Real Time Transaction Power Management

Introduction

If your application wants to manage the power available to the EV during a transaction, eDRV gives you a set of tools to do so easily in near real time.

Your application can read the power and current on an ongoing transaction in near real time (approximately 30 seconds) via Transaction metrics (available soon via Webhooks). Your application can then act intelligently to vary the power and current delivered to the EV in the transaction via the transactionpower API endpoint.

Use Cases

Some possible use cases for Transaction Power Management are:

  • Solar powered EV charging where the delivered power varies throughout the day due to weather
  • Battery assisted EV charging. If your application uses on site batteries, you may want to manage the delivered power to a bank of EVs depending on the battery state of charge
  • Utility Demand Response. If there is an upstream power congestion event, your application may want to manage the delivered power to chargestation(s) instantly.

Listening to Power / Amps delivered on a current Transaction

You can get the latest Power / Amps delivered in a transaction by calling the transactions API. Please see Get Transactions.

The latest current Power and Amps reported by the chargestation can be found in the meter readings embedded within the Transaction document.

"metrics": {
            "timeSpentCharging": 12955,
            "chargingStart": "2021-07-06T03:36:28.000Z",
            "wattHoursConsumed": 27180,
            "wattHours": 449150,
            "meterValue": [{
                "timestamp": "2021-07-06T12:47:58Z",
                "sampledValue": [{
                    "value": "31.1",
                    "context": "Sample.Periodic",
                    "format": "Raw",
                    "measurand": "Current.Import",
                    "phase": "L1-N",
                    "location": "Outlet",
                    "unit": "A"
                },{
                    "value": "6.80",
                    "context": "Sample.Periodic",
                    "format": "Raw",
                    "measurand": "Power.Active.Import",
                    "phase": "L1-N",
                    "location": "Outlet",
                    "unit": "kW"
                }]
            }]
        }

Set the Power/Amps delivered in a Transaction

Your application can alter the maximum power / amperes delivered in an ongoing Transaction. You can do this via eDRV's transactionpower endpoint

Example 1
The following example limits power to 3.7kW on this transaction.

{
  transaction: '5eafcdaf9e7760a2646be432',
    unit: 'power',
    limit: 3700
}

Example 2
The following example limits current to 26 Amperes on this transaction.

{
  transaction: '5eafcdaf9e7760a2646be432',
    unit: 'current',
    limit: 26
}

Expected Response
If the chargestation accepts the power limit request, the API call response should return an ID. Your application must store this ID, in case you want to cancel the power limits on this transaction.

{
  id : 19675644
}

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EV Response to a transactionpower command

The chargestation responds to a transactionpower command by changing the maximum current available to the EV via an (analog) Control Pilot signal. The EV's on board charging controller will take this new limit into account and adjust accordingly. The response time to a new command varies by EV OEM.

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On IDs

Currently eDRV does not keep a record of power / current limits imposed on a transaction. Your application must save this ID. Please note that power limits are only valid until the end of the transaction. You must send a new transactionpower command if you want to manage a new transaction.

Clear the Power Limits on a Transaction

If your application wants to remove the power / current limits on a transaction you can do so via the DELETE transactionpower endpoint.

{
    transaction: '5eafcdaf9e7760a2646be432',
    id : 19675644
}

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Do you need help with Smart Charging?

Do reach out to the eDRV team via chat or email for help for your specific Smart Charging use case.