Toyspeed.org.nz Message Board

by **ChaosAD** » Wed Apr 18, 2007 7:10 pm

Why is it that in workshop manuals etc you are always told to disconnect the battery on the negative side and not the positive side?
Eg, page 8 on this page http://www.autoshop101.com/forms/h8.pdf

Corolla FXGT · by **Brick** » Wed Apr 18, 2007 7:18 pm

because if the negative is attached and your undoing the positive and you hit a bit of the chassis/body/metal you will get big spark, possibly fry some stuff :lol:

AW11 Track Toy · by **Caveman** » Wed Apr 18, 2007 7:45 pm

yea lol undoing the positive lug and bridging the spanner with the chassis :lol:

red hot spanner and burnt hand

by **Luke28** » Wed Apr 18, 2007 7:56 pm

Caveman wrote:yea lol undoing the positive lug and bridging the spanner with the chassis red hot spanner and burnt hand

Lol Yup, done that before!!!

by **Adydas** » Wed Apr 18, 2007 9:27 pm

I manged to do some welding in the engine bay doing that.

PICS UPDATED DAILY · by **method** » Thu Apr 19, 2007 12:54 am

Managed to cross the terminals of a 1100CCA battery with a chrome molly spanner.

Biggest spark ever, i got such a fright i reacted and flung the tool a good 15m away.

One of the lead battery terminals was quite melted and the tool had a bit taken out, some of the metal had melted away and left a indent. All in a split second! But with over 1100Amps running through the spanner i'm not too surprised.

Very dangerous, so undo the negative first!

by **no_8wire** » Thu Apr 19, 2007 8:38 am

Hahaha U remember undoing the negative with a ratchet type spanner...hit the positive , and well I got one of the best frights I have had...haha

by **Mr Revhead** » Thu Apr 19, 2007 9:54 am

similar..... removing the exhaust from my aw11, which some muppet had made one piece! i hit the postive lead on the starter at the same time the muffler hit the body.... mass sparks while im under the car....

by **big_boy** » Thu Apr 19, 2007 1:05 pm

could have been more fun it you had bridged both started termanls together

by **Crucible** » Thu Apr 19, 2007 1:53 pm

...and pos on first when you're reconnecting the terminals

by **bluemaumau** » Thu Apr 19, 2007 6:26 pm

wtf i waas taught at school it was negative on first and postive off first :lol:

by **Blackstripe** » Thu Apr 19, 2007 7:50 pm

Because if you touch the positive with the negative still on, your in trouble. But if you touch the negative its always ok its like touching your car door for example since its just connected to the chassis.

by **ChaosAD** » Thu Apr 19, 2007 10:21 pm

Yea I did that the other night actually :oops:

I would have thought it would have been better to leave the negative on to help prevent the car rusting away. Or does that only work when there is current traveling through the chassis?

by **big_boy** » Thu Apr 19, 2007 11:32 pm

bluemaumau wrote:wtf i waas taught at school it was negative on first and postive off first

you had an old teacher that was arround in the postive earth days of genrators?

by **Mike-** » Fri Apr 20, 2007 4:26 pm

its because electricity actually flows from negative to positive (yes thats right, not the other way round) so if the negative is still connected and the postive lead is flapping around youve got a good chance of shorting something out.

Website · by **Emperor** » Fri Apr 20, 2007 4:51 pm

Lost a bolt down the engine bay of my mates Mirage.. Thought I could see it, so got the long magnet pen to grab it... Hit starter motor, fried the handle of the magnet pen lol

My hand had blisters for awhile

by **Flannelman** » Fri Apr 20, 2007 8:47 pm

one other thing to add, especially when a battery is charging, it relesese hydrogen. it dissapates quickly, but the chance of the battery exploding is possible as well. acid everywhere.

Bet no one has worn eye protection while changing a battery. myself included.

My mate blew a battery up by not realising he was charging a battery on the floor while welding. Blew the top off the battery and split the case, acid all over the place. No damage tho.

Whats the point of this? when an engine is running, it is always charging the battery...

AW11 Track Toy · by **Caveman** » Sat Apr 21, 2007 12:34 am

paul chinery wrote:one other thing to add, especially when a battery is charging, it relesese hydrogen. it dissapates quickly, but the chance of the battery exploding is possible as well. acid everywhere.

Bet no one has worn eye protection while changing a battery. myself included.

My mate blew a battery up by not realising he was charging a battery on the floor while welding. Blew the top off the battery and split the case, acid all over the place. No damage tho.

Whats the point of this? when an engine is running, it is always charging the battery...

Hence when you are jumping a car, connect all clips to the terminals except the negative going to the running car, connect it to the chassis, so the spark doesnt ignite the hydrogen

by **Xylotrope** » Fri May 04, 2007 10:07 am

I was up country in the hinterland (pouto) ..

tightening the battery clamp ... somehow I managed to bridge that gap .. ?!

it blew a 6inch by 3 inch junk of the battery and a lot of battery acid all over the show ...

manage to fix plastic case refilled with the acid and it went sweet ..

coulda been evil though .. acid in the eye or so ..

negative off first is BEST

by **Mr Revhead** » Fri May 04, 2007 10:17 am

manage to fix plastic case refilled with the acid and it went sweet ..

what with? chewing gum and some spit? :lol:

Toyspeed.org.nz Message Board

Why Should I disconnect the negative first?

Why Should I disconnect the negative first?

My battery blew up !

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