i have started adding electrical components and noticed at idle when i have everything going my lights dim down slightly. my list of current mods include dual 130 watt kc slimlight long range beams, dual 100 watt kc driving lights, cb radio, and dual 55 watt rear bumper lights. i plan on adding a winch in the future and possibly rock lighting.

my question is will the stock setup be ok to run all of the lights or is this going to draw to much on the battery/alternator. i realize that there will always be some loss at idle compared to higher engine rpm's. my only concern is if i should upgrade to prevent damage to the electrical system and what upgrades are available. what are my options...higher output alternator, higher quality battery like an optima, dual battery setup...or am i ok with what i have?

 

Total wattage for the lights you listed is 570 Watts. That is 47.5 Amps when everything is on.

Your alternator is rated at 140 or 160 Amps output. We will use a worst case scenario of 140 Amp output. At (engine) idle speed your alternator will only produce about 1/3 its rated Amperage or maybe 46 Amps. When the engine revs above idle the alternator output increases until it reaches its maximum output.

Now for your situation. You have 47.5 Amps of accessories and at idle an alternator putting out 46 Amps. The Jeep itself is drawing another (let's say) 20 Amps just for it's own onboard systems. The battery will have to make up this difference. 47.5 + 20 =67.5 System Needs. 67.5 - 46 = 21.5 The Amps the battery will have to provide.

Your stock setup will work for all of this. You just have to think about what you are doing. If you sit for an extended time at idle with EVERYTHING on, your battery will drain down. A few minutes running at higher RPM or idling with the lights off will bring the battery back to full charge.

1. A higher output alternator may give you give you a quicker recovery time, but isn't the best bang for the buck.

2. Different battery like an Optima: GREAT BATTERIES. I am not knocking them. Like the higher output alternator, it would give you better recovery. It is a better bang for your buck. And you are going to have to replace the stock battery in a few years any way so you may as well get a good one.

3. Dual battery: Consider that insurance. Expensive insurance after you consider the installation AND 2 batteries. Another battery would give you a higher reserve that would prevent your system from draining. It would also give you the ability to jump start your own Jeep.

4. Leave it as/is and just make sure you drive for a few minutes with the extra lights off and give the battery time to recharge.

Those are your options. And you are OK with what you have. You would just have to pay attention to it.

EDIT...The options 1 - 4 are listed from least desirable to most desirable. That's just me. I would start at #4 and go up the list from there.

 

First you gonna have to do the big 3 , and believe me you gonna see the difference.
1-change the cable from your alternator to the battery,you dont need to remove the stock one just had another,gauge 4 if fine.
2-Change your stock ground, the ground is week find a good spot grind all the paint to bare metal ,still same,you can keep the stock one just had another one ,i would say gauge 0 is preferable there .
3-The battery,just use what you are comfortable with .
The 2 first will stop your dimming,the 3 will just help on road.

 

Sorry but you're calculations are faulty.
Looks like you're using 12VDC as the power source, when in all actuality the stock battery in good condition puts out 12.6VDC during a static condition. When the JK is running, the alternator is supplying a nominal output of 14.7-15 VDC, and this can be measured at the battery terminals. With everything powered up, if the wattage is 570, the amperage draw would be 38.5.
As for the stock alternator, the 2007's were 160amps, at least ours was. I have heard that the newer models were dropped to 140, but in any case, either should do well supplying the requirement of 570 watts.
The key to providing nominal amperage is th keep the voltage high. As was posted, this can be done by using the proper size wiring, and larger. The larger wire/cable size will allow for a smaller voltage drop.
A dual battery is certinally a positive, however unless you are running a winch hard and long, or perhaps pounding out sound with a 5Kwatt amplifier, I do not see the need of spending that much money for an extra battery setup.
For what the OP has, the stock electrics should work fine.

 

The stock alternator is fine.

1 quality battery is a great upgrade, duals offer a ton more capacity and usefulness.

Just started offering the newest kits: https://www.jk-forum.com/forums/sponsoring-manufacturers-vendors-check-out-cyber-monday-specials-24/new-year-new-dual-battery-kits-benchmark-designs-113995/

[IMG]www.benchmark-designs.com[/IMG]

 

True. I did use 12VDC as the baseline for my calculations. Yes, resting the battery is at 12.4 or 12.5 VDC. When the engine is running the voltage does go up to 13.8VDC. Rather than intorduce other variables I stayed with 12VDC.

The alternator rated output whether it is 160 or 140 is the maximum output. That would be under ideal conditions and at higher than idle RPMs. OP stated observations while at idle. At idle RPMs the alternator only puts out 1/3, or less, of its' rated maximum. I erred on the side of caution and based my opinions on the lower rated alternator. At idle the alternator does not produce 160 Amps. With 570 Watts worth of lights on and the engine at idle, the battery will drain.

 

Have you checked your battery with a multimeter both static and with the engine running?
I checked mine with a Fluke 87lll, This is a true RMS meter which I use at work. The battery in the wifes 2007 JK is the stock 3 year old battery, and statically reads a good 12.86 VDC. If I turn on my headlights, factory foglights, and IPF 520 series foglights the voltage drops to 11.69. As you can see I am using the battery and in that state the battery amp hours will begin to decrease. The more I draw from the battery, the more volt/amps will be depleted to the point that the battery will loose it's charge.
With the engine running, that same battery indicates a reading of 14.96VDC. Here we can see the alternator is putting out proper charge to run the vehicle plus keep the battery charged to it's potential. When I turn all my lights back on, as well as my radio and heater on full, the reading drops to 14.81. This is telling me that the alternator, 160 amp in my case, is still supplying enough power to run all the equipment I have on yet still maintain the battery at the proper charge. This is at the idle speed of 1100 for an automatic.
I have not checked the amperage draw, as I do not want to put my meter in series for the check. There is no need as I know if the battery has lasted for 3 years with the charging system, then by my readings the alternator is supplying enough power at idle.




Most alternators have a breakover point. This is the point that the alternator puts out it's nominal amperage, which in the case of mine is 160 amps. For a 160 JK factory I believe the point is at 1200 RPM, provided the stock pully is used. Therefore, unlike a vehicle generator of the past, once the aternator gets to that point, the nominal output of 160 amps is derived, that is of course if the voltage regulator is working correctly, and the belt is at the correct tension.
Alternators are normally wound with this in mind.
My 94XJ came stock with a 110 amp alternator. After adding the lighting, a Warn 8000 winch and a sound system, I found myself lacking in power output. I ordered a bolt on high output 180 amp alternator, however I found that in winding this alternator for higher output, the breakover point was no longer at the 1100 rpm mark, but rather 1800, so in this case I was quite lacking at 1100. No problem however as my XJ is a stick, so I could just increase the RPM's at idle.
This is why I'm bringing this up, so that others don't think they can simply get a "high amp" alternator that will fit, and bolt it on, believing they will obtain those high amps at idle.
There are specialty amp alternators that will in fact produce the high output at a lower RPM using the same mounting and pully as the factory, however these are wound as 3 phase alternators that use a special rotor/stator combination, and are quite expensive at the $$$$ range instead of the $$$ range of a factory alternator.

 

Fluke makes great stuff. I have an old Fluke 73 III that they finally stopped making. It's a workhorse, but they finally replaced it with one of their new style meters. It's been used on my JK more than once while putting on accessories.

But the RMS is for measuring AC. In the US the power is supposed to 60Hz (cycle). If your electric company is having a bad day this may or may not be exactly 60Hz and perfectly sinusoidal. When non-RMS meter like my Fluke reads AC it assumes 60Hz and sinus in making the voltage calculation. If this isn't true the voltage displayed will be wrong. An RMS meter finds an average (of sorts - its the Root Mean Squared) of the cycle to plug into the calculation that it makes to determine your AC voltage.

Your automotive power circuits are all DC.

Regards, Tim

 

Upgrade your battery cables. I have these guys before to make me a heavy duty custom set and it took care of all of my dimming problems under full load.

http://www.innovativewiring.com/index.html

 

You're right, what was I thinking. Maybe a bit too much Patron Anejo left over from Christmas.