irish44j UltimaDork
May 19, 2017 7:12 p.m.

To fit a killswitch on the center stack of our e30, we need to splice into the OEM battery cable (I think it's 2ga, coming from the trunk-mounted battery.

Obviously it can be done with large butt connectors and a compression tool (which I don't have), but are there any other good options that will hold up to use in a rally car? Screw-type clamps, for example? Basically would prefer somethign that doesn't need any special equipment, since I only plan to do this one time...

Any suggestions are welcome.

paranoid_android74 UltraDork
May 19, 2017 7:44 p.m.

These can be found pretty cheaply, just add a BFH:

Just me, but i would avoid screw type connectors.

logdog SuperDork
May 19, 2017 7:56 p.m.

Ive wired 3 kill switches in Chumpcars with these from Tractor Supply

I used the far inside edge of pliers like these to crimp. Worked perfect for me.

imgon Reader
May 19, 2017 8:42 p.m.

Try a local electrical supply store. Many times they have a loaner tool for the compression lugs. If you can bring the wire in with you and they have the tool you could crimp them right in the building. If you can't bring the cables in, they may want you to leave a deposit. If they don't have the tool ask if they know any contractors that have one and they may let you borrow theirs.

Robbie UberDork
May 19, 2017 10:40 p.m.

I was gonna say bfh, but I was beaten to it.

Jumper K. Balls PowerDork
May 19, 2017 11:04 p.m.

Go to Napa and tell they you need a ring terminal for "insert wire gauge " to "insert stud size"

And then ask for the solder slugs to go with them.

Cut the cable, strip back the insulation, fire up a propane torch, heat the terminal with the slug inside and push the cable in.


44Dwarf UltraDork
May 20, 2017 6:15 a.m.

Moroso sells a kit that has ends with tapered split ferals all you need is two wrenches. They work great. the link below is for the post type terminals i've seen the extenders double ended units as well but a quick peak did not find'em

44Dwarf UltraDork
May 20, 2017 6:19 a.m.

round end type for the switch.1/2 hole terminal

Round end for switch 3/8 hole3/8 hole terminal

Knurled MegaDork
May 20, 2017 6:44 a.m.

I've soldered before with a torch.

The RX-7's battery cables are the solder cup style mooshed together with Vise-Grips. I did that 7 years ago. I let the starter hang by the battery cable when I change transmissions. It's still good.

If you specifically need to butt two cables TOGETHER... I wouldn't. I'd find an excuse to put a bulkhead connector there or something

dean1484 MegaDork
May 20, 2017 6:49 a.m.

I have used the solder type many times and never had an issue.

JtspellS SuperDork
May 20, 2017 7:00 a.m.
paranoid_android74 wrote: These can be found pretty cheaply, just add a BFH: Just me, but i would avoid screw type connectors.

Have used these on many forklift connections with some heat shrink with no issues what so ever, if needed I still have one down here.

blizazer Reader
May 20, 2017 7:53 a.m.

Lots of good advice here.

Also dont forget to preload 2 or 3 sections of shrink tube on the wire before you add the terminal.

HappyAndy PowerDork
May 20, 2017 8:16 a.m.
paranoid_android74 wrote: These can be found pretty cheaply, just add a BFH: Just me, but i would avoid screw type connectors.

I use one of these for repairs on forklift power cables all the time. Works great, I definitely recommend it. Mine is not from HF, and may be larger than the one in the pic, but I don't see why the HF one wouldn't work well for car battery cables.

TRoglodyte UltraDork
May 20, 2017 9:18 a.m.

Electrical split bolt should work. I have seen some HEAVY wire spliced with these . No special tools required and removable if need be.

irish44j UltimaDork
May 20, 2017 10:27 a.m.

I ordered up some pre-tinned compression connectors from a marine supply place (cheaper than automotive places...), so will just hit HF today and pick up the tool and die set, I think. Can't hurt to have it in the future, I guess.

Vigo UltimaDork
May 20, 2017 10:51 a.m.
44Dwarf wrote: round end type for the switch.1/2 hole terminal Round end for switch 3/8 hole3/8 hole terminal

Thank you for teaching me that this exists. For whatever reason, i've never seen one!

Knurled MegaDork
May 20, 2017 10:55 a.m.

It's weird, the MAC guy had the same crimper tool that Marvin posted, and so I impulsively bought it. I never had an opportunity to use it, but Da Boss finally got the urge to put a battery and winch on his trailer last week (we had a project car to move to storage, and the hairy bug got up his ass to finish the trailer instead of having people push cars on and off) so he borrowed it to crimp the lugs, and he said it didn't work worth a E36 M3.

I wasn't hovering over him to see how he was using it, because I'm busier than a one legged man in an ass kicking contest, so maybe his technique was bad or his expectations were high? Either way, we're getting a bolt cutters style cable crimping set now Hey, if my $31 or whatever was only spent in order to hasten us getting good shop equipment, that's still money well spent, and I'll get to USE the awesome shop equipment for personal stuff so it's no loss on my part.

curtis73 PowerDork
May 21, 2017 1:42 p.m.

That whack-crimper thing I have used with great success. For terminal ends, I bought some copper terminals in the right size, whack-crimped it, then hit it with a MAP gas torch and shoved a bunch of solder down in it. Worked great on 2/0 wire for a step van when I put coach batteries in the back for camping.

If you want to get fancy and precision, those crimper dies work great in a vice as well. (which is the "correct" way to use them... BFH is the GRM method and works fine)

Vigo UltimaDork
May 21, 2017 3:33 p.m.

I think the hammer crimper thing depends a LOT on how hard and square you smack it. After spending the last 3 years teaching auto tech i've belatedly realized how much of an acquired skill swinging a hammer is and how bad many people are at it.

codrus SuperDork
May 21, 2017 7:15 p.m.

For crimping big battery cables I use a Harbor Freight hydraulic crimp tool. It works pretty well, although the wire gauge size numbers on the dies don't seem to bear much relation to reality.


Dr. Hess MegaDork
May 21, 2017 8:21 p.m.

I have that HF hydraulic crimper. It's great.

Snrub Reader
May 22, 2017 10:17 p.m.

I'm not sure if this is the right way, but here's what I did in my car: I cut the battery cables at an appropriate point and soldered in cables that already had appropriate terminal ends. To solder it in I stripped a section of wire and slide thick heat shrink a few week away. I used a plumbing torch and kept feeding in the solder while clamping the wires together.

jere HalfDork
May 23, 2017 11:27 a.m.

I find some copper plumbing tube that is a little smaller than the cable. Then heat the tube, work the cable ends in and smash/solder. (You can also make ring ends this way if you smash only one half then punch a hole and file the corners round)

When I had more money I would buy these from homedepot Aluminum in line cable connectors

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