3- c8 in series

I’m wondering if 3/ c8’s can be run in series off a 12 volt lead acid battery.
For example , pos from battery to pos to light #1 .neg from light #1 to pos light # 2. And so on till you get back to neg battery.
Or will it just release the magic black smoke ,lol. I’d draw a picture if I had more computer savy.

if the C8s have drivers, the answer is no - the drivers usually have a fixed voltage range of 3-4.2V, so 12V will kill them. If they’re direct drive (no drivers), the answer is no - each LED will be getting ~4V which will kill them. Either 4 C8 direct drive in series (with a current limiting resistor) or 3 C8 with a big power resistor to burn off the excess voltage. Might be simpler just getting the right driver to run them at 12V…

Ok , thanks . I don’t have a good understanding of this , thought that the lights with drivers would share the voltage but guess not

no worries, it takes a bit of getting used to! Better to ask before blowing stuff up though :slight_smile:


Set the output for about 4V and you are all set.

I used these in my Light Bar 2.0 build ( I used the heads of 502b XM-L’s)

Thanks, I’ll have a look see

Cree have a 12V LED: XM-L EZW

There are a few moto running lights on ebay that advertise 12V as well.

Hmm, time to look at 18650s in series.

Already discussed: XM-L EZW T5 warm white for 4.92$ at GoodLuckBuy

Aren’t there flashlight drivers with a wider voltage range ?

Sure, but try to find one that ticks all these boxes:

-fits a C8 pill (17mm)

-works with a voltage range from 3v to 12-15v

-still gives a decent output worthy of a C8 (~3A) when used in normal-flashlight-mode, with one cell

What if you took the c8 out of the equation ?

Then you would just use a cheap DC-DC converter.

Are you trying make a “replacement” high beam for your car?

I live off grid and I’d like to make a few 12 volt lights . I have a fairly large 12 volt bank and an inverter but the inverter uses 45 watts just to turn on so dc led light seems the most efficient way to go and if they were flashlights I could still use them as flashlights if I wanted

One idea you may be able to use for ambient lighting. Not sure what kind of output you’re looking for. But I use this rig in my man cave and it works like champ.


The converter takes your 110 from the wall and makes it 12 volts to feed the lights. Some of these kits even come with a cigarette lighter plug to use in instead of the wall wart. So all you would have to do is plug that into your battery bank. I have done it with my solar rig. It works like a charm. Free light.

What are you looking to do here? Room lighting, outdoors, automotive...?

For DIY lamps these are neat: http://www.ebay.com/itm/300927996993

And cheap, too. One of those and a ~$1.20 LM2596 DC-DC converter, and you get a pretty good amount of light. No reflectors or optics needed, keep the drive current at 700-800mA and they don't need much for heatsinking but a smallish piece of flat aluminum plate. Add a semi-opaque white plastic bottle and you have a lamp.

Oops re read what you said didn’t realize it can be used right from the batterys

This would be good for someone with 110 but for me I have to make 110 from 12v.then back to 110 to plug the thing in then back to 12v. By then I’ve used more juice than the light uses.

Looking mainly for indoor room light

This looks pretty simple. So even though it’s a 12v led you still need something to limit the amps? So in a direct drive flashlight the amps are limited by the battery capacity? If this is so then it’s starting to make more sense

They are actually more like 9-10v, at a reasonable drive current. They're really nothing but nine 1-watt LED dies in a single package, three dies in series, three sets of three in parallel. Three 1W LEDs need right around 3 volts each so three in series equals 9v.

If you were to connect one straight to a fully charged 12v SLA, they would draw many many amps and not be very happy. More voltage allows more current to flow through the LED (any LED, not just these), so limiting the voltage will also limit the current at the same time.

I used one of the 10W things as a trunk light, it's maybe a bit more light than is really needed...

(different driver used here, just a fixed ~700mA output, the ebay LM2596 boards are better since they're adjustable)

Stock fixture/bulb:

10W LED @ 710mA:


Well, ehm. That is the brightest trunk light I have seen. :bigsmile: