DC-DC UPS for Generator Systems

  • I would like to protect my SG-2440 from the 30-second power loss that occurs when the system gets auto-switched to generator power. Other devices (modems, switches, WAPs, etc.) don't seem to be as adversely affected.
    A guy from TrippLite recently explained to me that inexpensive UPSs don't do well with systems that switch over to generator. Apparently due to the qualities of the generator-produced AC, the UPS does not recognize a suitable signal and continues to run off battery, until either grid power returns or the UPS battery runs out. Their cheapest generator-friendly UPS is an "online double-conversion" unit around $500, which is tough to swallow for a 30-second outage. Furthermore, reports of roman candle-like experiences with inexpensive UPSs have me leary about going the NUT/apcupsd route (having already been awoken by smoke detectors and putting a fire out in my basement at 2am).
    This DC-DC UPS is sold by Protectli for their routers, and seems like just what I need. Does anyone know if there are any reasons why it would not do the trick for Netgate devices as well?

  • Netgate Administrator

    If it puts out 12V and the connector is the right size I see no reason why it wouldn't. The current rating seems more than adequate. I doubt anyone has tested it though.


  • @stephenw10 thanks for bringing up the connector size!

    The Protectli Vault, which these batteries are made to work with, lists this for its power connector:
    5.5mm x 2.5mm barrel

    and the SG-1100 lists this:
    5.5mm x 2.1mm x 10mm jack, center pin positive

    no length dimension given for the Protectli Vault, or a polarity for the center pin, but I will ask Protectli for that info and report back. The ID 2.5 vs 2.1 measurements don't match up, but apparently you can buy adapters.

    According to wikipedia
    they both seem to be Type A connectors, albeit incompatible without an adapter due to the different IDs:
    Type A: 5.5 mm OD, 2.1 mm ID (with optional screw lock)
    Type A: 5.5 mm OD, 2.5 mm ID (with optional screw lock)

  • Netgate Administrator

    A 2.5ID plug will generally fit a 2.1ID socket but not the other way around. That UPS appears to just have sockets though so you could make up your own lead to fit if required.
    The SG-2440 was 2.5ID anyway.


  • @stephenw10 thank you! that is great to know.
    I have both an SG-2440 and a SG-1100, and it didn't occur to me that netgate devices might have different power plug sizes. Fortunately, the SG-2440 is on the system with generator power, so it looks like this should be easier than changing a light bulb :)

    I just heard back from Protectli, and they are center pin positive.

  • @billl As a rule of thump, trust noone with polarities Use a ( cheap ) multimeter and find out.
    Takes 5 seconds and assures a smoke free experience.
    As for the power quality of a generator (expensive enough to have an auto-start) does make me wonder why it is an issue.
    Generators produce pure sine wave power by design. Keeping the frequency stable is rather trivial unless you are powering up a factory.
    Modern generators do come with electronic avrs, which work like ups inventers.
    A modified sinewave output is expected at minimum. A ups must be very picky not to accept it.
    And since you have other systems too, (modems et al) its a good idea to protect them all by ups during generator failover.
    pfsense, having a file system is prone to shudden power failure, but in practice suddenly loosing everything else will also produce a lot of logs at least. And last, but not least, different power sources on the same rack can have small leackage currents that can damage equipment.
    (cause is phase/ neutral polarities and grounting loops. Not all generators are earthed!!.)
    Using a ups for all lan/wan equipment is highly recommended.

  • Hello!

    The DC/DC power packs look cool, but how do you monitor them?


  • Netgate Administrator

    It would be much cooler if you could read it's status. Even more so if it had a driver for NUT or similar.
    For this situation, where you're just bridging momentary interruptions, it's probably not necessary though.


  • @netblues I will certainly follow your advice re: multimeter - a two-pronged approach! haha :)

    You've got me taking a step back to reconsider a proper UPS, using NUT to shut down if it does turn out to be fussy with this generator's power. While I have yet to see a problem from power outages with my other network equipment, I appreciate the understanding that they could also get damaged. For the price of a UPS that is substantial enough to allay my (perhaps overblown, but nonetheless) concerns of being a fire hazard, and the eventual replacements of the unit and/or its battery packs, I could keep a cold spare for every other piece of network equipment aside from the router. The question there is, would I actually buy and shelve that equipment, just in case I need it? Kinda like buying insurance, or a UPS, I guess :)

    Thank you everyone, for your help with this!

  • For the record, I should mention that earlier this year, my SG-2440 would not boot after a power failure had caused the system to switch over to generator power. The system had switched over to generator numerous times without incident prior to this. Netgate support was great and they repaired the unit for me, however, that is a road that I wish to avoid in the future :)
    I'm currently also trying to decide on a cold swap backup device to complement the SG-2440, regardless of what I do to address power.

  • Netgate Administrator

    @billl said in DC-DC UPS for Generator Systems:

    a two-pronged approach! haha :)