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NMEA Power Management

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First, please forgive me for any lame assertions or comments regarding this quest since I'm green at NMEA. The only thing going for me is that I have been reading, reading and then reading some more.

My question is this: I assume that when a micro/mid powertap tee is installed (e.g. Maretron's CF-SPWR05-CF) then one side of the network can be isolated from the other side (power wise). This sounds great because one can split the network in two: the at-anchor segment running the essentials (e.g. high bilge sensor) and the underway segment running the remaining components (e.g. engine temperature). This would be very useful since after measuring my desired NMEA network with N2K builder I discovered that it could easily consume over 100 watts - wow that's 9 Ah.

The problem I see is that practically speaking this entails substantially more cable and routing headaches in order to separate the at-anchor from the underway devices, which in turn adds move cabling and thus Ah. This is where, I assume, that network bridges come into play (e.g. BEP Marine's CZONE).

If all of the above is correct then why are these network bridges late arrivals and hard to find. One would think they would be a standard and off-the-shelf device part of say Maretron's offering.

Again, please forgive the newbie and many thanks to all that have responded to past questions.

4 Replies

  • Hi Andre,

    You are right and wrong.

    The powertaps that I am aware of only have a single "+" input so they power both sides of the network. Even Actisense's 8 port QNB-1 with separate fuses for "right" and "left" doesn't have a separate power supply for right & left (although it would be easy to modify.)

    I think the power usage issue has only recently gotten more awareness in manufacturers now that they are getting more RL experience on sailboats and/or motor boats that don't have generators running, and the number of nodes is increasing as more stuff becomes available.

    For a comparable development look at the power distribution companies. The last 2 years a number have been introducing "version 2" or "version 3" of their power nodes, most of which offer distinctly reduced power usage of the nodes themselves.

    I myself also retrofitted a power split on my 2010 sailboat. I went for a complete split, with a PB200 + Mastervolt N2K i/f on the 1st network and everything else on the 2nd network.

    Both networks are tied together using my central Linux server and 2 x Actisense NGT-1. My software re-broadcasts the PB200 + Mastervolt data onto the secondary network.

    This way I have 24x7 insight into power usage (from the Mastervolt shunt) and GPS/weather data without needing to power everything up, as well as N2K network redundancy.

    So you're not going crazy ;-)

    PS. Don't mess up your A's from your Ah's. 100 W = 9 A @ 12 V, which makes for 2400 Wh per 24 hours. If you intend to do this on a sailboat you're going to be in trouble, but if I remember correctly you're a trawler man?

  • Actually Maretron's powertaps have always been four- wire split taps, and I also have an Airmar split powertap, though I'm not sure that's still true as they've changed suppliers. At any rate, Andre, you can definitely use a split powertap to have one leg of your backbone powered while the other isn't. You can even have more than two separate power segments on a single backbone, though there are some strict rules about common grounding and power supplies. At any rate, here's some discussion:

  • @Ben,

    Thanks, didn't know that as I've never seen those in the flesh, and didn't bother to look it up their online documentation. I stand corrected!

  • Gents:

    Thank you for the precious replies. Now here comes the inevitable question: who makes a good NMEA bridge?