In the latest versions of battery powered device firmware, we have implemented an Under Voltage Lockout (UVLO).
This will power down the device when the batteries are supplying too low a voltage to operate reliably.
Without this feature there are circumstances where the device may have enough power to boot up, but as soon as the modem/GPS is turned on and draws more power - the device will brown out.
The LED may also be able to flash. The UVLO ensures that a device that won't be able to connect reliably due to low voltage will also show no 'signs of life' - prompting the user to use a fresh set of batteries which will allow the device to operate correctly.
In addition - some users may want to power our devices via other means than LTC or LiFeSO2 batteries (reccomended)
Such as mounting their own primary cells or LiPo battery packs.
Modifying the device in this way will void the device warranty.
It is useful to know the minimum operating voltages for such applications.
- If <2.8V is detected on start up, the device will not start due to the UVLO
- In practice this is closer to 3V, as a load such as switching on the modem causes the battery voltage to drop, and this could trigger the UVLO threshold if operating in this range.
- If the voltage dips below 2.8V while running, the device will sleep for 3hrs to attempt to allow it to recover.
- The cellular modem requires at minimum around 3.1V to operate reliably.
Yabby GPS/Yabby Wi-Fi/Oyster v1
- Device won't start with <3V according to UVLO
- Yabbies Won't run with <2.8V according to UVLO
- The Oyster v1 UVLO threshold is 2.5V, turning on the modem causes the battery voltage to drop quite significantly, so the threshold is set a bit lower in firmware. So effectively the threshold is around 2.8V like the Yabby for what the batteries must supply.
Requires 3.8V to operate.