (No Payment)

Scenario: A rider has enough quota remaining to cover the full energy cost.

Steps:

Attendant scans rider's QR → quota shows 2.0 kWh remaining
Scans old battery → 0.2 kWh remaining
Scans new battery → 1.5 kWh
Energy difference = 1.30 kWh; quota = 2.0 kWh → fully covered
Review screen shows cost = 0 → Payment step is skipped
Done screen shows receipt → hand over battery

Expected Outcome: No payment is collected. Quota is debited and the swap completes.

Use Case 3: QR Scan Fails -- Manual Fallback

Scenario: The rider's phone screen is cracked and the QR code won't scan.

Steps:

Attendant attempts to scan QR → fails repeatedly
Taps Enter ID and asks the rider for their subscription ID
Types the ID manually → customer details load
Proceeds with the normal swap flow

Expected Outcome: The swap proceeds normally using manual ID entry as a fallback.

Use Case 4: Bluetooth Disconnects During Battery Read

Scenario: While reading the old battery, the Bluetooth connection drops.

Steps:

Attendant scans the old battery QR → BLE starts connecting
Connection drops mid-read (battery moved out of range)
Attendant moves the battery closer to the phone
Re-scans the QR code → BLE reconnects
ATT and DTA readings complete successfully

Expected Outcome: After reconnection, the battery read finishes and the swap continues from where it left off.

Knowledge Check¶

What are the 6 steps of the battery swap flow?
What two BLE services does the app read from a battery?
How is the swap cost calculated?
What happens if the customer's quota covers the full cost?
How is payment collected?
What gets reported to the backend via MQTT?
What should you do if the Bluetooth connection drops during a battery read?

Assessment Rubric -- Module 4¶

Criteria	Expert (4)	Competent (3)	Developing (2)	Novice (1)
Customer Identification	Scans QR and uses manual fallback; explains what data is retrieved	Scans QR and verifies customer details	Scans QR but doesn't verify details	Cannot scan QR or enter ID manually
Battery Scanning (Return)	Scans, reads ATT/DTA, explains both services, handles BLE errors	Scans and reads battery data successfully	Scans but needs help interpreting the readings	Cannot scan or connect to the battery
Battery Scanning (New) & Cost	Scans, reads data, explains cost formula, identifies quota coverage	Scans new battery and understands the cost shown	Scans but cannot explain how cost is calculated	Cannot complete the new battery scan
Review & Payment	Reviews all details, handles both payment methods, explains MQTT reporting	Reviews and collects payment successfully	Completes review but struggles with payment entry	Cannot navigate the review or payment screens
Full Swap Completion	Completes end-to-end swap under 5 minutes, handles edge cases	Completes full swap with minor hesitations	Completes swap with guidance at 1-2 steps	Cannot complete the swap without constant help
Knowledge Check	Answers all 7 questions correctly	Answers 5-6 correctly	Answers 3-4 correctly	Answers fewer than 3 correctly

Pass: Average score of 3.0 or above across all criteria.

Module 4: Attendant Training (Battery Swap)¶

Learning Objectives¶

Flow Diagram¶

Visual Reference¶

Attendant Dashboard & Swap Start¶

Customer Identification¶

Lesson 4.1 -- Login & Overview (5 min)¶

Key Points¶

Hands-On Exercise¶

Lesson 4.2 -- Step 1: Customer Identification (10 min)¶

Key Points¶

Hands-On Exercise¶

Common Issues¶

Lesson 4.3 -- Step 2: Return Old Battery (10 min)¶

Key Points¶

Hands-On Exercise¶

Common Issues¶

Lesson 4.4 -- Step 3: New Battery Assignment (10 min)¶

Key Points¶

Hands-On Exercise¶

Lesson 4.5 -- Steps 4-6: Review, Pay, Done (10 min)¶

Key Points¶

Hands-On Exercise¶

Use Cases¶

Knowledge Check¶

Assessment Rubric -- Module 4¶