While logged into TRMNL you can see WiFi + battery strength from your device picker or all devices view:
Calculating remaining battery power is a simple equation, but it becomes less reliable as energy is drained and playlist refresh rates change.
Low battery notification
When your TRMNL device has < 10% energy remaining, you'll be notified by the following screen on your display:
In the future you may be able to customize this screen. ;)
Charging your TRMNL
There are 2 battery options, 1800mAh (default) and 2500mAh (upgraded).
Assuming 0% energy:
1800mAh - 3.5 hours to full charge
2500mAh - 5 hours to full charge
When a TRMNL is plugged in to charge, you may notice its reported battery power seems to fully restore within minutes:
However this is not necessarily true. As of this writing, TRMNL's web interface does not differentiate between "now charging" versus "fully charged."
Therefore, whenever you see the low battery screen, we suggest plugging in your TRMNL for at least a couple hours.
Percent charged versus voltage
The X% charge value in your TRMNL account is approximated as follows:
def percent_charged
self.battery_voltage ||= 100 # assume full charge if device not yet set up
pct_charged = ((battery_voltage - 3) / 0.012).round(2)
case pct_charged
when 90..1000000 # account for '100+' charge, ie plugged in
100.0
when 10..90
pct_charged.round(2)
when -1000000..10
1.0
end
end
If you instead prefer to know your device's last reported voltage, just hover the battery icon(s) for a read out:
Understanding power consumption
One refresh cycle takes 32.8mA over a period of 24s. In this time the device will ping the TRMNL server, download an image, and refresh the display.
If there is no need to download and refresh the display with new image content -- for example if an image is not returned, or the returned image matches what is currently displayed -- power consumption will be around 20% of the above calculation.
For more comprehensive details on TRMNL device power consumption, see here: