Mis-wired 12VDC jack (let the smoke out)

[Spot]

This is a cautionary tale of what I did wrong and what I could have done differently. There was no loss of life or limb or machinery, only a burnt fuse and a blown 12VDC USB power adapter. OK, maybe a little of my pride went up in smoke too, but I am glad it was a driveway incident and not on the water.

I redid the electrical in the trailer sailor to remove some doorbell wire and failing switches and what not from previous owners. I was quite pleased with my work, even though it was going to be temporary until I got tinned wire and proper crimp connectors. Anyhow, I did that last fall and thought all was OK, battery being trickle charged by solar and looking good after the winter. Pride comes before the fall...


I went to plug my tablet to the 12v jack and there was nothing indicating a charge. I smelled a little something 'chemical' but thought it was just probably 'old boat' early season.
I unplug and eventually I go to investigate. No tools on board, so down and up the ladder for a screwdriver and multi-meter. Pulled out the 12v USB power plug and it smelled burnt. I took the USB plug apart to see that the the chip and coil of the circuit were destroyed, or in professional terms, I had 'let the smoke out'...


Started to suspect...probed the jack, turns out I wired the one and only 12VDC jack backwards so that the tip was negative and the shell was positive. I probably tested it previously with an incandescent bulb that will not indicate reversed voltage. Messed around some more, checked the fuse, it was also blown. No spares on the boat so down and up the ladder for fuses, colored tape, knife, and a pre-wired 12V plug to use as a jack tester.


I took the electrical panel apart, turned off master power (yes, in that order, part of the confessional), rewired the jack, and marked the white and grey leads of the jack with red and green tape to match other wiring in the temporary box. Checked it 2 or 3 times, reassembled panel, checked again, etc...

Lessons learned:
1. turn off master 12VDC power first or disconnect battery
2. double-check as-wired polarity of jacks before using them
3. mark wires if colors and polarities are not self-indicating
4. keeps spare fuses onboard
5. keep basic tools on board, even when in driveway

Happy weekend to all, Spot

[Ike]

good lesson. By the way I have the same multimeter. Good little meter.

[AndyEss]

Multimeters are cheap, no reason to do any electrical work without one. Your boat should have a minimum set of tools - including a DVM - onboard at all time.
Proper color coding for 12Vdc wiring is red for positive, and black for negative. Green is for 110Vac earth ground.
You had bell wire, re-wired with something else, and now will take the time to get the right tools and wire?
You must have an awful lot of free time.

[HopCar]

Did you order your replacement smoke yet?

[Spot]

Thanks for the reads, jokes, and comments.
If I get it wired seaworthy and correctly the next time I should only need one refill of smoke...

[john61ct]

Standard ciggie sockets are IMO a dangerous abortion, avoid like the plague for anything important, or that you use regularly, or for more than a few minutes.

inherently poor design, IMO a dangerous abortion,* avoid like the plague

Never more than 5-6A and for short periods, even then they are risky.

Blue Sea has a nice socket design that twist-locks with the matching plug, but will also accept standard ciggie plugs for smaller (<10A) loads.

Also the BMW/ Hella/ Merit/ Powerlet "Euro-style DIN" (ISO 4165) style is very robust.

Anderson plugs for high amps.

If you standardize on one of the last two types, there are adapters for guests, temporary use of devices with standard ciggie plugs.

[AndyEss]

USB outlets are another option. They are current limited to 5amps, I believe, but a lot of consumer electronics are USB power friendly. At 5Vdc, max power throughput is 25W.
I think the ciggie plug is 10A - and full 12Vdc - so you have at least 120W of power available to burn things.

[Spot]

Thanks for the additional input.

Main reason for 12VDC outlet was for USB charge plugs.
Maybe a pre-wired USB power setup would be better.
I will have to check the amps on the socket, it is purpose built as aux power and not a cigarette lighter.

[AndyEss]

That's nearly the only use my ciggie plugs are for - USB charging. There are plenty of 12Vdc USB replacement outlets on Amazon or MPJones too. They are pretty inexpensive, and often include some useful features like voltmeters or LED lights.
I just ordered a couple to retrofit my boat. I have a handheld vhf charger that needs the old style plug, so I'll save one.

[letsgetsailing3]

Spot,


Thanks for the honest anecdote, and the reminder to the rest of us to mind our p's and q's... (or rather, our amps and volts)

[john61ct]

Old school USB is low amps, but for future proofing QC3 /USB 3.1 Type-C "PD" are the higher current standards.

Direct wired to your DC distribution is definitely better than ciggie port type.

Plenty of modular "power panels" out there, also sites to order a custom layout.

Mix and match USB ports, switches, breakers, volt/amp readouts and power sockets.

Andersons, my choice of standard for the latter, can also be neatly panel mounted.

[basssears]

Originally Posted by AndyEss

Proper color coding for 12Vdc wiring is red for positive, and black for negative.

This is the color scheme you will find on most boats as that used to be the standard, but if you wish to follow current ABYC coloring standards it has moved to red for positive and yellow for negative, the thinking being if you use black of negative there is a danger of confusing a black DC negative wire with a black AC hot wire, not such danger with a yellow DC negative.

[AndyEss]

Yeah, that one is a bear. I didn't want to complicate the conversation to include Vac power.
I think a lot of automobiles went to brown as the Vdc negative.
Boats (and to a lesser extent RVs) used to be one of the few places where we had both Ac and Dc power systems in the same environment. With the proliferation of solar panels and to a lesser extent wind turbines for residential purposes, now homes and office buildings also have hybrid Ac and Dc wiring.
Do you know what land electrical codes are doing with this conflict in color coding hell?

[tkeithlu]

Hey, you missed out on one available experience; maybe you'll have it in the future: welding your screwdriver (or pocket knife) across the unfused terminals, complete with fireworks.

[Spot]

tkeithlu, LOL. So far only one snap-crackle-pop and that was the plug and wire rig I used checking the polarity of the rewired jack. Enough for me to hear it but not enough to blow the fuse. Right now the battery is not in a box, that should be my next upgrade before I drop a tool on it or knock it over.
The jack I have is a CASCO (Amphenol) 212711 20 AMP. At the moment I am fused for 10 amps



As far as wire goes, there is a vendor 1 hr away who has 14/2 UL 1426 Marine cable in all three flavors: white/black, red/black, and red/yellow.
I was thinking red/yellow to confuse my adult children enough from them using it as speaker wire...and to follow ABYC standards...Pricing is better from this vendor than at the boat stores.
Crimps and crimper...the wire vendor has all the big names in tools and crimps, I was also considering the basic ratcheting one at marinehowto.com https://shop.marinehowto.com/product...ink-crimp-tool and get a roll of their butyl while i am at it. The sticker shock for me is the actual crimps. The nicer heat-shrink ones go for quite a bit more than the hardware store types. Do people have a preferred source? Marinehowto.com send people for FTZ heat shrinks here: https://shop.sailboatowners.com/prod.php?2510

Thanks Everyone, Spot