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Author Topic:   NMEA Network Power
jimh posted 07-09-2013 09:21 AM ET (US)   Profile for jimh   Send Email to jimh  
NMEA Network Power

This article describes in detail the changes I recently made to the NMEA-2000 network on my small boat.

The NMEA-2000 network on my small boat had only four nodes:

--Lowrance EP-85R Data Storage Module

--Lowrance HDS-8 Multi-function display, chart plotter, and SONAR

--Evinrude Gateway Module from E-TEC engine

--Evinrude ICON RPM Gauge

There was no power node. The network power was provided by one of the devices on the network, the Gateway Module from the E-TEC engine ESM Network. Although NMEA recommends that a NMEA-2000 network be powered by a network power node, Evinrude chose to simplify their ICON and I-Command gauge installations when used with E-TEC engines having ICON controls by incorporating network power into the Gateway Module. This eliminated the need for a network power node on the network. The Gateway Module powered the network whenever the associated E-TEC engine had its ignition key switch in the ON position. This approach worked well, but I found there were often times when I wanted to access data on the network while the E-TEC engine was not running. To activate the network, I had to turn the ignition key of E-TEC engine to the ON position.

There are several things I did not like about that method. First, having the ignition key turned to ON makes the E-TEC engine accumulate hours of operating time, called "EMM Time." This is a separate count from the actual running hours, which only accumulate when the engine is actually running. After a few seasons of boating with the network powered this way, I could see that the accumulated EMM Time hours were becoming significantly different than the actual running hours. My second objection to this method of powering the network was the idea of having to power up the EMM of the E-TEC, a rather expensive circuit board of microprocessors and other solid-state devices, just to put power on my NMEA network. Why run a $2,000 computer system just to provide 12-Volts to a NMEA network? It did not seem like a good approach to powering the network when the engine was not running.

A further objection to powering the network in this manner was the source of the network power: it was coming from the engine starting battery. The Gateway Module is required by Evinrude to be powered from the engine starting battery, so when network power is derived from the Gateway Module, it is going to be power from the engine starting battery. I had gone to the trouble of completely isolating all my electronics from the engine cranking battery by installing a separate non-engine or House battery and House power distribution system, and now my most important instrumentation was being powered by the engine cranking battery. That did not seem like a good design.

To resolve these three problems, I have re-engineered the network power on my NMEA-2000 network so that it is powered from the isolated House battery, but it still is automatically powered-on whenever the E-TEC is operating. Power to the network can also be turned on manually with a separate switch for those occasions when it is desired to have network power when the engine is shut down.

The first problem to resolve was to isolate the Gateway Module and its power from the rest of the network. There are several ways to accomplish this. I used a simple, off-the-shelf solution. I found that Garmin is selling a network power isolation adaptor that fits into the usual network-T wiring appliances. This adaptor breaks the network power circuit but carries through the network data circuit. Inserting this adaptor in the network backbone will isolate the power in the network into two segments. The device is called a "NMEA 2000 Power Isolater" and is Garmin part number 010-11580-00. (I ordered mine from a good Garmin reseller, BOE Marine.)

The backbone of the NMEA-2000 network is then split into two segments by inserting the Power Isolator. In my application, the network segments consist of just a terminator and the Gateway Module node on one side, and all the other devices on the other side.

There is one mechanical problem with the Garmin device: the orientation of the connector keyway is different from the Lowrance network T-connectors I was using. This creates a bit of a mounting problem, as the Garmin network wiring device will not fit flush against a bulkhead when connected to Lowrance network wiring devices. There is a 30-degree offset. This can be overcome by using spacers to let the wiring devices stand off from the bulkhead.

With network power removed from the backbone by isolating the Gateway Module, I had to add a normal network power node to the backbone. The network power node is supplied with 12-Volts from the House battery. There are many ways to arrange for the power.

My method of providing House battery 12-Volt power to the network power node is through a relay. The relay contacts switch House battery power to the network when the relay coil is energized. The coil of the relay is operated from two sources. The two sources are isolated from each other by steering diodes (to prevent the power sources from becoming connected in common). One source of power for the relay coil is taken from the ACCY circuit of the E-TEC. The ACCY circuit has power whenever the ignition key is in the ON position, so this operated the relay, giving the network (House) power whenever the E-TEC engine is running. The NMEA-2000 network is automatically powered whenever the engine is running, just as it was before. A second source of power for the relay coil is taken from a toggle switch. The toggle switch provides power from the House battery. Whenever the toggle switch is closed, the relay energizes and the network is powered. This gives the option to operate the network while the E-TEC engine is shut off.

It is possible to power the network just from the output of the two steering diodes. I chose to use a relay because there is some voltage drop across the steering diodes, and I did not want the power from the ACCY circuit to be used as network power. The ACCY circuit is derived from the engine starting battery. By letting the steering diodes control the relay, I could be certain that the network power was always coming from the isolated House battery.

The steering diodes used have the following characteristics: a peak-inverse-voltage (PIV) of 1,000-Volts; a forward current maximum of 2-Amperes. The 1,000-PIV should be more than sufficient to withstand any voltage transients that might occur on the engine starting battery power line. The 2-Ampere current rating gives a generous margin for the relay power, whose 90-Ohm coil only draws about 0.14-Ampere. The ones I used came from my own parts bin. Here is a suitable choice:

The relay is an inexpensive, $3.22 automotive relay. There is one Form-C contact. The coil has a suppresor diode.

To mount the relay, I used a small mounting bracket accessory which provides for easy installation against a bulkhead with a single mounting screw. Crazily, this hunk of plastic costs more than the relay, $6.29:

The mounting bracket does not include the actual sockets for electrical contact. They must be ordered separately, at about $0.48 each:

These contacts require a crimper that can curl the crimp over the wire. Fortunately I have such a crimper. This style of crimp contact is rather common, so it is likely that many generic crimpers can fit these contacts. Feel free to omit the bracket and the expensive contacts; the relay has standard tab connections or you could solder to the contacts.

The toggle switch is the simplest component. Only a SPST switch is needed. I ended up using an illuminated toggle switch, obtained from my local boat dealer. It was Sierra brand switch and costs about $12: 373--view_id.491914

As it turned out, I don't like this particular switch because it only illuminates when the gauge illumination circuit is also energized. [But later, I decided I do like the switch; see below--jimh] I suppose I probably wouldn't be able to notice the tip illumination in daylight, anyways. I got this switch because I really wanted to fill an existing hole on the electrical panel. I was removing another switch that formerly operated a device that I have since removed from the boat.

In addition to letting the relay provide power to the NMEA-2000 network, I also wired a voltmeter in the circuit. The voltmeter reads the House battery voltage, and also provides a positive indicator that there is power being sent to the NMEA-2000 network. I did not want to leave the voltmeter permanently connected to the house power distribution, as it would then always be draining some current from the battery. Sometimes I have (unintentionally) left the primary battery power distribution swtich ON for a week or two when the boat is in storage, and I did not want that voltmeter to be draining current all that time. Switching the voltmeter on with the NMEA power circuit seemed like a good way to provide the House battery power to the voltmeter for measurement.

jimh posted 07-22-2013 09:59 AM ET (US)     Profile for jimh  Send Email to jimh     
After going to all the work to revamp the network power on my NMEA-2000 network (that I describe above), I am a bit disappointed with the outcome. The purpose of the change was

--get the network power on House battery

--enable network power when the engine key was off

In both cases, this has been accomplished. However, I am still disappointed. When the network was powered and the E-TEC engine was shut off, I was expecting that I would be able to read the data from the EP-85R Data Storage Device. That device holds information about the fuel tank level, seasonal fuel used, trip fuel used, and fuel remaining. I have found that this data is available, but only if the EP-85R is activated at the same time as the E-TEC engine. I explain below.

On my initial test of powering the network while the E-TEC engine was off, I found that I could not read any data from the EP-85R. This was a great disappointment. At first I thought perhaps there was some error in my wiring, and there was no power on the network. I soon checked into this, but I found the wiring was all proper and correct; there was power on the network.

With some more experimenting, I found that the EP-85R does not become active and present its data to the network unless it finds the engine it has been configured to monitor on the network. With the E-TEC powered on, the EP-85R showed all the stored data I was expecting from it.

Next, I found that once the EP-85R was powered on with the E-TEC on the network, the E-TEC could be powered off and the EP-85R would still present the data. From this I have concluded that there is some initialization process in the EP-85R at power-on that must search for its paired engine or engines on the network. If those engines are not found, the EP-85R considers its configuration to be invalid, and no data it available.

My interest in having this data available without having to power-on the E-TEC was to be able to see the data whenever I liked, without having to have the E-TEC EMM powered on. As long as I throw my manual power switch for the network power to ON before I shut off the E-TEC, the data will remain available. At least it remained available for several minutes. I will have to test to see if it becomes unavailable at a longer time interval.

There is a funny twist to this story. On the ICON Pro gauges, the fuel tank level is also tracked electronically. That data is available on the ICON gauges, even if the E-TEC engine is not on the network.

jimh posted 07-24-2013 11:06 AM ET (US)     Profile for jimh  Send Email to jimh     
Regarding the illuminated switch, I mention above that I dislike it because it won't illuminate unless the gauge illumination circuit is powered. I have changed my mind about this switch. In actual practice, this switch is really versatile. If you want it to illuminate only when the switch is closed and to be independent of the gauge illumination circuit, you can just connect your 12-Volt switched power from the switch contact to the gauge illumination circuit terminal. With this simple wiring, the red indicator illuminates when the switch is in the ON position.

Regarding the Garmin power isolator and its mechanical configuration with the connector offset being different, I found that the material of the connector is rather pliable, and, if you are not careful, you can create a bend in this wiring appliance at the end with the mating collar. One way to overcome the difference in offsets would be to use all Garmin network-T wiring appliances.

jimh posted 07-31-2013 08:42 AM ET (US)     Profile for jimh  Send Email to jimh     
Regarding the GARMIN Power Isolator NMEA-2000 network wiring accessory that I mentioned above:

I found there are two problems in using the Garmin Power Isolator with the Lowrance network-T devices. As I mentioned already, the orientation of the Lowrance network-T connectors and their keyway is different from the Garmin device. As a result, when interconnected the Garmin device does not mechanically align with the Lowrance devices. This prevents the Garmin device from being fastened to a bulkhead for support.

A second difference in the Garmin Power Isolator is the female connector's mechanical rigidity with the rest of the device. The female connector (that is, the connector with the sockets, not pins) seems to be able to float in the main housing of the Power Isolator, and this allows the connector orientation to move through a small range of motion. This may actually be a slight advantage to the Garmin devices, if they all have this feature, as it may allow the female connector to align better with its mating male connector. However, it complicates the interconnection of the Power Isolator to other non-Garmin network network-T devices.

The best approach to using the Garmin Power Isolator seems to be to mount a string of network-T devices to a bulkhead, but to include some spacers to elevate the string of devices above the backplane far enough that the Garmin Power Isolator can be inserted without interference with the backplane due to its misalignment. If the two network-T devices on either side of the Garmin Power Isolator are fastened to the backplane, they should hold the Garmin Power Isolator in place without allowing movement due to the flexibility of the Garmin's female connector.

jimh posted 09-05-2013 09:40 AM ET (US)     Profile for jimh  Send Email to jimh     
I have discovered a new anomaly in the function of the EP-85R and Lowrance FUEL MANAGER software. As I described above, in my network it is possible for the EP-85R to be powered and active when the E-TEC engine is not on the network. During a recent eight-day cruise, I discovered that the EP-85R recorded no fuel usage during one day of the cruise. I believe that the circumstances in which this occurred were as follows:

--the network power was left ON for a long period of time after the E-TEC had been shut off, perhaps 18-hours;

--when the E-TEC was switched on and returned to the network, the EP-85R did not return to functioning with the E-TEC;

--the fuel consumed during that day's operation was not recorded onto the EP-85R

I discovered this when I logged the fuel data at the end of the day. All the fuel data (taken from the EP-85R) was identical to the prior day, that is, no fuel consumption was recorded, even though the boat had certainly burned at least three or four gallons of fuel.

My hypothesis for the cause of this omission in fuel flow recording is:

--with the EP-85R left powered ON, and the E-TEC powered OFF, after a long period of time the EP-85R gave up on communicating with the E-TEC

--the E-TEC was likely reporting its fuel flow rate to the network,

--the instantaneous data, like MPG was being computed by the gauge

--the accumulator data, such a TRIP FUEL USED, SEASON FUEL, and TANK LEVEL were not being updated.

When both the E-TEC and the EP-85R were powered OFF, and, after a short delay, powered back to ON, the operation returned to normal.

Fortunately for my fuel tank level computation, the fuel actually burned on this particular day of the cruise was only about four-gallons at most. The fuel tank is a 70-gallon tank, so the values for FUEL TANK LEVEL and FUEL REMAINING were only off by a small percentage. Also, because I was logging the daily fuel used data, I noticed this problem right away.

jimh posted 09-24-2013 08:42 AM ET (US)     Profile for jimh  Send Email to jimh     
The Lowrance EP-85R Data Storage Device apparently contains some firmware which has been updated several times since I obtained my EP-85R device. It appears my device has firmware (v1.3.0 c.2008) that is several generations out of date. I will be updating the firmware on my EP-85R with the present generation firmware (v2.3.0 July 2013), and perhaps this will affect some of the anomalies in operation that I have seen.
K Albus posted 10-03-2013 09:42 PM ET (US)     Profile for K Albus  Send Email to K Albus     
Can you provide a pointer to the EP-85r update software? I checked the Lowrance U.S. website, and the page for the EP-85r shows no software updates available.

Side note: On our recent trip to Isle Royale, my Yamaha Command Link Plus gauge showed that I burned 89 gallons of fuel. I have verified, both in the past and earlier this year, that the Yamaha gauge's calculation of fuel used is very accurate. For the same trip, the EP-85r showed only 78.8 gallons of fuel used. The EP-85r has under-reported my fuel usage by 10%-12% all summer long.

jimh posted 10-09-2013 10:56 AM ET (US)     Profile for jimh  Send Email to jimh     
Let me add a bit more about the Lowrance EP-85R Data Storage module, which has become a sidebar topic in this discussion of NMEA network power due to some idiosyncrasies I noted in its operation.

I applied the firmware update patch to my EP-85R Data Storage module, bringing its firmware up to the 2.3.0 revision level. The updater was applied by using my Lowrance HDS chart plotter. The procedure is as follows:

--copy the firmware updater software file onto a SD Memory card

--boot up the HDS-8

--load the SD memory card into Slot 1

--use the PAGE carousal to navigate the HDS to the FILES option, see

--navigate to Memory Card 1

--expand Memory Card 1 to show its files

--navigate to the updater file

--a soft key option should appear with the legend UPDATE

--push the softkey; the update process should begin, first commenting that the EP-85R has been restarted, then showing a grow bar with the percentage increasing toward 100-percent.

I found that after applying the firmware patch, the EP-85R lost all of the stored data except the configured tank volume. If you want to memorialize that lost data, copy it down before applying the patch. Also, the updater left the EP-85R showing the present fuel remaining level to be the full-tank volume, and the present fuel tank level to be 100-percent full. This was something of a surprise. In my case, the fuel tank was not full and the fuel remaining was less than the tank volume set. I will have to wait until I burn off enough fuel to get back to my actual levels (that I wrote down before updating) so I can then make an allowance at the next fueling.

In my case the tank has about 58-gallons, not the 70-gallons now shown on the EP-85R. I will have to burn off at least 12-gallons before adding new fuel. When I add fuel, I will subtract 12-gallons from the actual amount added to the amount I enter into the EP-85R; this will get the EP-85R back to an accurate fuel tank level. This seems like a cumbrous process. It would have been simpler if the EP-85R update just set the fuel remaining to zero. I could then use the ADD FUEL function to add imaginary fuel to the tank to get it back in calibration.

[IMPORTANT ADDENDUM: updating the EP-85R firmeware as I described above caused all sorts of problems. These problems, and their resolution, are described in detail in a separate thread. If planning on using an EP-85R, it is strongly encouraged to read the separate thread of articles on problems with the EP-85R.--jimh]

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