I thought I am was very clever when I connected a second power supply with lower voltage at the ccr internal connector. Everything was working in the lab when I simulated a power outage on the primary psu. This morning (the ccr is running in production since about 3 month) the backup psu stopped ccr from working. All leds were flashing. After disconnecting the backup psu ccr started regulary and everything was save.
I wasn’t personally at the location so I didn’t have a look to the backup psu but I think it will have a short circuit.
Everyone with dual psu in the same manner should overthink this strategy.
Did you put a diode to protect the second power supply from being back fed by the primary? If so, even a short on the second shouldn’t impact anything.
This just one of the reasons why I bypass any internal power supply and connect direct from battery bank and trickle charge the battery bank, generally batteries are very very reliable and much more so than power supplies and especially SMPS types.
Correct and this was a question I asked some time back and was told from Mikrotik one PSU short would not effect a second working PSU, but what if the faulty PSU was giving out high voltage spikes in excess of the working PSU voltage!, could the board be trying to select this higher voltage as primary power source?
Yes you are right but telco power is 48V. We have that at most of our locations. On two locations we have an DC/DC converter from 48 to 24V running. The thing with the spikes is true too and after think again about the problem and it seems to be something like that because ccr was blinking with all led.
The solution as it is, is unusable. We will remove the internal power supply and use parallel DC/DC converters to one input of ccr or we use KISS
By the way: Wo had defective PSU in CCR or other RB1xxx ?
I think there is a lesson to be learned from this thread and that is a second power supply does not always guarantee failover when one fails, the question is how the PSU fails?
Can I ask how the dual PSUs will give failover support and like mentioned in this thread is there any scenario where the second psu will prevent the board from operating?