LED Wiring

[muskielaw]

I recently installed 2 Best King Kong string LED lights in my portable. 1-96cm and 1-48 I believe. I hooked them both up individually to the same vex battery and after a short period noticed that the connection were red hot and about to start a fire. Am suppose to wire these to lights together and then only make one connection with the battery or are two of these lights just to much power for one vex batter? As a side note the 96 cm light is so bright (highly recommend) I probably don't need the second light but would still like to know how to properly wire these two if needed. Thanks for any help.

[fishwater]

You must have a short in your connection that is pulling more current than the lights are using and is generating the heat. The lights don't use much current so you should be able to hook multiple strands to a vex battery without pulling enough current to create heat. I have 3 24cm strips and 2 12cm in one shack wired to a single battery in two separate circuits without a problem.

I'm a little surprised you would have a short and the lights are operating, but it is possible.

[muskielaw]

Thanks fishwater! I will check my wiring when I get home. I did not think they drew much current so was surprised when it began to overheat.

[B@ssmaster]

I also have the best king Kong strings, a couple 96's and a 48 (and a pair of fans). I measured the current draw (being an electronics tech, I had to check) and the 96's draw something like 60ma if I recall and the 48cm about half that. Shouldn't be enough to heat up small wire if everything is connected properly, assuming you have used a reasonable guage of wire. If somehow you have accidentally wired all those lights in series, then each string's draw will add to the others and that total could exceed the wire's capability. In parallel you should have no trouble I would think.......

[hydro]

I think that electronics advice above is backwards. Not knowing how the strings are constructed I would assume they are in parallel through the LED's, with two hookup wires to the 12V supply. The current draw across those wires is the 60 mA measured. If they are in series through the LED's the effective circut is the same for the concept below.

If you hook two of those strings in parallel to the supply, the total draw will be additive, or 120 mA. In series, the total voltage drop will be divided between the strings, resulting in 6 V drop across each string and quartering the wattage of each string. The result of this hookup would be dim or no light output and half the current draw at 30 mA.

Now either way the strings were hooked up, the calculated currents could not have caused the hot wiring that was described in the original post. With that in mind, either there is a short across the load in one of the strings or a short across the wiring somewhere else.

[B@ssmaster]

Hydro,

You are correct given your assumptions. I was unclear about what I meant, however. My mistake. Presuming each string has it's own lead wires, connecting two or more strings in parallel limits the total current through each string/lead wires to 60ma, if two strings or more are connected in parallel but off some form of common lead, the total current through the common lead is additive. Good catch, sorry for the confusion.

But as you said, in any case, the total current draw should not be heating the wires. There must be something else going on to create the heating issue.....

[hydro]

I guess the real question here is why the light strings stay illuminated while the wires heat up. That short needs to be located before the magic smoke gets out!

[B@ssmaster]

Exactly! Without that magic smoke, nothing works!

[muskielaw]

You guys are talking a little over my head but what I can tell you is that I just spliced some longer speaker wire onto what comes with the lights. Which if you have not seen these lights they come with about as small of a gauge wire as I think possible.(30 gauge ??). I then attached some alligator clips to each light and hook the clips right up to the same vex battery so that if I only want to use one light I can. I believe this would be parallel?

In any event if there is a short are you suggesting that it could be within the LED string itself? Or would it have to be in the wiring I have added? Furthermore, when I unhooked the second light I did not have any problems, so I would assume that it is probably the light I unhooked that had the short if either do? Thanks for all the help guys.

[walleyewild]

Muskielaw,

Did you try just the second string by itself, and did th wire get hot?

There could be a short in the string itself, unlikely but posible.

WW

[chris63]

One of the Best LED light strings I bought lit up(literally burned) the first time I used it.Sent it back burned up(melted conductors)and never heard back from them.I do like the one set from them that didn't short out though.It's a 96cm white string draws 30ma........cyac63

[hydro]

Muskielaw,

The circuit you describe is a parallel circuit consisting of the two strings. Think of it a separate circuits side by side. The best way to troubleshoot a circuit like that is to break it in half and check each half individually. The problem should show itself in one string and it's extension wire or the other. If you can isolate it to one string, then remove your extension wire and check it again at the factory leads ("break it in half"). if the problem is still there it is in the LED string, if not it was your wiring.

If none of the above isolate the problem, check anything else that you have connected to that battery.

[fishwater]

I then attached some alligator clips to each light and hook the clips right up to the same vex battery so that if I only want to use one light I can.

[hydro]

I guess I don't see how hooking up LED's in reverse polarity would cause high current flow. An LED is a diode and diodes only allow current flow in the forward bias polarity. If hooked up in reverse polarity no current should flow.

Is there some other circuitry in the LED string?

[lovebigbluegills]

I've got two 48cm strings hooked up the same as ML has described, and used them a couple times. I didn't even look to see if the wires were getting hot. I'll hook them up out in the garage tonight and let them go for a while and keep an eye on the wires/connections. I'll report back tomorrow morning

[fishwater]

I guess I don't see how hooking up LED's in reverse polarity would cause high current flow. An LED is a diode and diodes only allow current flow in the forward bias polarity. If hooked up in reverse polarity no current should flow.

Is there some other circuitry in the LED string?

In theory no current should flow, but they have a reverse breakdown that is generally around 5volts. Hooking up to a 12volt source with unlimited current potential can cause the gates to short and fail in a cascade.

[hydro]

In that case the LED's should go dark as they break down. That would be a good indicator to the original poster that this failure is happening. I like the earlier suggestion about loose strands of wire in the hookup. That should show up in my earlier post about taking the assemblies apart and checking the LED string only.