Hello I am new here - I live aboard my 37’ sailboat and am interested in installing a POE network on my boat using a POE switch that is hardwired into the 12v house bank. The switch steps up 12v to 48v and then has several POE outlets each with a 30 watt power budget. IP security camera, lights, sensors, raspberry pi, monitors, NMEA backbone, there are many devices that could be connected to this system.
The big disadvantage is the losses you’ll incur by converting 12v to 48v. Depending on the amount of devices you use that are PoE, it may be better to look at specific devices that could run off of 12v instead of PoE. In particular, things like lights, sensors, and raspberry pi would likely be better to run either natively off of 12v, or with specific converters that might be more efficient.
You’re probably going to find that a lot (most?) PoE devices are not expecting to operate on a low power basis. They’ll blow through 30w per port like nothing, unless you start digging and find ones that ARE designed for low-power use. Bearing in mind that most RV setups are expecting there’s a ready source of wattage in the form of a generator, engine or hefty battery setups.
Start with a plan, not with devices. You don’t want to find yourself painted into a corner with gear you’ve got on-hand that really might not be ideal for the intended solution.
Then there’s the problem of connector form-factor. The RJ45 connector is not ideal for marine environments. The contact surfaces are small and the connector itself isn’t sealed against moisture. You can, of course, get various bulkhead and other style connector shrouds that attempt to solve this. But then you’re into added expense and much larger connector footprint.
Don’t try to solve everything with just one platform. Things like NMEA-2000 exist and can do a pretty decent job of handling most of the things you need for boating. Not cameras or video monitors, of course, but quite a lot of other things.
There’s a tendency to want to find an all-in-one solution, I’ve been there myself. I don’t think it exists. And the ones that “sort of” come close often end up being a burden to use when you need actual boating navigation. Too many fiddly parts that end up getting in the way of being useful. Updates for this, conflicts with that, abandoned software/hardware… the list goes on.
Not that dedicated devices haven’t had their share of problems, but they continue to perform their functions for which they were purchased.
Thank you for the replies it gives lots to think about.
I was curious about power efficiency, I thought the 48v over Ethernet would be better than the 12v over longer circuits but it all depends on conversion efficiency? Going from 12 v to 48 v and then back down to 5v again instead of just going from 12v to 5v.
I previously installed a NMEA network (raymarine seatalk) which has one MFD/radar/AIS/autopilot/w,d,s transducers connected. That system works great and I like to keep it stand alone - not add any more devices to it. I also would like to get away from proprietary systems and devices and move towards generic or open source solutions.
My original plan was to install an IP security camera on my mizzen mast. Lots of reasons to have a camera up there mainly for security/insurance (getting hit by other boats when not there for example) but also for using as a floodlight and ir light. It is POE and so I thought of how to integrate this type of camera on the 12v house bank without running separate 12v power up the mast - just an Ethernet plug at the mast step in a waterproof housing.
I also found some relatively inexpensive POE powered, android based, smart displays that would support the ip camera app (as well as a chart plotter app). I would set up the display at nav station (now) and cockpit (in future if this setup works). Other than the camera (ip66 rated), everything would be installed in watertight compartments/housing. For a power source, I would connect from 12v panel a 150watt step up 12v-48v converter and on to the POE switch (90 watt budget @ 48v). This would give me the full 25 watts for each POE outlet which is enough for each device. (12-15 watts) When I connect the POE switch directly to 12v power, I only have a ~15 watt budget for each POe outlets.
I’ve connected the devices (camera, switch, display) together at home with a 12v car battery and it all powers up nicely and that is just direct 12v input with no dc-dc step up converter.
I can connect the switch to my existing modem and access the camera on the network from any other device.
Since there are VHF, radar, and dc power cables all running near the Ethernet cables, I am thinking shielded cat 6 cables be used and shielded connector? Is earth grounding achieved through the DC negative to the battery or does the Poe switch require a separate earth ground? There wouldn’t be any AC current/inverter running when this system is in use, but are there other considerations to take into account? I would be using solid copper and the devices are all relatively low power consumption (<15 watts).
I don’t know if shielding is overkill for this but I wouldn’t want interference with the vhf/radar/gps etc signals.
Thanks again for your responses I will continue to do more research.
There are definitely pros and cons with using both 12v only and converting it to PoE depending on the distance, power usage, and what the cabling will be next to, etc. 48v PoE would likely be more efficient in almost all cases for longer distance runs than 12v native.
I highly recommend using shielded ethernet cabling anywhere you’re running longer runs of cable, and especially near other power/electronic cabling. The biggest issue is likely other cables and devices having emissions or high amps passing through them that could potentially disturb the ethernet side of things.
On the earth grounding question - if you’re concerned about general grounding, the PoE switch should have provisions for this. Good ones have a separate ground for the case as well as details on grounding for the PoE side of things.