Wiring GPS and Sonar; seperate from charging circuit?

[Mark_VTfisherman]

I am looking for some input here on how various guys wire up their electronics. I recently had another failure of a color GPS unit; it was suggested to me by an associate of the manufacturer that the GPS and sonar needs to be wired to their own exclusive battery. This made me question some conventions I learned years ago, but I am not settled on changing my setup just yet.

First, let me relate how I am set up now. I have two batteries; a group 27 trolling/cranking battery and a group 29 deep cycle. The 29 runs my 50# Minn Kota. The 27 is my starting battery and is wired up to run everything on board: Mark 5x Pro sonar, stereo, power port for my VHF, socket for cell phone, Elite 5 combo unit, lights, bilge pump. The two batteries are wired through an A/B/Both battery switch just in case I ever 'need' the 29 for a starting battery but that is redundant because my Suzuki 40 pull starts so easily and readily. I have a master disconnect switch which kills everything wired to the terminal block behind it. The bilge pump is not on this circuit but is wired to its own harness and switch. All the other accessories are powered through the terminal block with fuses in the circuit. I have a second redundant "ground" (negative) wire installed which connects to the battery and motor negative leads for the purpose of bonding everything through a path that is not connected to the negative terminal block under the dash. Probably not needed in a 'glass boat but a friend who is an electrical engineer assured me that it wouldn't harm anything and 'could' eliminate non-preferred galvanic fields from existing. Downrigger to battery ground natural voltage is in the 036-ish range everytime it's checked.

The person I spoke with suggested that I needed to remove the GPS and sonar from the starting battery and connect it to its own battery. Not being particular enamored with the idea of having a 3rd battery on board my 14' boat and having 25 years + of exposure to marine and low-voltage wiring conventions I am not convinced this is necessary. I started with sonar on board in 1992-ish with an Eagle Supra Pro ID wired to the starting battery- the only battery aboard- and have never experienced any issues with electronic noise other than some spark noise on the VHF at near WOT. All my power wiring is done with heavy-gauge copper wire, connections are mostly soldered to lugs etc. I have no problems with performance of the GPS unit, but I am on the third unit to have the screen 'die' in 5 years.

Even while trolling with the gas motor my voltage seldom goes below 12.4 as my 40HP has an 8 amp charging capacity which seems to trickle just enough while trolling to keep everything happy, and usually running for a few miles back to the launch after fishing brings it up to 12.8 to 13.2 volts. I just don't understand how my alternator charging the battery would make the GPS display die an early death. That logic would mean that folks who use GPS units on snowmobiles, in cars, out west off road in Jeeps and such would not be able to run their units on their accessory circuits in their vehicles, right? But people do- even in the Baja 1000 I have seen dual GPS units (without the sonar) running in in-car photos of racers. I seriously doubt they are running the units off batteries not connected to the charging system.

This just doesn't make sense to me since bass boats come pre-rigged on the charging system with the exception of the electric trolling motor batteries- all accessories are on the charged circuit. Further, all my other electronics including my sonar(s) are wired the same way and even my 1992 Supra Pro ID still works- and fine. I have had to replace transducers, but never had the head unit die.

Now that my long winded diatribe is over here are the questions:
1] Do you run your electronics off a battery connected to your boat motor's charging system?
2] or, Do you run your electronics off a separate battery?

Thank you for your input-

Mark

 

[Thalasso]

Electronic are connected to a ACC switch that gets it's power from the circuit panel

 

[Silvertip]

I have always used a dual battery switch wired the way God intended it to be wired so there is no dedication. The electronics run from whichever battery is selected (or both if that's the case). The electronics do not care where power comes from -- with one exception. Some older motors did not have voltage regulators so when running wide open over long distances battery voltage could run 16 volts or higher. Electronics generally have high and low voltage cut offs to prevent damage but "generally" does not mean always. Unless there is something unusual going on with a charging system there is no reason to run electronics from a stand-alone battery.

 

[Mark_VTfisherman]

Aye, Supreme Mariner. I have yet to see your advice or opinions be wrong. But why does it say "Cadet" under your username?!

As far as "high volts" my motor is an '85 Suzuki which is voltage regulated. I always run a voltage display in my overlay settings and have never seen anything over 13.6V- and that was only once a several years back when I had a battery cell 'die' while fishing and the regulator was trying to charge it. On long near WOT runs I occasionally do see 13.2V but to my understanding that is "normal" for a fully charged battery.

Owner's manual states voltage range 10V to 17V as the operating range so I can't see my setup as a problem. I just needed some confirmation since a rep from the manufacturer suggested that the reason for the failures was due to them being connected to the starting battery and common terminal block.

"Wired as God intended..." Ha ha- I really like that analogy

 

[jhebert]

Do you run your electronics off a battery connected to your boat motor's charging system...Do you run your electronics off a separate battery?

Yes. Yes.

I don't know exactly what you mean by "separate battery." I have to assume that by "separate battery" you mean a battery that is not used for engine starting.

 

[sam am I]

Wire all mine separate(electrically isolated from starter when starting) BUT..........not due to being paranoid of damage per-se(but I'm sure it can and does happen, depending on designs), far from it. Think some have missed the/a point here/there.

I HATE starting up and sometimes having my device/s power off/re-booting because yes, our electronics do have low level voltage protection shutoffs. More so these days than ever and it's showing up in everything. Being wired to the starting batt, these devices(some more sensitive than others, faster response times, etc, just depends on manu's designs) can see (sometimes fast, sometimes slow, depends on crank time, load, Rout of battery,Batt. cables, etc, etc, etc) voltage sags(see below, typical) below their low voltage(10V ?) cut off's and POOF, off they go. No damage, just simply a pain in the ***!!





Simple solution, takes certain variables out of the "smoked because of xxx" equation/s and I don't have to deal with maybe some new piece, depending on a slight design difference once installed, potentially crapping the sheets out in the pond someday/somewhere due to this(low chance, but who knows, sounds like OP's device is, it's out of the/my equation as I'm wired), But mainly, I prevented the shutting off due to dropouts anymore.......

Personally OP, I'd do as instructed by supplier/manu., they tend to know their designs of course at a more macro level, and it's limitations(good or bad) based primarily by their field service failure analysis trending histories and by charting those failure causes. I would think they are instructing you based on these real data failure analysis of your(their) unit and in order to best run it, ya might need to do as they suggest. It might have a certain design aspect/s that as designed, may warrant this and as such......

I'd wire perhaps any potentially susceptible (critical especially) electronics to a battery/or use devices that auto isolates said battery on start-up, such that the device/s batt. doesn't have any potential to see the starter's load causing voltage drops(or inductive spikes, low chance, none seen above, but who knows? Starter is just a big ole coil eh? See below theoretical model) significant enough that the electronics in operation, at/while starting are not potentially able to shut off due to said/shown voltage drops/spikes.........But, IMO? Not God, Just Science!!


Simplified schematic/model of device/s attached to start battery(R Starter Windings = 0.0685 ohms, R Series Wires = 0.001 ohms, R Series Batt = 0.20 ohms, R On Switch = 0.1 ohms, R Load Electronics = 1K ohms, L Starter = .1H )


Theoretical, not theological voltage waveform as seen by device attached to start battery at starter run time of 1 sec(.1 - 1.1 Sec). High freq(1.1-1.5 Sec) high/low amplitude(19V- 4.5V) "ringing" envelope due mainly to inductance of starter windings and inherent resistances of starter windings, solenoid contacts, wires, battery etc..DC dropout(.1 - 1.1 Sec, 4.5V) due to inherent resistances of starter windings, solenoid contacts, wires, battery etc..



All JMO of course, your results can vary.

 

[Mark_VTfisherman]

>sam am I

I get what you are saying here. Noting that you do state "theoretical" voltage spike (I would assume following as a response to the sudden load of the starter being responded to by the voltage regulator after startup) I have thought about the implications. Since my starting battery actually is "oversized" by a very significant amount seeing that my motor is only a 40HP, I wonder if the theoretical voltage spike isn't much, much less than 19V. Not only that, but my units do have low voltage shut-down and high voltage shut-down and this has not occurred in years (new batteries solved the charge maintaining issue).

I say all that to say this: with all the technology we have these days I simply can't imagine that they manufacture things that won't/don't survive when used in the conventional environment they were designed to operate in. Having a 3rd battery aboard just for my sonar and GPS units seems absurd!

 

[sam am I]

>sam am I

I get what you are saying here. Noting that you do state "theoretical" voltage spike (I would assume following as a response to the sudden load of the starter being responded to by the voltage regulator after startup) I have thought about the implications. Since my starting battery actually is "oversized" by a very significant amount seeing that my motor is only a 40HP, I wonder if the theoretical voltage spike isn't much, much less than 19V. Not only that, but my units do have low voltage shut-down and high voltage shut-down and this has not occurred in years (new batteries solved the charge maintaining issue).

I say all that to say this: with all the technology we have these days I simply can't imagine that they manufacture things that won't/don't survive when used in the conventional environment they were designed to operate in. Having a 3rd battery aboard just for my sonar and GPS units seems absurd!

I hear ya Mark, you make good points......sometimes s**t just happens and nobody yet has made a 100% bulletproof design that can meet 100% of every possible implementation variations it's designed to exist in, but I truly think we try. But "try" as we do, "try" is as best we can do though........

http://www.philly.com/philly/busines...5f6fd9f1e.html and the list just keeps getting bigger :facepalm:

I think the key term here is "CYA" and it comes into play w heavier weighting on it if it's dependent on certain higher of levels human safety and security factors. Somethings, it's a "no biggie" when and if it happens and that's what you might have here.....IDK. In other's, it's a "what if?" because as ya know, it will happen! It's just a matter of when it does.

Theory is where we typically reference from and wing the rest..... ya just do what ya can to keep yer butt safe as ya leave the launch pad eh? Sometimes more, sometimes less, sorta like seat belts I suppose......Ya don't have to use them at the dinner table, but in any car ya really should and really really should if you're driving a GM!! (Nothing personal, just using it as an example, many others out there to choose from, yes)

Are you at Applebee's? Who cares then, wire it however, moot point, wire'um up to the plug coils(J/K, don't do that, but my point is, ya don't need to worry either way)

Are you in a Volvo? Well...... Gotta good safe designed car, probably won't crash anyway, but ya might just wanna buckle up for safety sake.............You know what theory says!!

Are you in a GM? Oh S**T!!!(Is your design a GM? Hope not, but............we'll know how some manu's can operate now eh?)

Just say'n Mark, maybe the manu(GM type or not) is saying "ya best buckle it up. It is designed to run in that(your) enviro yes, but there is theory/evidence out there that supports why you should buckle it up. We don't have 100% bulletproof designs that covers 100% of implementations variations(yours, mine, his, hers, theirs, everyones) that can exist and we've seen failures that could be related to this"

.
BTW, three batt's? That's not necessary!! Not sure how you're wired, but just two batteries can be wired as needed/recommended, start and house, house being iso'd on start up.....just an FYI.......GL

 

[Mark_VTfisherman]

Yes. Yes.

I don't know exactly what you mean by "separate battery." I have to assume that by "separate battery" you mean a battery that is not used for engine starting.

A separated battery exclusive to running the GPS and sonar not connected to the charging system (which is what the rep I spoke with suggested)

So because I have a house battery that does everything including starting, and a second deep cycle for the electric trolling motor, the suggestion made to me was to have a third battery on board.

 

[dingbat]

Two major concerns, the electronics manufacturer and the "redundant" ground.

I've seen more things happen because of improperly terminated grounds than just about any things else. Multiple ground paths with a "hot" down-rigger is just asking for problems.

 

[sam am I]

Hold the phone.........

The person I spoke with suggested that I needed to remove the GPS and sonar from the starting battery and connect it to its own battery.

1] Do you run your electronics off a battery connected to your boat motor's charging system?
2] or, Do you run your electronics off a separate battery?

Mark,

Two different monsters here, my apologies for missing/not addressing the second. I addressed ONLY devices in the starter's path, but obviously "removing electronics from the starter battery" and the "running electronics off a batt connected in a charging system" can be vary different circuits eh?

So perhaps this person stating that you should "remove from start batt and moving to its own batt" did not say to also "remove it from a/the charging circuit"? as I didn't see as I re-read where you stated that they had.

My electronics are NOT(as belabored above) wired such that any can see(electrically isolated) the starter upon starting, BUT yes, they are wired such that they are on a battery(or batteries) that does see the charging system(mag shunt rec/reg).

BUT, the charging systems will have certain infrequent failures modes that are typically quite obvious(assuming not your case, so stayed wired to) that can negatively impact attached electronics and not so much the always inherencies as the starter has(maybe your case, manu suggested to iso) and is perhaps all the manu was asking you to do.

 

[AndyHUK]

Ok being an automotive and marine electrical design engineer I tend to have an opinion on these things

There are several issues associated with the 2 battery model you are talking about.
Mostly, it needs to be charged and remain charged during operation and use. NO engineer would design a system that is not charged!!

Ok what the people above have said is mainly correct, starter current (more importantly induction) is the killer as is a poor wave form on the charging circuit.

Ways to improve this are simple enough, your grounds (earths...whatever you wish to call them) need to be split up, any ground from the starter and charging need to be put together (Dirty grounds, like high induction loads..starter, alternators, ignition systems etc). All others need to be separated (Clean grounds) for instrumentation and on board electronics. That way you are removing a lot of inductive and dirty signals floating about the wiring.
However most *modern* electronics are capable of withstanding these issues and will also operate from 9V to 17V without any long term damage.

When I am designing the wiring systems for large yachts (40 to 70 footers) I tend to use split battery and charging systems, I NEVER use the starter battery for anything other than the engine start and run functions...everything else is *house batteries* run. If all else fails at least you can start and run the engine if the house batteries go flat, the same is true with a small sports boat up to an ocean going liner. My advice would be to have a battery for your engine only, then use a split charger relay to charge your house battery only when the engine is running.
This solves almost all of your problems, it gives extra capacitance to help stop erroneous signals making it back to your electronics, it supplies only clean grounds and feeds to your electronics as the charger relay will only operate when the charger is in charge mode (not turning over and not firing) as the engine needs to be running at idle or above.

Just my humble opinion any way

 

[Mark_VTfisherman]

@ AndyHUK and dingbat:

Thank you for that info and your time.

Q: Would a "filter" (like we used to put on radios to get rid of alternator noise in our cars) between the terminal block and the GPS and sonar units solve any of this?

Incidentally, that starter and charging circuit negatives are connected via the motor 'chassis' - all other equipment negatives are connected to the battery via a 10 gauge multistrand wire that runs forward to a terminal block under the dash. This is for power grounds...earth...whatever. I have the separate second wire that runs back to the battery negative that is for chassis bonding only- all equipment (helm, stereo, housings) that have a metal chassis is daisy-chained to this wire. It should not support any power returns as such as all power negatives are connected to the terminal block. It *may* be part of a circuit, but it shouldn't be part of the equipment power circuits. There should be no battery current on this redundant wire.

I am really appreciating the input and have both gotten food for thought and learned from everyone's comments. One of the reasons I love the iBoats forum

All the best- Mark

 

[dingbat]

Q: Would a "filter" (like we used to put on radios to get rid of alternator noise in our cars) between the terminal block and the GPS and sonar units solve any of this?

Not if your having grounding issues.

I have the separate second wire that runs back to the battery negative that is for chassis bonding only- all equipment (helm, stereo, housings) that have a metal chassis is daisy-chained to this wire. It should not support any power returns as such as all power negatives are connected to the terminal block. It *may* be part of a circuit, but it shouldn't be part of the equipment power circuits. There should be no battery current on this redundant wire.

Or so you think.... by running two "ground" wires to separate locations, you have the potential to have the two "grounds" at different potentials. Electric will always take the path of least resistance.

Ultimately, the water is your ground. Every light or piece of electronics should be wired with its own DC return wire. The DC load returns of all branch circuits should be tied to the negative bus of the DC distribution panel. In turn, the negative bus of the DC distribution panel should be connected to the engine negative terminal or its bus. The battery negative is also connected to the engine negative terminal or its bus. The key factor here is that the boats electrical system is connected to "seawater" ground at one point only, via the engine negative terminal or its bus.

The first thing I would do is get rid of your chassis bonding. It's not needed

 

[Mark_VTfisherman]

Well it's sorta funny I am looking back at this almost exactly one year later. I have a big MFG Edinboro I am working on, plus a Starcraft Holiday 18 I am gutting. So what I wanted to do was review this 'textbook' to avoid any issue when I get to the rebuilding/customization portion.

First, I like the idea of an exclusive starting battery, with an auto isolated house battery, as suggested above. If I install an electric troller on either of these that will have its own battery. Not likely to have electric trolling motor on either, especially the starcraft.

Second, I have not changed my setup other than cleaning and reinstalling all the negative terminals whether they needed it or not. Observations: the replacement GPS runs HOT under extended use. It has blanked and rebooted on two occasions when the sun was on the unit on a hot day. Same type of thing went on with the other units 'till they died... Conclusion, all the Lowrance suggestions are trying to remove fault from the manufacturer's design flaw, and overheating causes the anomalies and eventually death. Keeping the unit out of direct sun keeps the unit cooler BUT it sorta blocks the GPS signal. Ahem. So my solution if I stay with Lowrance will be to flush install the unit in a panel that will keep the sun off it and mount a remote GPS puck on the hardtop...

However a big thanks to the great info above because I have referenced this several times. I so much appreciate each responder for taking the time to type their detailed lengthy explanations. Grateful

 

[dingbat]

To increase daytime visibility, they backlight the displays. This is what is causing the heat buildup. Don't know if lowrance has adjustable backlighting or not. If so, turn it down a bit and see if it helps.

Flush mounting can make the problem worst. I know two guys with flush mount installations that had to install fans in the compartments to keep the units running on hot days

 

[Mark_VTfisherman]

To increase daytime visibility, they backlight the displays. This is what is causing the heat buildup. Don't know if lowrance has adjustable backlighting or not. If so, turn it down a bit and see if it helps.

Flush mounting can make the problem worst. I know two guys with flush mount installations that had to install fans in the compartments to keep the units running on hot days

Got that. The display backlight is adjustable, but in bright light one is inspired to run it on the brightest setting as you can imagine.
My flush mount isn't going to be enclosed - fully open to below for air, with some convection slots. The thought is to keep it out of the sun cuz it acts fine at night, overcast days, or when the sun is overhead and not on the unit. If this approach proves ineffective I'll know it!

 

[oldboat1]

just a hands-on comment related to your original post. I had a H.Bird Helix5 SI installed on my boat before launch this Spring. It’s a two battery system with a battery switch. My new unit cut off if the engine was started while the depth finder was on (wired into the panel). The switch was set to both batteries.

I rewired the depth finder directly to the house battery (both pos and ground wires). The unit now works fine with no interference at all. Curiously, I replaced the depth finder because the older unit on the boat was giving strange readings when the engine was running (worked fine with the engine off). I haven’t gotten around to it yet, but think direct wiring to the aux battery will take care of the issue with the old one too (still in place, with wiring detached).

The engine/alternator interference apparently occurs through the battery switch — not if both pos and ground connections from the depth finder go direct to the battery. (The house battery used for the depth finder still charges fine, just as it did before.) Anyway, the separate battery recommendation probably means independent connections direct to the battery. Maybe the common ground at the panel is the issue — just not sure. Additionally, direct wiring might work to the starter battery as well — not sure of that either. I chose the house battery. Depth finder works.

[inline fuse....]