LED CCS notes

Connecting four LEDs to a 12 V, 7 Ah battery

Ask Question

Asked 4 days ago

Modified 4 days ago

Viewed 60 times


enter image description here

I want to power four LEDs using a 12 V, 7 Ah SLA battery.

I connected four LEDs in series and connected them to the battery, and the light glows.

Can I use this for a long time or does it need some additional components? Will the big capacity battery harm the LEDs?




edited Jul 24 at 16:25

user avatar


4,7081414 gold badges2121 silver badges2929 bronze badges

asked Jul 24 at 14:09

user avatar

Sasi Kumar

2733 bronze badges

  • 1Can we have a link to the LEDs, or a photo of the LEDs wiring to the SLA battery? – tlfong01 Jul 24 at 14:27   
  • it is taken from 220v ac bulb Philips 10w f6500 – Sasi Kumar Jul 24 at 14:36
  • 2You need at least a series resistor to prohibit thermal runaway – Jens Jul 24 at 14:45
  • it is taken from 220v ac bulb Philips 10w f6500. i have nt permanently connected just checked with 12v sla battery by using only 4 leds to match arround 12v .tried 5 leds in series,glowing but brightness is low.6 leds are not turning on.updated image – Sasi Kumar Jul 24 at 14:45
  • how much value can I use – Sasi Kumar Jul 24 at 14:51
  • We don’t know what LEDs those are and at what voltage/current they originally were powered with, so your question is unanswerable. – Justme Jul 24 at 15:55 
  • mouser.in/datasheet/2/239/… . i think it’s this – Sasi Kumar Jul 24 at 16:35
  • Your photo shows an LED assembly containing a large number of LEDs, not an individual LED. How that assembly reacts when connected to the battery will depend on how the individual LEDs in that assembly are wired. – Peter Bennett Jul 24 at 19:44
  • You might need a CCS (Constant Current Source) for your, possibly sort of 1W 350mA LEDs. The following has some CCS references. How can Rpi Python PWM GPIO pins control and dim LED strips of 1W 350mA? Asked 1 year, 4 months ago Modified 1 year, 4 months ago Viewed 744 times raspberrypi.stackexchange.com/questions/122187/… – tlfong01 1 min ago  Edit  

Add a comment

Start a bounty

1 Answer

Sorted by:                                              Highest score (default)                                                                   Date modified (newest first)                                                                   Date created (oldest first)                              


Philips make their own LEDs. LEDs all have different forward voltages so they must have a current limiting circuit. Didn’t you notice that the datasheet you posted and all other LED datasheets show a wide range of forward voltages from 2.6V to 3.2V? Then four 2.6V need no more than 10.4V (12V will explode them) and four 3.2V need 12.8V (they barely light with 12V).



answered Jul 24 at 17:18

user avatar


2,51133 silver badges77 bronze badges

  • Such LEDs typically have a fairly “soft knee” so forward voltage is highly dependent on current as well as temperature and color. One reference from Rohm shows an LED that passes 1 mA at 1.8V and a still “safe” current of 20 mA at 2.2V. rohm.com/electronics-basics/leds/led-circuit-configuration The 2.6 to 3.2V variation is also +/- 10%. However, I/V has a positive temperature coefficient, so thermal runaway can happen. – PStechPaul Jul 24 at 22:59

Add a comment

Categories: Uncategorized

Leave a Reply

Fill in your details below or click an icon to log in:

WordPress.com Logo

You are commenting using your WordPress.com account. Log Out /  Change )

Twitter picture

You are commenting using your Twitter account. Log Out /  Change )

Facebook photo

You are commenting using your Facebook account. Log Out /  Change )

Connecting to %s

This site uses Akismet to reduce spam. Learn how your comment data is processed.