Arcs and Sparks During Cable Cutting

[rmoore]

A Posting from Ron Moore, Forum Moderator
Rmoore@firehouse.com

Many times I'm asked why we must cut or disconnect the negative battery cable FIRST, before the 'Hot' cable. The reason is that there is less chance of arcing or sparking with your hand tool when working on a negative cable. If your cutting or disconnecting tool is touching the 'Hot' terminal and as you move to make your cut, you tough bare metal, you are grounded, completing an instantaneous short circuit. Let the fireworks begin. You'll be taking your melted Craftsman side cutters back to Sears for a replacement!

Most rescuers seem to be aware of why you cut the negative first. Recently, I was cutting the battery cables on a 1996 Toyota Tacoma extended cab pickup. I knew there was a load on the truck's electrical system because the right turn signal was still blinking. As I cut into the negative battery cable, there was arcing and very definite snapping sounds. I saw the sparks as the strands of battery cable were cut. I thought that if battery acid vapors (or fuel vapors had been present) within their flammable range, I could have had a problem.

Anytime this may happen to you, you can make things safer for yourself by covering the battery work area with shaving creme.

Put your tool into place first on the negative cable; I used electrician's side cutters. Close the cutter blades gently around the covering of the battery cable and hold on to the handle. With your other hand, shake up a can of regular shaving creme ( or menthol if you want your gloves to smell good afterwards) and foam the tool blades, battery cable and top of the battery. Make it a big gob of foam.

Now, close the blades of the hand tool to cut through the cable under this blanket of shaving creme foam. You've reduced the potential of ignition of vapors as the cut was made because of the shaving creme.

What have been your experiences?

Will this technique be helpful to you in the future?

[SCCARESCUE]

Hi Ron! You make some valid points. I have a tip for everyone. Most of the times I have seen the battery cables cut and there are lots and lots of sparks, usually followed by an exclamation or two, I discover that the wrong tool is being used. A lot of times the only cutting tools we carry are BOLT CUTTERS. They are designed to cut material thicker and stronger than wire. Using bolt cutters requires several cuts and a lot of twisting and pulling, all of which increase the chance to complete an electrical circuit. A lot of depts use electrical side cutters, usually the 4-6 inch style. These are designed to cut smaller gauge wire, and again, several cuts and twisting and pulling are required to make them work.
What is really needed is the right tool. The cable on most vehicle electrical systems is 4 gauge or 6 gauge wire. The right tool for this size wire is a CABLE CUTTER. The type used to cut power cable. The jaws of the cutters are both very sharp and actually pass by each other, similar to the design of a hydraulic cutter. This tool is inexpensive - $25 - $30 each - and will work with a single cut every time. I work with very high current DC power every day, and this is the best tool to use that I know of.
Keep up the great work!

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Dan Martelle

[ccc530]

I don't know about the shaving cream Ron, but using the correct tool for the job is the best idea. We use "high leverage cable cutters" manufactured by Klein Tools. (I have used them for 20 years in the phone business). They are available from Granger or Graybar Electric for $15-$20. They are insulated and compact so for those accidents when you can't get complete access to the battery, you can still slip these in and make your cut. They cut like a hot knife through butter. Regardless, safety first. Face shield down, coat, gloves, etc. Some departments require you to be "on air".

[LifeRescue]

I prefer to remove the battery cables from the battery terminals with a couple of wrenches for several reasons. First, the sparking reasons cited above. I can't remember ever seeing sparks while removing the terminal clamp. Hold it in place while loosening up the clamps, and there shouldn't be a problem. If concerned with accidental reconnection, tuck the terminal clamps in a couple of latex gloves, or other insulating material, and secure them with wire ties if necessary. Second, in the event I need to reconnect to operate a power feature, i.e. seats, windows,locks, trunk access, etc., I still can. Not likely to happen, but I like to still have the option. Third, it forces me to gain complete access to the battery compartment, and to make a thorough assessment of the battery, its connections, and to assure there is no spill of acid on something that could create a greater problem, e.g. battery acid on a fuel hose, coolant line, etc. I see a lot of rescuers cutting the battery cables by reaching through a hole and snipping a piece out of a cable and leaving the rest in place. Call me overcautious, but that's what I am.

[This message has been edited by LifeRescue (edited March 06, 1999).]

[hrt42]

We also try to remove the clamp, then when we do, we cover the terminals with caps, that we acquired from our nearest battery store. We keep a small supply of all different terminal caps. There is no taping or moving cables once you have them in place.Also at times it proves to be good PR, we've had owners complimenting us on using caps, instead of cutting the cables. If we can't remove the clamp, then we cut the cable with a set of cable cutters as mentioned above, without having any arcing.

John Hanlon


[This message has been edited by hrt42 (edited March 05, 1999).]

[ccc530]

I should have stated that removing the cables from the battery is always the first choice and yes, gaining access to the compartment does give you the ability to make a complete accessment. BUT, how much time to do spend getting access to the battery compartment to carefully remove the cables and visualize the battery? We don't waste any time. If you can quicly use the wrenches, great. And remember, you can always use a battery jumper cable to reconnect if you have to. Lastly, I have worked on cars for over 30 years and I assure you that if there is a load on the electrical system, you can draw an arc, no matter which method you use.

[natemarshall]

Ron,
I first doubted your shaving cream idea, but I tried it anyway it worked great when I had to cut the cables on a car last night.

Also can you do some stories on bus rescue, we have hundreds of casino tour buses going through our jurisdiction and we have had several in meighboring communities roll over.
Can you cover shoring, and what the best ways to remove victims are. As well as possible mechanism of injury.

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Shadow

[jpm]

craftsman has taken the design of its popular robo-grip pliers and applied it to a new pair of wire cutters.

the handi cut wire cutters offer some extra power because of an offset pivot point.

steel cutting blade is replaceable

these cutters tackle aluminum,copper and soft steel

NOT FOR HARDENED STEEL

just a tim type guy thanks gadjet !!!!

[Yahi]

I am not a professional fire fighter by any means, but as I sit and look at the contents of my can of Barbersol The two ingredient that jump out at me are propane and iso-butane. A quick controlled experiment shows that the cream, once formed does not seem to burn, but if you spray it with an ignition source it will light off. (poof) Second remeber any time a lead acid battery is exposed to a high electrical load in either direction(charging or discharging) it can release hydrogen gas, heat up and even explode.(just go by any service station and ask them how many batteries they have seen blow up wile jump starting a car) I don't redily see how battery acid on a rubber fuel line is much of a worry, The sulfirec acid reacts most activly with metals. In the case of metal fuel line, I have seen lines with stand months of exposure to battery acid. But obviously you would want to prevent any contact of effluent from the battery contacting any victims. For those who are are intersted 90% of all sidepost batterys are 8mm I carry a ratchiting wrench for this(not a ratchet and socket) the other 10% are 10mm and top post are usally 12mm or 1/2 inch. top post batteries do have a wider variety of nut sizes though. If you have to cut the negative side of a battery cable please remeber that many modern vehicles use more than just one cable to the engine block they often have an additional smaller wire that can be overlooked easily running to the chasis. Sorry got a bit long windy there. All feedback is greatly appreciated

[cp-ny]

If the shaving cream poses a problem, read the article on the firehouse homepage regarding the gel in baby diapers being used as a fire "barricade". This sounds like an excellent application? I wish this were my product. Thumbs up to the firefighter with the diapers!

[meegs]

Ron,
One thing I noticed and it might or might not be assumed that if you reduce the battery load first, i.e; kill the ignition, lights, turn signal etc.. you will minimize the potential for an arc. After we secure all or as much as we can we cut cables. we use the cable cutters that were mentioned. they work very well. Also you can get the same pair through your local hardware retailer cheaper than say graingers. Either way there far better than bolt cutters.
I have had success with this for many years.


[This message has been edited by meegs (edited April 29, 1999).]

[This message has been edited by meegs (edited April 29, 1999).]

[nbfd131]

All of our ambulances and our rescue truck have a batter cable cutter on them. It's about the size of a normal pliers. It has two blades that are very narrow and very sharp. Cuts through batter cables like butter. Two snips and your done.
Gregg

[nbfd131]

In reference to gaining full access to the battery, that's good if you have access to it. Many of the new cars, especially imports (camry for one), have the battery in the wheel well ahead of the front drivers wheel. Unless you take the time to remove the front wheel, you have zero access to it. Thus, the only access you have is to the fuse box area. Your only option is to pull fuses and snip the power lead to the battery.
Gregg

[lutan1]

For anyone that reads this from Australia, BEWARE!

We have both positive and negative earthed electrical systems on our cars, so dependant on the make and model of car will dictate which lead to disconnect first.

We should ALWAYS be removing the "earthed" lead first. (The lead that earths back to the engine block, chassis or panel.)

Remember to remove if possible. Cutting leads should be a last resort...

[MalahatTwo7]

Lutan brings up a good point about "reversed" polarity vehicles. I don't know how many people might have noticed with exception to those who are either long haul drivers or heavy diesel mechs, but on the frame rails of most heave trucks you will see a warning sticker that cautions welders in particular about how to hook up. I can't remember the exact warning itself (been a really long time), but it is a very large yellow sticker, with the big electrical lightening bolt running through it.

Also, as someone pointed out earlier, many newer vehicles are being equiped with multiple power sources. We found at one scene that cutting the obvious cables didn't do the job completly. When we tried to remove the battery to prepare the vehicle for transport, we found that there were two other "hot" wire leads connected. We couldn't see them from the angle of access, and so missed cutting them. In this instance, we were lucky no harm was done. As a result though, we look very carefully now when we cut cables.

As a matter of note we use proper cable cutters to do the job. I don't know the actual name brand though.

[JimDVFD]

On multi wire terminals I think it is safest to cut the smaller wires first. The large negative goes to the engine block. The small wire usually connects to the sheet metal. If the system is under load cutting the small wire first will transfer the current to the large wire. Cutting the large wire first could transfer current to the small wire and through the potentially damaged sheet metal causing wires to overload.

[Rescue101]

Anytime you disconnect a "loaded" automotive power circuit you WILL create an arc regardless of what method you use.It gets worse in newer vehicles due to increased electrical load.Also remember that a majority of "domestically" produced DIESEL vehicles will have multiple batteries for your attention.Be aware also there is a push from manufactures to go to 42 volt systems on non hybrids which will further complicate matters.The suggestion to shut off as many "draws" on the circuit as possible before disconnection is a Validated and correct procedure.Beware of wiring on TT units as they generally have several batteries and often have redundant circuits.T.C.

[EFFD131]

Ran in to an interesting one last night. Pick up truck into a stone bridge abutment. (moved the stone abutment about 6"...20' long with 2 8'sides 4' tall)Hit passenger side front into corner. Passenger side crushed almost up to the firewall. Of course the side with the battery. Of course a battery with side terminals. Slight odor of gasoline no major leak, but enough to worry about.The thing that helped us was the plastic window washer resevoir was crushed between the battery and the firewall. Once we were able to pry the resevoir out we had about 2" to work.I also tried turning off the lights but with the switch in the off position they were still on. (Dash was pretty badly damaged)I was able to cut the Neg. cable easily with my 8" cable cutters. When I went to cut the Pos. cable someone had slid a piece of heater hose over the cable. When I tried to cut this with my cable cutters it wouldn't cut. The cutters had to be opened so wide to get around the hose that i lost my leverage. (I only have the space in the buckled up hood to work, It is not open.)I was able to work my way down the cable, and found the piece of hose was only about 10" long and was able to cut it. When I cut the cables with the lights on I did not notice ANY arching.

Driver was flown to hospital with an open head wound and chest trauma but was concious. Don't know his condition yet.

Sorry it got a little long but thought it was an interesting scenario to share with everyone.

Work Hard
Stay Safe

EFFD131

[Rescue101]

You might not have noticed it,but I can assure you an arc WAS present.Do your own test.At night,without a light disconnect a battery lead from any vehicle.WATCH CAREFULLY,you will see a TINY spark.Now try it with sat the brake lights on,the spark will be bigger.ANYTIME you disconnect an automotive electrical circuit you will create a spark.It might be very small,short duration,but it will exist every time if there is ANY load on the circuit.This includes keep alive power for the computer or radio.Try it,it's a real mind bender.T.C.