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Author Topic: How important is crimping low voltage DC wiring?  (Read 3714 times)
stephendv
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« on: August 18, 2013, 08:28:22 AM »

I need to replace my existing 60A breaker between charge controller and battery with a 100A version.  Problem is the 100A model has screw terminals so I'll need to add lugs onto the end of the cable.  How dangerous would it be to not use a crimper, but just smash the lugs with a hammer?  Grin

I can understand that high voltage DC could suffer from arcing so needs proper crimping, but have the feeling that at 48V, it's not so serious?  Thoughts?
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Justme
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« Reply #1 on: August 18, 2013, 08:39:44 AM »

What current will be passing through the terminal?

As you are increasing the breaker size I would guess 80amps ish at 48v so thats nearly 4kw.

I would crimp them properly.

A high resistance joint could produce a lot of heat.
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Iain
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« Reply #2 on: August 18, 2013, 08:42:00 AM »

Hi
Unless you can crimp it properly I would be tempted to solder it. Although crimping is better, providing you can solder it properly you should be OK. Try to make sure all the flux is removed on completion, it is corrosive and can cause damage to cables/crimp over time. As the cable is now soldered, if the wire is allowed to flex at the solder joint it can work harden and fail. try and support the area of the wire with solder on it with a couple of layers of heavy duty heatshrink or ensure the cable is clamped to stop any movement of the soldered cable. although it is low voltage the current will be higher and that is the most dangerous due to fact that any resistance in the joint will cause heat/failure. The heat is caused by the current squared multiplied by the resistance. (double the current multiply the heat by 4)
Iain
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stephendv
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« Reply #3 on: August 18, 2013, 08:53:18 AM »

Yes about 80A peak through the connection.  Don't have access to proper soldering equipment either Sad  Sounds like I'll have to take the cables down to an electrician and ask him to crimp them.

Thanks chaps

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clockmanFR
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« Reply #4 on: August 18, 2013, 09:01:24 AM »

stephendv,  I am shocked Shocked

" Don't have access to proper soldering equipment either Sad  Sounds like I'll have to take the cables down to an electrician and ask him to crimp them".

No soldering equipment,  wackoold wackoold.

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« Reply #5 on: August 18, 2013, 09:03:45 AM »

Good mornng StephendV,
                     Maybe the spark would show you how to use his crimper and hire it to you for a few hours.Preparing the wire before crimping is important and so is matching the wire width with the terminal.The more you crimp the better you get at it.
                                                                                Biff
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stephendv
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« Reply #6 on: August 18, 2013, 09:10:32 AM »


" Don't have access to proper soldering equipment either Sad  Sounds like I'll have to take the cables down to an electrician and ask him to crimp them".

No soldering equipment,  wackoold wackoold.

Hehe.  Yes it is sad.  I have a soldering iron for electronic work, but don't do much thick-cable electrics so haven't needed one.  The place where I bought the original DC breakers were kind enough to crimp cables for me too, so have managed to get by, until now.

It's really just 2 lugs on 2 cables and the RE system will be done and finished forever  whistlie
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« Reply #7 on: August 18, 2013, 09:15:40 AM »

Ahh ,Good Morning C/M,
                     There are more than Stephen who have bypassed the fine art of soldering on their way to success.In fact it is something which I personally am still trying to get to grips with.I have the gear as I also have the Mig welding gear but somehow the hands and fingers wander off on some other more mind boggling art form.
        We have exellent wind here at the moment,something round force 5/6 and great shards of sunlights are raking the bog as I type,So its an off-gridders paradise,full batts,warm water and plenty of power on tap.I trust your experiences are similar in Normandy,Lang may it be so.
                                                                                Biff
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clockmanFR
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« Reply #8 on: August 18, 2013, 09:17:25 AM »

I hate crimps, and always solder. (Seen crimps come apart)

All you need is a blowtorch, thick reel of solder, bit of flux and away you go.

My underground cable joints are firstly fluxed, cables (16mm/Sq) each end shoved in the brass joint, the screws tightened up, then solder the whole lot, remove excess flux.

'bob's you Uncle'

Terminal ends, I lightly crimp with pliers then solder the joint.
 
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« Reply #9 on: August 18, 2013, 09:29:49 AM »

Morning Biff,

Good to hear you and your domain are in good fettle.

Mrs spent all night making plum stuff, good crop this year. Oh heck  Shocked, she has made some plum and chilli jams at different strengths.

Next week is my welding month, feel free to visit and I can get you welding like a Pro, (sort of) and heavy soldering.

 On the welding month....
1.  By order from her indoors....make and weld up the new entrance side gate panels/railings.
1.      The new 3.7m dia HP wind turbine tower, then erect and commission.
2.     The no 3 tracker main hinge unit and panel frame.
3.      Forgotten......   facepalm, ....... Oh yes installation of some Navitron static PV panel rails, and PV stuff for the conservatory under floor heating etc, need to make special mounts.

Always looking for volunteers out here.
http://www.echorenovate.com

« Last Edit: August 18, 2013, 09:34:38 AM by clockmanFR » Logged

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Tinbum
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« Reply #10 on: August 18, 2013, 09:46:58 AM »

The first secret to good welding is to buy a good welder! I could never get to grips with mig and when someone tried to show me how easy it was using my machine, he couldn't.
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clockmanFR
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« Reply #11 on: August 18, 2013, 10:14:05 AM »

Tinbum,

I am not a great champion for mig, tig,  etc  as the way they work just adds to the extra messing. Yes they have their place if they are doing a set weld on set materials day in day out.

Me, I am a stick welder, but nowadays the MMA Inverter units, no stonking great Transformers, (Oxford, Bantams etc). These MMA, are excellent as the unit is light and has DC at smooth output, (full of stonking great Transistors I understand).

With MMA stick units the voltage required is about 20% less than the old Transformer units.

The guy that taught me in the late 1970's used to weld Submarine sections and he was tested every week under the Lloyd's registration. His tips and process were very valuable info for me and I try to pass them on.

MMA, this 120 is equal to the old transformer 180a,  something like this.......  http://www.ebay.co.uk/itm/MMA-120-DC-IGBT-CHIP-PORTABLE-INVERTER-WELDER-/360342667596?pt=LH_DefaultDomain_3&hash=item53e618c14c

Mind you do make sure you get good rods, most are awful Chinese jobs where the quality is rubbish. Good stuff is available but the price can be 3 or 4 times more than the chinky.  But you soon realise the quality.



  
« Last Edit: August 18, 2013, 10:16:29 AM by clockmanFR » Logged

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julian
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« Reply #12 on: August 18, 2013, 10:22:02 AM »

Yes about 80A peak through the connection.  Don't have access to proper soldering equipment either Sad  Sounds like I'll have to take the cables down to an electrician and ask him to crimp them.

Thanks chaps




If you dont have any other tools, most people have an oven.  Sure, you wouldnt want to go into production using your hotplate, but, for a couple of terminals, its perfectly feasible.
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derekmt
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« Reply #13 on: August 18, 2013, 10:34:10 AM »

Tinbum,

I am not a great champion for mig, tig,  etc  as the way they work just adds to the extra messing. Yes they have their place if they are doing a set weld on set materials day in day out.

...
Tig has a lot of solar applications.
if you get a DC tig set up you can weld copper! that means DC bus bars can made out of copper tube. cheap high temperature pipework for solar thermal.
An AC tig means you can weld Ally and that open up a lot e.g. Welded Lightweight PV frames, welded ally rod tube bus bars etc... Ally thermal stores
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Tinbum
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« Reply #14 on: August 18, 2013, 10:46:48 AM »

I used to do a fair bit of stick welding but stopped when I moved house and I couldn't get my inverter welder to work at the new house. (Turned out our 5kva transformer on the pole was knackered). I like stick but MIG is good for small stuff. I have a TIG but haven't used it yet- doing too many other things. All my stuff is MUREX you cant go wrong with it.

The other great things are plasma cutters. A friend of mine was surprised when I'd mentioned I didn't use gas and didn't have much experience of it. I had the equipment and he insisted on showing me how to best use it. I then showed him the plasma and he understood straight away why I didn't use gas!
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