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Integrations Contributing

Sleep and battery alert

WiCAN stays powered when the vehicle is parked, so it has to know when to stop drawing current. It reads the battery voltage: high while the engine charges, lower when the car rests. Below a voltage you choose, for a few minutes, it goes to sleep; when the voltage comes back it wakes and starts afresh. The same voltage can raise an alert over MQTT when the battery runs down. All of it is on the Power Saving tab.

The Sleep Mode card: Sleep Mode Enable, the Sleep Voltage slider at 13.1 V, the Sleep After slider at 2 min, Battery Alert

Power Saving. Sleep mode is off from the factory; the sliders set the voltage and the delay.

How it decides

Rule What happens
Sleep The voltage stays below the Sleep Voltage for Sleep After minutes: WiCAN switches the CAN controller, WiFi and Bluetooth off and sleeps. Factory values 13.1 V and 2 minutes.
Wake Asleep, WiCAN measures the voltage every 2 seconds. Above the sleep voltage it restarts, like a fresh power-on.

Asleep, WiCAN draws under 1 mA. It wakes by itself when the engine runs, because the alternator or the charger lifts the battery above the sleep voltage.

Setting Range Factory
Sleep Mode Enable, Disable Disable
Sleep Voltage 12.0 to 15.0 V 13.1 V
Sleep After 1 to 30 min 2 min

Typical numbers: a healthy 12 V battery rests at 12.4 to 12.8 V and charges at 13.8 to 14.8 V, so the factory 13.1 V sits between the two. Cars with a smart alternator sometimes charge lower than that for a while; if WiCAN falls asleep while driving, lower the sleep voltage towards 12.9 V. The Battery Voltage on the Status tab is the reading sleep mode works with.

Keep sleep on in a parked car

With sleep mode off WiCAN draws power continuously. A car that is driven every day will not notice; a car that sits for weeks will.

Everything stops while asleep

Polling, MQTT, the web interface and the apps are all off until the voltage comes back; Home Assistant keeps the last values. There is no way to wake WiCAN from the network. Enable sleep mode only once the rest of the setup is done.

The battery alert

With sleep mode on and Bluetooth off, Battery Alert can be set to Enable. While WiCAN sleeps, if the battery sinks below the Alert Voltage, it wakes briefly, joins the WiFi named in the alert settings, publishes one MQTT message and goes back to sleep. It repeats the alert every 1, 6, 12 or 24 hours while the voltage stays low.

The Battery Alert card: SSID, Password, the Alert Voltage slider at 11.0 V, Alert Protocol MQTT, Alert URL, Alert Port 1883, Alert MQTT User and Pass, Alert Topic CAR1/voltage, Alert every 1hr

The Battery Alert card, shown once Battery Alert is set to Enable.
Setting What it is
SSID, Password The WiFi WiCAN joins to send the alert: your home network, if the car is parked in its range. The station settings of the Settings tab are not used for this.
Alert Voltage 8.0 to 15.0 V, 11.0 V from the factory: a 12 V lead-acid battery below 11.5 V at rest is nearly flat.
Alert Protocol MQTT is the only one.
Alert URL, Alert Port, Alert MQTT User, Alert MQTT Pass The broker, as on the MQTT card; plain MQTT only. The factory values point at a public test broker, mqtt.eclipseprojects.io, which is fine for a try and wrong for a real car: use your own broker.
Alert Topic Where the message goes, CAR1/voltage from the factory.
Alert every 1 hour, 6 hours, 12 hours or 1 day.

The message:

{"alert": "low_battery", "battery_voltage": 11.400000}

A broker on your home network and an automation that sends you a notification turn it into a text on your phone before the battery is too flat to start the car.

Troubleshooting

Symptom Likely cause What to do
WiCAN sleeps while driving the car charges below the sleep voltage for stretches (a smart alternator) lower Sleep Voltage a little below the lowest charging voltage you see on the Status tab
WiCAN never sleeps sleep mode off, or the resting voltage sits above the sleep voltage Sleep Mode Enable; read the resting voltage on the Status tab and set the sleep voltage above it
WiCAN wakes and sleeps repeatedly at night the resting voltage hovers around the sleep voltage raise the sleep voltage by a tenth or two
No alert arrives the alert WiFi is out of range of the parked car, the broker is unreachable from that network, or the voltage never fell below the alert voltage a network the car can reach; a broker on it; the voltage
The Status tab shows a voltage that makes no sense WiCAN OBD hardware version 2.10, which has no voltage measurement sleep mode is not available on it