Weird sudden loss of 12V DC.

[wingssail]

Originally Posted by tkeithlu

Thank you for a bunch of good advice. Regarding the various "Know your boat" posts, I built the boat and designed the electrical system. The switch in question cuts off the house bank, and has not been used since construction was underway - I've had no reason to isolate the house bank.

I'm very much a fan of redundancy, and there actually are three tracking GPS's among the instruments (Open CPN, backup GPS, and AIS), all of which, of course, failed. The paper chart is right beside me and (usually) gets half hour locations marked.

Again, thank you for all the good advice.

Just out of curiosity tkeithlu, why did OpenCPN go down? Was it on a desk top computer plugged into an inverter?

If so, maybe a laptop with a battery is a good idea? Otherwise, why?

[Uncle Bob]

Tkeithlu and John, thanks for the posts, I have three pairs of 6 volt batteries forming my house bank, each with an isolation switch, which will from now on be exercised on a very regular basis.

[tkeithlu]

I think OpenCPN went down because the inverter is downstream from the switch that failed. I suspect that we had been running on the laptop's battery for several hours without knowing it, but that is a question in my mind too, since it failed at the same time as everything else.

My moves will be:
1. replace the switch (on order)
2. add a prominent voltmeter to the backup battery. I've found an LED meter for $12 on Amazon that flashes when the battery drops to 11.5v.
3. add a nav program to my iPhone. SeaIQ, probably.
4. Move one of my old handheld GPSs to the boat
5. Add a backup battery to the OpenCPN laptop
6. Stop being sloppy about using my paper charts.

I already have ways to cross connect various batteries. In this case, it was the next day and at the dock before I figured out that the batteries and charging system were just fine and went looking for the source of no voltage in the wheelhouse. Thank you for a bunch of good ideas.

[goboatingnow]

Originally Posted by wingssail

Sorry goboatingnow, even if you do understand it (and I am sure that I do, as well as anybody would) it will be damn hard to diagnose and resolve (diagnose, mostly).



Then, impossible to have someone on the payroll as you sail across oceans or in remote places. Even only slightly remote places, you cannot have an electrical engineer on board, and resolving issues by phone with photos won't be easy either.



As for "you shouldn't own it"...I'm afraid that is going to apply to a lot of people who discover over time that the wonderful electronic magic which controls everything on their boats just isn't going to be 100% reliable,no more any any boat electronics.



You know, I've got a simple boat, with maybe 5 electronic pieces in the electric system, and I'm pretty much on top of it all, carry spares and diagnostic equipment, etc, and I have issues every year. I solve them, but it is often hard and it takes time. This guy I described has dozens of electronic pieces and no diagnostic equipment other then the items themselves, and little technical knowledge. And he is typical. I'm not wrong about the future of these vessels, they will be broken down in foreign ports inthe future.

The reality is electronics are typically very reliable my St60 is as old as the boat and works perfectly.

The issue is system design and then installation of complex electronics is unlike many fields ( say aircraft or cars ) is often carried out by amateurs or “‘pseudo professionals “ even just boat dealers. Little thought goes into redundancy , or failure mode analysis and therefore planed workaround systems. It’s even worse where subsequent owners are bodging installs etc.

I’m a retired professional embedded systems engineer, I’ve designed solutions to survive in space etc.
It can all be done properly. On my boat I have a considerable amounts of typical electronics AP , AIS , nnea2000, MFDs , multinstation vhf , Wi-Fi , cellular links , monitoring systems , solar , invertors & dcdc converters

I removed Significant amounts of stupid wiring practices , including the manufactures , trashed every hidden and in line fuse o could find ( finally removed the last one yesterday ) Re did new control panels new breakers etc etc

I can run my boat on a 9v battery if it came to it ! I can bypass all critical auto interlocks and I use a set of long jump leads !! No fuses only circuit breakers

My winter project is new MOSfets based circuit breakers to replace the mechanical ones ( urs everything has a manual override as well as double redundancy , every consumer group on the boat will have active current monitoring.


It can be done but it takes knowledge and money

I have zero fear of electronic complexity on board., I can disable bypass or workaround every system.

Ps my sextant remains on board !

[goboatingnow]

Originally Posted by tkeithlu

It was a learning experience yesterday. We were going into Apalachee Bay on the Florida panhandle, headed for home. Everything was fine, and I was being lazy and not marking our position on the paper chart. The house batteries were sitting at 13.4V, so the charging circuit off the engine was just fine.



First, the autopilot reported low voltage. WTF?! Then over about five minutes we lost all DC electrical power. Zero. No instruments and no autopilot, including no compass given a steel boat that does not like magnetic compasses.



I was surprised at how much we had to adjust to using a paper chart and Mark I eyeball. A general but not specific knowledge of where we were was not reassuring or adequate. We make it home OK, but got well off course once in very familiar water. My confidence took a beating.



Examination showed that a single ordinary Perko rotary switch in the DC circuit had failed, leaving us with only the back-up battery behind the panel to cover all DC needs. The house batteries were fully charged, but isolated, and the five minute course of failures was the backup battery going to zero.



So, our next move is a compass app on my cell phone, and perhaps a completely isolated power source for the nav computer with OpenCPN. My summary feeling is that even with our attention to having paper chart backup, it is easy to get dependent on the electronics and out of practice doing it the old fashioned way.



I’ve pontificated on the forum about keeping at least some instruments separate from a glass cockpit, because a monitor or CPU can go PIFF, but I didn’t think about loosing the source of electricity beyond having the backup battery to use to call for help if the house batteries flooded with seawater. The switch from the house bank to the single backup battery went unnoticed, because the voltmeter still said 13.4V as the backup battery was drained.

A simple set of jump leads and a DC multimeter would have both diagnosed the issue and allowed you a workaround

[Lake-Effect]

Originally Posted by goboatingnow

A simple set of jump leads and a DC multimeter would have both diagnosed the issue and allowed you a workaround

Agreed, but not the sort of diagnosing one wants to do when underway and stuff goes sideways. A panel meter on each bank is relatively inexpensive and would have told the story almost immediately.

[Lake-Effect]

Originally Posted by goboatingnow

The reality is electronics are typically very reliable my St60 is as old as the boat and works perfectly.

Our home surround AV receiver went flaky (main DSP board) after about 7 years, yet I have 30+ year old audio gear that is as good as new. 3 of 5 major appliances in our house have had significant electronic failures, all of which have to do with cutting corners in design (eg omitting pullups) and especially the cheap-ass connectors. Yet my Mom's 35 year old washer and dryer soldier on. Our ST40 depth instrument lasted only 6 seasons... So, I'm a bit down on some modern electronics; even the "marine" premium doesn't always mean reliability.

(but I do love modern SBCs and embedded stuff )

[Cadence]

Originally Posted by SeanPatrick

And what happens when the electricity is not there and they have not kept their chart work skills sharp?

Chart skills isn't rocket science.

[wingssail]

Originally Posted by SeanPatrick

And what happens when the electricity is not there and they have not kept their chart work skills sharp?

I think chart skills are like riding a bike, if you've ever learned it and used it, it will come back.

[ChrisJHC]

Another backup option is a GPS watch.
I use a Garmin Fenix 5 and get 7-8 days between charges (not using the GPS).
Around 3 days using the GPS for about 8 hours a day.

Gives me current position, heading and speed.

I can also put in waypoints etc but usually use other systems for actual navigation.

[goboatingnow]

Originally Posted by wingssail

I think chart skills are like riding a bike, if you've ever learned it and used it, it will come back.

No not really, you probably learned how To factor equations in school , can you do it now ?

With cheap gps , people can have multiple independent sources on board , i have 6. There’s really no reason to loose all of them.

[Cadence]

Originally Posted by goboatingnow

No not really, you probably learned how To factor equations in school , can you do it now ?

With cheap gps , people can have multiple independent sources on board , i have 6. There’s really no reason to loose all of them.

That is nonsense. Factoring equations and having a compass, chart, parallels, dividers and a pencil has no relevance.

[ACOrton]

Glad you made it back safe. Had a similar issue as well. I was running a little 1/4 hp vacume cleaner working on some projects as I had done many many times before when the DC powered lights began to ship off and on and the vacume then tripped the breakers. First time it had done that. I reset and go back to work when it happened again and then the low voltage alarm went off. I inspected the power distro area visually and all seemed well except for a cracked insulation end going to a terminal on the main battery switch. I then touched it and it was definitely warm. I proceeded to pull it apart and found the back of the switch to be melting on the terminal. In the end it was my fault. I had over sized the wires using 2/0 insulated welding cable but didn't think about strain relief when making tight turns and it just placed alot or torsion and tension on that lug and during higher loads the terminal would heat up and give way until eventually the contacts for the switch had such a gap they started to arc across causing an even larger resistance in the system.

TLR, strain relief or run your larger stiff calbles at larger radi.

[goboatingnow]

Originally Posted by Cadence

That is nonsense. Factoring equations and having a compass, chart, parallels, dividers and a pencil has no relevance.

Unless you practice chart work , remember how to do running fixes etc. Chart work gets sloppy

I used to teach it for YM courses , you’d see people that had got used to gps struggling to remember the basics and generally getting it wrong.

Try asking someone used to gps to look up tidal stream data and chart a CTS , unless they do it reasonably regularly they make a mess etc.

As I said these days there’s no reason to loose position data irrespective of the wiring on your boat.

[LittleWing77]

Originally Posted by waterman46

Probably very little effect due to current. The magnetic field of wires is quite small at the levels of current found in any devices you'd usually have near the steering compass. The compass at the steering station, on a sailboat anyway, is usually much higher and meters away from any major DC current drawing devices like watermakers, reefers, battery chargers and HF radios. There can be a lot of deviation due to other devices nearby, but that deviation is caused by the metals in those devices, not the current they draw.

I checked my compass with the nearby radar and chart plotter both on and off and could see no difference. On the other hand, I had to compromise a bit when I added the 12" chartplotter since just holding it where I really wanted it, without connecting the wiring yet, made the compass deviate more than 4 deg.

Thanks for that explanation, Waterman.

I have never seen the compass-swinging/deviation adjusting being done, so my thinking-outloud was speculative (and obviously, my 'understanding' - sketchy)

Thanks for taking the time to explain,
Gratefully,
LittleWing77