screwed up again

[JohnEd]

I recently posted my idea of the perfect battery cable end.  I suggested that the wire be sprinkled with non acid flux, the lug soldered and then some silicone be applied and that shrink tubing be rolled up the wire on top of the wet silicone.  Just on the off chance that there was something wrong with that I played it to my bud that owns the automotive electric/rebuilder shop.  He said silicone is funny stuff. It outgases some nasty acid that can wreck electronics in a closed space.  He siliconed some wires in a water proof box associated with a heavy duty alternator and the wires and all inside were eaten up when he repaired it again 6 months later.  I think that sealing RTV in a stranded wire would have the same affect. so I advising that once again i screwed the pooch.  Rick asked me why I didn't just do as the industry does and use the preglued and weather proofed shrink that melts inside when you apply the heat to shrink it.  Who Gnu?  You do..now.

John

[Len Silva]

John,

There is only one secret to good quality battery connections and that is the use a good quality terminal (Thomas & Betts, Amp, Burndy) and to use the proper hydraulic crimping tool from the same manufacturer with the proper dies.  These are very expensive but widely used in telephone and power construction.  The best solution is to pay someone with the proper tools to make up the connection.  A T&B hydraulic crimper and set of dies can easily cost a couple of thousand dollars.

Properly done, the wire and the terminal are fused under tons of pressure into a single metallic unit that will never fail.

Len

[boogiethecat]

The trick would be in the type of silicone you choose.  Most of the older silicones are acetic-acid based and will definitely corrode stuff in a closed environment.  They cure by atmospheric moisture carrying away the acid molecules.
  As of late, silicones have been changing slowly to a more friendly chemistry based on methanol being the chemical whisked away during the cure.   I first found this with an amazing but costly GE silicone, RTV167, which quickly became my favorite for many purposes with the one caveat that it costs something like $30 per tube!  Ouch, but in a lot of cases it was worth it because it withstands weather, heat, and engine goo; it's amazingly strong and sticks well to most things. Better in fact than any silicone RTV I've used in 40 years!

Happily, Permatex recently came out with a silicone that, for the most part, performs just as well as RTV167 and is quite a bit less expensive. It's called "permatex ultra-gray oxygen sensor safe"
and it's only $4-5 per tube depending where you get it.  Most auto parts stores carry it.  Because it's the same style of chemistry as RTV167 it contains no acids and is great to use where corrosion might be a problem.  In fact its great to use almost anywhere from electrical to gasketing, and sealing to gluing glass.  The only hit is that you have to give it 24 hours to cure at least, maybe longer for very thin sections...

So John, if you use the permatex stuff, yes you'll have a very nice system for battery cables.  Soldering does, of course, cause a vibration sensitive spot at the transition between the soldered and unsoldered area, where strands may break easier due to vibration, but practically speaking it probably isn't an issue.  Other than that, with the right silicone,  good idea!!!

[JohnEd]

Boogie,

Thank you very much for that info.  I will pass it to my Starter and alt rebuilder cause I know he isn't aware of it.

We were taught to barely tin the end of the stranded cable and also tin the inside of the lug.  After heating the cable we fed the solder in very slowly and stopped when the solder just reached the rim.  Getting it to capilary flow up into the cable insulation was bad and you got a poor grade because of it.  We were  taught that any crimp was inferior to a properly assembled soldered on connector and my teachers would be 120 about now.  Old School!  Those crimpers cost 2 or 3 hundred when I was buying them for the Gummint but I am sure they are cheaper now....right?  Sure!  I guess they would pay for themselves if they only saved a few connectors and the splice free run from being QA'ed out due to solder runs up the cable.  Copper prices are outta sight.

Thanks Boggie....Really,

John

[CraigC]

I once soldered a battery cable at the starter without any crimping. I hit the starter once it turned over but did not start. I hit the starter a second time and nothing. I discovered the cable was laying on the ground. Sorry I do not remember the details that lead up to this.. The terminal was pointed straight down.

[JohnEd]

Craig,

Way back there was a sorta rule that said all joints must be "electrically complete AND mechanically secure".  In the case you describe I guess we can add Temperature hardened.  Best I can come up with.  When I worked in a radio transmitter rebuilding shop I graduated to the power amp tuner module.  It was a bear because we had to "silver solder" all the wires.  The coil tubes were carbon and ceramic.  It wasn't that the wires that were carrying all that much current but the heat in the module was tremendous.  If the situation that you describe were a normal one then all the cable ends would be silver soldered.  With that much heat the wire to lug connection would deteriorate and the joint would become very hot and eventually melt the copper if it were merely crimped.  I don't think that that is what happened to you.  You simply had a poor joint or a cold solder joint.  The lugs on the battery end are cast lead alloy and they don't melt.  Soldering on a lug is good practice but it has to be done correctly.  The lighter gauge cables have crimp er ends but the serious stuff is all welded lead alloy or cast.

A lot of things could have caused your terminal to fail.  A real good suspect would be a "cold" solder joint. They look good to the uninitiated and pass scrutiny.  Another is insufficient solder to fill the "tube".  Insufficient rosin to allow the cable strands to completely tin or the inside surface of the tube to tin.  Dirty connector stud or washers, oxide or my all time favorite the loose lug that "felt tight".  happens to all of us at least once so don't panic or alter your good practice based on a single event.  Add lug made out of the wrong material cause they are spected for max current like wire.

HTH,

John

[OneLapper]

Last fall I was having starter problems.  I had the starter rebuilt and it was better, but I still had hot start problems and the engine was difficult to start.

My part time tech that works for the local transit outfit took one look and pointed out that the cables were too small.  I bought 25 feet of 4awg cable, new terminals, double wall heat shrink in black and red.  I used a 1/4 hydraulic hose fitting die for Parker fittings on our hose fitting press.  By turning down the clamping pressure, you could make perfect cables with crimped on terminals, then use the heat shrink to cover the insulation and terminal gap.  After replacing all of the cables, the engine spins fast enough to start in nearly all temps.  Before, she'd only start about 60 degrees.  I took her to Canada last winter for a ski trip.  It took some cranking, but started without ether!

Mark
4106

[JohnEd]

Mark,

I hope that mention of "4AWG" was a typo on your part.  My inverter draws 300 amps and NEEDS 4 "ought" cable(0000).  Here it costs $13 per foot so we can tell you to the inch how long our runs are.  It sounds like you didn't understand the tech or he was wrong when he told you the size you needed.  If you have your starter connected to 4 gauge wire the starter will be suffering from "low" voltage during cranking.  Also, the 4 gauge wire should be getting hot enuf to want sex.

Any bat run to a starter that is longer than 5 feet needs to have a separate run of cable from the starter to the neg term of the battery as well as the starter to the positive..  That would be 0000 or 000....whatever DD calls for and you need to find out what that is....I don't know exactly.

Sounds like you did a really good job on the assembly of the cables though.

Do something for me, please.  Crank your engine with the fuel turned off.  Have someone measure the voltage "across" you starter "at the starter terminal stud(not the nut or wire lug)..  Voltage is ?  Touch you battery terms, and wire and the connection to the starter and any other junction in the run and check for heat.  Carefull as any of those may be VERY VERY hot.

25 feet scared me a little.  You read often here about Knuts relocating their bats to the engine compartment.  It isn't to balance the coach...honest.

Hope to hear back from you,

John

[gus]

Craig,

I pretty much agree with John about the cold solder joint.

It could have arced across the solder and blown out the cable which wasn't held very much by the cold joint anyway. However, it could have just fallen out. A cold joint isn't much better than nothing at all.

My theory is to mechanically join then solder to fill the lug. Sort of like a belt + suspenders.

[CraigC]

John & Ed

I was just pointing out one of my " screwed up again ideas". That was many years ago. I now crimp and solder my joints. I usually have my cables supported along the way.

This is what makes the board so interesting. You learn the correct way of doing things.

Thanks for the comments!

Craig

[NJT 5573]

Napa sells a commercial battery cable crimper for around $300. I didn't want to spend that much and modified a set of Harbor Freight bolt cutters with the grinder and some angle iron about 10 years ago. Think it cost me about $60.