I want to add these 55w driving lights

I'm mostly nightblind, so I need a little bit more light than than stock bulb would allow. I upgraded to Halogen 55/60w which is better, but in the dark roads of the country, I'd like more lights to kick on as necessary.

I am adding a customized (read: ghetto rigged) highway bar to mount my highway pegs to my 81 750e. I bought these 55w lights to mount to it.



It wasnt until I told a friend that I was reminded that the alternator may not be up to the task. Any thoughts on the matter, as the search provided nothing telling. I cannot find output specs on the alternator anywhere.

Should I be concerned if I add them AND/OR if they are OK, will it be OK to use them for longer durations than just periodic use?

I mounted a second 55W light to one of my bikes. Yeah, it's tough on the charging system, but I did a couple things first though: installed relays for the coil (wg's "coil power mod") and the aux light, and changed to LEDs for the turn signals and tail light (nice big radianz cluster for the tail). I don't leave the light on for long stretches, so I don't really know or remember if it is all that harmful...

20 amp output for most (if not all) KZ alternators except the KZ1300 (and at least some of those had dual alternators).

I was a little concerned about this myself, so I did some research. It's in the Factory Service Manuals (all that I have anyway), either listed by wattage (on the 1980 and older) or by amps (1981 and later).

As Steell said, 20 amps is the max. The main fuse will blow at 20 anyway.

The ignition (stock) uses an average between 3 and 4 amps.
The tail uses about .5 amp.
Let's say the gauges and all may use about 1 amp.
The 55w headlight uses about 4 amps.

So normally, the bike is using around 10 amps plus whatever the battery needs to be re-charged, but let's assume the battery is charged.

I run two 55 watt bulbs OK, but three 55 watt bulbs will be pushing your luck. Maybe try using one driving light first.

Also, the extra current will show any weak spots in the wiring if you put the extra load on the stock wiring. You'd be better off using the wiring that comes with the lights and going direct to the battery (with relay etc). Also make sure all of the connections to the reg/rec are good and clean and the connections to the alternator are good and clean. If not, they will overheat.

Post edited by: loudhvx, at: 2007/01/04 02:54

This is the info I think I need - Keep it comin'!

I think when the kit comes in, I will see what bulbs they use and buy some 25-30w bulbs for less draw. My thoughts are that I'd rather have 2 dimmer bulbs with 2x the projection/reflection area than a single that lives on one side of the bike.

If that's not a possibility, then I'll be a Biquetoast disciple.

Thanks y'all

loudvhx? Is there a way to measure amperage directly off the regulator/rectifier, on the white/red wire that is used to keep the battery charged? Would a battery load tester do that? That would be the BEST way to gauge how much the charging system is really cranking out. The 20A figure Steve mentioned kind of scares me as I really doubt this figure would be accurate on an older bike. Testing amperage after the reg/rec would also be a good way to verify whether 20A total for most bikes is reasonable. I just don't feel like it probably is but can't prove this.

More modern bikes with much stronger (and newer) charging systems generally use 35W bulbs MAX for light bar spots and mostly use relays directly off the battery (main fuse).

wiredgeorge wrote:

loudvhx? Is there a way to measure amperage directly off the regulator/rectifier, on the white/red wire that is used to keep the battery charged? Would a battery load tester do that? That would be the BEST way to gauge how much the charging system is really cranking out. The 20A figure Steve mentioned kind of scares me as I really doubt this figure would be accurate on an older bike. Testing amperage after the reg/rec would also be a good way to verify whether 20A total for most bikes is reasonable. I just don't feel like it probably is but can't prove this.

More modern bikes with much stronger (and newer) charging systems generally use 35W bulbs MAX for light bar spots and mostly use relays directly off the battery (main fuse).

One way is to just put an ammeter in line there. I believe RonKZ650 did this and it's posted here somewhere. His numbers were in the ballpark of my estimates above.

I don't know if a battery load tester has an accurate ammeter built-in, but it has a load built-in and if the draw is much more than 20 amps it could fry stuff.

Remember, Steell is saying 20 amp max. That certainly is not happening at idle. I would think 20 amps is attainable at optimum RPM which may not necessarily be at redline, but will be at a much higher RPM than idle.

At idle is where the battery gets drawn down, and 81red750 will definitley notice that, if he idles for any length of time. But to fix that, all you need is a switch to turn off the brights when you're not moving.

81Red750:
You're theory of using two lower wattage bulbs is right on. On one of my bikes I had the two MR-type 55w halogens that come with the built-in hyperbolic reflectors. They were too bright so I went to Home Depot and bought two 35w replacements. It worked great and was way cheaper than the auto-parts store bulbs.
I haven't had any luck finding lower wattage halogen bulbs for the H1, H2, or H3 type which is probably what yours use. So on another bike I kept the dual 55W. It works fine, but at idle the voltage is a little lower.

Dyna S ignitions use over twice as much average current as the stock electronic ignition, so it's not wise to use the Dyna S on a bike with dual 55W bulbs.



Post edited by: loudhvx, at: 2007/01/04 13:03

The yellow bike uses two 35w MR type bulbs. You can still occasionally find those type lights at parts stores like Autozone. Then you can replace the bulbs with 35W ones from Home Depot.

The orange bike uses two H3 type 55w bulbs.

I ride mostly around Chicago so I don't need a lot of lighting. On really dark roads they're as good as the stock headlight, but you can always use more distance in the dark. The problem is I have no Hi/Low option. Because I live in the city, I have the bulbs aimed down for a permanent low setting. It would be nice to aim them up on a dark road, but I almost never end up on roads that dark.

81red750, maybe just put in a switch to kill the main headlight when you use the driving lights. The same switch for the driving lights could kill the headlight by using one relay. It would be automatic. Then you should be fine. Aim em high to get good distance on it.



Post edited by: loudhvx, at: 2007/01/04 13:07

Thanks everyone! what if I increase the impedance by adding resistors? If I remember ohms law correctly (its been 15 years), lowering the V raises the current draw, which defeats the purpose, but for some reason I feel this is incorrect.

what says y'all?

81Red750 wrote:

Thanks everyone! what if I increase the impedance by adding resistors? If I remember ohms law correctly (its been 15 years), lowering the V raises the current draw, which defeats the purpose, but for some reason I feel this is incorrect.

what says y'all?

Yes, resistors would do what you say, but that's not the best way to go. What about killing the headlight with the driving light's relay ( I edited my post above)?

loudhvx wrote:

What about killing the headlight with the driving light's relay ( I edited my post above)?

Elaborate, I'm not completely following you.

You'll use a double-throw relay.

When the driving-light switch is off, the relay will be off, and the battery power will be routed to the normally-closed contacts. Those contacts will feed your stock headlight circuit (through the stock headlight fuse).

When you turn the switch on, the relay will power up, and the battery power will be routed to the normally-open contacts. Those contacts will power the driving lights. (The headlight will turn off automatically.)