I've worked around various electric crcuits for most of my life and the first rule I was taught was ABC (always be careful) no matter what the voltage. Arby has pointed out the differences between the body's reaction to AC and DC voltages. I was also taught that one ten thousanth of an amp across the heart can kill you ac or dc. So don't let that happen. A good rule is insulate, insulate, insulate. Don't let any part of your body come between a ground connection and one of a higher voltage. Yes, I've been shocked sometimes at rather high voltages of several thousand volts. But, it was always because I did something I really should not have done in the first place. Wear insulating gloves if you want. It can't hurt to do so if you are not to sure of what you are doing at first. Don't wear metal rings, wristwatches etc... when poking around batteries and electrical circuits. Safety is really just a lot of common sense, being careful and moving slowly. As has been said: "don't be scared just be careful". Capt. Mike
--- On Wed, 1/19/11, Arby bernt <arbybernt@yahoo.com> wrote:
From: Arby bernt <arbybernt@yahoo.com>
Subject: Re: [Electric Boats] Re: voltage
To: electricboats@yahoogroups.com
Date: Wednesday, January 19, 2011, 2:16 AM
Dear Kevin, There is a fundamental difference between mains power and battery power. AC vs DC. I spent many years working on residential and commercial electrical installations. I've been shocked many, many times by AC. I routinely use my fingers to test for 120vac. Sometimes I even need to wet them first to feel the tingle.
DC, on the other hand, has no trouble making itself known. While 12 to 30vdc is just a little burn, 48vdc can deliver a good shock, and the 300vdc systems I'm now working with are absolutely deadly. I've been shocked by 300vdc twice, once passing a charger over a battery pack, where I had the inertia to disconnect, and a second time, where I moved my elbow into a live terminal. That time knocked me on my back, and burned my skin.
UL recognizes this as well, and classifies DC into low voltage, less than 42vdc, and high voltage, over 42vdc. In my lab, I have an assistant with a six foot fiberglass watching me work when ever I go over 65vdc. I cannot imagine that you have felt a high voltage shock and made this posting. I hope you never do. DC across your chest will kill you. AC offers the chance to release, DC locks you up. The two are entirely different.
I hope you have an assistant when you are working on your battery bank. One slip, especially in rough seas, and it would be your last.
Be Well, Arby Bernt Advanced Marine electric Propulsion
From: luv2bsailin <luv2bsailin@yahoo.com>
To: electricboats@yahoogroups.com
Sent: Tue, January 18, 2011 3:04:15 PM
Subject: [Electric Boats] Re: voltage
Kevin, Nice write-up on the "Green" conversion. Any chance you could give us a cost breakdown? Jim McMillan --- In electricboats@yahoogroups.com, "kjshepherdca" <kevin@...> wrote: > > Hi all > I have been reading for 5 years but seldem post. This site and some regulators seems to be stuck on 48v this voltage is ok for small boats, but we cannot advance without accepting the facts. I am an electricain and work daily with 120 v to 600 v and I make these systems safe for the public. I use breakers and mechicnal protection. This is not rocket science. The currents at low voltage are hard to manage, they create heat everywhere . the heat losses are to the square of the current. > I read all the time of users having heat issues with controllers and building noisey and inefficent gear reductions. I have a soloman 4.5 kw with an off the shelf AMC controller ,cool, to the touch all day long even in summer. My sweet spot is 4 A (600W) at 3.5kts in chop. Direct drive means only 1 moving part. low currents make for happy batteries. Green is full keel sloop at 5 ton. > My regret is the propeller I was 16X7 27 hp diesel, I went to 16X16 3 blade I wish for 4 blades or 16X20+ . The aggersive prop acts as a sea anchor so I spin at low speed (150W) while sailing ,like a dynamic neutral, and for a 100 watts more I can point a few degrees higher. I use a 3KW russco charger and Honda 2000i (1600w@ sea level,1400w up here on the lake) to reach amost hull speed, a 3000 would do it but they are too big. > With recycled electric vechicles available in comming years we will go to 300 votls . Dont be afraid ,be safe.. > > > PS good luck to the Soloman team in Florida wish I was there. > > Kevin Shepherd > E/SV Green > B.C. Canada > > www.green-power.info>
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