diff --git a/custom_components/ocpp/api.py b/custom_components/ocpp/api.py
index 9e5fd5c5..7e147aa6 100644
--- a/custom_components/ocpp/api.py
+++ b/custom_components/ocpp/api.py
@@ -651,7 +651,7 @@ async def start_transaction(self):
         if resp is True:
             await self.configure(ckey.authorize_remote_tx_requests.value, "false")
         req = call.RemoteStartTransactionPayload(
-            connector_id=1, id_tag=self._metrics[cdet.identifier.value].value
+            connector_id=1, id_tag=self._metrics[cdet.identifier.value].value[:20]
         )
         resp = await self.call(req)
         if resp.status == RemoteStartStopStatus.accepted: