How much current do these things really draw?

It all started innocently enough; try to figure out why, on my 750J, my right turn signals weren't blinking (loose connection, it turns out) and the auxiliary light was bad.

So, I start emailing Chacal. After discovering it was in fact an OEM modular unit and not a sealed beam as I had first thought, I noticed that he said the 35W aux light bulb could be upgraded to a 55W bulb without penalty.

Okay, wait a second. I was led to believe that with the paltry 19 amps that the stock alternator puts out, and all the stuff we have on here, that the XJ electrical system was constantly on the ragged edge as far as current draw goes -- after all, we're constantly being told that upgrading the stock 55/60W headlight bulb is a Bad Thing(tm).

So, we sat down and started adding stuff up. We have:

Headlight: 4.58A (low beam)
Aux light: 2.91A
Gauge backlights: 0.58A
Tail lights: 1.33A (0.66A x2)

Total so far: 9.38A

Pressing the brake pedal increases the draw in the tail light from 1.32A to 4.5A. Turn signals also add 4.5A, but even when they're blinking, that's only half the time.

With turn signals and brake lights: 13.88 - 18.38A peak

Yep -- that's ragged edge, alright. Now, here's the 64,000 watt question: does anyone have any idea how much the coils, TCI and pickups draw? A quick bit of Ohm's law scares me -- running 12v through a 2.5ohm primary coil winding tells me that it's pulling 4.8 amps?!?

This can't be right. We're pulling far more than the alternator is putting out while we're sitting stopped at a light with the foot on the pedal and the turn signals on. Can someone check my math on this? Polock? Anyone?

 

with the engne at idle you arent getting 19 amps, so yes you are definitely drawing more. one thing to consider is that the coils are not always drawing, so they can be drawing 5 amps when they are drawing but overall the a/h draw vs charge rate is still ok.

for example: mitsubishi runs 150amps through 16guage wires for the injectors on a particular diesel they make. how can they do that without melting the wiring, or run the batteries dead drawing 600 amps (150x4)? the injectors are only live for a small fraction of a second, so the overall draw is minimal, and a 120 amp alternator has no problem keeping up.

remember too, as voltage drops the amperage will drop as well which gives the alternator a fighting chance. i run a 100w h4 headlight. it dims at idle, but in traffic jams i havent had the bike run very low on voltage so... it must even out to a happy medium probably around 10 volts.

 

Remember, if you're stopped at a light with your foot on the brake and the turn signals on and you have a soggy battery those signals won't be blinking...

The whole bloody system IS right on the ragged edge; old connectors don't help, and it relies on the battery for assistance in those high-load instances.

 

This is a prime example where an LED tail light, signals and gauge lights really help to take some of the load off the charging system. As soon as they can come out with a suitable LED headlight, I'll have one of those too!

 

They're already out there. The only problem is that you have to decide whether to buy the LED lights or buy food for your family for a while.

Loren

 

Not to totally detour this thread... I bit the bullet and grabbed one off eBay for $210 last night. I'll be posting about it when its installed. (Fairing that holds the headlight is out of state for painting at a relatives). Yes I'm crazy but someone has to try it and post REAL feedback about it... 8O
If/when I get $300 more in "fun money" I want to buy the Full Throttle Denali LED Driving lights - THOSE look BRIGHT!!!!!!!!

 

True, and the same goes for the turn signals, as I mentioned earlier. The 4.8A figure I cited was for one coil, which would seem to be correct -- only one coil at a time is firing. The two alternate, however, so wouldn't that be a fairly steady current draw? Actually, now that I think about it, no it wouldn't -- like your example below, the coils too are a momentary load, I'm thinking.

You're also not pulling 600 amps because you're not running the four injectors simultaneously.

Here's something you might be interested in. The place I work at, the machines have a timer box on them. Keeps them powered on, but shuts off the drive motor after about 3 minutes or so. When user activity is detected, a relay is triggered momentarily which restarts the motor.

We were having trouble with one machine where this relay was failing. I found one that looked the same, dropped it in, it looked like it was working... then I discovered I had put a relay with a 24v coil in a place that wanted a 110v coil. By the time I got the proper relay swapped in, the white cover wrapped around the coil had started to turn brown.

Right. They'll be drawing the 4.5A all the time instead of half the time.

Got any specs on that thing? Even a make and model would be enough to look it up.

 

Trucklite 27250C - Normally retails "around" $300

http://www.truck-lite.com/ledheadlamps/27250C.html

Most reviews (the few real life reviews I could find) poorly compare them to HID kits instead of vs. H4 Halogen setup.

Yes I'm crazy but the $200 ebay price had been staring at me for a few weeks...

Damn OCD-like obsessions

I will post a full review (good or bad - cheering or crying) in due time.

 

WOW, that's kinda steep for a headlight. I hope it works for ya.
Most of the LED headlights and driving lights I've found so far are basically just for show or to BE seen, and not very effective for lighting the road ahead of you at night. Hopefully there will be more on the market at an affordable price.

 

i have driven a few trucks that had the led replacement from Grote or trucklite, and i felt that they were USELESS. this was a few years ago however, so for your sake metalbob i hope they have improved. i await your review, because if they are good now i would certainly shell out for one. i had a bulb go out in pitch black on the highway. $300 for a light that wont blow is fine by me, as long as i can see when its on of course.

for those in search of leds for auto, home or commercial......
http://www.superbrightleds.com/

 

every bike i've ever owned has always ran off the battery at an idle. including the maxim 650 i bought brand new. around 1300-1400 has been the range of where the battery starts receiving instead of sending.

back in the day. it was pretty common for people to put automotive headlights in place of the stock light. i think they were 50/60 watts back then. never heard anyone complain about there charging system. but we weren't adding things to our bikes like we're doing today.

 

All my old Hondas did that had to rev them up to get them to blink. But you could always tell when the battery was going bad

 

I have one of those oval shape truck tailights on my Seca and it's twice as bright as the stock light. I like the LED tailights and marker lights just for the brightness and the fact that they take so little juice to operate. Just using the LED marker lights are bright enough to use for signals.

 

I'm doing a full LED/HID conversion on my XJ700 and using single filament turn signals with regular bulbs to retain the stock flasher so they only draw current when the flasher is on. Reason for I am doing this is I am doing a EFI conversion on my bike.

 

I was under the impression that the only way you could use a 55w bulb in the aux light was to re-wire a relay into the mix (controlled by the aux light switch) as the connector/switch/wire path would not support 55w. However, a 10w LED unit would work very well here w/o any wiring changes.

To really find out the answer you need to use an inductive ammeter around each of the +12VDC inputs. Add them up and you will have your answer (but it will be higher at WOT than idle so for OCD's sake you will need multiple tests :lol: ).

 

Going from the 35w light to a 55w light bulb? I'd use a relay and fuse for safety measures. All my accessories are run off of relays. Switches don't always carry the load. And the nice part about them is they go off with the switch so you don't accidently leave them on.