Electronics power feeds, what’s truly bad?


Bert van den Berg, proprietor of Cruz Pro, writes that “Once every few weeks or so we get an instrument back or get a call from someone who says one of our instruments is acting erratically. Almost invariably it ends up that the customer (or worse, their electrical installer) has done something dumb and wired it so that the instrument is susceptible to voltage transients. For this reason I have written an article to help show how electronic installers would wire electronics into a boat as opposed to how many electrical installers wire electronics into a boat…Please have a look and let me know what you think.”

Well, I’m not sure what to think of Bert’s advice.  I don’t doubt that it’s good practice to keep electronics off circuits that sometimes get loaded hard, but I’m not sure it’s a good idea to have numerous circuits running directly to the battery bank (nor is it common).  I do know that the NMEA likes to see a dedicated battery for electronics, but I don’t see that done very often in the real world.  And I’ve observed that Gizmo’s electronics seem to work fine despite intermittent loads like water and maceration pumps and refrigeration that share at least the heavy pos/neg cables that feed the main breaker board.  Then again, I’ve discovered that some circuits, like the (damned) wipers and my shippy “clear view” spinner, bypass the main breaker board (fuses still unfound), and wonder if that’s because they caused some electronics problems? 
   So what do you make of Bert’s good/bad electronics power pointers?  And, while we’re at it, why is that some electronics seem much more sensitive to voltage transients than others do?


Ben Ellison

Ben Ellison

Panbo editor, publisher & chief bottlewasher from 4/2005 until 8/2018, and now pleased to have Ben Stein as a very able publisher, webmaster, and editing colleague. Please don't regard him as an "expert"; he's getting quite old and thinks that "fadiddling fumble-putz" is a more accurate description.

16 Responses

  1. Dan Corcoran (b393capt) says:

    1) My first thoughts in regards to Bert’s piece:
    If you don’t take what Bert wrote literally … it seems just fine, but the diagrams and descriptions are wildly over generalized and easily distracting to the reader vs the core point being made that “Problems can occur when a piece of electronics and an electrical device such as a motor or solenoid share a common electrical path”.
    Some constructive criticism Bert … if I had drawn the diagram, I would have included a common bus and DC panel to make my point and perhaps differentiated between a few things as “good” (go to the panel) and “best” (go direct to battery) in cases like bilge pumps. For example those halogen lights won’t be a problem going to the DC panel, the huge voltage drop will still be isolated to the wiring on that light circuit of the DC panel.
    2) An additional though in regards to Bert’s piece:
    The diagram clearly seems aimed at preventing problems when using devices’ such as those that Bert sells, it nags me a little that in providing “some simple wiring techniques that can help prevent serious problems when connecting sensitive electronics”, the entire subject of preventing ground loops was left out … something that becomes important with sensitive audio electronics … which could be served with a good high level diagram of a boat’s grounding and bonding system. I suspect ground loops could disrupt Cruz Pro products also.
    3) In regards to Ben’s question on dedicated batteries: I had a problem with my starter motor resetting my chart plotters on my 39 foot sailboat. My sailboat came from the factory with a very simplified two battery bank (starter & house) system that didn’t actually allow you to separate the banks while underway (and still be able to charge your starter battery). I went thru considerable expense to isolate my starter battery and engine starter from everything else, and life has been good since.
    4) In regards to bypass of wipers and clear view spinner: I suspect the first motivation of previous owner to bypass main breaker board was to eliminate noise on the VHF and/or stereo, especially if either wipers or spinner was in contact with the metal frame of the window (ground loop time), but even if not it’s easy to imagine the wipers generating noise. Perhaps the wire run goes all the way to one of your batteries? (any mystery connections on your batteries ?)

  2. Bill Lentz says:

    Ben I think it would be very important to add a fuse in series with the zener the size of the fuse would be determined by the zeners current handling ability. I use 3 Lifeline 8D AGMs that are isolated from the starting circuit by a large BlueSea ACR. In addition I am using a noise filter rated at 150 amps on the output of the ACR that feeds a #2 ground and power isolated buss. When starting the engines the ACR is forced to the off position. I have no heavy loads on the electronics buss other than my Norcold DE0061 that draws about 3 amps peak. In addition because my engines have are computer controlled I have a smaller high current bank on it’s own shore power charger using qty.3 -31 series AGMs that run the windlass, bow thruster and watermaker. I never run the watermaker if I have to use the 2 inductive kick motors on the Windlass or Bow Thruster.
    Take care. Bill Lentz

  3. bcl says:

    The reason why some devices are more or less sensitive to voltage problems lies in their power supply designs. In general if they have larger capacitors on the incoming side of the supply they will be able to survive a longer outage, providing enough voltage and current to last until the line level returns to normal.
    It also depends on how much current the device uses. If it is a lower current device, but has a fairly beefy powersupply compared to its needs, it will be able to survive.
    Anyone designing electronics for boats or automotive use should be taking into account that the voltage supplied isn’t always as clean as we get from a benchtop powersupply.

  4. Bill Lentz says:

    I have one correction my ground buss is common throughout the entire vessel. 4/0 cables run from the Xantrex shunt to common grounds, each engine has 4/0 to the common ground and all starting batteries connect to this ground through high current buss bars or negative buss. Obviously the MorningStar controller from the solar panels, multiple battery chargers and the inverter all have the largest gauge wiring they will accept. Supported 4/0 positive cables come off the engines and entire inverter/charger house bank systems positive and negative connections. The sub panels for the electronics are fed with #2 cable. The runs come off 4/0 feeds with the correct resetible fuses or breakers. Every battery in the boat is AGM and the chargers all have remote temp probes and remote charge status monitoring including a Link2000 on the inverter. The boat has 11 AGM batteries in total all my favorite Lifeline battery’s.
    Bill Lentz

  5. Anonymous says:

    “Ben I think it would be very important to add a fuse in series with the zener the size of the fuse would be determined by the zeners current handling ability.”
    why so the Zener can protect the fuse!!. its going to blow first every time.

  6. The best way of running the ground wiring is with a large main buss with branch circuits. The main buss or trunk needs to of sufficent gauge as to provide a very low resistance path back to the battery. The branches should not contain loops.
    Recall that the ABYC recommends that only a maximum of 4 wire terminals be attached to a single feed point. The too commonly seen multiple wires hanging off of a battery terminal is not a good idea.
    Noise generated that gets onto ground or positive wiring can be radiated or conducted. If the noise is radiated then physical separation, running wires at right angles or shielding of the source or wires may work. If the noise is conducted then filtering may be the solution. Voltage filtering can be accomplished using capacitors and current filtering with inductors or chokes. The values of the capacitors and inductors need to be chosen to be most effective at the interfering frequency. Different values are needed for audio noise or radio frequency noise.

  7. Mike says:

    While the general comments are worthwhile – avoiding hi-side droop and ground-bounce from pulse loads, while snubbing transients right where they start – there’s something more troubling going on.
    this kind of environment is not at all uncommon in transportation electronics and it is seldom the wiring can be re-plumbed to placate one piece of hardware with insufficient tolerance for the really ugly Real World.
    any modern piece of marine electronics should stoically tolerate input voltages as low as 9-10 volts and as high as 36 (or even 48 volts) operating while surviving regular spikes from alternator dumps and the like. the automotive electronics guys have done a good job of codifying what’s required in this space and this information is not hard to find.
    the good news is that the proliferation of automotive electronics has made wide-range power supply components much easier to come by. While it’s true that one can build cheaper kit
    with simple regulators and marginal input protection,
    that is why there is a HUGE difference between
    “inexpensive” and “cheap”.
    when it comes to making electronics survive in the Real World, there’s just no substitute for sucking it up and
    doing the right thing.

  8. Thanks for all the good suugestions. I have already added some of them to the article.
    I am not suggesting for one minute that you run multiple circuits direct to the battery. I am suggesting that one circuit be run direct to the battery for your electronics. Why not prevent the problem in the first place by getting the transients and voltage drops/droops OFF the power supply line powering the electronics instead of trying to fix the problems?
    Every CruzPro product has 600 watt transient diodes built in and some power circuits have 1500 watt transient diodes built in. There are some people that still manage to blow even the 1500 watt transient diodes (almost as thick around as your little finger).

  9. Dan Corcoran (b393capt) says:

    Bert asks ” I am suggesting that one circuit be run direct to the battery for your electronics”
    –> Because the manner in which the DC Panels of our boats are prewired before we purchase them prevent that. On my own panels I have lights, fans, autopilot, large fridge/freezer, vhf, chartplotter, instruments, more lights all intermixed.

  10. Bob Austin says:

    Point well made that the majority of boats are inadequately wired for modern electronics. I have re-rigged several “new” boats in the last couple of years, and the first thing I did was to run adequate wire from the house or electronics battery to the common bus for electronics at the helm–in my cases 25 to 27 foot boats, and added #8 wire (both positive and ground)–plus isolated the electronics or start battery with a voltage sensitive relay.
    One of the first things to do on a “new boat” is to run a fish tape to the batteries/and where transducers go–then follow with a “pull string” which is replaced each time a wire or cable is run through this passage. Too bad the boats don’t come this way. It would make rigging much easier.

  11. Dan,
    From your point of view I can see that you want instruments to be bullet proof and able to handle any transients or voltage brown outs that might occur on your boat. From a manufacturer’s point of view the level of protection only needs to be “adequate”. If you’re manufacturing an expensive instrument or one that’s going to be used on a space shuttle there would be plenty of justification for doing the best job possible. However, it does not make financial sense to add another $5.00 worth of parts to a low cost instrument when only a few dozen a year out of 30,000 units suffer a failure due to transients. Remember that adding $5.00 to the cost of an instrument adds about $15.00 to the retail price (in our case that’s about 10% of the retail cost of the instrument). We currently add about $0.50 of transient protection to our instruments. If we increased this to $5.00 we could probably prevent another 0.1% of the instruments from failing due to transients.
    Why should 29,950 customers have to pay $15.00 each more when 99.8 % of them don’t need that extra protection? Now multiply that cost by the number of instruments on a boat and you can see the true financial scope of the situation. Also, no matter how much protection you add, it will never be enough for some situations (lightning strike being an obvious example). Why not take the effort to run a single separate line to power all your instruments?
    Best Regards,

  12. Dan Corcoran (b393capt) says:

    Bert … can’t figure out what I wrote to get that reply from you … did you mean to reply to someone else, maybe Brian/bcl ?

  13. Ernie says:

    I am experiencing this very problem. I have a Nordhavn 40 with 3 8D AGM batteries for house and electronics. 1 8D is in the bow with direct connections to the bow thruster, while the other 2 8D’s are in the lazzarette, directly connected to the Zantrex 2500w inverter/charger. There is a huge Positive bus in the engine room, where DC power is fed to the DC panel in the pilot house, and to feed the parallelling switches to connect the house batteries to the gen and wing engine starting batteries. I never had a problem with this arrangement until I installed a stern thruster. I wired it directly to one of the 2 8D batteries in the lazarette. Now when I operate the 2 thrusters all my electronics shut down, but worse yet, I blew my radar pedestal (I dont know if I blew the magnetron or the power converter board), and an LCD TV. My initial plan was to dedicate a battery to the DC panel via a battery isolator, and the proper place to do this is at the DC bus in the engine room where the panel gets fed from, unfortunately there isnt a ground bus nearby. So my next solution is to dedicate a battery to the stern thruster, and use a battery isolator in order to charge the battery but keep the transient spikes from affecting the rest of the DC system.

  14. Dan Corcoran (b393capt) says:

    Ernie … there isn’t a lot of information here, but in combination with http://www.boat.com of how a Nordhavn 40 is configured, let me take a stab at this.
    Your using two thrusters against (3) 8D batteries and an alternator? Probably deep cycle batteries, eh ? Alternator upgraded too 200 AMP or more ?
    Each thruster (8hp = 6 KW ?) is about 500 Amps of current draw. The first thruster benefits tremendously from the engine running (upgraded alternator output 200 Amps ?), so the load on your (3) 8D batteries is 300 Amps with 1 thruster. When you added the 2nd thruster the power consumption from the batteries jumped from 300 to 800 Amps ? A 285% increase in load over 1 thruster. This is too much for your batteries, your ground bus, and other wiring.
    I also doubt your ground bus is sized to handle this on top of undersized wiring in several places with just 1 thruster, that now have crippling voltage losses with two thrusters.
    Four problem areas:
    1. If you have deep cell batteries, they can’t deliver (even in combination with the 200 AMP alternator) on 12 KW, so your voltage falls off a cliff, but moreover this is a job for starter batteries and their unique plate design that can deliver more current faster … you are badly damaging the plates on your deep cycle batteries if you continue.
    2. If you have starter batteries, they can’t deliver 800AMPS at 12V either … so now your talking 10V best case.
    3. With starter batteries at 10V your drawing nearly 1200AMPS best case across your entire electrical system (alternator + batteries), but the additional voltage drops in your electrical wiring is probably staggering … and your still below the minimums your need for your electronics.
    4. And to restate … I doubt your ground bus is sized to handle this on top of undersized wiring in several places with just 1 thruster, that now have crippling voltage losses with two thrusters.
    Adding one battery to the aft end, alone is not the answer.
    Consider the following:
    1. Be sure the battery in your bow is a starter battery, and sized large enough to power the forward thruster on it’s own without aid from your aft battery bank and alternator, plus separate it with a switch or one of those combiners that will disconnect under a certain voltage level insuring the bow thruster exclusively draws power from the forward battery. Whatever voltage drops happen are isolated to that circuit.
    Now your aft thruster will have 200AMPS from the alternator and 300AMPS from the (2) 8D aft batteries. That seems doable.
    2. If #1 isn’t enough, add a third deep cell battery to your aft bank, which probably has advantages of simplicity in the charging system over dedicating another starter battery to your aft thruster.
    Would love to know how you made out, please be sure to update me.

  15. Dan Corcoran (b393capt) says:

    In keeping with this thread, part 1 isn’t enough, as it would be rated “VERY BAD” by Bert.
    Bert would probably not like my part 2 either, but I am adverse to having too many battery banks and too much weight. A GOOD variation on part 2 (part 1 is still necessary), add another battery to your engine starter battery bank and share that bank between your engine and aft thruster … which in keeping with this thread would be a GOOD solution. 🙂

  16. Hi Dan,
    I didn’t mean to pick on you – a case of mistaken identity and/or lack of coffee at 5:00 AM.

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