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04-07-2012, 08:16 AM
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Join Date: Jan 2005
Location: NC25
Posts: 3,508
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My father is 82 and turns 83 this year. He ran a service station when I was born. He always taught me to connect the negative jumper / charging cable to the frame last and not the battery plus to always disconnect the negative cable from the battery first and to hook the negative terminal up last.
I do it that way because that is how I was taught and have done it that way all my life.
__________________
Gary A. Sobek
NC25 RV-6 Flying
3,400+ hours
Where is N157GS
Building RV-8 S/N: 80012
To most people, the sky is the limit.
To those who love aviation, the sky is home.
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04-19-2012, 10:32 PM
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Join Date: Feb 2008
Location: Tucker GA
Posts: 190
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Guys,
Take the advice seriously. If you don't believe it, watch an old film of the Hindenberg airship trying to dock at Lakehurst NAS. Same reaction, just smaller quantities at your airplane. Or car, or stationary engine driven generator, pump, or whatever. Batteries these days are much better at not leaking hydrogen, but not foolproof. 24" away might be good, because a hydrogen/oxygen mixture is just like a gasoline/oxygen mixture, if it is too rich or too lean, it won't ignite. Immediately out of the leak, the H2 gas is most concentrated, or richest, and after a short distance (how short depends on many variables, just remember that farther is better) may become too "lean" to ignite, i.e., not enough H2 molecules mixed with the O2 molecules to get a reaction, i.e. explosion, started. In between, an explosion (strictly speaking, what we are calling an "explosion" is more accurately called a deflagration, because the resulting pressure wave is subsonic, as opposed to a detonation, in which the pressure wave is supersonic, as with dynamite) is completely possible given an ignition source, such as an arc when the connection from the charger to the battery circuit is made, or when an open circuit from the battery to a switched on load in the airplane is closed, as when connecting the second battery cable to the battery post with the master switch left on.
Bottom line, always, always, always make the last connection or the first break in the circuit away from the battery.
__________________
OldSam 
RV7A, Empennage, Wings & Tanks complete
Fuse under way
Last edited by OLDSAM : 04-20-2012 at 12:05 AM.
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04-19-2012, 10:37 PM
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fugio ergo sum
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Join Date: Apr 2006
Location: Carlsbad, NM
Posts: 1,912
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I too have seen quite an impressive explosion from jumping a battery directly. Connecting the negative at a distance from the battery seems prudent.
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Larry Pardue
Carlsbad, NM
RV-6 N441LP Flying
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04-20-2012, 05:39 AM
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Join Date: Jul 2007
Location: St. Louis, Missouri
Posts: 135
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Lots of discussion about venting of gases from the battery but if his Odyssey battery is like mine (PC680) it does not have any vents to vent gas from.
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Bill McAllister
St. Louis, MO
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04-20-2012, 07:34 AM
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Join Date: Dec 2010
Location: Alpharetta, GA
Posts: 88
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I believe those Odyssey precautionary instructions are more oriented towards "jumping off" than charging, where you can't reasonably avoid making live connections. It's all about understanding what you're trying to prevent. It should be totally safe to: - Turn off and unplug the charger from the wall.
- Short the positive and negative leads of the charger together to dissipate any residual charge.
- Connect the charger's leads to the battery.
- Plug in and turn on the charger.
There should be zero risk of spark if those simple precautions are taken.
- John
Last edited by John R. Graham : 04-20-2012 at 07:36 AM.
Reason: Typo
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04-20-2012, 07:42 AM
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Join Date: Jan 2005
Location: St. Paul, MN.
Posts: 4,792
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This has always been the standard when jumping a car battery. The negative charger connection is connected to a metallic part of the engine block.
The way around this seems pretty clear to me: Don't make any battery charger connections while the battery charger is plugged in.
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04-20-2012, 09:41 AM
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Join Date: May 2007
Location: Quincy, Florida
Posts: 680
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batteries
I have seen battery explosions twice and vowed to figure out why they happened. It seems to me that the different cells that make up the battery are connected at top and bottom by lead connections and the entire cell assembly is submersed in electrolyte to produce the energy. If the electrolyte level falls below the lead connections between the cells in the top of the battery and one of the connections is weak or broken, the battery will not function properly. Therefore a "jump start" is required to get things going again. When you attach the good battery to the bad one and a spark jumps from one cell to the other across the bad cell connection inside of the battery......Kaboom. The spark is not submersed under the electrolyte and the void area is filled with oxygen from the atmosphere and the gases produced by the battery. The explosion occurs from the inside of the battery out (of course). I don't believe that ignited fumes outside of the battery would be nearly as spectacular as the fumes ignited from inside.
My theory at least.
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04-29-2012, 01:20 PM
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Join Date: Feb 2010
Location: Peachland
Posts: 15
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yea new guy here, just had to comment, in my younger and smarter days ( 17 ish and knew it all ) had to jump a car, now here is the kicker, it was a sealed batt, i DID connect the negative to the frame but none the less guess the cells were shorted out, BOOM cuts from the plastic case on my face ,arms and hands, acid in eyes and all over me and the car. was **** lucky, no scars, no loss of vision, but i think I needed new underwear.
so while you are doing all this and need to jump, hook up the DEAD batt first, so your not near it, should things go bad. also consider hooking up the batt, then plug in the charger. hope this saves someone else from my mistakes.
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