Alternator/ Battery Question-- For 800w LED light bar

10562 Views 12 Replies 8 Participants Last post by smufguy, Jan 10, 2017

Gopal Kandhasamy

Discussion Starter · Dec 23, 2016

All-

Considering a 32W LED Light bar (PHILIPS 7D+ 32" INCH 810W TRI-ROW LED LIGHT BAR SPOT FLOOD COMBO WORK OFFROAD) which is listed ~ 800W (translates ~68A @12V).

Couple of questions--

1. Whats the current output rating of the stock alternator? Will the stock alternator is good enough to supply around 80-90 Amps current during average drive (assuming running at 2K RPM).

2.How long I can run the light from Battery-- Stock Honda Battery. I can not use the CCA rating for calculations. What number I can use it to get the AH rating?

3. Should I just stop worrying the numbers and change the alternator to high output alternator or additional battery?

Any thoughts?

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djmoose

· #2 · Dec 23, 2016

68A is a LOT of juice. I mean, a LOT.

You're going to need 4 AWG wire to safely handle 68A.

I have a feeling if you get that bar and hook it up, you'll get much lower readings...more like ~20A

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Gopal Kandhasamy

Discussion Starter · #3 · Dec 23, 2016

djmoose said:
68A is a LOT of juice. I mean, a LOT.

You're going to need 4 AWG wire to safely handle 68A.

I have a feeling if you get that bar and hook it up, you'll get much lower readings...more like ~20A

THanks, Not worried about the wires at this time, and also Light bar close to battery, I could reduce the length of the cable to minimize the voltage drop.
My concern is, a) whether the stock alternator can handle this load, b) will the batter sustain ?

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IanRTL

· #4 · Jan 6, 2017

I have a compound miter saw that draws 15A. You're telling me a strip of super efficient LED lights draws 4.5 times that much amperage?? I doubt that. 68 amps would drain your battery in a matter of minutes. It would also put a huge strain on the alternator and would likely fry it. That bar has 135 LED's that are 6 watts max each. I'm no electrical engineer, but, being that they are likely wired in series, the amperage draw is going to be more like 8-10amps. No more than a decent sized audio amplifier. Nonetheless, I would consult the manufacturer. The Ebay seller likely won't know much about it, but you can try them, too. Although the pictures do show it installed on smaller vehicles with inferior electrical systems than the RL, it's still a very valid question to ask before you go forward with the time and expense of installing such a product.

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ridged

· #5 · Jan 6, 2017 (Edited)

I agree with Ian. I find it almost impossible to believe that it draws that much current. If it does, I would stay away from it.

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OhSix

· #6 · Jan 6, 2017

OEM alternator is rated 130A @ 13.5V. The field service manual makes no reference to duty cycle at that rating.

The referenced light bar would place a steady state 50% demand on its capacity.

Given the stupendous demand of this device, its overall installation requirements and potential functional pitfalls, (if were considering this) I would reexamine my need for such a light source and explore other more efficient options.

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windchill

· #7 · Jan 6, 2017

amp draw is lower due to this explanation...

The most sophisticated LED light bars have LED drivers that use Pulse Width Modulation to control LED current. There are also available external PWM units that effectively do the same thing for LED light bars without built-in PWM.

A PWM adjusts the energy frequency applied to the LED. It turns the LED off and on at a high, controlled rate within milliseconds. The rate is well above what the human eye can detect, so there is no flickering effect. This technology offers several benefits:

LEDs do not overheat even at 100 percent capacity.
LED lifespan is increased.
With an external control, you can dim or strobe the light bar.
Amperage draw is reduced overall
It adds protection against voltage spikes from vehicle electrical systems

this site should help you out, good articles on theory, wiring and wire size, setups ,light color, etc... Best LED Light Bar Reviews & Ratings For 2016

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smufguy

· #8 · Jan 6, 2017

First off, Dont go off the EBay rating on these lights........... It is just garbage. The Philips 7D+ is a marketing gimmick and has no connection to Philips NV (Philips Electrical). BTW your 32" light bar maybe putting out 130 watts at the most, if that.

FYI a 30" Rigid RDS light bar puts out 225 Watts and draws 16.3 Amps. On average, 30" to 40" bars draw between 16 to 17 amps of current. LEDs do not pull the same amount of current as incandescent bulbs, to produce the same lumens. Example, a 4000 lumen Incandescent (non Halogen) light source has to make 300 watts of power at 120 volts to achieve that drawing 2.5A, whereas an LED has to produce just 40.5 watts drawing 0.34A.

Do not get fooled by marketing numbers and also read up on electronic conversions and nominal power consumption.

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Elkhunter

· #9 · Jan 7, 2017

Assuming it is actually 810W, the power rating is 10-30V. I would guess the 810W would be at full power 30V. Thus highest case you'd have 27A. I'm guessing it would be even less than that

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IanRTL

· #10 · Jan 9, 2017

Using smufguy's calculations for LED amperage draw, the bar itself would draw a little less than 7 amps. It is an inexpensive bar that may not perform as well as advertised. For $100, you can't expect too much in the way of longevity, build quality or performance. There is a reason that good light bars are so expensive. But, then again, for only $100 it's probably worth a shot to try it out.

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smufguy

· #11 · Jan 9, 2017

IanRTL said:
Using smufguy's calculations for LED amperage draw, the bar itself would draw a little less than 7 amps. It is an inexpensive bar that may not perform as well as advertised. For $100, you can't expect too much in the way of longevity, build quality or performance. There is a reason that good light bars are so expensive. But, then again, for only $100 it's probably worth a shot to try it out.

Hey Ian, my calculations are not really calculations. They are advertized by Rigid and other brands. The latter part of Lumens and power consumption are relative numbers, that can be considered as being approximate than accurate. That said, You are still looking at a max of mid teen in Amps.

Btw, not all cheap light bars are bad. I have Eyourlife 22" lightbar that I bought for $45.00 on Amazon. It has seen two winters so far and its been going well. It may not be as great are Rigid and others, but I am not rock crawling in pitch black looking for some name brand light for bragging rights. It is watertight and is puts out decent light. With the combination of my HID projectors, Hella Driving lights and this light bar, I can see enough to pass the blueridge parkway with no worries in pitch black darkness.

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IanRTL

· #12 · Jan 9, 2017

^^ That projector retrofit is awesome! Great work.

I am fully aware that not all "cheap" things are necessarily "cheaply made". I have a $16 Pyle backup camera that has been serving me very well for the last two years through all sorts of weather. If it ever craps out, I know I can just buy a new one and throw it on. Similarly, I am using a $50 pair of Jensen Carbon component speakers, a $45 Jensen Power 2ch amp and a Boss Audio Chaos series slim subwoofer. All of them have been performing flawlessly for nearly 5 years now. The components are VERY well made with soft silk dome tweeters and real crossovers. The amp is small and powerful and the sub is punchy and strong. I spent my money on a very nice Pioneer touchscreen head unit to drive it all. Proof that there is value in "bargain" audio gear.

That being said, I'm sure there are $50 light bars out there that are great (yours) and $200 light bars that are absolute junk. It's just a matter of trial and error. The Philips bar posted by the OP looks to be fairly well made and is probably worth the $100 to give it a shot. As you said, there's no way it draws more than 15-17 amps. It would be like running a moderately sized audio amplifier and the same rules apply - don't run it for long periods of time with the engine off and it won't kill your battery.

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smufguy

· #13 · Jan 10, 2017

IanRTL said:
^^ That projector retrofit is awesome! Great work.

I am fully aware that not all "cheap" things are necessarily "cheaply made". I have a $16 Pyle backup camera that has been serving me very well for the last two years through all sorts of weather. If it ever craps out, I know I can just buy a new one and throw it on. Similarly, I am using a $50 pair of Jensen Carbon component speakers, a $45 Jensen Power 2ch amp and a Boss Audio Chaos series slim subwoofer. All of them have been performing flawlessly for nearly 5 years now. The components are VERY well made with soft silk dome tweeters and real crossovers. The amp is small and powerful and the sub is punchy and strong. I spent my money on a very nice Pioneer touchscreen head unit to drive it all. Proof that there is value in "bargain" audio gear.

That being said, I'm sure there are $50 light bars out there that are great (yours) and $200 light bars that are absolute junk. It's just a matter of trial and error. The Philips bar posted by the OP looks to be fairly well made and is probably worth the $100 to give it a shot. As you said, there's no way it draws more than 15-17 amps. It would be like running a moderately sized audio amplifier and the same rules apply - don't run it for long periods of time with the engine off and it won't kill your battery.

Thanks for the kid words Ian

Not to beat this light bar/power drawn issue to death, but it appears that Philips 7D, Oslamp, Autofeel and Auxbeam are basically the same units manufactured by one company and branded/packaged differently. However, with that said, a big of searching for each of them yields a cross check and reference to each other through Chinese sellers. Interesting part is all of them have their own marketing strategy. Philips 7D is advertised for 125,550Lm, Oslamp & Autofeel for 40,500Lm while Auxbeam c3 is 13,500Lm. They all have the 'famous chips' while their product is identified by CREE, which is most probably false. A good review, above a couple of hundred, may provide a direction to make an educated purchase.

REFERENCE >> How to convert lumens to watts (W) is a nice way to visualize the whole Watts to Lumens concept. Again, it is just one of many sources, but can get you the perspective needed.

What is Lumens >> Lumens vs Watts | LUMEN Coalition

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Alternator/ Battery Question-- For 800w LED light bar

Gopal Kandhasamy

djmoose

Gopal Kandhasamy

IanRTL

ridged

OhSix

windchill

smufguy

Elkhunter

IanRTL

smufguy

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