ShadowsPapa
Well-Known Member
- First Name
- Bill
- Joined
- Oct 12, 2019
- Threads
- 178
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- 29,091
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- Location
- Runnells, Iowa
- Vehicle(s)
- '22 JTO, '23 JLU, '82 SX4, '73 P. Cardin Javelin
- Occupation
- Retired auto mechanic, frmr gov't ntwrk security admin
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There are times I feel sorry for Sheldon Cooper......... this is one. (sort of a personal, inside joke in a way)Well, according to that, I hook the negative up after the positive (but above, they said that order of polarity didn't matter which got hooked up first or last), and the only thing I didn't do the same as that, was hook to an engine ground, instead of the negative terminal of the dead vehicle...
So, even though it will still spark if you touch something under the hood (while connecting it to an engine ground, and you happen to touch something ferrous under there), since it's telling you to do that step LAST, that it will make THAT much difference going directly to a grounding strap, than it will connecting it to the negative terminal of the battery?
I'm seriously asking these questions, I'm not being a smartass... I want to know WHY this is suddenly incorrect in the last 10 years, than it was the previous 120+ that we've had batteries?
I will apologize up front as I have no idea your experience, background, training, whatever - I don't know if you are a person who loves working with electricity or would prefer to avoid it where possible. So I may miss the mark and go too basic, or too far the other way!
I see others have tossed in the first thing - hydrogen. Hindenburg.
Water and acids have oxygen and hydrogen and other compounds in various mixes. When they break down or change state, hydrogen and oxygen may be released. Almost certainly, hydrogen. Very flammable gas. Again, Hindenburg.
Batteries charging OR discharging will generate hydrogen gas, even oxygen gas.
NOT TRYING TO BE SMART - and maybe you got this part but I'll put it here again because hundreds of people besides us will see it....... lurkers, non-members doing a google search.
My wife's GC - she left the tail gate open, it did oddly seem to close on its own at some point, anyway, by the time she wanted to drive it, days had passed. There was little risk because the battery was down for hours if not days, any hydrogen was likely gone in the ambient air moving in the garage.
My car sitting over winter and I forget the battery tender - dead battery come March, likely safe enough....... maybe, hydrogen should be gone by then.
Crank the car until the battery dies, then go to jump it - you have fresh hydrogen and oxygen right there above the down battery. .
Internal short, quickly drains battery, generates hydrogen - perfect explosive mix.
Power will always flow from the battery with the higher voltage to the one with lower voltage. So you have current flow. One is almost like a load, like a motor, and draws current, sort of like a short against the higher voltage battery.
So the idea is to keep the last connection away from any battery, especially one generating hydrogen, because there will be a spark if there's enough difference between the two and the lower battery is seen as a big enough load.
Sorry, not real good at explaining. I can show it, draw it, demonstrate it, but putting it in words so it's not insulting or talking down to - not easy for me.
I guess the summary is that there could be hydrogen - batteries being charged, discharged, whatever, can and do generate hydrogen. It burns really fast and hot - even explosively.
The only way to be dead certain to keep a spark away from a source of hydrogen is to make the last connection away from any hydrogen source, so the last connection to a ground point away from the battery is always best.
Even the battery that's good there's possibly hydrogen gas above it as the alternator is working to top it off, or if there's a minor draw the alternator isn't keeping up with.
Disclaimer - have I always done it "right" or the safest" HAHAHA -no.
Lest someone wonder what it takes -
I mentioned I use electrolysis for derusting parts - that involves a bucket, water, washing or laundry soda, electrodes, battery and/or charger, wires to connect it all. Water is broken down into hydrogen and oxygen in the process. It bubbles a lot. Not NEARLY the current involved in jumping a vehicle, not even close. I use 18 gauge wires and those are plenty big.
I explained to another engine guy how to set it up.
He had it running just inside the walk-in door of his garage. Then his daughter and grand daughter came for a visit. The little one went running out into the garage, tripped over one of the wires knocking it loose from the electrodes and flash bang boom. No one was hurt but the poor little girl was really shaken. Water everywhere. He let us all know as sort of a warning to be careful.
All I want is for no one to get hurt, everyone be safe, and no JTs burned down.
pretty poor explanation I'm sure. I guess it's easier if you have a background in electric and chemistry.
I think I'll just stop while I'm behind here. No intent on demeaning anyone in this thread.
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