Gentlemen,
As my first ever led DIY project I would like to upgrade cheap and crap 24v (for a truck) Chinese light bar with better chips like Cree XHP70.2. But I`m stuck on few questions.
They quote following on their listing: Power: 360w (90 chips * 4W)
How are they wired?
If in series (voltage gets added, current stays same), then, if 4w chip has forward voltage of 3.5v for example, that would be 315v. So, they are not wired in series, but in parallel.
If in parallel (voltage stays same, current gets added), then 3.5v and for example 700mA would be 63 amps, which is massive. Truck has about 120 amps available. For 60 amps, cable would be as thick as broom stick!
Voltage is limited to 24v, so must be wired in parallel? But 24v would blow chips with 3.5 fv when wired in parallel.
But what about thermal runaway risks when wired in parallel?
They also state this:
Operating Voltage: DC 9-32V (Fit 12V/24V vehicle).
They cannot predict it will be used in 12 or 24v system, so how do they know how to wire them in factory? If they pre wire them for max 32v combined forward voltage, then using it in 12v system would mean it would not be that bright? 12v is nearly 3 times less than 32v.
If I`m looking to replace them with xhp 70.2 (unless there is better option?), how do I calculate max I can drive them at, so that light bars case is able to handle the temps?
I noticed, the harder you drive chips, less efficient they get. But I can imagine for light bar which has sole purpose to throw light as far as it can to illuminate road and roadsides ahead, there is no option to have efficiency, because driven at something like 700ma, they would be super efficient, but quite dim? From my understanding - to have max long throw of light, chip needs to be driven as hard as possible (which xhp70.2 can be).
Why do led bars have 90 x 4w chips, but not 3 x CXB3590 driven at high current? So that they can spread heat across whole length of the bar?
Sorry for noob questions, I`m learning.
Thank you