Weird sudden loss of 12V DC.

[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.

[BillKny]

What’s the issue with magnetic compasses on your boat? Compasses have been installed on steel boats for 150 years. It’s not trivial to swing and compensate them, but it certainly can be done by someone who knows what they are doing. Seems like a skill a steel boat sailor should learn?

And if a proper navigation compass can not be made to work, why do you think the tiny little magnetic sensor inside you phone will do any better? They both have to use exactly the same magnetic field, distorted in exactly the same ways.

[LittleWing77]

Great story, tKeithlu!

It's scenarios like this which are behind my expressed Forum opinions that people always continue to navigate, take hourly positions, etc. and retain in the back of one's mind that electrics could fail at any time in a marine environment (especially saltwater), so contingencies are VERY good to have in place.

Thanks for sharing your experience,
LittleWing77

[LittleWing77]

Originally Posted by BillKny

What’s the issue with magnetic compasses on your boat? Compasses have been installed on steel boats for 150 years. It’s not trivial to swing and compensate them, but it certainly can be done by someone who knows what they are doing. Seems like a skill a steel boat sailor should learn?

And if a proper navigation compass can not be made to work, why do you think the tiny little magnetic sensor inside you phone will do any better? They both have to use exactly the same magnetic field, distorted in exactly the same ways.

Isn't a compass-swing and adjustment for deviation related to the onboard electrics?

If Keith suddenly lost all of the onboard electrics, his compass headings would have immediately been impacted by the loss of electricity because compass deviation would have been set with the electrics working.

LittleWing77

[rslifkin]

I'd add a volt meter to the backup battery. That way you know voltage at the closest point to the nav equipment as a better indicator of a problem.

Nav apps on a cell phone or laptop with a GPS puck make a good backup, as it has its own battery to run it until you find an alternate source or method to charge it. I figure that by the time you can't keep any form of electronics running, you've likely got much bigger problems.

[more]

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 try this on a phone or tablet. this is far better from opencpn.
https://www.navionics.com/fin/apps/navionics-boating

because good smartphone catch all satellite for navigation + A-GPS
A-GPS , draws its information from local cell towers and enhances the performance of standard Galileo,GPS on mobile devices connected to a cellular network.Assisted GPS positions a phone or mobile device when GPS signals are weak or not available. GPS satellite signals don't penetrate storm cloud very well . Assisted GPS uses proximity to cellular towers to calculate positions when GPS signals are weak or unavailable.

Second you must know wire route on your boat blind.

from battery to switch,from switch to fuse,from fuse to master busbar.

Also must know wire on engine,you must know how start engine without master command and bypase fuel valve (if egsist)

[Lake-Effect]

Originally Posted by tkeithlu

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.

Surprised that the battery switch failed, but not impossible I guess. Any theory as to why? Age? Mechanical failure? Damaged contacts?

In your Docksiders, I would do the following:

1. replace the switch with a better one
2. add a voltmeter or a low-voltage warning light for every battery bank
3. bigger backup battery, sized for at least 30 min?

With #2, you would have had instant confirmation that you were depleting the backup while the house was still fine and charging. [agreeing with rslifkin]

It might even be argued that your backup system gave you a false sense of security because it masked that switch failure.


(also, keep a $10 pocket compass around )

[GordMay]

Originally Posted by BillKny

... And if a proper navigation compass can not be made to work, why do you think the tiny little magnetic sensor inside you phone will do any better? They both have to use exactly the same magnetic field, distorted in exactly the same ways.

In a smartphone, there is a compass chip, which senses the magnetic field, in two or three axes. The chip measures the magnetic field, in each axis, and converts it to a voltage, that the phone computer can read.
Those devices are usually based on hall-effect, or magnetoresistive sensors [magnetometers], because they are cheap, and reasonably accurate.
In a smartphone you also need to know the orientation of the phone, and this is provided by accelerometer chips.
The magnetometer function is usually integrated with the accelerometer into a single, small chip.

FWIW: Your smartphone has a number of magnets inside, for example, the speaker, the camera, and the vibration module, none of which would work without magnets. Even the Apple Watch uses a magnetic induction wireless charging system, to ensure that the watch is aligned to the charging dock.

[Chotu]

This is why I like to carry a few redundant chart plotting systems.

You shouldn’t have a single point of failure like that. I use:

1) a nav computer

2) a handheld gps/plotter/anchor alarm

3) my phone with a chart plotter installed

4) paper

The truth is, I would struggle from being out of practice doing the old dead reckoning also. It’s been decades. But with all of the redundancy in electronics, if a couple fail, it’s still not that big of a deal.

[s/v Jedi]

You need to establish a clean DC power supply for electronics, with a backup. For us the primary supply is a DC-DC converter supplying 12V from our 24V lithium house battery. A secondary supply is the 12V battery bank that starts diesels and gets charged by alternator, as well as DC-DC converters.

There’s a backup to the backup: in case the 12V battery system fails, I can get 12V on those bus bars using a center tap from the house bank and an emergency switch.

[TrentePieds]

Do ye not wear an analogue wristwatch?

If you do, you have a compass, right there, that is prolly good enuff for the bit of navigation you had to do, and one that doesn't care what your boat is made of.

Luddite, of course, but it works!

Surely, in that bay, all you have to do if you get lost is steer due north till you notice that the seagulls are walking, then do a port 90 and follow the coast till you see some sort of sign of civilization ;-)?


TrentePieds

[Sailshabby]

+1 on Navionics for tablet and SeaIQ for phone.

[dadster3]

You might consider a tablet back up for navigation purposes.



https://sailingkerguelen.com/en/best...android-apple/

[wingssail]

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.

I think often about this scenario (battery switch or other failure which cuts off the DC system including the main DC distribution panel hence all the instruments) and potentially engine starting supply since they all go through the battery switch.

I am comforted by the knowledge that my laptop running OpenCPN has an internal battery which will keep the computer going for several hours. I also have a GPS puck which runs off of USB so the laptop's battery will run the GPS. At least we will have an active charting system showing our position and track.

Portable VHF Radio is also battery powered so we will have that for several hours.

One problem I won't have is unnoticed automatic devices which switch battery power around. We do not have any battery combiners, ACR's, DC-DC chargers or other electronic devices in charge of stuff I can (and would rather) do myself. We don't even have an audible low voltage alarm. If we were on deck and under sail or power the first indication would be failure of the instrument displays which seem to be pretty intolerant of low voltage. This would trigger immediate investigation.

My recommendations for all people navigating on a vessel with important electronics is:

• Make sure you have redundant battery powered devices which can continue if the ship's DC is lost.
• Avoid automated electronic switching devices which can take you out of the loop on important power decisions.

An extreme example:
I toured a new yacht with the latest electronic and electrical systems. I observed that this vessel, with 6 24 volt Lithium batteries each containing eight cells, had at least 6 BMS and ostensibly 48 temperature and HVC, LVC, and other sensors, plus a significantly complex and important Electrical Management system (with its own BMS) to manage the very large 48 volt alternator and the battery banks, and a complex display and control device (similar to a phone). They also had four NPPT solar controllers (one for each solar array) all managed by BlueTooth to a laptop app, and 10,000 watts of inverter plus DC-DC converts, plus a "normal" 12v system and battery bank connected to the other engine. And of course battery switches and the full array of electronics.

It was all totally impressive and the capabilities astonished me.

However the complete manifest of electronic devices was shocking to someone who has spent 40 years keeping a "simple" boat's electronics all functioning. One concerning aspect is that the monitoring system does not have the same granularity as the level of electronics has. If the system shuts down, how do you know which part, or which of the 48 or so little electronic devices has fried its little brain?

The one thing you'll know when you granddaughter comes to you and says, "My phone won't charge" is that something has gone horribly wrong. I guess at that point you pull over and call a tow truck.

Maybe I am a Luddite, and maybe today's electronics will never fail, but I doubt it.

[dadster3]

I just finished a 2-day course in boat electrical systems with Nigel Calder. Many if not most of his nightmare images in the presentation were of brand new boats at boat shows. It really is frightening. You cannot trust manufacturers to get it right.