Why EV Charging at Fleet Depots Is a Scheduling Problem, Not Just an Infrastructure Problem

O P E R AT I N G F R A M E WO R K · D E P OT P OW E R FLEET DEPOT CHARGING IS A SCHEDULING PROBLEM Why clocks beat charger count Core constraint Departure clock & SoC deficit Grid limit 15-minute sanctioned demand Economics Demand charges + capex rightsizing Execution OCPP sequencing over raw kW Departure schedules, missing battery energy, sanctioned grid headroom, and tariff bands dictate depot success—not physical dispenser count. D E P OT P R OTO C O L DOC-FDC-01 01 Gate-out timetable & route energy target 02 Sanctioned grid connection & 15-min limits 03 OCPP automated contention priority 04 Simultaneous plug-in failure point 05 Time-of-day tariff window optimization

S E C T I O N 0 1 · O P E R AT I O N A L V U L N E R A B I L I T Y PBK-SIM-02 The failure starts when every vehicle plugs in together A depot can hold ample overnight kWh yet still fail morning dispatch when uncoordinated starts trip peak demand limits. T H E U N M A N AG E D T R A P Drivers return between 18:00 and 19:30 and plug in immediately. Unthrottled draw creates an artificial spike that collides directly with evening DISCOM limits. D I S PATC H C O L L A P S E ▪ Feeders trip on sanctioned overload. ▪ Chargers throttle down unpredictably. ▪ Priority delivery routes wake undercharged at 06:00. SCHEDULED SEQUENCE (MANAGED) Coordinated profile SIMULTANEOUS SPIKE (UNMANAGED) Peak collision risk 1. LOG RETURN · Record arrival SoC and required gate-out time. 19:00 OVERLOAD · All vehicles draw maximum gun rating at once. 2. CALCULATE · Allocate kWh based on battery deficit, not cable speed. DEMAND PENALTIES · Exceeds 15-minute sanctioned kVA ceiling. 3. STAGGER · Queue heavy charge cycles into late-night tariff valley. PREMATURE CUTOFF · Thermal limits choke charge currents. 4. PRE-HEAT / READY · Top off to 100% just before morning rollout. 06:00 SHORTFALL · Cold batteries sit at 45% SoC at gate- out. E X E C U T I V E D E C I S I O N PAC K · C O N F I D E N T I A L 0 2

F L E E T D I S PATC H P O L I C Y PBK-PUB-03 Public charging is a backup, not the overnight plan Public and captive charging networks have expanded, but uptime, physical queue times, and connector availability remain highly volatile. Return-to-base commercial fleets must control their own depot plug, electricity tariff, and dispatch clock. OPERATING REALITY The depot ʼ s allowed draw in each 15-minute period is a hard operational boundary, not a billing footnote. Exceeding it triggers severe demand ratchet penalties. PUBLIC NETWORK DEFICITS ▪ No reserved turnaround guarantees. ▪ Commercial rate markups erode margin. ▪ Driver downtime waiting in urban queues. RULE: Treat external charging strictly as a route-contingency tool for unplanned detours, never as the baseline fleet replenishment plan. E X E C U T I V E D E C I S I O N PAC K · C O N F I D E N T I A L 0 3

G R I D CA PA B I L I T Y V S E X E C U T I O N PBK-INF-04 Infrastructure constraints are real, but they don’t solve the queue Transformers, feeders, land footprint, and software silos all bind the depot. Specifying oversized kW does not eliminate queueing. T H E OV E R B U I L D FA L L AC Y Buying larger transformers and high-power DC guns incurs steep capital costs without guaranteeing ready vehicles at gate-out. CONTROL NEED: Intelligent orchestration beats raw connection sizing every time. 01 Grid Feeder Substation allocation limits 02 Transformer kVA thermal step-down cap 03 Demand Charge 15-minute peak billing spike 04 Software Silos Telematics decoupled from BMS Physical & Site Limitations Trenching runs, switchgear clearance, and vehicle parking geometry restrict how many high-power dispensers can physically activate simultaneously. Algorithmic Orchestration A dynamic scheduler throttles charging guns dynamically across dwell windows to match the transformer ceiling while fully servicing every battery. E X E C U T I V E D E C I S I O N PAC K · C O N F I D E N T I A L 0 4

O P E R AT I N G F O R M U L A Five Variables Define Every Session: ▪ Required departure SoC ▪ Energy deficit + 15% margin ▪ Latest acceptable start ▪ Contention priority level ▪ Off-peak tariff alignment S E C T I O N 0 3 · D I S PATC H M E T H O D O LO GY PBK-DSP-05 Work backward from gate-out Charging must be designed as an orderly queue governed by departure deadlines rather than an immediate plug-in event. 1. Gate-Out Time Anchor to the delivery shift departure clock. 2. Required kWh Calculate missing pack energy plus buffer. 3. Dwell Window Map available hours from arrival to gate- out. 4. Tariff Match Fit charge profile into cheapest night valley. Q U E U E E N F O R C E M E N T When grid headroom is constrained, vehicles with earlier dispatch times or larger deficits preempt long-dwell, high-SoC arrivals automatically. E X E C U T I V E D E C I S I O N PAC K · C O N F I D E N T I A L 0 5

D E M A N D F L AT T E N I N G & G R I D I N T E G R AT I O N PBK-STG-06 One connection can serve more vehicles when starts are staggered Sanctioned Limit (kW) Staggered Schedule (… Unmanaged Demand… 18:00 20:00 22:00 00:00 02:00 04:00 06:00 Hour 0 100 200 Staggering cuts peak demand by ~58%, keeping charging under the 80 kW sanctioned grid cap while delivering 100% target SoC. TA R I F F T I M I N G Sequence into the valley Use Telangana ʼ s tariff shape as an operational input, not an afterthought. Shifting charging into off- peak night hours avoids solar sunset peaks and unlocks low night energy rates. CA PAC I T Y M U LT I P L I E R A fixed 250 kVA transformer serves 18 unmanaged vehicles or 42 sequenced vehicles without upgrading high-voltage grid lines. E X E C U T I V E D E C I S I O N PAC K · C O N F I D E N T I A L 0 6

H A R DWA R E A R C H I T E C T U R E · F L E E T I N F R AS T R U C T U R E Build the smallest hardware mix that can meet the timetable O P T I M A L C H A R G E R P O R T F O L I O 01 AC 7.4 kW – 22 kW: Use for 8–10 hour overnight dwell vehicles. Lowest capex per gun, minimal thermal stress. 02 DC 30 kW – 60 kW: Dedicated to short midday turns and priority catch-up before gate-out. 03 OCPP 1.6J / 2.0.1: Mandatory smart connectivity to enforce dynamic current limiting and priority shedding. C O M P L I A N C E & SA F E T Y Electrical design strictly follows CEA safety practice and standards. Certified switchgear, proper earthing, and site load studies remain non- negotiable. CEA COMPLIANT R U L E Size the sanctioned grid load to the sequenced timetable peak, never to the sum of every charger gun at maximum output. E X E C U T I V E D E C I S I O N PAC K · C O N F I D E N T I A L 07

F I N A N C I A L R E P E R C U S S I O N S · CA P E X & O P E X PBK-FIN-08 The schedule changes both capex and monthly opex Sequencing shrinks upfront transformer requirements and slashes ongoing 15-minute demand charges month after month. DEPOT SCALE CAPEX BAND INFRASTRUCTURE DRIVER SCHEDULING SAVINGS Small Yard 5–15 3W / light vans Tens of Lakhs LT connection, AC smart wallboxes, sub-metering Avoids demand contract escalation Medium Hub 20–60 delivery vans High Tens of Lakhs to >1 Crore Dedicated DTR step-down transformer required Downsizes transformer size (e.g. 500 to 250 kVA) Heavy Depot 50+ e-buses / trucks Multiple Crores HT yard, multi-MW switchgear, high-power DC guns Mitigates peak kVA demand ratchet penalty S TO R AG E AS A P E A K M A N AG E M E N T L E V E R Integrate India Energy Storage Alliance context when evaluating BESS to shave top 15-minute spikes, deferring costly transformer upgrades. O P E X I M PAC T Demand charges can represent 30–50% of an unmanaged electric fleet ʼ s monthly utility bill. E X E C U T I V E D E C I S I O N PAC K · C O N F I D E N T I A L 0 8

S E C T I O N 0 5 · R E G U L ATO RY C O M P L I A N C E PBK-REG-09 Use the rule book, then do the site work De-licensing does not remove DISCOM load sanctioning, CEA safety mandates, or electrical inspection rules. REGULATORY AUTHORITY MANDATE & OPERATING BOUNDARY DEPOT ACTION Ministry of Power (2024) The 2024 charging-infrastructure guidelines de- license charging, cap service fees, and govern open access rules. Establish legal framework for captive fleet charging. Local DISCOM Sanctioned load contract, HT/LT metering, 15-minute billing window, and TOD tariff enforcement. Submit detailed load profile based on staged charging. CEA Safety Regulations Mandates ground fault protection, breaker coordination, fire suppression, and emergency disconnects. Conduct pre-commissioning site electrical inspection. BEE & BIS Standards Use BEE ʼ s certified-equipment context for tested hardware reliability and protocol interoperability. Deploy certified chargers to prevent field failures. PREREQUISITE: Always execute a complete site electrical study before issuing purchase orders for charging hardware. E X E C U T I V E D E C I S I O N PAC K · C O N F I D E N T I A L 0 9

S E C T I O N 0 6 · I M P L E M E N TAT I O N P L AY B O O K Make the timetable the first design decision Hardware sizing succeeds only when built around vehicle return windows, gate-out SoC, and grid limits. 01 Map Shift Windows: Pin exact vehicle return times, battery deficits, and departure deadlines. 02 Size to Sequenced Peak: Procure the minimum AC/DC mix that meets rollout without exceeding grid caps. 03 Layer Solar & Storage: Use renewables and BESS to eliminate residual tariff spikes, not to invent time. For turnkey engineering and commissioning support, consult Spider Energy ʼ s EPC services . Maintain external public charging as a documented contingency. E X E C U T I V E D E C I S I O N PAC K · C O N F I D E N T I A L 1 0