Hi,
We need a battery backup and I think of this setup 2026-05-26T09:46:09Z
Primary power: 12V powercord
Secundary power: PoE power from chargable 12V Lithium
Querstion:
Will hEX switch automaticly between Primary & Secondary and prefer Primary ?
If so - it would be safe to charge the battery when "external power" is present !
Best Regards
Knud-Erik
KES Net
The hex has not two power connectors, only jack and PoE, and it has to be seen if in practice the transition is "smooth".
Of course a divider/combiner can be made (modifying the motherboard, so say goodbye to warranty) or an external circuit can be created to be interposed between the jack on the PSU cable and the jack socket on the device.
Maybe too obvious a question, but why you don't get a router/switch "MINI UPS"?
Something loosely like (example only):
https://www.aftertech.eu/mini-ups-powerbank-pacco-batteria-al-litio-liion-24v-3200mah-82wh-12v-e1e1-p-17036.html
Generally Mikrotik devices with multiple power inputs will draw power from source with higher voltage. That's due to hardware design, different power sources [**] are more or less conected together via simple diode (so power won't leak out via power inputs with lower voltage). Transition between different power sources will be (in most cases[*]) instantaneous and without service interruption.
[*] As always there's a gotcha: if power source is standard/active PoE (802.3 af/at/bt), then it only gets activated if it's the only source available at device boot. Reason is that it seems that MT PoE-in only performs 802.3 power negotiation if it's being powered on when connection between PSE and PD gets established. Most standards-compliant PSEs won't provide power without first completing power negotiation procedure (and this includes MT's own PoE-out gear if set to auto as opposed to forced-on).
So if device gets initially powered via PoE-in and later also recrives other power source (e.g. power jack), then there will be multiple power dources sctive and device can switch between them. If, OTOH, device starts by being powered by another power source (e.g. power jack) and PoE only becomes available later, then PoE-in won't be active and hence there won't be power redundancy. And the same will hapoen if PoE power source fails and becomes available again ... it doesn't get negotiated again.
In such case, if power sources fail and come back ... then failing non-PoE source will cause device reboot ... first it'll loose power and right after that it'll negotiate PoE-in power and start again on PoE-in power. Transition to other (e.g. power jack) power source will be smooth.
[**] This is true for powering device's board. In case when device is PoE-out and has multiple power jacks (for providing selectable PoE-out voltage), then clearly power buses are separate for PoE-out circuitry and if one voltage source fails, device doesn't provide power to PoE-out ports configured to provide that voltage (devices don't have internal voltage conversion circuits).
Thx. for your answer.
It helped a lot.
BR/ Knud-Erik