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I am helping my brother installing a stern thruster on a boat.

We need to install 70mm² electrical cables to the battery bank to keep voltage drop within the manufacture's limits. I have bought a hydraulic crimper, which handles up to 120mm cable to ensure that it is man enough, 70mm² cable and lugs from Amazon.

When I try to crimp a lug onto the cable, the crimper cannot crimp it tight enough and it slides off.

I seem to have three options

1) complain t Amazon that one or more of their products are off spec and get them to sort it out.

2) use a smaller eg 50mm² die in the crimper

3) push some single strand 2.5mm cable into the 70mm² bundle to pack it out so as to get a tight crimp.

Any advice or further ideas?

John

John_S wrote: ↑Sun Feb 04, 2024 1:40 pm I am helping my brother installing a stern thruster on a boat.

We need to install 70mm² electrical cables to the battery bank to keep voltage drop within the manufacture's limits. I have bought a hydraulic crimper, which handles up to 120mm cable to ensure that it is man enough, 70mm² cable and lugs from Amazon.

When I try to crimp a lug onto the cable, the crimper cannot crimp it tight enough and it slides off.

I seem to have three options

1) complain t Amazon that one or more of their products are off spec and get them to sort it out.

2) use a smaller eg 50mm² die in the crimper

3) push some single strand 2.5mm cable into the 70mm² bundle to pack it out so as to get a tight crimp.

Any advice or further ideas?

John

Hi JohnI paid small money for a hammer crimper. It gets the job done. I'm not up on 70mm sq. Is that pinkie or first finger size? If its pinkie the hammer crimper will deliver.

I'd go for option 1 and a hammer crimper. Had a quick Google search and 70mm sq looks like arc welding cable size. Hammer crimper will piss that and give you the solid termination.

I've done a hammer type on 70mm, although I do prefer the hydraulic crimpers.

I would prefer your option 3 if you can get it tight enough.

Or maybe option 2, have a go with the 70mm crimp first, then swap to 50mm crimp but not crimp quite all the way. Then release and rotate the cable 90 degrees and crimp again to get as symmetrical a crimp as possible.

Just use the next dies down, you may end up with wings, you can file or hammer these flat easy enough. I have done this for a living and it was common practice, shouldn’t be, but was.

You cannot really blame the crimper, the dies should ideally be same brand as lugs but also some cable comes up small if some obscure brand. A Cembre crimper with Cembre lugs and Nexan cable will be fine but lives rarely that easy for a jointer with cheap customers.

Thanks everyone. Nice variety of answers and shows that my line of thinking was right. I did not feel that a hammer crimper was up for 70mm² and a hydraulic crimper is easier to use on a boat.

I don't think I am going to bother Amazon. It is one of the risks of getting different manufacturers' kit, mostly of chinese origin.

I shall go with using the 50mm² dies and hide it in the heat shrink tubing.

John

Had the same issue with my cheap Chinese hydraulic crimper, maybe due to using flexible welding cable but the 50mm2 crimp works fine and no excess steel to fold over.

Are you sure that “ 70mm²” really is what it was sold to you as? If the 50mm² lugs fit on it better than the 70mm² ones then it is very likely that the cable is really 50mm². Unfortunately fraud is very common in this sector.

My cable measured fine, that was my first check before moving to a smaller die. So either the lug was oversize or most likely the crimping dies were wrongly sized.

I have not tried 50mm² lugs.

The 70mm die worked fine and all crimps passed the pull test today.

Stinsy wrote: ↑Mon Feb 05, 2024 2:41 pm Are you sure that “ 70mm²” really is what it was sold to you as? If the 50mm² lugs fit on it better than the 70mm² ones then it is very likely that the cable is really 50mm². Unfortunately fraud is very common in this sector.

Yeah I bought some 70mm2 cable from Amazon or eBay recently and it was also showing up looking a bit small and visually compared more closely to an old 50mm2 welding cable, but the diameter, count and layout of the strands, can all affect it, when cleanly cutting through the cable sheath and seeing the compressed cores side by side the 70mm2 did actually look more realistic, as the welding cable had more and finer strands that puffed out a bit more when exposed.

Some lugs are different thicknesses themselves, I've also got a cheap 10T hydraulic crimper and I've also started with a 70 die then gone to a 50 etc when they looked like they weren't secure enough for a pull test. Glue Lined heat shrink is the best for boats to stop any corrosion getting into the strands and using capillary action up the sheath, but Sounds like it's all good now.