How Much Lighting Before Alternator Upgrade?
#11
JK Super Freak
Different people have tried to work this out before. With enough research, you should be able to find some good info. Bottom line, Take the rated output of the alternator. Subtract about 60 amps for the Jeep OEM circuits. The remainder is about what you have to play with.
80 amps is 1120 watts, assuming the loaded alternator puts out 14 volts (reasonable). FYI, 500 watts of light is continously 500 watts, but a 1000 watt stereo does not draw anything close to 1000 watts continuously, even when playing loud.
Battery capacity does not come into play unless you are using more power than the alternator can deliver, or if the engine is off. Anytime you depend on battery capacity you are looking at a very limited time line. That time line is longer when the engine is running, and it is longer with a new top-of-line battery than with a 5 year old stock battery, but it is always limited.
#12
JK Super Freak
Whether the alternator can or cannot restore the battery juice as fast as you burn it with multiple lights, adding dual batteries are great insurance to ensure your rig starts and will get you home.
I put in dual yellow-top optimas on Benchmark's dual battery tray, with the 2nd battery hooked to five offroad lights, a 12-volt camping fridge and a winch. The 1st battery is hooked only to the Jeep's stock electrical system, thus always ensuring enough juice to start the engine, power the stock electrics and prevent an unplanned extra night in the boonies.
This way, the stock alternator has sufficient time to slowly charge the batteries back to 100% on the drive home.
I put in dual yellow-top optimas on Benchmark's dual battery tray, with the 2nd battery hooked to five offroad lights, a 12-volt camping fridge and a winch. The 1st battery is hooked only to the Jeep's stock electrical system, thus always ensuring enough juice to start the engine, power the stock electrics and prevent an unplanned extra night in the boonies.
This way, the stock alternator has sufficient time to slowly charge the batteries back to 100% on the drive home.
#14
JK Super Freak
Whether the alternator can or cannot restore the battery juice as fast as you burn it with multiple lights, adding dual batteries are great insurance to ensure your rig starts and will get you home.
I put in dual yellow-top optimas on Benchmark's dual battery tray, with the 2nd battery hooked to five offroad lights, a 12-volt camping fridge and a winch. The 1st battery is hooked only to the Jeep's stock electrical system, thus always ensuring enough juice to start the engine, power the stock electrics and prevent an unplanned extra night in the boonies.
This way, the stock alternator has sufficient time to slowly charge the batteries back to 100% on the drive home.
I put in dual yellow-top optimas on Benchmark's dual battery tray, with the 2nd battery hooked to five offroad lights, a 12-volt camping fridge and a winch. The 1st battery is hooked only to the Jeep's stock electrical system, thus always ensuring enough juice to start the engine, power the stock electrics and prevent an unplanned extra night in the boonies.
This way, the stock alternator has sufficient time to slowly charge the batteries back to 100% on the drive home.
#16
JK Enthusiast
Join Date: Oct 2006
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The stock Jeep alternator is supposed to be 140 amps. If the OEM demand is 60 amps then you have 80 amps to play with if you are comfortable loading the alternator to 100%. (I wouldn't on an ongoing basis.)
80 amps is 1120 watts, assuming the loaded alternator puts out 14 volts (reasonable). FYI, 500 watts of light is continously 500 watts, but a 1000 watt stereo does not draw anything close to 1000 watts continuously, even when playing loud.
Battery capacity does not come into play unless you are using more power than the alternator can deliver, or if the engine is off. Anytime you depend on battery capacity you are looking at a very limited time line. That time line is longer when the engine is running, and it is longer with a new top-of-line battery than with a 5 year old stock battery, but it is always limited.
80 amps is 1120 watts, assuming the loaded alternator puts out 14 volts (reasonable). FYI, 500 watts of light is continously 500 watts, but a 1000 watt stereo does not draw anything close to 1000 watts continuously, even when playing loud.
Battery capacity does not come into play unless you are using more power than the alternator can deliver, or if the engine is off. Anytime you depend on battery capacity you are looking at a very limited time line. That time line is longer when the engine is running, and it is longer with a new top-of-line battery than with a 5 year old stock battery, but it is always limited.
I have no idea how much operational amperage the 3.8L JKs draw, but you'd need to add a good bit of lighting to overdraw. As Freewill said, assuming your computers, relays, stock lighting, etc. are drawing 80 A total (which is probably an over-estimate), you have 60 A / 1,120 W left for aftermarket draw (W = A • V, assuming alternator output ≈ 14 Vdc). That's roughly five pairs of 100 W lights.
Adding a dual-battery setup will ensure you'll always start, but if you draw near or over 140 A total you'll always be running a negative charge. Granted, this is only if you ran with all your lights on, or winch plus lights, all the time, which you wouldn't be realistically doing.
#17
If you are going to go dual batteries for the love of baby Jesus don't even consider the yellow tops. If anything go to sears and get the the Die-Hard platuimn group 34. Its a re-badge Odyssey battery which is one of the best companies in the market today other that Deka. Plus they use all the space in the battery and not 6 cylinders (cylinders in a rectangle leaves empty space that could be filled with matts and etc).
Upgrading the ground AND the power output wire from the alternator will make things happier to. If you do use the Dual battery setup make sure to use the battery isolator (The smart one)
Upgrading the ground AND the power output wire from the alternator will make things happier to. If you do use the Dual battery setup make sure to use the battery isolator (The smart one)
#18
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If you are going to go dual batteries for the love of baby Jesus don't even consider the yellow tops. If anything go to sears and get the the Die-Hard platuimn group 34. Its a re-badge Odyssey battery which is one of the best companies in the market today other that Deka. Plus they use all the space in the battery and not 6 cylinders (cylinders in a rectangle leaves empty space that could be filled with matts and etc).
Upgrading the ground AND the power output wire from the alternator will make things happier to. If you do use the Dual battery setup make sure to use the battery isolator (The smart one)
Upgrading the ground AND the power output wire from the alternator will make things happier to. If you do use the Dual battery setup make sure to use the battery isolator (The smart one)