In some countries and most USA states, an "Always On" daytime headlight is the law. Not really strictly enforced here in California but it IS the law ... and has been for about 30 years.

So, every bike you buy will be wired for an "Always On" headlight.

If an owner does mods or changes lighting set up (like I did), then it's easy to
install an ON/OFF switch. I like this as it saves battery on start up. If your headlight comes on with the key (as most stock bikes do) and it's very cold and your battery is low, then that can be the difference between the bike starting or not.

I always have my headlight switched OFF before start up. Then switch it ON once under way. I would like an additional low wattage spot light for night time running, but would never use it in daytime.

Having an ON/OFF headlight switch is also very handy if you ride a low elec. output bike like my DR650. With only a 200 Watt output it's hard to run accessories. On very cold riding days when running heated gear (Gerbing elec. jacket (77 watts) and heated grips (30 watts) I switch my headlight OFF. This frees up 35 watts. (I run a 35 Watt HID light instead of stock
H-4 55 Watt bulb).

This makes a nice difference in how well the elec. jacket works. With a total output of just 200 watts you only have about
90 watts free. Adding 35 Watts by switching off headlight helps quite a bit and you never risk running down your battery.
The DR650 Suzuki will keep running even if you run your battery down flat. But then it will not re-start ... unless you Bump start it. So I try never to over tax the system.

But when riding in 30F temps one really needs that heated gear. Huge difference in survival. The DR650 needs at least 400 watts but no way to get that. After market stators give you 250 Watts but are unreliable Chinese units (not Denso).

The headlight helps a cold start. The current draw while minimal warms the battery. The cut out relay then kills it while the the starter motor turns. If you have a switch its better to turn it on for about two minutes then off just before you push the button.

I will never again rely on heated kit after I knelt on the plug just south of the North Cape one February. Minus 18 has to be survivable using food and insulation not electrical gizmos. They can make you comfortable though.

Andy

Ah yes ... the cut out relay! True, most Japanese bikes have this feature but not all. In fact, neither my Suzuki DR650 nor my Triumph 1050 Tiger have a cut out relay for the headlight. I wish they did!

I've heard of "warming" batteries with the new Lithium-Iron batteries like the Shorai and others, but not with standard lead-acid, AGM maintenance free batteries. Does it really work?

NO cut out relay on Tiger so headlight stays ON while your trying to crank over the engine. NOT GOOD.

Does not get BETTER with use, gets weaker then stops altogether. I stupidly installed a crap battery that is not even as good as the standard Tiger battery,
so most of this is MY FAULT.

Next up will be higher spec batt, a Deka or Yuasa. It's slightly BIGGER than standard batt but can just squeeze in the compartment.

On my visits to UK riding around I noticed not many riders used heated gear.
That was in '03. I lent my friend my Gerbing jacket and he immediately bought himself one for X-mas. Maybe heated gear is catching on there? Was brutal cold around London when I was there.

I've used heated gear for 25 years, never travel far without it. If you know how to use it and have a bike with enough elec. output, it can be a life saver. I only use a heated jacket (Gerbing) and heated grips. My heated grips are not very good. (Some riders have heated socks, pants and gloves.) A high output touring bike is best to power elec. gear. (at least 400 Watts)

The good news is many new bikes now come with very effective heated grips. MUCH better than aftermarket ones. Triumph factory ones are fantastic, as are most BMW ones. Even some new Jap bikes now come with heated grips.

The DR650 is a challenge for heated gear given its meager 200 watt output.
But I sneak by most times although I did freeze recently riding in 27F temps.
Had to slow down, then pulled off at Cafe, waited for things to warm up. This in Arizona! (not always hot there!!! ) But I was wearing Summer gear only ... as I had been in Mexico , on the way home.

Some riders don't use heated jacket correctly, layer wrong. Even so, once below freezing it will be less effective no matter what. But DOES help and can at least extend your riding time before hypothermia sets in.

Once you get the routing, hook up and connector issues sorted it's a no brainer far as I'm concerned. Never leave home without it. No more Michelin Man over dressing.