Will it harm anything to run an extra 150 watts off a 55A alternator?

I have a 1985 Corolla SR5, 217,000 miles. Car runs well, no problems. I put a pair of auxiliary driving lights on it and use them primarily
during the day as DRLs because I have the pop-up headlights. However, they do help a lot at night too, but was concerned that I would be overloading the alternator.
The headlights are 55w high output sealed beams (instead of the standard 35w). So, I guess i'd be drawing an extra 150 watts total, thats about 14 amps.
Any thoughts? It's always appreciated.
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
Where is the extra 150W coming from?

Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
Steve Mackie wrote:

+20w for each headlight (since i'm using 55w high output bulbs instead of the standard 35w ones), and 55w for each auxiliary lamp. So 75w x2 150w.
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
actually its only about 1.5 amps more. A 55 amp alternator doesnt sound like it has much room for slop. Maybe it does... but that 14 amp number you have is wrong. maybe a decimal got lost in the translation.
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload

You're thinking house (120) volts to get 1.5 amps. Do the calculation at 14 volts.
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload

As long as the circuit is fused, then there should be no problem..... if you are drawing more than yo ushould, the fuse will blow and you may want to consider piggybacking off another circuit that doesn't require as much amperage, or use a blank circuit and put in its own fuse.
good Luck...
Fwed
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload

So, how much are you drawing during idle with the headlights on? From this, you can figure the idle load on the alternator. Be sure to turn all the other accessories on when you measure it.
Even so, I would be much more worried about the headlight wiring harnesses and overheating the lamps than I would about the alternator. But measure it and see! --scott
--
"C'est un Nagra. C'est suisse, et tres, tres precis."

Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
Masospaghetti ( snipped-for-privacy@mail.gatech.edu) writes:

The auxiliary lights would normally use a 55W bulb, as would the headlights, so the extra draw should be 110 Watts. If the draw is too great for the alternator, then the alternator may overheat (and smell hot), it likely will make a whining noise, and the lights will dim noticeably when the engine speed drops to idle. The risk is that you wear out the alternator or drain the battery. The risk increases if you are in slow moving traffic or are using the rear window defroster, wipers, etc. That said, I have never heard of a problem with adding a pair of auxiliary lights to a modern car. Dan
(This account is not used for email.)
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
Masospaghetti wrote:

Hmm, 2x55w = 110w, and 2x35w = 70w. Not sure where you get your 150w? Anyway, no, those extra headlights should not be a problem if you wire them correctly.
Ulf
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
Most times that I see folks upgrading to 'high output' headlights in older vehicles, they fast burn out the headlight switch. I would physically try to 'gently' grab the headlight switch looking for heat. If it is hot, then you should wire a bosch style relay in with it's own 10 ga. fused power line direct to the battery and only use the headlight switch to trigger the low amp side of the relay.
You could be amazed at how white your lights become. I was when I did mine.
The same goes for the auxiliary lights. If you want the headlight switch to run those too (like for extra highbeams) you need a relay for sure.
You also need to pay attention to the ground path. I added an extra ground cable for the extra load a new fan and lights put on the existing body ground. The ground can be too small and/or they get corroded connections and forgotten about often.
When I added two 100 watt Hella Black Magic driving lights into my 86 Jeep with it's 65 amp alternator, I added a massive GM heater blower fan motor at the same time. I turned on everything in the vehicle and ran it for a while, then felt the alternator for heat. I already checked it running normal and the added lights and fan didn't make a difference. The volt gauge also didn't seem to react any difference.
You also need to pay attention to the ground path. I added an extra ground cable for the extra load a new fan and lights put on the existing body ground. The ground can be too small and/or they get corroded connections and forgotten about often.
My alternator is now about 6 years old. Kits can be had for most of the old ones fairly cheap.
Here is a site on wiring a Bosch style relay. http://www.classictruckshop.com/clubs/earlyburbs/projects/bosch/relay.htm
Mike 86/00 CJ7 Laredo, 33x9.5 BFG Muds, 'glass nose to tail in '00 88 Cherokee 235 BFG AT's Canadian Off Road Trips Photos: Non members can still view! Aug./05 http://www.imagestation.com/album/index.html?id !20343242 (More Off Road album links at bottom of the view page)
Masospaghetti wrote:

Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
Mike Romain wrote:

Thanks everyone for the responses!
I might have to try the relay setup, the auxiliary lights already have their own relay.
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
I think you're okay as you are -- 150 watts at 12 V is 12 A.
Seldom will the car be all the way up to its alternator capacity of 55 A. It's worth thinking about because in the winter you're more often running a few to several power-hungry accessories at once (headlights, defroster or heater with its blower motor, wipers...) and perhaps are more likely to be sitting in traffic at idle, where your alternator is not making its full output, though it's still better than the old-fashioned generator under those circumstances.
When this happens the car is essentially running from the battery. Ammeters tell this tale directly by sagging a bit to the negative side, though of course you can infer it from voltmeters. (It has to be pretty gloomy to trigger an idiot light.) When you pick up a little speed the ammeter swings to the positive side for a while as the alternator pays back the battery.
Anyway, if you're not scaring its full capacity I wouldn't worry. What you don't want to do is go into the winter with extra loads and a dodgy battery, so make sure it's in good shape and has nice clean solid connections.
As for overloading switches or whatnot... operate them with an aftermarket relay, and a *fused* line from the battery to said relay. Parts and kits are pretty readily available these days because of the popularity of both auxiliary lights and large trunk-mounted stereo equipment.
Cheers, --Joe
PS. You didn't mention whether you are configuring these as proper DRLs or manually controlling them with a separate switch. I assume that by "auxiliary driving lights" you mean the ones that are like extra high beams, rather than fog lights. Especially in the former case, be sure to turn them off at night when there is oncoming traffic. And don't make the opposite mistake either, of failing to turn on your "real" headlights (and thus taillights too) in dark or rain, just because you have a DRL-like accessory. Not that YOU'D make either of those mistakes, of course, but since so many drivers do, and one never knows who's going to read these postings, I thought I'd mention it.
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
Ad absurdum per aspera wrote:

They're not actually DRLs, just manually activated lamps...I just tend to use them during the day as DRLs. They aren't actually fog or driving lights but something like a "multipurpose utility lamp", but they help a lot with forward vision and they didn't seem that glaring when I tried looking at my own car. But definitely, I don't use them by themselves - when its dark the headlights are definitely the way to go.
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
Masospaghetti wrote:

You are probably okay with the lights, as long as you wire the auxillary lights up properly, but you should take a look at the total continuous electrical load you are likely to run before deciding to kick in the extra lights. This includes the rest of the lights, ECU/Ignition, electric cooling fan if it has one, Blower motor/AC, wipers, rear window defogger, plus any fancy stereo equipment it might have.
I found my 65 amp alternator on my F-150 could not keep up with auxillary lights and a power amp for the stereo, especially at night with the A/C blower on medium or high. I can also remember another time I might have fried an alternator on my '78 Horizon when it started raining. On came the lights, rear window defogger, and defrosters, while the radio played on. The ammeter never worked well on that car, so I didn't know about the dead battery that was about to cause my car to grind to a halt until the dashboard went nuts and the engine started misfiring.
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload

Motorsforum.com is a website by car enthusiasts for car enthusiasts. It is not affiliated with any of the car or spare part manufacturers or car dealers discussed here. All logos and trade names are the property of their respective owners.