48v PoE with 48v Battery bank... Simple right? ?

[AKExcalibur]

Hello Solaristas! I'm installing a 48v system over the next few weeks and need some advice about Power over Ethernet (PoE). This is for an off-grid vacation cabin.

My battery bank will be a 48v bank, and I'm planning to power always-on cameras and some Raspberry Pis for weather and power monitoring, security, and irrigation control. Since all that stuff runs well off of PoE and everything is DC, I figure why take the hit of having the inverter always being on, and just use PoE for the always-on gear.

I'm having a heck of a time finding equipment to power 48v active PoE (802.3af) directly from 42-56v that the battery bank puts out. Curious what others have done here? I may try out a Victron 48/48-Volt converter, but I'm not 100% sure that's the best fit for my application. Can PoE equipment handle the 42-56v actual battery voltage without the need for a converter? If so, I'll happily save a bit.

Perhaps I'm worrying too much about the loss from having the inverter on full time? Curious what others think.

 

[dweick]

Take a look at

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[johhen]

Hello Solaristas! I'm installing a 48v system over the next few weeks and need some advice about Power over Ethernet (PoE). This is for an off-grid vacation cabin.

My battery bank will be a 48v bank, and I'm planning to power always-on cameras and some Raspberry Pis for weather and power monitoring, security, and irrigation control. Since all that stuff runs well off of PoE and everything is DC, I figure why take the hit of having the inverter always being on, and just use PoE for the always-on gear.

I'm having a heck of a time finding equipment to power 48v active PoE (802.3af) directly from 42-56v that the battery bank puts out. Curious what others have done here? I may try out a Victron 48/48-Volt converter, but I'm not 100% sure that's the best fit for my application. Can PoE equipment handle the 42-56v actual battery voltage without the need for a converter? If so, I'll happily save a bit.

Perhaps I'm worrying too much about the loss from having the inverter on full time? Curious what others think.

What’d you end up doing?

 

[zanydroid]

What’d you end up doing?

Not OP but passive POE injector that can handle this is pretty easy to find. I haven’t shopped for active injectors lately. I wouldn’t recommend passive injection fwiw. If all else fails one can try to find a switch that speaks active PoE, that itself can be powered from 48V

POE standard I believe covers the top range of this voltage (IE PoE is 48V nominal, nor 48v exactly), but do check the standards and Wikipedia tables yourself.

 

[TorC]

PoE is up to 56V at the head end, which is fine for a 16S LFP bank direct. What circuitry is required to safely get it onto the wires is another question altogether. The proper PoE spec says it should only put a small voltage on the wire to give a device enough power to say, "Hi there. Yes, I need some power. Fire up this spec's worth, please." This is an important protection for devices that aren't designed to take or use PoE.

For lower power devices, up to 30W consumption & 100Mbps comms, I'm pretty sure you can just connect the correct two pairs to power, disconnecting them from the switch, and I think same through gigabit. Make sure to have a video going if you try it, so you can entertain us over in the Up in Smoke section if it goes wrong.

 

[zanydroid]

You can just get one of these to get up to gigabit compatibility. Gigabit uses all 4 pairs so you do have to use transformers

Single Port Gigabit Mode A/B Passive PoE Injector (Power Supply Not Included)

Gigabit single port PoE Injector (power supply sold separately)

shop.poetexas.com

NOTE: Passive injector. 99 times out of 100 you will fry non-PoE ports this way. Which is why this kind of injector is just for professionals.

Or pay some more money for active PoE. 15W power level for $10

PoE Adapter - Ubiquiti Store

An adapter that can power UniFi PoE devices with wireless mesh applications, or offload PoE switch power dependencies.

store.ui.com

 

[TorC]

Nice. And yes, you'd better know what you're doing if you think about passive PoE.

If you want more ports, this injector looks interesting to feed a fused link to a 48V LFP bank.

 

[pollenface]

Why not use a buck converter (48->12v step down) for your PoE needs?

 

[zanydroid]

Why not use a buck converter (48->12v step down) for your PoE needs?

Not sure what you're suggesting actually.

For standard active PoE usually there's a buck converter at the receiver end.

For passive PoE you could use a buck converter at the sender end. But why would you want to use passive PoE.

Another place to get burned with PoE is positive/negative ground (not sure if this is standardized in active PoE, at least when you inject from your battery you should know what convention is followed) and whether a non-isolated buck converter is referenced vs + or -.

 

[Checkthisout]

Just take the power supply out of a cheap POE switch and replace it with a 48V DC voltage STABILIZER Buck/Boost converter and you're done.

Bonus if it's adjustable up to like say 52 Volts in case you want to power something with a bit higher draw.

 

[CJM]

Just take the power supply out of a cheap POE switch and replace it with a 48V DC voltage STABILIZER Buck/Boost converter and you're done.

Bonus if it's adjustable up to like say 52 Volts in case you want to power something with a bit higher draw.

there's a youtube about it?

 

[Checkthisout]

there's a youtube about it?

No.

It's a straight forward task

 

[Quattrohead]

If you are worried about the voltage being a little high you can always use some regular silicone diodes in series to drop the voltage, 0.6 volt per diode.

 

[bazza14]

You can just get one of these to get up to gigabit compatibility. Gigabit uses all 4 pairs so you do have to use transformers

Single Port Gigabit Mode A/B Passive PoE Injector (Power Supply Not Included)

Gigabit single port PoE Injector (power supply sold separately)

shop.poetexas.com

NOTE: Passive injector. 99 times out of 100 you will fry non-PoE ports this way. Which is why this kind of injector is just for professionals.

Or pay some more money for active PoE. 15W power level for $10

PoE Adapter - Ubiquiti Store

An adapter that can power UniFi PoE devices with wireless mesh applications, or offload PoE switch power dependencies.

store.ui.com

Be careful with Ubiquity, they use 24v for POE to make you use their adapotors with their kit.

 

[zanydroid]

Be careful with Ubiquity, they use 24v for POE to make you use their adapotors with their kit.

That’s old news. Their new kit and injectors are 48v and active POE. You look for the ones that have the right IEEE standard in the sheet.

That said they still do sell older kit and injectors, and some of their active PoE components are non isolated which can lead to a bad day in some scenarios, even if it is permitted by standard and harmless when used with access points.

EDIT: Passive PoE is another way to give yourself a bad day

 

[bazza14]

Hello Solaristas! I'm installing a 48v system over the next few weeks and need some advice about Power over Ethernet (PoE). This is for an off-grid vacation cabin.

My battery bank will be a 48v bank, and I'm planning to power always-on cameras and some Raspberry Pis for weather and power monitoring, security, and irrigation control. Since all that stuff runs well off of PoE and everything is DC, I figure why take the hit of having the inverter always being on, and just use PoE for the always-on gear.

I'm having a heck of a time finding equipment to power 48v active PoE (802.3af) directly from 42-56v that the battery bank puts out. Curious what others have done here? I may try out a Victron 48/48-Volt converter, but I'm not 100% sure that's the best fit for my application. Can PoE equipment handle the 42-56v actual battery voltage without the need for a converter? If so, I'll happily save a bit.

Perhaps I'm worrying too much about the loss from having the inverter on full time? Curious what others think.

Probably the simplest way to achieve this is to buy a switch with PoE ports that is powered by a wallwart and power it from the battery using a suitable DC-DC converter.