Measuring Light Bar Current Draw

[ahmadtaha1988]

Hi all,

I want to verify the current draw of my lightbar for the purpose of determining how long can I leave it on without the car running.

Most multimeters have a 10AMP limit, if its supposedly a 400 watt light bar would not that imply 33.33 AMPs at 12 volts...

If so how can i so the measurement?

many thanks

Sponsored

 

[CaJLMetalHead]

a Lightbar is unlikely to consume 400 Watts... that is more likely marketing.. do you have a photo or details of the lightbar?

 

[ahmadtaha1988]

YITAMOTOR 42 Inch 400W Curved LED Light Bar Spot Flood Combo Offroad Lights with 12V Wiring Harness for Truck, Jeep, SUV, UTV, Boat https://a.co/d/d3m3LXH

I understand that it is unlikely to be 400w and mkst likely they are talking about lum equivalent vs a conventional bulb. However my multimeter is giving out of range error, so it is either above 10A or I have a defective multimeter (ordered a new one to check).

Let us say it is above 10A, how does one measure?

a Lightbar is unlikely to consume 400 Watts... that is more likely marketing.. do you have a photo or details of the lightbar?

 

[Headbarcode]

You'd have to either peirce the positive lead to the light in question, or use a multimeter with an integrated Amp measuring clamp to get a non invasive reading. This would be done while the light is powered on.

 

[ahmadtaha1988]

My conventional multi meter said out of range, I do have a non contact model but it seems that feature is only for AC current (did not work and the dial states AC).

are there ones that measure without contact for DC? Anyone recommend a model...?

You'd have to either peirce the positive lead to the light in question, or use a multimeter with an integrated Amp measuring clamp to get a non invasive reading. This would be done while the light is powered on.

the

 

[CaJLMetalHead]

I went through the Q/A in Amazon for this lightbar... so it seems it consumes either 6 amps.. or 15 amps.. I have a very similar lightbar.. although mine is a bit bigger.. mine consumes around 12-14 amps ...

I cannot recommend a clamp meter... but Amazon / Harbor Freight has plenty of options.. both cheap and expensive... here is an example

KAIWEETS HT206D Digital Clamp Meter T-RMS 6000 Counts, Multimeter Voltage Tester Auto-ranging, Measures Current Voltage Temperature Capacitance Resistance Diodes Continuity Duty-Cycle (AC/DC Current): Amazon.com: Industrial & Scientific

Going back to your original question... determining how long you can run the lightbar depends on which battery... are you talking about running it from your JL main Battery?... I would not recommend running it for long... as depleting the main battery is bad ... it will shorten the battery life... I guess we need more detail about what exactly you are trying to achieve... are you hunting for space aliens in the forest?

 

[ahmadtaha1988]

I went through the Q/A in Amazon for this lightbar... so it seems it consumes either 6 amps.. or 15 amps.. I have a very similar lightbar.. although mine is a bit bigger.. mine consumes around 12-14 amps ...

I cannot recommend a clamp meter... but Amazon / Harbor Freight has plenty of options.. both cheap and expensive... here is an example

KAIWEETS HT206D Digital Clamp Meter T-RMS 6000 Counts, Multimeter Voltage Tester Auto-ranging, Measures Current Voltage Temperature Capacitance Resistance Diodes Continuity Duty-Cycle (AC/DC Current): Amazon.com: Industrial & Scientific

Going back to your original question... determining how long you can run the lightbar depends on which battery... are you talking about running it from your JL main Battery?... I would not recommend running it for long... as depleting the main battery is bad ... it will shorten the battery life... I guess we need more detail about what exactly you are trying to achieve... are you hunting for space aliens in the forest?

thanks , I have an extra battery that I carry around for longer trips. Sometimes after a hike in a remote area I set up campy for just a couple hours and was looking to see if I can get away without having to carry my second battery.

 

[CaJLMetalHead]

thanks , I have an extra battery that I carry around for longer trips. Sometimes after a hike in a remote area I set up campy for just a couple hours and was looking to see if I can get away without having to carry my second battery.

that lightbar is perhaps overkill for camping.. some campers install a much smaller lightbar in the rear of the JL (let's say.. a 4 inch lightbar) that is still plenty bright and won't kill your battery as fast...

Also... look into these types of modules... this one allows you to set a low voltage disconnect .. so when the lightbar depletes the battery to a certain voltage threshold then the module disconnects the lightbar to prevent damage to the battery... this is just an example.. I am not recommending to get exactly this one... I am sure there are tons of options on Amazon, Ebay and Aliexpress..

Amazon.com: CZH-LABS LVD Low Voltage Disconnect Module. (12V / 30Amp) : Health & Household

 

[ahmadtaha1988]

that lightbar is perhaps overkill for camping.. some campers install a much smaller lightbar in the rear of the JL (let's say.. a 4 inch lightbar) that is still plenty bright and won't kill your battery as fast...

Also... look into these types of modules... this one allows you to set a low voltage disconnect .. so when the lightbar depletes the battery to a certain voltage threshold then the module disconnects the lightbar to prevent damage to the battery... this is just an example.. I am not recommending to get exactly this one... I am sure there are tons of options on Amazon, Ebay and Aliexpress..

Amazon.com: CZH-LABS LVD Low Voltage Disconnect Module. (12V / 30Amp) : Health & Household

great idea.thanks

 

[Bronson90]

I have the Klein Tools CL390 Clamp Meter that reads AC/DC current through the clamp. It was like $90 and in stock at my local Home Depot. At first, I was reluctant to spend the money as I was replacing a perfectly fine Fluke Multimeter that I have had for 15+ years, but it does so much more and now I use it all the time.

 

[Some Random Guy]

It's been 20 years, but you can use a resister to modify the "reading" on your existing multimeter. I'll keep the math simple:
Add a 1 ohm resister (with sufficient current capacity) in series with your light bar. Measure the voltage across the resister while the light is on. Since V=IR and R is 1, your volts equal your amps.

Now wait for someone more experienced than me to suggest what parts to use for this concept that you might have around or can find easily/cheaply. You can also use ohm's law to do this with a parallel circuit. Again, easy numbers not matching reality:
Measure resistance of your light circuit. Let's say it's 10 ohms. Then, hook up a 100 ohm resister in series with your multimeter set to read amps, then put that "circuit" in parallel with your lights. Turn on the lights and measure current, then multiply by 10. That's what your lights are drawing.

 

[GATORB8]

It's been 20 years, but you can use a resister to modify the "reading" on your existing multimeter. I'll keep the math simple:
Add a 1 ohm resister (with sufficient current capacity) in series with your light bar. Measure the voltage across the resister while the light is on. Since V=IR and R is 1, your volts equal your amps.

Now wait for someone more experienced than me to suggest what parts to use for this concept that you might have around or can find easily/cheaply. You can also use ohm's law to do this with a parallel circuit. Again, easy numbers not matching reality:
Measure resistance of your light circuit. Let's say it's 10 ohms. Then, hook up a 100 ohm resister in series with your multimeter set to read amps, then put that "circuit" in parallel with your lights. Turn on the lights and measure current, then multiply by 10. That's what your lights are drawing.

I don't think LEDs have static resistance, the resistance changes based on the input. Sucks, cause that'd be the easy way P=V/R.

Using voltage drop like your first example is a great option.

Little archaic, but another option, from the amazon pic, looks like it's running a green (30 amp) fuse. Swap in a couple smaller 50 cent fuses, and it'll blow when you get below the current (of course turn the switch off when swapping).

 

[azwjowner]

You don't need a new multimeter. Just measure the voltage drop across the fuse: https://www.meeknet.co.uk/E64/Fuse Voltage Readings To Give Current Readings.pdf

 

[GATORB8]

You don't need a new multimeter. Just measure the voltage drop across the fuse: https://www.meeknet.co.uk/E64/Fuse Voltage Readings To Give Current Readings.pdf

Wow, great find.

Basically uses @Some Random Guy’s trick with the fuse as a tiny resister.

 

[azwjowner]

Wow, great find.

Basically uses @Some Random Guy’s trick with the fuse as a tiny resister.

On a modern vehicle with computers that run for some time after doors are closed, draw startup current when power is first connected, etc., this is really the only good way to isolate a parasitic draw. You can't just unplug fuses and measure current in series with the circuit anymore. Thus, I'm very surprised that no one else mentioned it.

Sponsored