How to safely stretch aluminium cables in automobiles? - Page 1
Forum section: electronics / general

author: VinzC
author_rank: Frequent Contributor
timestamp: September 05, 2016, 02:25:36 pm
content: Hi all.My company's business is stretching and armouring cars. As a result we also have to stretch the  cables. So far all of them were copper. Now is the day we find aluminium cables. Since copper and aluminium do not go well in wet conditions as they corrode, I'd like to know if any of you has had experience or tips as to "joining" copper and aluminium. I'm not yet aware of any connector/crimp that would bridge the two however; I'm lacking info and experience in that very matter.In case you might wonder, we excluded replacing the wires for there is then the problem of connectors, which are specific to the car manufacturer and not all of them are available. We are no brand partner hence have no such exclusive deals. So we must stretch the wires one way or another.Could anyone point me to the right direction(s)?Thanks in advance for any hint or suggestion.

author: uncle_bob
author_rank: Unknown
timestamp: September 05, 2016, 04:06:09 pm
content: HiYour best bet is to stick with copper and copper or aluminum and aluminum. Depending on the stretch, you may not have a choice between replacing and adding to the cables. The voltage drop goes up as the cable gets longer. In some cases they have already sized the wire near minimum / designed the load near the existing drop.All that said, there are crimp connectors designed for burial or marine applications. They aren't cheap and they all seem to require custom crimp tools that cost a bit. I would go with one that has good support in your country. Hassling with customs each time you hit a new wire size is a real pain.Bob

author: DenzilPenberthy
author_rank: Frequent Contributor
timestamp: September 05, 2016, 04:24:08 pm
content: What vehicles are using aluminium wiring? And for what circuits? It seems completely mad to me given their reputation for dodgy terminations and surely they would work harden and break in a high vibration environment? Surely it can't give any significant cost or weight saving?I'm sure the manufacturers know better than me though

author: chris_leyson
author_rank: Super Contributor
timestamp: September 05, 2016, 04:49:58 pm
content: Airbus use aluminium wiring in the A380, it was done to save something like 500kg. I believe they had to develop special wire and connectors to inhibit corrosion. I think you can get about 50% weight saving by using aluminium.

author: ECEdesign
author_rank: Regular Contributor
timestamp: September 05, 2016, 05:11:16 pm
content: I thought aluminum wiring was a safety hazard and thats why they removed it from the building codes in the USA? I don't know much about it though

author: nctnico
author_rank: Super Contributor
timestamp: September 05, 2016, 05:18:00 pm
content: I second the suggestion to use aluminium wires on aluminium wires. Unfortunately I think this also means you'll have to invest in the right crimping tools and contacts. Going cheap is prone to end up in a dissaster.http://www.assemblymag.com/articles/93072-a-new-crimp-for-aluminum-wire

author: chris_leyson
author_rank: Super Contributor
timestamp: September 05, 2016, 05:48:23 pm
content: ECEdesign, you might well be correct on the building codes, I couldn't find a definitive answer. Nctnico, yep you're right on joining aluminium to aluminium but I think crimp tools and connectors are not going to be cheap, besides, many automotive connectors are full custom and difficult if not impossible to buy. To avoid the connector issue I would think about cutting the cable and splicing in a section using aluminium ferrules of some sort.

author: SeanB
author_rank: Super Contributor
timestamp: September 05, 2016, 05:58:01 pm
content: How about simply getting a set of appropriate automotive plug and socket housings, ones that are aluminium cable and copper rated, and then simply make up wiring loom extensions that plug in using that connector tooling to crimp the wires on the connectors. That way you only have a single tool set to use, and with connectors in assorted numbers of ways you can easily make up the correct connector sections, and then make the appropriate loom to fit in the length. that way you have the luxury of not having to undo entire loom sets, and can thread the splice section into the chassis extension easily during assembly, with it being able to undo at each end.Just use a cable numbering system to match the original each end, or a lot of reels of assorted colours of wire and some automotive rated sleeving and braiding.

author: uncle_bob
author_rank: Unknown
timestamp: September 05, 2016, 05:59:47 pm
content: Quote from: ECEdesign on September 05, 2016, 05:11:16 pmHiAluminum is fine. It does not, by it's self, present a safety hazard. Screwing aluminum down under a bolt *is* a safety hazard unless it is done with care. Stuffing aluminum into certain other retention mechanisms that are not designed to use it is also a problem. What happened was that people were not being careful matching aluminum wire up with the proper terminations. The simple answer was to outlaw it except in building feed applications. There, the assumption is that the guy doing the work *must* be certified to do it right.Bob

author: Len
author_rank: Frequent Contributor
timestamp: September 05, 2016, 06:03:26 pm
content: Quote from: ECEdesign on September 05, 2016, 05:11:16 pmNo, aluminum wiring is still permitted by the national electrical codes in the US and Canada, from what I was able to find. (There may be local bans but I didn't see anything about that.) However you do have to use fittings and connectors that are approved for aluminum.References:http://www.alwirerepair.com/aluminum-wiring-whats-the-problem#What%20does%20the%20Code%20(NEC)%20sayhttps://www.halifax.ca/fireprevention/AluminumCopperWireBasics.php

author: LabSpokane
author_rank: Super Contributor
timestamp: September 05, 2016, 07:55:43 pm
content: The problems are oxidation and galvanic corrosion. Use aluminum to connect aluminum, make sure to prep the connections to remove the oxidation layer, and use "No Ox" on the joints and you should be fine.Aluminum conductors are not inherently dangerous. Much utility cabling is indeed stainless over an aluminum core.

author: VinzC
author_rank: Frequent Contributor
timestamp: September 06, 2016, 09:10:36 am
content: First off thank you guys for your hints. As a dedicated electronics engineer I suspected Aluminium wouldn't be a bed of roses and it appears it really isn't. I've received some suggestions that I'll investigate. Our main supplier seems to have solutions and we're meeting a product representative.Quote from: DenzilPenberthy on September 05, 2016, 04:24:08 pmMost notably Toyota Landcruiser 200. Half of the cables in harnesses appear to be aluminium. Also Mercedes S class come with thick aluminium power cables. So far the thin wires still are copper.

author: Brutte
author_rank: Frequent Contributor
timestamp: September 06, 2016, 10:14:26 am
content: The problem with connecting Al and Cu is that these have a seriouselectrode potentialdifference. It is 0.6V in between those. Take a glass of electrolyte (H2O with dissolved CO2 would do), dip separated copper + aluminum wired to voltmeter and you have a 0.6V electrochemical cell. Stack in series and you can charge an iPhone. However, your customers won't be happy as this reaction is irreversible and would eat up an anode (aluminum harness).So, you have several choices to prevent that:1. either you can keep wires in electrolyte as long as you like but do not connect both electrically. I admit this trick may not be practical with electrical harness..2. or you can connect Al+Cu safely but do not allow the electrolyte to get involved in between them.3. or you can separate metals with something that has an intermediate electrode potential. A 0.1V difference would slow the process to a safe level.4. or make the electrolyte path long enough to discourage serious current to flow there ,5. or you can use a sacrificial anode (give an electrolyte something tastier than Al harness)6. or apply a constant >0.6V in reverse (which is similar to trick #5)7. etcAnyway, usually the cheapest is to do trick #1 if you do not need electrical connection or #2 if that electrical flow is necessary.You can buysheets that are made of two/three layers of adequate electrode potentialsthat are cold rolled together. No electrolyte can get in between. Mind that sheet works only in standard conditions (humidity) so won't help much if flooded in electrolyte because it still has Al+Cu edges. Also won't work if you flip the sides so it is a quality control problem.

author: XOIIO
author_rank: Super Contributor
timestamp: September 06, 2016, 10:37:29 am
content: They could also replace the aluminum wiring entirely, but that would probably be a lot more work.

author: VinzC
author_rank: Frequent Contributor
timestamp: September 06, 2016, 11:25:59 am
content: Quote from: XOIIO on September 06, 2016, 10:37:29 amNo, we cannot. Because then we'd have to also find  crimps for the  connectors [read: unavailable for sale] or, worse, replace the whole harness with a copper copy, cut and extend. So not practical.Quote from: SeanB on September 05, 2016, 05:58:01 pmHad we only a couple of cables to lengthen that would do. But there are hundreds of them, many times several dozens of cables in a single harness. There are several of those harnesses to prepare and several cars to extend that way so crimps and sockets unfortunately appear to be impractical, time and margin consuming.Quote from: Brutte on September 06, 2016, 10:14:26 amThanks for the details. From your explanations, it looks like the most practical implementation for us would be to insulate the wire at the joint. We've found numerous insulated sleeves (read: crimp + shrink) that seal the wires after being heated. We've not found aluminium cables nor anything that would not cost us too much. Our supplier doesn't even provide aluminium cables. The cupal sheets look really interesting but we've got hundreds of cables to extend so we're kind of stuck with solution 2. I guess.

author: uncle_bob
author_rank: Unknown
timestamp: September 06, 2016, 11:38:08 am
content: HiIf you have ever looked at the production line for an automotive wiring harness .... there is a *lot* to the process. For whatever reason, they really love using a range of connectors and are *very* picky about what goes where. One of the things not yet mentioned is the EMI / EMC impact of doing all this. The auto guys spend a lot of time working out where grounds go and how power flows. From the papers they present at conferences, when they miss something, stuff stops working.Bob

author: Brutte
author_rank: Frequent Contributor
timestamp: September 06, 2016, 12:43:28 pm
content: Quote from: VinzC on September 06, 2016, 11:25:59 amTo be precise: you have to insulate the Al+Cu connection. If anything that undergoes dissociation to ions gets near, the circuit would close, the current would flow and the process of galvanic corrosion (a.k.a. electrochemical cell) takes place.QuoteBy insulating I did not mean mice, ants and dust. I meant ions (teeny-tiny ones). Like for example H2O vapor with dissolved CO2 (which in aqueous solution is known as carbon acid H2CO3) or other like salts for example. If you can prevent that getting in near Cu and Al then that is ok but I seriously doubt what you propose is the way to go. These insulate electrically but not against vapors.QuoteWell, the cupal sheetisthe trick #2. It does not allow an electrolyte in between. Just separate the metals and crimp/rivet/nut the connector.Are you aware that 10% of a stranded wire cross section is just a bunch of air ducts?? What do you think happens after 10 years of humid air blowing through that?BTW, as with any cell, this cell stops when you disconnect it electrically so it is impossible to inspect visually, it stops just after it ruins your day. And starts again just after being repaired.

author: VinzC
author_rank: Frequent Contributor
timestamp: September 06, 2016, 01:38:49 pm
content: Quote from: Brutte on September 06, 2016, 12:43:28 pmSorry, the proper term was "sealed crimp splices" instead of "insulated sleeves" — I'm not even familiar (yet) with those technical terms in my mother tongue so bear with me. The accessories we found so far are likethis one. That category of crimp splices is used in aeronautics and the maker guarantees a hermetic seal in the long run.Quote from: Brutte on September 06, 2016, 12:43:28 pmI am. If the Cupal sheet *is* the way, keep in mind — I've just confirmed with my colleague, who actually does the lengthening work — there are about 200 cables to lengthen, various sections between 0.5 and 2.5 mm². We generally count 4000 hours x man per car. Suppose it takes 5-10 minutes per cable, the total spent on just cables amounts to 16-32 hours more *per car*. And I think I'm optimistic. So yes, these are certainly the most recommended way. But we also have to balance that with the cost, unfortunately.The problem will probably disappear when aluminium cables and crimp splices are available together. But that's for another time, right now we have to compose. So the above family of sealed crimp splices seem to do the job — confirmation would be nice though.

author: batteksystem
author_rank: Regular Contributor
timestamp: September 07, 2016, 05:59:07 am
content: Quote from: VinzC on September 06, 2016, 09:10:36 amAre you sure they are aluminium wire, or they are actually CCA Copper Cladding Aluminium?

author: Brutte
author_rank: Frequent Contributor
timestamp: September 07, 2016, 08:29:37 am
content: Quote from: VinzC on September 06, 2016, 01:38:49 pmI am sure the sleeves you show do seal the connection fromoutsideenvironment adequately. But IMHO these won't work on a stranded Al+Cu wire because these sleeves solve a wrong problem.Do yourself a favor, take a sheet of paper and calculate the cross section of a stranded wire/hollow space. If one end of the wire is under the hood and the other is in the trunk then the difference in air pressure would push the air through that 10% of the cross section and yoursealed crimp splice.So with your cutting corners that is a journey through unknowns. If such circuit opens after 30-50 years then perhaps that is the way to go. But if it opens after 8-20 years then one out of those 200 connections would eventually drive someone crazy.

author: mikeselectricstuff
author_rank: Super Contributor
timestamp: September 07, 2016, 08:45:03 am
content: Just a thought - can you ultrasonic weld aluminium ? If so then that may be a viable way of joining.How easy is it to even get aluminium wire to use for the extensions ?

author: CM800
author_rank: Frequent Contributor
timestamp: September 07, 2016, 10:03:49 am
content: Quote from: mikeselectricstuff on September 07, 2016, 08:45:03 amI'd suggest trying to contact someone from Alibaba, e.g.:https://www.alibaba.com/product-detail/single-stranded-aluminum-core-wire-pvc_727779416.html?spm=a2700.7724857.0.0.QgvMRx

author: HwAoRrDk
author_rank: Super Contributor
timestamp: September 07, 2016, 07:31:56 pm
content: Here's a couple of interesting papers I found on aluminium wiring harnesses and connectors from Sumitomo Wiring Systems and Furukawa (large OEM suppliers):http://global-sei.com/technology/tr/bn79/pdf/79-02.pdfhttps://www.furukawa.co.jp/review/fr041/fr41_02.pdfThe take-aways from that seem to be two-fold: tin-plated-copper crimp terminals can be used, but must have fine serrations to break through the oxide layer in order to make a good electrical connection, and the terminal itself must be sealed to prevent corrosion.Also, here's a presentation from USCAR on automotive aluminium wiring technology:http://ewcap.uscarteams.org/AluminumWirePresentation_2012.pdfThere was some info in there regarding a need for differing wire gauges of alu versus copper.

author: helius
author_rank: Super Contributor
timestamp: September 07, 2016, 10:24:35 pm
content: There are splices available that seal the wire ends with both a solder fillet and an insulating adhesive. That should head off electrochemical corrosion, since the wires would be kept (reasonably) dry and the space between them filled with tin.

author: LabSpokane
author_rank: Super Contributor
timestamp: September 08, 2016, 05:38:44 pm
content: Quote from: mikeselectricstuff on September 07, 2016, 08:45:03 amYou'd need a hell of a transducer to get enough heat. It could well be possible, but it would be a shop bench procedure due to the size of the horn/booster/transducer required.But you are right on, some type of welding would sure solve the connection issue.

author: uncle_bob
author_rank: Unknown
timestamp: September 08, 2016, 05:43:08 pm
content: Quote from: LabSpokane on September 08, 2016, 05:38:44 pmHiThe "other" answer is:Yes, of course you can. It is routinely done on wire up to and including 0.002" in diameter ...For anything with the cross section of an automotive cable, a proper arc welding system with purge gas is about the only way you would get it done. There will be enough heat in the weld that the insulation on the wire will be trashed for a long ways down the cable. That's not so much a function of the welder as a function of the temperature you have to get all that very heat conductive metal up to in order to get it to melt.Bob

author: Brutte
author_rank: Frequent Contributor
timestamp: September 09, 2016, 07:36:41 am
content: An interesting YT about. I think those are the crimps that OP referred to. These are actually two wall-separated tubes with an inspection hole.Initially I thought it is just a pipe so it would not be air tight even after heating up the sleeve but now I think it does the trick.Clever thingy.

author: Brutte
author_rank: Frequent Contributor
timestamp: October 14, 2016, 08:21:42 pm
content: Quote from: Brutte on September 06, 2016, 10:14:26 amOk, so here is what happens when you put Cu + Al to a tap water (H20 + dissolved ions) and load the circuit. The cell is theoretically around 0.6V with no load. The output impedance of this cell is quite high because of low surface of electrodes (4mm^2 wires) and low ion content in a tap water. Even though tap water is a poor electrolyte, its ion concentration does not influence the voltage of the cell but only the impedance. The load (voltmeter input impedance) is around 10 megaohms.