Add Grafana error troubleshooting tip

README.md

@@ -96,7 +96,6 @@ Note: the influxdb.sql file is set to use `America/Los_Angeles` as timezone. Use
 
 * The database queries and dashboard are set to use `America/Los_Angeles` as the timezone. Remember to edit the database commands [influxdb.sql](influxdb/influxdb.sql), [powerwall.yml](powerwall.yml), and [dashboard.json](dashboard.json) to replace `America/Los_Angeles` with your own timezone.
 
-* InfluxDB does not run reliably on older models of Raspberry Pi, resulting in the Docker container terminating with `error 139`.  
 
 ### Troubleshooting Tips and Tricks
 
@@ -109,6 +108,10 @@ Check the logs of the services using:
   docker logs -f grafana
 ```
 
+* Docker terminating with `error 139`:  InfluxDB does not run reliably on older models of Raspberry Pi. 
+* Grafana Error: Invalid interval string, expecting a number followed by one of "Mwdhmsy" - This indicates that the Grafana setup for InfluxDB is missing the time unit, "s", in the "Min time interval" field:
+  - Min time interval: `5s`
+
 #### Missing String data?
 
 * String data only shows up for Tesla inverters as part of Powerwall+ systems.  Unfortunately, non-Tesla inverter data is not available via the Tesla API. If you find a way to pull this data, please submit an Issue or Pull Request to get it added.