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Old 21-12-2010, 09:09   #1
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Challenge: Electrical System / Charging

Dear fellow cruisers,

We have an electrical mystery that we’d love some help solving/troubleshooting.

On Saturday, December 18, we had a small electrical fire on the ignition serial bus bar. After putting out the fire and calming down, we removed the bus bar and found that the ignition hot wire connection was severely corroded and had been dislodged, probably during the removal of our mizzen mast right next to it. It appears that what caught fire was the bus bar or gunk on it. However, this wire goes directly to the starter battery (B2), and there’s a switch in-between -- which was turned off. We’re not sure how this happened, and to add to the mystery, that wire is still showing 12 volts -- even with the switch off.

The whole thing happened at about the same time that my husband turned on a space heater, which we were running through the shore power AC (we’re now running from an extension cord from the dock), but we don’t think the two are connected.

But that’s not the oddest part.

Afterwards, our energy monitor (EMON II-H1) alarm went off, showing that the house battery bank (B1) was below 50% amp hours remaining. The batteries are new, installed this summer - Deka Sea Mate 6 Volts, AGMs. We had been hooked up to shore power the whole time. We are not sure when it stopped charging -- the timing of the alarm may have been totally coincidental. At this point, the EMON was showing the B1 and B2 battery voltage readings up around 14.6 and rising, so we shut off the shore power, thinking that this was too high and we’d gas the batteries if it kept going. (Since then, we’ve read the EMON manual and re-read Calder’s Boatowner’s Mechanical and Electrical Manual and found that the absorption voltage at 32 degrees F, which is the current temperature, is 15.25.) Once we established that the higher voltage was safe, we turned it back on, and now it’s not charging from shore at all.

The solar panels seem to be very slowly charging the batteries, about an amp-hour per hour of daylight, and 1% per day.

We initially thought that perhaps the charger wasn’t working, so we checked and the fuse is good and the LEDs are showing it charging at absorption rate.

The voltage on the batteries when they are charging under solar alone is 13.25-14.03, and when we turn on the shore power charger, it rises to around 14.5. We understand that the EMON should adjust for temperature and allow the voltage to rise to the 15.25 recommended at this temperature, but that doesn’t seem to be happening. We are wondering if the EMON is limiting the voltage to the 14.2 that the previous owner set the voltage set-point at for 77 degrees and not adjusting for temperature, which would explain why the batteries are not charging. We have not tested the voltage at the batteries.

We have also noticed that some of the connections on the back of the instrument panel are also corroded -- which connections should we clean to see if this is perhaps the problem?

Can you suggest some next steps for troubleshooting?
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Old 21-12-2010, 10:05   #2
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How familiar are you with the boat and its electrical systems??

Are you sure there is no interconnect between the house and start batteries??
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Old 21-12-2010, 10:20   #3
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As the previous poster alluded to, I would suspect that the starting battery was feeding power to the buss independently of the shorepower battery switch being off.

Later in your post you describe the EMON adjusting the voltage. An EMON monitors battery voltage and current. It has no capability to adjust them.

Your situation is rather complex. I would suggest getting a boat electrician to help you figure this out. Needless to say your life or boat could be at stake.

David
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Old 21-12-2010, 15:06   #4
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Thanks

Thanks, all. After troubleshooting with the yard electrician, we are pretty sure that the apparent charging problem comes from not having reset the EMON baseline when we installed new batteries, as the batteries are reading full voltage but the energy monitor says they're 50% drained. We're letting them settle without charging or using them then will reset the EMON baselines tomorrow; hoping that works! (And, yes, I mis-spoke -- the regulator, I believe, adjusts the charging voltage...) The live wire from the starter battery is still a mystery; the switch is not on shore power but in-between the starter battery and the buss (we traced the line...). Heckuva learning curve but it looks like everything is working out. We have to learn these systems in any case.
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Old 21-12-2010, 16:47   #5
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Hether, you will find that in the long run the best, and perhaps the only, way to troubleshoot an electrical system is by making a schematic drawing of it. Even if that is just a sloppy and corrected pencil drawing on a large sheet of paper, make that drawing. You can make it prettier later, don't worry about that.

Yes, you can have an electrical fire simply because "gunk" got onto a wire, or more often onto a loose connection which then overheats as corrosion builds up resistance at that spot. Or the heavy draw from a space heater could have caused an overload--which was enough to create the heat on the corroded connection, etc.

That switch you found may have been a "secret switch" designed to prevent the boat from being stolen. I found one of those once in the wiring to the starter key, putting one in the battery wire might be even better assuming the switch was rated to handle the current in that cable. If all it does is disconnect the starter battery--that's a good way to make sure someone doesn't borrow the boat from your mooring or dock.
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Old 21-12-2010, 17:23   #6
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+1 on the schematic....
I'm having difficulty with the fire/space heater scenario, as (I'm assuming) the fire was on the DC buss and the space heater runs on AC..... UNLESS some goober wired the bonding system to the AC Neutral or Ground, and then somehow a hot leg got tied to one of them. If that is the case any GFI on the boat should have popped... and you would be seeing bubbles from your underwater metals being eaten off!
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Old 21-12-2010, 17:43   #7
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"UNLESS some goober wired the bonding system to the AC Neutral or Ground,"

Which is exactly why DC wiring is now YELLOW and red, no more BLACK for the negative or ground side, since that conveniently matches the HOT side of AC wiring.
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Old 21-12-2010, 18:55   #8
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If you really do have substantial corrosion in the electrical system, it will be a constant headache. Battery chargers, alternators, batteries, inverters, led lights, nav gear are all sensitive to seeing a correct and steady voltage. Time and again I've fixed the unexplainable by running new wires.

So I'd lay in a supply of high quality tin plated crimp fittings, an ACCO double ratchet crimper, contact cleaner, some sandpaper and some marine grade tinned wire. Disassemble each connection. Clean all touching parts to bright. If there's corrosion on the crimp fitting install a new one (assuming there's a little slack). Check for any corrosion at the crimp and strip any corroded wire back to bright. If a wire becomes too too short, replace the whole length with new tinned marine grade wire. Reassemble with a a dab of dielectric grease or anti-corrosion spray. If the location is at all damp or spray prone, use adhesive shrink wrap on the crimp fitting.

It really won't take that long and you can do your schematic diagram at the same time.

And for safety turn off all power while doing this work and check with a test lamp or mulitmeter. Both DC and especially AC. Disconnect at the dock and the master battery switch. Make sure any inverter is shut down at both the DC and AC side.

Carl
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Old 21-12-2010, 19:50   #9
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I couldn't agree more with Carl's post. Corrosion in your electrical system will cause you no end of problems and possibly more fires.

An infrared thermometer can be used to check all of your high power electrical contacts when they are under load. This should show up high resistance connections.
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Old 21-12-2010, 20:23   #10
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So are you saying your ignition bus bar has 12vdc on it when the switch that disconnects it from the battery is off?. If so disconnect the wire and see if the bar is still hot. If not switch is bad. If it is something else is bringing in the power.
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Old 21-12-2010, 20:36   #11
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Gotta echo CarlF and DeepFrz. If your ends are getting gunky and/or corroded, best solution is a systemic repair/replacement. Generally speaking, if there's corrosion showing on one wire in a given circuit or even in a given panel/compartment, the other wires in contact with said bus/terminal (or even just in the same compartment) are subjected to similar effects.

So take a good, careful look at your wiring. It doesn't take that long to go through and redo the ends on a couple dozen connections, it just seems like a big job. An hour or two and you should have all-new ends and clean wire to work with. No more fire hazard, and perhaps more importantly, supremely peaceful sleep

I cannot stress enough CarlF's advice to use a di-electric grease or anti-corrosion/battery terminal spray after you're done. Especially with crimped fittings. Those little crimps are such a perfect spot for moisture to collect, and they also cause a bit of resistance by their simple nature, so you get a little bit more heat there than at other points of the wire. Doesn't seem like much, but thousands of on/off cycles with accompanying temperature variations can have strange effects on metal in a marine environment.
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Old 21-12-2010, 21:17   #12
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I think you may have a serious problem (or problems) and the thing that sets my teeth on edge is that the electrical person you tasked with looking at the job looks past a fire, corrosion, an unknown live wire and sets about the task of advising how to reprogram a battery monitor, I think that is not good, not good at all.

So the best thing to do here is, like with all things marine, take the job on yourself as then you will know what is happening and why and that gives tremendous peace of mind when offshore.

First off, get a digital voltmeter that also reads resistance and amps (they nearly all do) then tackle this weird switch you found. It may not be some advanced anti theft device but perhaps some bodge to prevent the batteries draining via some unknown path. Put the meter in circuit measuring current and switch it on and turn everything else on the boat off, everything. Does current flow? If so is it uA or mA. If there is any appreciable current you need to find where and why (If for example you have a stereo that keeps its programmed stations or a GPS that has no batteries inside yet retains wayppoints this would be a uA current drain). The only thing that should be switched manually in and out is the solar panels because the solar panel voltage will confuse the regulator when the engine is running and it will not charge as it will measure the batteries are topped up when it sees the solar panel voltage. Hence it either solar or alternator, never both.

Similarly This live wire, best way I have found when tackling similar is disconnect all the batteries at the terminals and with the DVM measuring ohms (on the beeping continuity setting) measure from that wire to the 12V + red wires that would be connected to the batteries and find where and how many places you get the beep denoting a path. Then go back through all those beeps with the meter measuring ohms and you can find the lowest possible reading and thereby locate the origin of that wire.

As to the fire, you may be seeking coincidence to explain why it happened when it happened, but unless the fire kicked off the moment the ac power went on, I find it unlikely that the two are related and the only real tests you can all involve some exposure to testing 110V circuits under load and you may not wish to do that. I would suggest that you get a fire extinguisher and then try AC loads on shore power again and turn on a lot of 12V circuits to get everything working. Now go through and test the wiring from a couple of potentially sound DC grounds on the negative lead and measure DC and AC volts to every point you can. If you do not read a battery voltage on the DC setting when you are sure that it should be a low voltage DC circuit then try another ground point on the -ve side and if that still yields nothing switch the meter to AC and see if an AC voltage is present.

At this point you can either start drawing a schematic as advised by others but as an alternative I like to get a hand held sticky tape printer and tag each wire with what it does.

Then sniff around to find any potential hot spots on low voltage circuits and then (and here opinions may differ) you want to test the wiring to find if anything gets hot. The way to touch an insulated wire is wear rubber shoes and no wristwatch, put your free hand in your pocket and then with the other hand using the back of your fingers, bump the insulation, then if the insulation is poor and the circuit is an unmarked 110V the muscle spasm will contract your hand away from the wire as opposed to using the front/tips where a shock may cause you to grasp the wire. To recap you are doing this on battery voltage dc wires and protecting yourself in case there is an AC fault that you did not find with the meter (though if you ever need to touch an unknown wire at home, this is the way to do it).


Finally the corrosion, it all has to go, but my two pennies on this is to never use a abrasive unless you have to (ie removing corrosion on a equipment terminal that is integral) even then use a cleaner first and a electrical terminal grease/conductor afterwards. As to the crimps, yes replace, but I avoid those rachet devices and with good reason, the only time you see them in use in aviation is when they have been calibrated and in a controlled environment. When they are good, they are OK but when they go wrong its hell to pay. Get something like this and they will last a lifetime.
9-1/2" Wire Crimping Tool

Test each crimp (original or those that you replace) by doing your best to pull it off.

The good news is that with electrical problems although it looks and feels dire, when you get it resolved you will marvel at how easy it was.

Cuthbert
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Old 21-12-2010, 22:22   #13
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Cuthbert as an industrial electronics engineer I second your advice except in the use of rachet crimping . It's the only way to apply the correct force and function. The manual non rachet ones result in terrible crimps.

All the major crimp manufacturers Amp, molex etc recommend such rachet crimp tools for manual assembly

The best crimps are put on uninsulated and then a sleeve is heat shrunk over it. This is what the car industry does the pre-insulated ones an abomination but widely used unfortunately.

Tip: never solder crimps it leads to stress cracks work hardening and premature failure

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Old 21-12-2010, 22:32   #14
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Cuthbert, I've got to disagree strongly with you on that crimper. You may well be an expert who's done thousands of crimps and knows a good crimp by feel but that's obviously not the OP (or me).

An Ancor ratchet crimper will make reliably good crimps. The dies are properly sized for each terminal size and the ratchet won't release until enough force has been applied to make a good crimp.

Oh - and for anyone out there using the Ancor double ratchet there is a right and wrong way to put in the terminal. Make sure the wire is on the color coded side of the die. The die is formed to make slightly different size crimps on the insulated part of the terminal and the screw end of the terminal. These also aren't the best crimpers to use with heat shrink terminals since the insulation size is different. In wet locations, I prefer to use regular terminals and then put a separate bit of adhesive shrink tubing over the finished crimp.

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Old 21-12-2010, 23:03   #15
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I would add a few things on crimping

1) Never, never use anything like this

or this (even worse yet more costly)

The temptation is that you can strip and crimp and it actually does neither well.
Unless you are really practised at holding a wire cutter between thumb and ring/little finger strip with somthing like this


Klein Tools 409-11063 Automatic Wire Stripper#

And then again, I don't use a rachet crimper and was steered towards a forged crimper some years ago when working with industrial electricians. Just in terms of reliability of the crimp (I'm an EE and have previously worked in avionics where they are used under calibration control) you are relying on that device to stay consistant. Once you hold and use a solid forged crimper, you will never use anything else. Works every time and much cheaper, more reliable and easier to store on a boat (and in summary FWIW just better)


(as previously harbor freight sell one which I own at $5.50, most electricians buy similar but brand names for much more)

I'm not against the time saving complex devices for the important task of stripping the wire, but none can match a forged crimper even when used by a novice.

(I hope the pics work)
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