Terminal blocks: evil or OK?

Technical discussion on converting internal combustion to electric
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coulomb
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Terminal blocks: evil or OK?

Post by coulomb » Sat, 18 Feb 2012, 15:23

It has been stated that terminal blocks are a bad thing to use in a vehicle. I can see the argument: the vibration inherent in a vehicle environment will eventually cause the screw to shake loose, creating a high resistance and/or intermittent or open circuit connection. However, I see terminal blocks on all sorts of industrial gear, and it seems that industrial gear, often running 24 hours a day, 365 days a year, will receive more vibration amplitude over its life than an EV will.

Granted, it may be that billions of small amplitude vibrations as seen in industrial gear are not as bad as hundreds of thousands of high amplitude vibrations as seen in an EV.

I note that made-for-EV components seem to be using terminal blocks:

Evnetics Shiva controller:

Image

From Evnetics "Big Sol" coming! (DIYElectriccar.com) .

Zilla "hairball":

Image

From DriveEV.com Jeep Conversion .

I'm interested in this, because Weber and I received some criticism for using terminal blocks as part of our build, staring about here:

Weber and Coulomb's MX-5 (two other authors agreed with Electrocycle in the next half dozen posts).

Is it possible that these controllers use the "less worse" type of terminal block that squeezes the cable between two parallel pieces of metal (not just pushing a screw against the furruled wire)?

Is it possible that these use star or other washers to make them more vibration proof?

Perhaps the larger terminals are not so bad (but the Zilla hairball has many small terminals), because the bolt stretches more (in proportion to its length), and this gives a better torque that prevents screws and bolts from coming loose? One rarely sees spring or star washers in cars, for example, and I think that's because the bolts are stretched an appropriate amount (set by their tightening torque setting).

My apologies if this posts twice; I appear to have lost the previous post because it decided I needed to log in.

Edit: formatting
Last edited by coulomb on Sat, 18 Feb 2012, 04:25, edited 1 time in total.
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Terminal blocks: evil or OK?

Post by Johny » Sat, 18 Feb 2012, 18:47

The guru at work who keeps telling me how much I've done wrong in the Vogue has approved clamp style terminal block when used with pin crimps. He did not allow plain wires into terminal blocks or screw only terminal blocks. We do mobile radio installations for all emergency services, ambulance, fire, police, SES etc.
Last edited by Johny on Fri, 24 Feb 2012, 05:50, edited 1 time in total.

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Terminal blocks: evil or OK?

Post by coulomb » Sat, 18 Feb 2012, 18:56

Thanks for the reply, Johny.
Johny wrote: ... when used with pin crimps.

By pin crimp, do you mean something like this?

Image

[ Oops! Didn't realise its full size was this big. Sorry. ]

So the wire is crimped to the pin, and the pin is clamped in the "right kind" of terminal block.

Have I got that right?

[ Edit: I originally had a pin designed for use in a connector; I think that there are some (not sure if the above is one) that are designed just for use with terminal blocks. ]
Last edited by coulomb on Sat, 18 Feb 2012, 08:01, edited 1 time in total.
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Terminal blocks: evil or OK?

Post by Johny » Sun, 19 Feb 2012, 01:18

I have been using the utilux style that supports part of the insulation as well.
Image
But he had something a bit smaller that exactly fit the insulation of a typical instrument multistrand wire. I hadn't seen them before and I won't be chasing them for me as they appear to be hard to get. I'm using what you see above - in fact from them as well (see picture url).

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Terminal blocks: evil or OK?

Post by Renard » Sun, 19 Feb 2012, 02:49

What about using Loctite on the terminal screw?
Would that mitigate the "evil"?
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Terminal blocks: evil or OK?

Post by Electrocycle » Sun, 19 Feb 2012, 22:57

crimp on pins help a lot.

On anything with screw terminals like the EVnetics controller in the top pic I try to use ring terminals on the end of the wire (with heatshrink for strain relief)

I don't like the Zilla hairball connectors, but it's easy for DIY people, which is why they do it.

It's not the screw coming loose from vibration that's the problem, it's the strain on the wire where the screw terminal clamps it. There's no nice way to reduce that, and the wires tend to crush more over time so the terminal can come loose without the screw ever moving.
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Terminal blocks: evil or OK?

Post by coulomb » Mon, 20 Feb 2012, 13:40

Electrocycle wrote: It's not the screw coming loose from vibration that's the problem, it's the strain on the wire where the screw terminal clamps it. There's no nice way to reduce that, and the wires tend to crush more over time so the terminal can come loose without the screw ever moving.

Ah, my mistake then.

But doesn't putting the wire in a ferrule (sometimes called a bootlace pin?) fix that problem? The strands of the wire can't spread, and my understanding is that the spreading is the major reason that wires in terminal blocks come loose over time.
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Terminal blocks: evil or OK?

Post by Johny » Mon, 20 Feb 2012, 14:30

Now you have jogged my memory. That's what he called them (guy at work), bootlace pins. The ones he had included a small plastic section that went up the wire insulation about 5mm.

Edit: Fixed typos
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Terminal blocks: evil or OK?

Post by Richo » Mon, 20 Feb 2012, 20:43

Nearly all car audio amps have screw terminals.
Majority are wired into bare stripped cable.
Lots are attached to enclosures subject to massive vibration.(ie Subs)
I haven't heard of this being a problem.

Bootlace ferules are nice.
Ring stlye crimps are good also - assuming they fit in the screw terminal.
Star or wave washers would be fine too.
Spring wahser may not be as good.

Don't use Loctite on the screw terminals - they are designed to conduct electricity.
Most loctites are anerobic and would require you to put them on the screw thread which would reduce the conductivity.
There are some tamper proof glues but are expensive for wht they are.
Quick grip I have found to be quite good as it is slightly elastic and only requires a small drop on the outer of the head of the screw.

If the cable is left to flap around in the breeze this could increase the chance of the individual strands breaking.
But that is just a poor install.
So the short answer is NO but the long answer is YES.
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Terminal blocks: evil or OK?

Post by Johny » Tue, 21 Feb 2012, 16:56

Bootlace ferrule kit on eBay.
(When this link fails, search for: bootlace ferrule)
eBay
Image

Edit: Added image
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Terminal blocks: evil or OK?

Post by Electrocycle » Wed, 22 Feb 2012, 01:02

Richo wrote: Nearly all car audio amps have screw terminals.


they are usually not in the engine bay though, and a failure doesn't involve the car stopping mid manoeuvre, or a high capacity battery pack shorting out :)
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Terminal blocks: evil or OK?

Post by jonescg » Wed, 22 Feb 2012, 02:48

This is an interesting point... I'm looking at using screw terminal blocks to connect my battery balance wires to a breakout board. My problem was finding enough terminals for a 170 cell pack Image I found if I go for the blocks with 3.5 mm pcb pin spacings I can fit them all on. The trick is to secure the wire going into the block from being able to move around - i.e. cable tie it down or something.
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Terminal blocks: evil or OK?

Post by CometBoy » Wed, 22 Feb 2012, 02:52

IMHO the bootlace ferrule crimpers that do the full 4 sided crimps are better.

I see that the same company on Ebay does offer such a tool as well but not sure of the quality – most likely fine and a fraction of the price of the ones used in the business.

Ebay again

I’ve only used the Germany Greenlee Textron tool. These are very good but aimed at the more professional market.

This style of tool uses a full cycle ratchet mechanism that assures complete crimps. They also adjust automatically to the correct crimp size.

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Terminal blocks: evil or OK?

Post by bga » Wed, 22 Feb 2012, 05:04

Bootlace ferrules -- yes good
Altronics has a selection. I have found them to acceptable and very similar to the ones RS sells.
The altronics ferrule crimp tool also works well.

I have had a good run with vise type terminals, the ones that have parallel jaws that the screw closes. These are common in switchboard terminals like din rail types and also available as PCB types, again I have used the altronics ones for years with no problems.

Altronics has a miniature 3.81mm (0.15 inch) pluggable terminal block (see P/N P2662 for a 12-way version. These and some ferrules to stop the wires fatiguing off would be a good option.

Something I've done with multi-stranded skinny wires is to strip them long (20mm) and then wrap the stranded conductor around the insulation several turns, then clamp the lot in the in the jaw-type terminal. It stops the wire fatigue failing at the end of the insulation. Good for cat-5 conductors.
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Terminal blocks: evil or OK?

Post by weber » Wed, 22 Feb 2012, 14:42

bga wrote:Something I've done with multi-stranded skinny wires is to strip them long (20mm) and then wrap the stranded conductor around the insulation several turns, then clamp the lot in the in the jaw-type terminal. It stops the wire fatigue failing at the end of the insulation. Good for cat-5 conductors.

But this has to be a bad idea for the same reason it is bad to solder wires before clamping them. Both solder and plastic insulation undergo creep deformation over time. That is, they slowly "flow" so that the original clamping pressure is lost.
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Terminal blocks: evil or OK?

Post by Richo » Wed, 22 Feb 2012, 20:36

Electrocycle wrote:
Richo wrote: Nearly all car audio amps have screw terminals.


they are usually not in the engine bay though, and a failure doesn't involve the car stopping mid manoeuvre, or a high capacity battery pack shorting out :)


They may not stop the car but I would think they would complain no less if they failed.
I have seen car amps connected to similar guage welding wires as DC eV's with multiple batteries and many Farad caps.
Also mounted in ute trays.
I doubt it is any less than what an eV would be subjected to.

There are a truck load more car amps than eV's and being used some 10x longer than eV controllers.
If they were that bad they would have slowly migrated to something better.
So the short answer is NO but the long answer is YES.
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