I have the stock battery that comes with the 2009 jk. i already have a set of piaa 510 fog lights, but that did light up the road as nicely as i was hoping. Now i am looking at a set of Hella 500FF driving lights. Can the battery run the headlights, the fog lights and the hellas all at the same time, or is that too much?

 

Are you planning on sitting in the middle of the road with the engine off - or are you planning on driving?

No, it's not a smart-aleck question.

If you're out in the boonies partying with the lights and stereo on and the engine off, you need to worry about your battery (or adding a 2nd).

If you're turning on all your lights and your engine is running, you need to worry about your alternator.

 

I was planning on using them on the road while driving. So driving with them all on would not be wise unless i get a better alternator?

 

Hi Mate
The answer to your question relates to the size / capacity of your alternator (this is the device attached to the engine via the drive belt that generates electricity) and has little to do with the battery - unless you plan to run all the lights with the engine switched off - then battery capacity will be an issue, because while the engine is running electricity is being generated by the alternator which can power electrical equipment

Alternators are rated in AMPs - I have an JK07 with the bigger 160Amp Alternator fitted at the factory.

heres some basic math for you to determine how many lights you can run

I will use my JK as an example

The engine computers, Coil packs and fuel pump use approx 10 - 20amps
the electric windows use 15amps - only when operated
the headlights std use 60watts - which can easily be converted into amps the formula is Watts divided by voltage = Amps;
60 divided by 12 = 5 Amps

OK so you have 2 headlights thats 5 Amps each x2 headlights = 10amps
rear lights and parking lights etc are around 10w each = less than 1 Amp

Add your AC and fan = 2 - 20 amps depending on demand & temerature
add your electric fan that keeps the radiator cool 20 - 40 Amps depending on what speed the computer demands and the ambient temperature

Add your Radio, Stereo and SUB amplifiers - 2 - 20Amps
CB radio = 1 amp when transmitting only
dash illumination, cell phone charger & GPS = total <1 Amp

So as you can see if you have a 160 Amp Alternator there is plenty of available capacity

The Piaa fog lights probably have a maximum rating of 50watts each which = 100w total or 8 Amps

The Hellas are 100w each = 200 watts or 16 Amps

I can safely say that if you have the 160 Amp Std Alternator and you put everything on at the same time provided the engine is running (and generating electricity) you will still have extra unused capacity.

Click on the link if you want to see what I did to keep an eye on all the electrical equipments current draw in real time https://www.jk-forum.com/forums/show...ighlight=hunty



the pic below is of my 160 Amp Alternator so if you have one that looks like this and has the same part number - then it should be the 160 Amp - if you are still unsure you can request a build sheet printout from your local Jeep dealer it is full of useful info inc diff ratio's and factory fitted accessories - this will confirm how powerful your alternator is - and if you need more juice there are many beefy / high power aftermarket Alternators you can simply buy and bolt in - if you do a lot of winching or run a camp fridge for days on end you should consider at least a second battery!

cheers Hunty

 

Nice writeup man, very informative

 

Wow! Thanks for all that info! That was very easy to understand even for an electrical noob (me).

 

That was EXTREMELY helpful to me as I've been adding new things to my 2010 JKU (ie~CB, Accessory outlet in back seat, and I'm about to install some KC slimlights to my windshield). One of my concerns was how much stuff can I install before I put too much stress on my alternator. THANKS for that very understandable writeup.