Umm, ouch anyway. 121 amps at cruise is beyond the output of the altinator. It will put out a nominal max of 130. That doesn't mean it always puts out 130, or that it puts out 130 at idle...
Alternators put out more at idle than the old generators, but the amount of output is still a function of RPM.

If you seldom drive at night, don't have a lot of other power extras you use, a better battery might, to even out the load, might do the trick. Especially if you freeway a lot (recharging at highway speed.)
You would have no safety margin, though. I visualize you having a great time, cruising around the malls, wherever, one warm night, using your A/C, etc. and blasting the tunes. Then having the embarrassment of being towed home...

The battery holds the charge, to start the car. If you are drawing more amps than you are putting in, it will slowly run down. Period.

The guys around here running the loud noises (and here in Southern California, a pair of 12 inch subwoofers in a Honda Civic is a quiet system) Run over sized alts, and duel (at least)batteries.

A work-around is finding somewhere to mount a 'deep cycle' battery, and a dual isolator switch for two batteries.
Mount the second battery where it is close to the amps. Short cables are best, for high power. You would also run really thick ground cables for this. Remember, your power is only as good as the ground.

A cheat work around to the alt swap. Anybody make OVERSIZE not undersize pulleys for that amp? That would get you more power at low RPM, at a cost in horsepower of course, but not too bad.
Chris

 

bigtruck311

May I recommend this nice handy site for anyone who is playing with electronics?

http://www.angelfire.com/pa/baconbacon/page2.html

Chris

 

I might also point out that a very powerful computer, with 20 inch monitor, peaks at peak 550 watts, and draws about 400 watts under normal draw. An LCD Dell computer will draw one half that. He is running the same as 11 full workstations.

Or 2 large microwaves ovens, running full time. Or a side by side refrigerator, and a 600 watt microwave at the same time.

This is in addition to his other stuff, headlights, A/C, blower, turn indicators, power seats, windows, etc.


Fuses might not work the way you think....
Also, I would imagine he has more than one fuse in the circuit, and more than one connection to the battery. Four is about average for a loud sound system. Fused at 120 amps total. That will allow you to pull about 160 amps steady. Not thirty.
The amp ratings are the amount the WONT blow at...
Chris

 

ChrisAdams, if all this is true than my alt should have exploded in flames, 500 watt offroad lights my highbeams and fogs on, both e fans on(30 amps a peice) 900 watt amp and 200 whatt sterio, 50 amp draw on my onboard air system all running at the same time at idle parked and no dimming, ok very slight dimming bearly notisable, how can this be explained? stock charging system

 

I don't understand the question. If you are arguing with the laws of physics, not my department. If you are saying that Ohm's law is wrong, well I don't think I'm qualified to discuss that...

If you are asking an actual question, you answered it already in your post.
If the lights dim at all, you are overloaded. Badly. It means you are not running on the alternator, but slowly discharging your battery.


Do you really want to be told about cold cranking amps, drawdown, median draws, warm vs. startup draw, average equipment variance, etc.? I kinda think you just want to be told you aren’t doing anything to overload your system. Can’t tell you that.

I'm not sure where ‘exploded in flames’ comes from? I discussed overloading the system, and running your battery too low to sustain the charge.

A few bouts of that and we start talking alternator damage.
Also damage to the equipment that is running on less than 10 volts. Just for fun you might hook up a volt meter to your system, and see how many volts you are running all that expensive equipment at. You can then amuse yourself by reading the warnings on all that expensive equipment.

I was posting to help a guy who asked a good question. Not flaming you for wanting to tell me the laws of physics don't apply to your truck. I wouldn't have that information....

But just for fun let us look at your load;

500 watt off road lights. You run those all the time? Are they 500 watts nominal, or 500 watts peak load, or ‘500 watts’ equivalent. Common usage with florescent, krypton, halogen, etc. lights that draw a fraction of incandescent tungsten filament bulbs draw for equivalent light?
High beams are not a big load.
E-fans, are not 30 amp draw. They are 30 amp fused. The draw is less than half that on startup, and under steady load conditions, between 8-12 amps each to run.

900 watt amp draws up to 900 amps on startup, some only draw 350-500 on steady usage. Some draw 800 plus every time it hits hard. Not a steady draw. Also, with that kind of spread, well it doesn’t really tell you. The 2000 watt amp system in my house draws about 300 amps just turned on, but while watching a loud movie, with lots of explosions, it draws up to about 800 watts.

A ‘200’ watt stereo might draw 200 watts, provided you are using the high side outputs, and it’s at full volume, and the maker is not pulling your chain, just a little. My 200 watt Kenwood usually draws about 80 watts. I split my load high side/low side using an amp just for the bass. It would only draw 200 if it was at absolute full volume. I have a 300 watt stereo (off brand) motorhome. Draws about half what the Kenwood draws…

What is an "onboard air system" just curious.

 

All I know is if I play my stereo and monitors at a car show for more than say 10-15min with out cranking the truck up and letting it run for 15 or so minutes my battery is dead as a door nail. I have had higher watt stereos in other vehicles (including my Jeep Wrangler) and not had this problem. In fact this is really the only one true complaint I have about the truck. I think its the battery....I plan to replace it very soon. Would the yellow top be the one to go with??? If so where is the best place to get one?

BTW...my lights dim a lot when the stereo hits too.

 

RamSS/T, Sounds like you draw a lot of power. How many watts, nominal, is your sound system? Do you have lights, etc going?
If running the truck for 15 minutes, after pulling the power out to start it is sufficient, then you must be cranking a lot of amps from your alternator.

Better battery sure would be indicated.

I’m not a loud stereo buff, just worked in electronics and car stuff for 30-40 years. I do know there are some great sites and forums devoted to 'portable stereos with wheels'. I was just addressing a specific question.

Still, is there no local A/C power? When we were displaying cars at a corporation I worked for years ago, power was one of the requirements.

We sponsored a lot of shiny, fun, cars, mostly funny cars and gassers, but show cars of all kinds. Power was available, so we used float chargers and just plugged em in.
Chris

 

ChrisAdams sorry if it seemed like i was being rude or argueing with you, i was not i was trying to see if i was overloading my charging system/ doing damage, and it seems you know alot more about ohms watts and amps than me, i know just the basics, so i will refrase my ?, do you think that running all these components stated earlier will damage my alt. if ran like that( to the point of lights dimming slightly) 1 to 2 times a month? ohh yea onbaord air system is a hard mount air compressor that states it pulles 40 amps at full draw on 100% cycle it is on only when the air tank falls bellow 150psi, used for running airtools and filling large tires, thanks for any info

 

Glad your cool, you know how hard it is to tell attitude on line..
I know I come across a lot more 'jerk' than I really am.
Don't ask my wife about this, please.

OK, thanks for the info on the onboard air compressor. Do you use it for work? I carry an air compressor in my motorhome, but it's A/C never thought about the power consumption, as I just fire up the 'jenny' when I need it.

On 'hurting' your alternator, Well a couple times a week (yeah, I know you said a month) won't hurt anything that is not very delicate. Example, LCD monitor, CCD Camera's are voltage sensitive in the extreme. You should shut them off when starting, for example. That info is from the manufactures guidelines.
A really expensive sound system doesn’t' like running at under 10 volts.

The alternator would just be working pretty hard. Might fail early, might not. I wouldn't lose any sleep about it.

It's the heavy constant load that can cause the problems. If you are taking more out of the battery than putting in, eventually it catches up to you.

If you do spend much time using this stuff, why not spring for a better battery? Stock batteries are for selling the truck.

If you use this truck for work, heck, the larger battery might be tax deductible.... part of the tools.
Chris

 

i have the optima yellow top deep cycle in it with no problems so hopefully i am allright, nope i use the truck just for playing, the air compressor and 5 gall airtank comes in real handy airing up 4 38" 15.5" tires from 12 psi to 35 psi takes about 8 min, thanks agian chris for any help and sorry again if i seemed like an arshole earlier, i just dont like being proved wrong(i tend to think i am the best mech in the world and i know all) this beers for you

 

Oh Man!! I am really confused now!! Do I need a yellow top then? Seeing how you told Ram/SST that it should be sufficent. I have a loud system but very rarley use it at night. If I do use at night it with windows down and AC off.

 

i think you will be fine with the deep cycle yellow top optima, because i am and i think i am pulling more amps than you, but i will bow down to what chrisadams says becuase he knows more about this than me, i can just acount for my truck, but good luck

 

Im planning on doing 2 Kicker L7 8's powered by a Kicker KX 850.2 with some nice component door speakers powered by a little amp, along with a DVD in dash unit. Am I going to need a Ultima Yellow Top? Im thinking yes because if RamSS/Ts trucks dim when it hits mine should dim too. How much are they also?

 

125 to 156 on E-bay. That's before shipping..... The blue top cranks more amps.

I have deep cycles in my MH, but not in my truck. Don't need it, as my amp/stereo/ power windows/ express systems/power seats/ monitor/ camera/ etc. don't come anywhere near exceeding factory specs. I don't draw as much power as a fully equipped Lariat with the same alt.

But if I had a 1000 watt up system, sure, the battery is a cheap way to keep the volts up while idling and thumping...

The guys who get in trouble are the ones slowly cruising through the mall/etc. with the loud thumping, lights, A/C etc. and the engine at 1000 RPM. A half hour like that, and the gear is running on 10 volts. This is not the way you want to do it, and another 100 or two is not much compared to the cost of the goodies.
For the guy who has the big sound system, and really only uses it to show it off, probably doesn’t need anything special.

Of course the factory battery is not the best made, it is intended to get you 12,000 miles with no problems. Most guys will get 30-40 months easy out of it. Some will last 7 years. Some will last 6 months. That’s the way car batteries are.
Chris

 

Chris, what would you suggest that I do with my set-up?