Best type/designation of 2-strand wire to buy in bulk for generator and ebike lights

Question

As a US-based shop mechanic, every time I try to buy 2-strand wire that can do the same things as what comes with generator and ebike lights, it gets deceptively complex. A lot of what's out there from industrial suppliers is bigger, thicker, more colorful, and/or not designated for direct exposure to the elements. All I really want is something exactly like the Busch and Muller wire that comes with generator lights, but in a big spool.

Getting individual B&M wires is possible but inconvenient, since only a handful of US wholesalers have it, and not in bulk. The Schmidt coax and Rene Herse offerings are also available and very nice, but they're expensive and not as fast to work with like the parallel strand pull-apart style.

What are some simple terms to search for? In the generator light countries, what do shops keep for these purposes?

Note this question isn't about a specific product, but rather what type or category to look for. Also note I'm only asking about 2-strand and light installations that call for it here.

Answer 1

For wire size - have a look at this question - What gauge wire is used for dynamo hubs and lights?

Easy option is "twin core 22AWG speaker wire" - could look for 20AWG or 0.75mm (which is 20AWG). Can also search for Automotive wire of the same saice (probably the same stuff with different label. Ideally use one with an outer sheath, but I do not believe it is required. Modern plastics are reasonably resistant to exposure to elements, and such a thin cable is vulnerable to mechanical damage without the extra plastic. You are not dealing with high voltages and lethal electric shocks, a damage cable is a nuisance not an injury risk.

There are plenty of sources of 500m rolls of thin speaker wire.

If the installation uses the frame as earth, you can either buy a second roll of single core, or just run twin core. I personally would just run twin and connect each end of one conductor to the frame.

Answer 2

"stranded twin core true-rip" was what an old-timer told me to buy when doing an install of a rubbee-style bottom bracket dynamo from Sanyo.

Apparently speaker wire makes an excellent substitute for dedicate "bike light wiring" and because speaker wire is used in longer lengths, it tends to be cheaper.

Some setups don't require two separate wires, they can use the frame of the bike as one of the conductors. This works fine generally, but crossing the headset bearings can be a loss point due to resistance, so its not uncommon for the ground to be bridged from frame to fork with a dedicated short wire, often coiled to allow for movement over time.

Thickness - the thinner the wire's conductor, the lighter it is. The outer insulation has no bearing on the wire's capacity, but a thicker outer will provide more abrasion resistance. IMO 20 AWG is as thick as you need to go, and I've successfully used 24 AWG stranded.

Never ever use solid core wire for anything on a bike - its a recipe for failure.

Also one consideration is the water-resistance of the insulation. One might assume that all plastics are waterproof, but some cable rated for indoor use might not have as much waterproof-ness as you might presume. In this case, it is possible to add heat shrink over the outside of any exposed or wear locations.

Answer 3

bigger, thicker

If you search for low-voltage cables, you should get reasonably thin ones. You also need to specify the cross section in mm²; but if you specify low-mm² low-voltage wiring, you should find a good match for your properties. However, what complicates this a bit is that you want wiring where the two cables are joined together, but not wrapped around a second layer of insulator. This limits your options a bit, since the second layer of insulator would make the wire too thick.

Speaker cables usually have two cables joined together, with no second layer of insulator. However, speaker cables usually are too thick for this low-current use.

more colorful

Black wire is standard. However, if you buy 2-strand wire, it's unfortunately very likely that the second wire is a red one, and not a black one with white stripe.

and/or not designated for direct exposure to the elements

I don't really believe this one. Wires are made out of copper and insulator. About the only problem could be if the insulator is not rated for cold temperature, but that's only a problem if the bike is ridden in very freezing temperatures AND someone flexes the wire so much that the insulator breaks. Quite unlikely that both of these conditions could happen at the same time. Any copper is equally good when exposed to the elements, insulators have differing temperature properties but as long as you don't flex the insulator in the cold, even PVC should work in the cold.

TL;DR: low-mm² low-voltage wiring, two cables joined together, no second layer of insulator around them (as in speaker cables, but speaker cables are unfortunately usually too high-mm²)

Edit: I may have been wrong related to speaker cables, it seems I found a 0.5mm² speaker cable that should be a perfect match apart from its colorfulness: https://www.karkkainen.com/verkkokauppa/nedis-2-x-0-50-mm-kaiutinkaapeli