IMO , although most DC powered Mikrotik devices show a voltage range for operation , you should avoid running your Mikrotik at the lowest voltage.
If you are operating at the lowest voltage , then you are border-line of being below the proper voltage and you can create problems.
The Mikrotik will often write to the Flash system. If the Mikrotik is writing something to flash and the voltage drops below operating voltage , then it is possible to corrupt the flash system with garbage.
A Mikrotik that is sending ( transmitting ) WiFi will always require more power ( amps/watts ) than a Mikrotik that is idle. When a Mikrotik is idle and operating at the lowest operating voltage , a WiFi transmit operation can temporarily use more current which can reduce the operating voltage - and if during this time the Mikrotik writes ( and or possibly reads ) flash, the flash can get corrupted because the operating voltage is to low.
I would suggest , two things.
- Don't use PoE ( Power over Ethernet ) to power the Mikrotik - instead use 14 or 12-gauge wire directly to the power connector on your Mikrotik. The larger wire will help reduce voltage loss.
- Consider , instead of running your Mikrotik directly from battery power to instead use battery power to power a voltage regulated DC-to-DC power supply. You might want to consider something like the now discontinued Mikrotik mUPS ( battery backup PoE injector ). You might want to also consider something like an ALGcom 24-Volt DC-UPS.
* The mUPS connects to a 12-Volt external battery and 24-Volt power supply. When there is 24-Volts from the AC power supply , there is 24-Volts to your Mikrotik. When the AC power is removed , the mUPS then outputs about 20 to 21-Volts to your Mikrotik. Note - the mUPS is not very powerful , so only power one device with a mUPS.
** The ALGcom 24-Volt DC-UPS uses an external 24-Volt battery system ( two 12-Volt batteries in series ). When AC power is applied , you get 24 Volts. When AC power is removed , you still get 24-Volts out , until your external batteries drop to somewhere about 21 Volts. The ALGcom power supply will simply just shut off when the battery is to low , which helps protect your equipment from operating at to low of a voltage.
By keeping your supply voltage to your Mikrotik devices regulated above the minimum operating voltage , I suspect you will no longer brick your DC-powered Mikrotik routers.
North Idaho Tom Jones