Help with H4 headlight upgrade with 12 gauge wire and relays

I know this has been done before by a few members and I've searched but couldn't find the answers to the questions I have..
I've read the tech on http://www.danielsternlighting.com/tech ... elays.html and understand most of what he's talking about.

I've emailed him but have yet to get a reply. So my questions are:
What amp relays do I need? I'm guessing I just need 2 SPST relays about 20amps or so.. I'm just planning to use one H4 bulb in a 7" housing.
Does anyone know of a good place online to get these or what kind to get?
For the guys that have done this, where did you mount the relays?
Do you just ground the 85 for both relays?
If I use this http://www.delcity.net/delcity/servlet/ ... em=1&new=y
fuse holder, what amp fuse do I need or did you just use an inline fuse on the power wire coming off the battery?

Basically tell me everything I'll need to know to do this project. I have some wiring experience but nothing with relays. They do seem quite simple but I just would like to get a good plan and buy the right stuff before I start. Thanks.

 

Caveat - I have not done this - but:
1 - a good H4 bulb should never be drawing more than 5 amps anyway, so you could use even a 7.5 amp fuse either in the holder or an in-line and it'll work just fine.
2 - you can also get an automotive dual relay to minimize all the extra wiring. Ask at an auto parts store for a 10 to 15 amp automotive dual relay.

As for mounting and wiring - once you decide on the fuse holder & relay, you can see where they fit best and go for it.

Good luck, and take some pictures for us!

 

Re: Help with H4 headlight upgrade with 12 gauge wire and re

H4 High beam is 60 watts. 60 watts / 13.8 Volts = 4.35 Amps. The bulb will draw slightly more amperage just after being switched on, and will also draw more current at lower voltages. I'd use a 7.5 or 10 Amp fuse which will protect the circuit without being prone to blow for no good reason.

Yes, you want to ground terminals 85.

I wouldn't put in two fuses, I'd use the same one for both high and low beam.

I just put in a single relay for auxilary lights on my XJ650. I put it on top of the airbox under the rear of the tank. There also should be room underneath the frame under the tank.

 

Well thanks for the info guys.. I'll be sure to take pictures of the project. anyone else have anything to chime in?

Also does anyone see anything wrong with using a standard 30 amp relay if that is all I can easily find? Will that use more power than a 10 or 15 amp relay would use to operate? And even if I do use a 30 amp I could still use a 7.5 or 10 amp fuse correct? Thanks

 

Re: Help with H4 headlight upgrade with 12 gauge wire and re

Just go up to RadioShack and tell them you need two 275-226.

Glue them together back to back and hang from the upper frame rail under the tank.

 

Re: Help with H4 headlight upgrade with 12 gauge wire and re

I got to looking at some wire today.. isn't 12 gauge a little bit over kill? Does anyone think I'll be able to tell a difference if I go with 14 instead? My cars use the same H4 bulb and have more than 16 gauge on those

*EDIT*
Alright.. I did some calculations..

assuming 5amps and a 10 foot circuit

18gauge = .64 volts drop
14gauge = .25 volts drop
12gauge = .16 volts drop


And the table from http://www.danielsternlighting.com/tech ... elays.html
10.5V : 510 lumens
11.0V : 597 lumens
11.5V : 695 lumens
12.0V : 803 lumens
12.5V : 923 lumens
12.8V : 1000 lumens ←Rated output voltage
13.0V : 1054 lumens
13.5V : 1198 lumens
14.0V : 1356 lumens ←Rated life voltage
14.5V : 1528 lumens

I'd be willing to bet if I measure the actual voltage drop at the headlight with the stock wiring it would be much more do to all the connections and longer runs of wire. I think any direct wiring of the headlight is going to result in an improvement so now I'm trying to justify the .09 volt difference between the 12gauge and 14. Maybe tomorrow I'll take some measurements.

 

Re: Help with H4 headlight upgrade with 12 gauge wire and re

Apparently no one cares, but since I took the time to do it, I'll let you know what I found..

The voltage drop was 1.01 volts at the headlight on the low beam. I didn't check the high beam.. As suspected, the drop was more than the calculation due to all the connections, switches, old wires, etc...

So that's quite a bit and it looks like I might as well just go with the 12 gauge to reduce the drop by as much as possible. If I could get the drop to just .16 volts, that would be about 200 more lumens or at least 25% more output with the same bulb!

 

Re: Help with H4 headlight upgrade with 12 gauge wire and re

travis i don't think it's that nobody cares but maybe you have a better heater than us
if your running new wires and taking the old ones out maybe 12ga is what you want but if you leave the original and just put in another +12 volt source then
even a 16ga will get you what you want
i paralleled a +12 to the coils on my kawasaki thru a relay and it made a noticeable difference

 

Sorry Travis, been off-line for four days. Looks like your 12 gauge wire is more than adequate for the task. Overkill? Na, can't harm to have a larger gauge in place, lowers the voltage drop over longer distances (as you have so amply point out, thanks for posting it!).