diff --git a/lib/features/power/implementations/crelay/README.md b/lib/features/power/implementations/crelay/README.md
index be59e0e..c83aeac 100644
--- a/lib/features/power/implementations/crelay/README.md
+++ b/lib/features/power/implementations/crelay/README.md
@@ -5,10 +5,11 @@ This implementation is to be used when a relay is being used that is controlled
 
 ## Dependencies
 
-- alpine distribution 
+- alpine distribution
 - git
 
 ## Configuration
 
+- `CRELAY_SERIAL`: the relay serial number, in case crelay detects more than one available device
 - `CRELAY_POWER_CHANNEL`: the relay channel connected to the DUT power
 - `USB_RELAY_CONN`: `NC` or `NO` - for normally open or normally closed relay configuration
\ No newline at end of file
diff --git a/lib/features/power/implementations/crelay/index.ts b/lib/features/power/implementations/crelay/index.ts
index e3606de..9fa61d3 100644
--- a/lib/features/power/implementations/crelay/index.ts
+++ b/lib/features/power/implementations/crelay/index.ts
@@ -4,18 +4,20 @@ import { promisify } from 'util';
 const execAsync = promisify(exec);
 
 export class Crelay implements Power {
-    private relayId: number
+    private relaySerial
+    private relayChannel: number
     private connOn: string
     private connOff: string
 
     constructor(){
-        this.relayId = Number(process.env.CRELAY_POWER_CHANNEL) || 1; // indexing of relay channels starts at 1 for this device.
+        this.relaySerial = process.env.CRELAY_SERIAL || '';
+        this.relayChannel = Number(process.env.CRELAY_POWER_CHANNEL) || 1; // indexing of relay channels starts at 1 for this device.
         this.connOn = (process.env.USB_RELAY_CONN === 'NC') ? 'OFF': 'ON' // if the user specifies they have set up the connection to be NC
         this.connOff = (process.env.USB_RELAY_CONN === 'NC') ? 'ON': 'OFF' // if the user specifies they have set up the connection to be NC
     }
 
     async setup(): Promise<void> {
-        // install craly tooling
+        // install crelay tooling
         try {
             await execAsync('apk add make build-base');
             await execAsync('cd /usr/app/ && git clone https://github.com/balena-io-hardware/crelay.git');
@@ -23,8 +25,8 @@ export class Crelay implements Power {
             await execAsync('cp /usr/app/crelay/src/crelay /usr/local/bin/crelay');
 
             // this retrieves info about the relay being used, and its serial
-            let info = await execAsync(`crelay -i ${this.relayId}`);
-            console.log(`Crelay controlled relay being used for power, channel: ${this.relayId}.`);
+            let info = await execAsync(`crelay -i`);
+            console.log(`Crelay controlled relay being used for power, serial: ${this.relaySerial}, channel: ${this.relayChannel}.`);
             console.log(info.stdout);
         } catch(e){
             console.log(e)
@@ -35,18 +37,34 @@ export class Crelay implements Power {
     // Power on the DUT
     async on(voltage?: number): Promise<void> {
         console.log(`Powering on DUT...`);
-        await execAsync(`crelay ${this.relayId} ${this.connOn}`);
+        if(this.relaySerial) {
+            await execAsync(`crelay -s ${this.relaySerial} ${this.relayChannel} ${this.connOn}`);
+        } else {
+            await execAsync(`crelay ${this.relayChannel} ${this.connOn}`);
+        }
+
     }
 
     // Power off the DUT
     async off(): Promise<void> {
         console.log(`Powering off DUT...`);
-        await execAsync(`crelay ${this.relayId} ${this.connOff}`);
+        if(this.relaySerial) {
+            await execAsync(`crelay -s ${this.relaySerial} ${this.relayChannel} ${this.connOff}`);
+        } else {
+            await execAsync(`crelay ${this.relayChannel} ${this.connOff}`);
+        }
+
     }
 
     async getState(): Promise<string> {
         // TODO return state of power on/off
-        let state = await execAsync(`crelay ${this.relayId}`);
+        if(this.relaySerial) {
+            let state = await execAsync(`crelay -s ${this.relaySerial} ${this.relayChannel}`);
+            return state.stdout;
+        }
+
+        // No serial.
+        let state = await execAsync(`crelay ${this.relayChannel}`);
         return state.stdout;
     }