Balancing different LED lighting in automotive trailer

Thread Starter

nevink

Joined Aug 18, 2020
4
I am working on redoing the lighting in 4 cargo trailers of various sizes with LED strips and ran into an issue last evening.

In one trailer i have one premade string of LEDs on a switch. Last evening i added a 3" flood light to the outside of the trailer to illuminate the drop gate. After doing so, the string of LEDs on the inside were much dimmer. I'm sure it's just the different loads of the two lighting devices. Need some help figuring out how to balance these two loads so they both work well.

These are the strings i'm using:
Onforu 16.4ft LED Strip Light, 5m 12v Ribbon Light, 2835 LEDs
Voltage: 12V
Max Current: 1A
Size of LEDs: 2835 LED
https://www.amazon.com/dp/B07DZRNQCW

This is the flood light:
ROADSHOCK 3 In. LED Flood Light
Voltage 12/24
Number of LEDs 4 (no other specs)
Wattage 15
https://www.harborfreight.com/3-in-led-flood-light-64322.html

*Wired in parallel on the same switch. Should they be wired in series? Would that help?
(sorry, thinking of options while i'm writing this...)

The setup will be the same in all 4 trailers, the only difference will be how many of the LED strips i use.

So far i've done:
Trailer #1 (16') - one 5meter LED string spaced out every other rafter (4 sections), one 3" flood light
Trailer #2 - one and a half 5 meter LED strings spaced out every other rafter (6 sections)
Trailer #3 -
Trailer #4 (large gooseneck) -

We are converting or adding interior lights to get light in the trailers without having to run the trucks they are connected to. This type of lighting can run for a long time with minimal effect on the battery.

Trailer #1 (16') - had two tiny incandescent (turn signal style bulb) dome lights
Trailer #2 - has an inverter, but only runs when the truck is running, had 3 fluorescent light fixtures
Trailer #3 - has an inverter, but only runs when the truck is running, and a couple fluorescent light fixtures
Trailer #4 (large gooseneck) - has absolutely nothing
- All trailers are of various sizes & age, each one is different.
- Each truck/trailer's voltage varies with the large gooseneck being the lowest at planned tapping spot. I may run a new line up to the hitch, ...it's that bad, and not positive that will be that much better.

As far as budget.... All of this is for a non-profit. (so out of my pocket as a donation)
- I bought 6 of the LED strips so far
- 2 Flood lights were donated
- i'm sure i'll have to add some kind of booster/driver or balancer as well.

Let me know if more info is needed. I can measure current voltages or current draws later this week.

Any suggestions would be greatly appreciated.
Thank You.
 

dl324

Joined Mar 30, 2015
11,833
Welcome to AAC!
In one trailer i have one premade string of LEDs on a switch. Last evening i added a 3" flood light to the outside of the trailer to illuminate the drop gate. After doing so, the string of LEDs on the inside were much dimmer. I'm sure it's just the different loads of the two lighting devices. Need some help figuring out how to balance these two loads so they both work well.
Measure the voltage across the inside LEDs before and after adding the 3" flood light.
*Wired in parallel on the same switch. Should they be wired in series? Would that help?
(sorry, thinking of options while i'm writing this...)
Series won't work.

Didn't read the rest...
 

Thread Starter

nevink

Joined Aug 18, 2020
4
Thanks. Will do. I just finished it before practice ended last evening and realized the issue. Didn't have time to dig into it further.
 

scorbin1

Joined Dec 24, 2019
44
Putting them in series will, at best, reduce the voltage at each light in the circuit by a factor of approximately how many devices are connected in series, if this voltage too far below the rated voltage it probably wont work at all. Definitely not recommended. It sounds like the problem is with current supply. LEDs consume a lot less current when compared to incandescent, but still consume a significant amount of current. Floodlights generally pull a large amount of current compared to other lights. When you throw them in the mix, regardless of the architecture, you are going to be pulling some power. I assume these circuits are originally meant for marker lights or simple dome lights which are generally a very small current draw compared to floodlights. Also could have a weak or loose connection in your trailer wiring, or the wiring just isn't large enough to supply all of the current. if that is the case, eventually you will have a burnt wire or possibly a fire. It is very important to calculate the current capabilities of the circuit feeding your device and size your device accordingly, or make arrangements to upgrade the feeding circuit to meet the demands of your devices.

What size wires are feeding the trailer wiring, what size breaker or fuse does it have, and what is the rated current draw of each of the LED lights you are connecting?
 

Tonyr1084

Joined Sep 24, 2015
5,196
First, welcome to AAC.

As far as your lighting dimming when you added in the second set of lights - it could be the size of wires. Too small a wire will have higher resistance. When you pull a load (current) that may cause the voltage to drop. LED's are current based lights, not voltage. So a system that is rated for a specific voltage will have a current limiting system built into it. So when you add a second (or third or subsequent) string of lights and if they dim the only two possibilities I can think of is the size of the wiring or perhaps an insufficient ground path. More diagnostics is going to be required. It could be the plug that plugs into power. Dirty contacts may cause high resistance, thus dropping the current. When you draw a larger load the current is so limited that the lights dim.

While typing, someone else posted. If we cover the same things - that happens sometimes.
 

Thread Starter

nevink

Joined Aug 18, 2020
4
What i ran for the lights is more than acceptable (22ga). What the contacts & shape of the trailer's wiring harness looks like is another story. (old & probably needs cleaned/checked). All my wiring was soldered (no crappy connectors)
- flood light should only draw 1.25-1.75A
- the full LED string says max current is 1A
- don't see an ohm/ft rating on the wire

The strip was running very well till i added the flood light.

I will have to get back out there in the next couple days and get some actual readings of voltages & current draws.
 

Thread Starter

nevink

Joined Aug 18, 2020
4
I get what you're saying. The thing that gets me is the strip was working great until i added the flood light. And that was added up by the switch, not at the end of the string.

switch
|--flood
|--st----ri----n----g
 

Tonyr1084

Joined Sep 24, 2015
5,196
Here's an analogy you may be familiar with. You're taking a shower. The shower works great. Then someone flushes a toilet. Suddenly you're being scalded because the cold water supply is being diverted to the toilet.

Your second string of LED's is diverting electrons from the original working string to the second string. Neither has sufficient current to light.

Now, if you put larger pipes carrying the hot and cold water then you don't get the scalding affect. I upgraded my plumbing from 1/2 inch to 3/4 inch. Now when one is showering and someone else flushes the toilet - there's almost no difference in the shower. Same would be true if you changed from 22 gauge wire to - say - 18 gauge wire.

You know what you have to do to make this all work.
 

Stevepl11

Joined Jul 20, 2020
5
What about the wire to the switch? You know, from the connector on the vehicle. Even the wiring within the vehicle. That part is common to both lights so how close the flood light is to the switch is not important. Make sure your supply cabling is capable of much more than you need
 

Tonyr1084

Joined Sep 24, 2015
5,196
The size of the wire matters from the power source (battery) to the load (the lights). The switch has to be rated to handle sufficient current too.
 
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