Terminals on heavy battery /starter cable

contessaman

contessaman

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Chaps,as part of my engine replacement I've decided to rip out the spaghetti mess of heavy cable from my boat and start from scratch. I'll be re - using cable that's in excellent condition and replacing any thats not.

I want to do the best job I possibly can of it so I'm after some wisdom and advice on the best way to create ring terminals on the end of such heavy cable. The sort of terminals that attatch to isolator bolts and the engine starter motor. Looks like you can get large crimp terminals and a hand held hydraulic press for these... But is there an alternative or a way of improving the crimp? Can they be soldered as well? Finished off with heatshrink over the join? Sealed in some way?

I'm all ears.

Thanks
 
Solder in a crimp terminal is a bad idea, solder is ductile and will flow with age releasing the crimp pressure. Note that tinning isnt pure solder, what is left on the cable is an amalgam of copper and solder and is not ductile.
About the only improvement would be glue filled heat shrink sleeve to prevent oxidisation creeping up the cable (not an issue with tinned wire)
 
You will need a seriously heavy crimper to do battery cable ends. Not worth buying one for a one off, but find an auto (or marine!) electrician who has the kit. cut your cables to length and have him crimp the terminals.
 
As you cannot achieve the pressure needed for a good crimp with anything else, the cheapest viable solution is a hydraulic crimper. It doesn't need to be a very expensive one, mine was under £20 and while I wouldn't want to work with it in a boat production line, it's absolutely fine for the odd terminal and I wouldn't shy away from using it for rewiring a boat. I've crimped my 70mm² battery terminals with this just fine. Soldering terminals of that size is insanity and will not work well, if at all (too much copper transporting away the heat - all you'll get is damaged insulation).

Also important is the actual crimp lug. It is very common to find ones that do not crimp well because in order to save material, the crimp fitting has been made too thin to compress well onto the cable it is specified for. The only way to crimp such "skinny" lugs is to use the next smaller crimp die. Better to buy good quality lugs. I've had good luck with "All-Trade" ones from Amazon". Good lugs have a breather hole on the side opposite the cable entry to avoid pneumatic pressure squeezing the wire out during crimping.

Before you slide the lug on, put some appropriately sized heatshrink on the cable, to cover the "stem" of the crimped lug when done. Comes in red and black, so you can avoid buying two-colored cables.

Lastly, if your battery has posts as well as bolt terminals, the bolt ones are much better - easier to install in confined spaces and less likely to fail. Always use a bit of waterproof grease (silicone grease) on the contact areas to prevent corrosion. I used to advise also putting grease on the wire prior to crimping, but changed my mind, as a good crimp does not need this and it makes it much more easy for the cable to slip partway out during crimping, resulting in a poor crimp. You can achieve the same corrosion protection with the heatshrink and squeezing a small amount of silicone grease into the breather hole after crimping, leaving no part of the copper exposed.
 
+1 with all that Yngmar writes (not least those infuriating crimps with too little wall thickness).

If your circumstances are such that you can safely lend them to sailing friends at a bottle of wine per pop, the cost soon erodes.
 
Yeah so I'm definitely going to buy a set of hydraulic crimpers. My dads boat could do with a rewire so he can use them and the ones I'm looking at are only 30 odd quid.

So we're going with

1) buy the thickest wall good quality lugs not cheap thin walled crap
2) don't solder ?
3) definatley heat shrink over the wire/ join/ shank of crimp lug.

Is it worth Vaseline inside the terminal to prevent corrosion?
 
contessaman said:
Yeah so I'm definitely going to buy a set of hydraulic crimpers. My dads boat could do with a rewire so he can use them and the ones I'm looking at are only 30 odd quid.
Click to expand...

Good idea, i bought a set from Ebay and they work very well. I even crimped some guardwire fittings with mine (8 ton ones).

So we're going with

1) buy the thickest wall good quality lugs not cheap thin walled crap
2) don't solder ?
3) definatley heat shrink over the wire/ join/ shank of crimp lug.
Click to expand...

4) Use quality cable. This is very flexible and tinned : http://www.autoelectricsupplies.co.uk/product/885/category/124

AES also do quality terminal lugs.
 
Boo2 said:
Those are very heavy, Yngmar, what did you need such high current capacity for may I ask ?

Boo2
Click to expand...

Surely the bigger the better = less voltage drop.

Same subject different topic.. My boat currently (no pun intended) has the starter and domestic battery bank under a berth in the aft cabin and a third battery in the bows for the bow thruster. Bizarrely my windlass is currently fed off the domestic bank. Anyway, at the moment all the battery isolators are under the companionway meaning the starter current has to go from battery about 3 metres to isolator then back about another 2 metres to engine. Also, it means there's a fair bit of high current cable unisolated to the switch. I'm changing things with isolator switches right next to batteries in the aft cabin. Am I going to get an earful of my surveyor telling me I should be able to reach in from cockpit to isolate? I don't really care I'd rather have the isolators right next to batteries and a Much shorter wiring run. I'm going to change things so that the battery at the front does both the windlass and the thruster and just takes its charge from the bank at the rear of the boat.
 
pvb said:
Yes, you can improve the crimp by also soldering the joint. Indeed, Trojan Batteries recommend this method (see http://www.trojanbattery.com/pdf/WP_BatteryCableGuide_0512.pdf). Using adhesive-lined heatshrink will help keep moisture out and improve the appearance.
Click to expand...

What trojan say makes sense. I always solder and heatshrink normal little crimp terminals when I do those for that very reason. Just crimp = only outside of wire touching hence those thermal images. Soldered means its wetted out and a solid piece.
sadly the trojan guide doesn't actually say how to do it. I guess the cable would need to be tinned to start with and then one would need the power of a blow torch on the terminal to heat it through and plenty of flux as you feed the solder in. I'd respect this to melt an awful lot of the wire insulation though? And the risk would be that if the solder wicked a long way up the wire then it would become brittle and inflexible...
 
contessaman said:
Am I going to get an earful of my surveyor telling me I should be able to reach in from cockpit to isolate?
Click to expand...

Only if the surveyor is a bell end.

I don't really care I'd rather have the isolators right next to batteries and a Much shorter wiring run. I'm going to change things so that the battery at the front does both the windlass and the thruster and just takes its charge from the bank at the rear of the boat.
Click to expand...

All good thinking.

No need to solder the terminals, properly crimped is fine.
 
contessaman said:
What trojan say makes sense. I always solder and heatshrink normal little crimp terminals when I do those for that very reason. Just crimp = only outside of wire touching hence those thermal images. Soldered means its wetted out and a solid piece.
sadly the trojan guide doesn't actually say how to do it. I guess the cable would need to be tinned to start with and then one would need the power of a blow torch on the terminal to heat it through and plenty of flux as you feed the solder in. I'd respect this to melt an awful lot of the wire insulation though? And the risk would be that if the solder wicked a long way up the wire then it would become brittle and inflexible...
Click to expand...

I crimped and soldered all the connections when I increased the size of the domestic bank on my old boat from 2 to 6 batteries. First, I crimped the terminals on to the cable. Then I wrapped wet kitchen paper around the insulation close to the terminal, held the terminal in a blowtorch flame and applied solder through the little vent hole in the terminal. There was minimal damage to the insulation. The cable didn't seem inflexible afterwards.
 
Downstairs from my office is a workshop full of time-served wiremen making panel enclosures and cable assemblies all day. The vast majority of their work is crimped - even where wires go into a spring or screw terminal, they get a ferrule crimped on first. I was in there the other day and noticed a board on the wall recording calibration due dates for all their crimping tools - they take quality joints seriously. Cable sizes range from ethernet and serial to hundreds of amps DC.

They do a little bit of soldering where awkward pieces of equipment demand it, but never ever combine it with crimping.

Pete
 
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