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thomas_cher

join:2012-11-26

How to do a circuit diagram for 12v LED strip

Hi guys, recently I've bought a 12V LED strip, 12V battery, battery holder and a switch.
I connected the switch to battery holder then to LED strip. It works but the battery get very hot after a few second and the lights seems to grow dimmer and dimmer after a few second. Does anyone know why this happens?


SparkChaser
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join:2000-06-06
Downingtown, PA
kudos:4
Reviews:
·Verizon FiOS
Not knowing what your strip is, I can't say for sure BUT it sounds like a classic over current to the LEDs. Which is killing them and the battery. You have to limit the current to the LEDS. Do you have a link to the LED strip so we can see what it is or at least specs.



aurgathor

join:2002-12-01
Lynnwood, WA
kudos:1
Reviews:
·Frontier Communi..
reply to thomas_cher
The battery is not capable of supplying the current the LED wants for an extended period of time.

You need to measure the current going into the LED strip -- if it's more than the spec, you need at least a current limiting resistor, or even better an LED driver.

If the current is within spec, you need a bigger (or more) battery .
--
Wacky Races 2012!


cowboyro
Premium
join:2000-10-11
Shelton, CT
reply to thomas_cher
In order to power LEDs with a voltage source just slightly higher than the rated voltage of the LEDs you will need a driver. A resistor won't do it as a slight variation in the voltage of the source will cause a major variation in the current and the light output.
Now if the voltage of the source is much higher then a resistor will do - but pay attention to the current dissipation.

lutful
... of ideas
Premium
join:2005-06-16
Ottawa, ON
kudos:1

1 recommendation

reply to thomas_cher
»www.digikey.com/product-search/e···20RCD-24

Here is a list of (reasonable cost) DC-DC LED drivers at Digikey. Choose one which can supply the maximum allowable current for your LED string. FYI it is better to use lower than rated maximum current. For example 700mA LEDs which are run at 500mA may last twice as long.

You should also buy a cut-off device which prevents battery from being drained too much. It is best to recharge around 11V if you want the battery to last a long time.


cowboyro
Premium
join:2000-10-11
Shelton, CT
said by lutful:

»www.digikey.com/product-search/e···20RCD-24

Here is a list of (reasonable cost) DC-DC LED drivers at Digikey.

They won't work with a 12V LED strip from a 12V battery - they are all buck converters...

lutful
... of ideas
Premium
join:2005-06-16
Ottawa, ON
kudos:1
*** Google search finds this $15 LED string driver which accepts 7V-12V input and comes with a remote.

»www.lowpricerc.com/product_info.···ab04e7e0

a few buck-boost modules at digikey: »www.digikey.com/scripts/dksearch···1098=310

lutful
... of ideas
Premium
join:2005-06-16
Ottawa, ON
kudos:1
reply to cowboyro
Click for full size
said by cowboyro:

They won't work with a 12V LED strip from a 12V battery - they are all buck converters...

These strips are nominally 12V but will light up even at 9V and will actually last longer at lower than max voltage and lower than max current.


cowboyro
Premium
join:2000-10-11
Shelton, CT
said by lutful:

These strips are nominally 12V but will light up even at 9V and will actually last longer at lower than max voltage and lower than max current.

It means they have a ballast resistor - which OP's lights don't seem to have.

lutful
... of ideas
Premium
join:2005-06-16
Ottawa, ON
kudos:1
reply to thomas_cher
said by thomas_cher:

I've bought a 12V LED strip, 12V battery, battery holder ... battery get very hot after a few second and the lights seems to grow dimmer ...

thomas_cher See Profile ... whatever happened to you?

We are just guessing what kind of LED strip and battery you bought and some of our suggestions may not be appropriate.

Most probably you have a small capacity 12V battery whose voltage drops rapidly as it tries to supply the rated current to the 12V LED strip.

Can you please post a photo of your setup with some details?


SparkChaser
Premium
join:2000-06-06
Downingtown, PA
kudos:4
Reviews:
·Verizon FiOS
said by lutful:

thomas_cher See Profile ... whatever happened to you?

I think it was a drive-by post. It's the only one he's ever made.