Perko Switch - Dave Bowman mistake

[Racerock]

Dave Bowman made a real bonehead move when describing the installation of the Perko Battery switch. If, and I mean if, the wires went to where he claimed them to go, as soon as you moved the switch to either of the batteries, or to both, you would have been directly connecting the positive to ground, frying the cables, and perhaps blowing up a battery, or two.

You see, there were three cables poking out of the hole put in the hull. Two red (most likely going to the pos terminals of the two batteries directly), and one black. Well, the black one (I used red in my boats) should be going to the starter terminal, or the battery post for accessories, and on to the starter.

Dave Bowman referred to the black cable as going to "Common". LOL, I figured that someone else mocked up the boat, he came in for the camera shot, and since the cable was black, figured it must be ground.

Another thing, is that the switches are usually placed in an out of the way location, away from the weather. Sometimes hard to find on a center console, but not impossible.

Guess he should stick with cars.

[KA9MOT]

Technically guys, the connection you are speaking of is common. It is common to both batteries. Common usually means ground but not always. I did not see this show but it makes sense that the wire went where it was supposed to. Color coding is smart but not necessary and common doesn't always mean ground,

[Racerock]

I understand your point, and when installing batteries, never take color coding as where the cables actually go. But, the way it was presented, and the lack of clarification would lead people to think, "now Dave told me to put this cable to "common", which is the block, right? yeah, right, run the cable there, lets fire it up"

Then boom goes the bilge from the fuel vapors.

[KA9MOT]

Using the term common is correct.... it is up to the installer to know what he is doing so he understands the terms and technique. It is very basic really.

[Racerock]

I understand your point, but the point of the show is to inform, especially for those that may not understand. When you watch the show (which I think you had said you had not), look for it.

At this time, I will agree to disagree.

[KA9MOT]

Actually, come to think of it, Common does NOT mean ground. Not even sometimes. What Common refers to is a connection that is common to anything. This connection could be the one connection common to lights, pumps, batteries or that new set of electric chairs down at the Jail House. LOL

Common Ground is a separate term that describes a connection to ground that is common to another item that is also connected to ground.

There are also chassis and circuit grounds. The two should never be mixed or you'll let the smoke out of your expensive electronic equipment. Really, they should find a better way to keep the smoke in.

I'll have to make sure I see the show.

[Racerock]

Your description of common is on the money. Think of the Common in your AC circuit breaker panel. That is where the (white/return) Neutral wires get connected to Ground.

On to the Circuit board commons, Often times you will have Power Ground separate from Analog Ground, and a separate Digital Ground (if there is a board with analog and digital circuits). To make things more complex, some circuits could have common at a different potential than ground ground. Telecommunications with their -48Vdc comes to mind, as well as some other circuits I have either designed around or worked with.

Dave should have spent 5 more seconds on the connection of the switch. Otherwise it was a decent show, though.

[KA9MOT]

AC? That stuff will kill ya! Get an electrician! LOL

Most of my experience is in low voltage applications.
BTW, contrary to popular belief, your car battery can kill you if certain conditions are met. LOL

I once stuck my finger in the cigar lighter socket of a Freightliner to "clean" it out. I burnt the tip of my finger off.

[Racerock]

Yes, dc voltage is dangerous. I'd have to pull out the spec sheets, but as I recall, the levels of current that cause bodily harm, or death, is actually lower for dc voltage than ac. It is also amazingly low. It also depends on the path. Going through a single hand is not nearly as bad as from one hand, through the heart to the other hand.

[Racerock]

OK, just watched with my kids this episode again, and boy did I pay careful attention to his exact words when describing the wires and the switch.

Dave definately referred to the black wire as going to "Common Ground".

When the wires were poking out, there are two reds, going to the batteries. He does not really say what the black one is going to. Then when pointing to the switch, he says to connect the two batteries to the two terminals, and to connect "Common Ground" to the third. Everything stated above stands in my book.

Not to rehash the above, but he was way wrong, and if someone did connect the switch as he described, there could be a battery explosion.

[BigBry]

We know. He miss-spoke. We hooked it up correctly, he just said a word wrong. Please don't blow up your boat.

[zigzag03]

hey bigbry, you need to get some perspective here. you are wrong if you think people won't take what was said on that show and hook it up wrong specifically because it was said on tv, even if you only left out one itty bittly little word. and believe me, the situation is potentially dangerous. instead, you cop an attitude, which makes you sound unreliable and uninformed (not my first choice of words). if you can't take constructive criticism then i suggest you are in the wrong biz. meanwhile, you and your show lose a lot of cred with me, and i'll spread this thread around amongst friends and coworkers, as word of mouth is powerful. and i hope you get what you deserve, you will have earned it.

oh and btw, why would you close my thread on this subject. preventing further comment there??


to racerock: good to find another boat pro and race fan online, keep in touch, zz03


ps> to bigbry, from my wife, her first reaction... "i would have thought their response would have been 'thank you!' "

[BigBry]

Ugh.... You are getting me totally wrong here. This is old news. This is a repeat show. I realize the implications of this. There is nothing I can do. We've gone over it now in at least 3 threads.

It's not like I am being ungreatful for you guys saying that it is dangerous and setting us straight.

I take a ton of constructive criticism and I totally agree with you all. Just like I did months ago when the show first aired.

Thank you..

Dave screwed up. He knows he did. It happens. It just sucks that we didn't catch it before it aired.

[zigzag03]

that explains the "old news" reference. i thought that because racerock had posted on the subject several days before i did, it had prompted your response. sorry to bust your balls so late in the game, but i would think that every time you ran the eposide you'd have someone catching you out. it seems silly to not acknowlege it somehow, maybe a short disclaimer tacked on after the show? it's your butt in the sling, not ours. anyway, i was responding viscerally to what i percieved as you blowing us off, and that was probably wrong, as i clearly hadn't heard the whole story. please carry on. zz03

btw, what is your position with the show?

[BigBry]

I do everything non automotive. I'm a TV guy.