Puzzled by COB LED behaviour.

[Skyliner33]

I bought a 5m strip of COD LEDs. I wanted to us 2 1.5m lengths, so I cut the middle 2m out leaving me with 2 x 1.5m lengths with connectors on each.

When I wire them to a battery in parallel both strips light up.

When I wire them in series then neither light up. Any suggestions?

 

[DXX]

Too much resistance?????????

 

[drinfinity]

What voltage is the strip expecting? In parallel to have 12v across the strip, in series you only have 6v.

 

[Skyliner33]

What voltage is the strip expecting? In parallel to have 12v across the strip, in series you only have 6v.

Oh damn, what an error. How embarrassing.

I was focussing so much on fuses, never spotted that.
Now I need to think, In parallel they would pull 2x the current. So if I stick a single fuse in it maybe above the rating of the wires that came connected to the LED strips.

 

[Dellmassive]

You can't wire them up in series in that fashion. .. for the series operation.

For connecting in series you need to take the plus and minus from the end of one strip and connect to the plus and minus of the second strip.

 

[Dellmassive]

The few size needs to be size to protect the cable.

So depending on what gauge cable you've got feed in the lights.

But normally you would be around 2 amp or 5 amp or 10 amp blade fuse.

3m of LED strip light won't use much power.

 

[Skyliner33]

The few size needs to be size to protect the cable.

So depending on what gauge cable you've got feed in the lights.

But normally you would be around 2 amp or 5 amp or 10 amp blade fuse.

3m of LED strip light won't use much power.

Yes, I agree. But my brain keeps saying, if the original LED strip was designed to take 3A. they may have just used 4A wire (making numbers up for explanation).

Therefore when I wire 2 in parallel, if I fuse near the battery, I need to use a fuse, for eg 7A, that would cope with the 2x3A = 6A current draw, but then the bits of wire that were on the LEDs would be fused too high.

 

[drinfinity]

Suppose you bought a 5w/m strip. So your original wires would cope with 25w @ 12v = 2A.

Now you are only using 2x1.5 m length, = 15W @ 12V = 1.25 A total. So whatever your new current draw on the cut down strips is, it is always lower than the max they were designed for.