Backend unreachable

How it presents

Symptom

Delta UFC100 loses its link to CSMS/cloud while the local HMI may still show Ready or Available, creating a mismatch where drivers see a working screen but the backend lists the station offline or flapping. Heartbeat gaps and delayed StatusNotification are the giveaway; sessions started locally may not sync until the link recovers.

Root causes (by observed frequency)

1. #1 DNS resolution or TLS handshake failure to the CSMS URL

   Check DNS first — a stale or wrong CSMS hostname is the single most common Delta backend flap.

2. #2 Backhaul instability: weak cellular RSSI, flapping Ethernet link, or ISP outage

   Compare disconnect timestamps against modem signal logs before touching the controller.

3. #3 chargePointIdentity or OCPP credentials mismatch after a controller/board swap

   A re-flashed or replaced controller often reverts to default identity strings.

4. #4 CSMS-side rate limiting or maintenance window rejecting reconnects

   Confirm with the network operations team before assuming site hardware is at fault.

Diagnostic procedure

1. 1. Compare the local HMI ready state against the CSMS portal's last-seen timestamp to size the outage.

   Expected: Gap between local Ready and CSMS last-seen confirms a comms-only fault, not a power fault

   Tools: CSMS portal, local screen

2. 2. Resolve the configured CSMS hostname from the site network to rule out DNS failure.

   Expected: Hostname resolves to the expected CSMS IP; failure to resolve confirms DNS as the cause

   Tools: laptop with site network access, nslookup/dig

3. 3. Check cellular RSSI or Ethernet link light and compare drop timestamps to the OCPP disconnect log.

   Expected: RSSI above -95 dBm and stable link light; correlated drops indicate a backhaul cause

   Tools: modem diagnostics page, OCPP disconnect log

4. 4. Verify the chargePointIdentity and OCPP endpoint URL configured on the controller match the CSMS registration.

   Expected: Identity string and URL match exactly what CSMS has on file

   Tools: installer config tool

5. 5. If all local checks pass, open a ticket with the network operations team to confirm CSMS-side health.

   Expected: NOC confirms no server-side rate limiting or outage affecting this station

   Tools: NOC ticket

The fix

Fix the network/identity path before touching the controller board — most UFC100 comm faults are configuration or backhaul, not hardware.

• Cellular modem / SIM

  Only after RF/backhaul proven bad

• Ethernet switch port / patch cable

  Site network hardware

1. Confirm whether the outage is comms-only by verifying the local HMI still reports Ready while CSMS shows the station offline, which rules out a power or controller failure before any parts are ordered.
2. Correct DNS, TLS certificate, or CSMS URL configuration errors first, since a single wrong character in the endpoint address explains the majority of Delta backend flaps in the field.
3. Stabilize the physical backhaul by reseating Ethernet connections, relocating or replacing a weak-signal cellular modem, or engaging the ISP if the outage lines up with a carrier event.
4. Re-enter the chargePointIdentity and OCPP credentials if a controller or board was recently swapped, then confirm a clean reconnect and at least three consecutive Heartbeat intervals before closing the ticket.