Fuel and charging look like the same operational problem from the outside. Both drain your vehicles, both require someone to act before the next rental, and both carry fraud risk. In practice, they are different enough that mixing them up in your planning will cost you time and money. The logistics, payment models, and failure modes are each their own discipline.
In this lesson, we'll cover how refueling actually works in practice, including who does it, how customers are reimbursed, and how the transaction is handled. We'll also look at the two EV charging models used in car sharing, and how to defend against charging fraud, the fastest-growing operational risk in electric fleets.
Who Refuels, and When?
In the overwhelming majority of car sharing operations, refueling is the customer's responsibility. Not on every trip, which would be unworkable, but through a minimum threshold rule: the vehicle must be returned above a defined fuel level.
The Minimum Threshold
For station-based services, a common threshold sits around 25%. For free-floating, where most trips are short urban hops, the threshold is often lower, around 10%. In free-floating especially, many customers complete their trips without the tank dropping anywhere near the threshold. They are not expected to refuel, and in practice most do not need to.
Incentivizing the Customer
Operators do not just set a rule. They make refueling worth the customer's time. A common mechanism is a voucher automatically issued at the end of the rental, calculated on the fuel percentage added during the trip. A customer who picks up a car at 30% and returns it at 70% receives a credit proportional to that difference.
The voucher rewards the behavior and reimburses the customer for time spent at the pump. It also naturally aligns customer interests with operator needs. The customer is effectively providing a service and is compensated for it.
Paying for the Refuel
The operator covers the cost of fuel. The customer fills the tank on the operator's account, using one of two payment models.
Fuel Card in the Glovebox
The most widespread model is a physical fuel card kept in the vehicle. The customer uses it at the pump, and the transaction is charged to the operator's account. This approach works because a significant part of fueling infrastructure still does not support app-based payment, and in many markets it remains the simplest solution to deploy.
The main drawback is fraud exposure. Physical cards can be skimmed, stolen, or shared. Without authentication tied to the active rental, misuse is difficult to detect and even harder to prove after the fact.
App-Based Payment Partnerships
A growing number of operators use app-based or in-car payment systems through partnerships with fuel payment networks. The customer initiates the refueling through the app, selects the pump, and the transaction is handled automatically, sometimes without the customer entering the gas station at all. Authentication is tied to the active rental, which significantly narrows the fraud surface.
The operator receives digital receipts and automatic accounting. For the customer, the experience is noticeably smoother than handling a physical card.
EV Charging: One Model Per Fleet
Most car sharing fleets run one primary charging model, and that model follows directly from the service type. Mixing approaches introduces complexity without a clear operational benefit.
Station-Based: Charge at the Hub
In station-based car sharing, the station is the charger. Vehicles are plugged in between rentals, and the next customer picks up a car at or near full charge. When the customer returns, they plug the car back in. One rule is non-negotiable: the rental cannot end until charging has actually started, not just until the cable is connected, but until the session is confirmed active. A car left connected but not charging leaves the next customer with an unexpected shortfall.
"A car with an empty battery is not the reliable mobility we are committed to offer."
Paul Kreiner
Product Manager / Electrification Strategy Lead | cambio
Source: Insights Interview on Station-Based Car Sharing with cambio
For longer trips that take the vehicle outside the station network, a charging card in the car gives customers access to public chargers along the way.
Free-Floating: Public Chargers
In free-floating, there is no dedicated charging spot. Cars get charged by customers who plug in at public chargers in exchange for credits or vouchers, and operator staff who move cars to chargers, often overnight when demand is lowest and logistics are simpler.
One constraint shapes everything here. Many public chargers bill significant fees once a vehicle finishes charging but remains connected. Cars need to be moved promptly, which is why overnight operator-driven charging is common. Staff can manage pickup timing in a way that customers cannot reliably do on their own.
Source: Insights Interview on Free-Floating Car Sharing in Emilia-Romagna
Source: Insights Interview on Free-Floating Car Sharing in Bulgaria & Lithuania
Charging Cards and the Fraud Problem
The standard payment method for EV charging in car sharing is an RFID charge card, one per vehicle, kept in the car. The customer taps it at the charger to start a session, and the operator is billed through a roaming network. The operator holds the contract with the charging service provider, not the individual customer.
This arrangement works until someone uses the card for something other than the rental vehicle. Charging fraud is significantly worse than fuel fraud. It is harder to detect, easier to execute at scale, and more valuable to attack as EV adoption grows. These are the three most common vectors:
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A customer books a vehicle, takes the charge card, and uses it to charge their own private car or a friend's.
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A more sophisticated version involves physically cloning the card and selling copies promising free charging.
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The simplest version is card sharing, where a customer passes the card to people outside the rental.
Building a Layered Defense
No single measure closes all the gaps. Fraud prevention for EV charging is a stacking problem. Each layer blocks different attack vectors and raises the overall cost of misuse.
Match Card Location to Vehicle Location
Telematics data gives the operator a live view of where each vehicle is. If a charging session is billed at a location that does not match the vehicle's current position, that is a strong fraud signal. This verification is not possible without real-time location data from the vehicle.
Verify the Charging Port Status
The vehicle's onboard system reports whether a cable is connected and whether a charging session is actually in progress. A billed session with no cable plugged in is a clear indicator of misuse. This check requires the vehicle to report port status in real time, which is another function of the telematics layer.
Two-Factor Authentication
Pairing the physical RFID card with an in-app confirmation step means that a stolen or cloned card cannot start a session without access to the associated app account. It closes the most common attack vectors without adding significant friction for legitimate users.
Real-Time Session Monitoring
Continuous monitoring across sessions flags suspicious behavior such as unusually large sessions, charging at locations far from the vehicle, or patterns that match known fraud profiles. High-confidence fraud sessions can be stopped mid-session, limiting damage before it accumulates.
Credit Limits and Pre-Authorization
Capping the maximum charge per session limits the damage from any successful attack. Limits can be raised gradually as the driver's identity is verified over time, similar to how digital banking calibrates trust based on account history.
The data running through all of these layers (charge level, vehicle location, port status) feeds into fleet health monitoring and alerting. None of it works without the telematics infrastructure that makes each data point visible in real time.
Key Takeaways
Who is responsible for refueling in car sharing?
Usually the customer refuels, not the operator, while the operator pays for it. Most services set a minimum fuel threshold the vehicle must be returned above, typically around 25% for station-based and 10% for free-floating.
How do operators encourage customers to refuel?
Through automatic vouchers issued at the end of the rental, calculated on the fuel percentage added during the trip. The customer is reimbursed for their time and the operator avoids a more expensive operational task.
What is the difference between station-based and free-floating EV charging?
Station-based fleets charge at the hub between rentals. Free-floating fleets rely on public chargers, combining customer incentives with operator-driven overnight charging to keep vehicles available.
Why is charging fraud worse than fuel fraud?
RFID charge cards are easier to clone than fuel cards, harder to authenticate, and more valuable to misuse as EV fleets grow. Without telematics data, the main vectors (private vehicle charging, card cloning, card sharing) are nearly invisible to operators.
What is the most effective way to prevent charging fraud?
Layer multiple defenses. The strongest setups combine telematics-based location and port-status verification with two-factor card authentication, real-time session monitoring, and credit limits per session.
What happens if a customer does not plug in after returning a station-based vehicle?
The next customer picks up an undercharged vehicle. Operators prevent this by configuring the platform to block rental completion until an active charging session is confirmed, not just a connected cable.