100ish watt xhp 70.2 watercooled build.

Pounsfos

Newly Enlightened
Joined
Jun 13, 2022
Messages
2
Location
New Zealand
Howdy all

I've built alot of dolphin torch leds with big battery packs etc...

My next build I want to go big and have decided to go for an xhp 70.2 over driven to put out roughly 60-100w (yes that is some amps)

I have chosen the 6v version as it seems to be more compatible with drivers etc... but this is my biggest problem I'm having, I know mosfet drivers can dump some amps but how would I go about limiting the amps going through the drivers or to the led.

My build will probably have a 3s5p lithium pack behind it where the cells can do 10amp discharge so will easily be able to dump 30+ amps into this led, which I dont want, am I over thinking it or do mosfet drivers have a limit to how much amps they can "put through"

Also if someone can point me to a driver suitable for my needs, that would be awesome, size doesn't matter as it's going into a custom box.

Thanks in advance for your input and suggestions


Scott
 

DIWdiver

Flashlight Enthusiast
Joined
Jan 27, 2010
Messages
2,718
Location
Connecticut, USA
When most people talk about a mosfet driver, they talk about a device where the fet is intended to operate like a switch, and the current is limited by a number of things, including the battery, LED, wiring, and yes, the fet. For this to work, the LED and the battery generally have to be pretty closely matched, at least for high-power LEDs.

But fets can be used to limit current. Check out this thread: https://www.candlepowerforums.com/t...ear-led-driver-new-and-improved.264687/page-2

Post #33 shows the basic schematic of how a current limited mosfet driver is built.

Perhaps the most significant limitation of this type of driver is power dissipation. Unless the battery voltage is just higher than the LED voltage, this can be pretty high. Take the difference between the battery voltage and the LED voltage, times the current. This is the power dissipated by the FET.

Switching regulators can do the job with much less power dissipation if the voltage difference is larger. A number of CPFers (myself included) have attempted to build 10+ amp switchers for flashlights. As far as I know, none have come to market. Removing the size limitation is a huge advantage, and modules like this are available that would work for you if your battery voltage is 10+ volts: https://www.ebay.com/itm/1545631896...jcRNp5WK5F4Vidp+IzoEWBUKDgTa|tkp:BFBMzKui4bFg

Note that I don't endorse this particular module, it's just shown as an example. Most of these are made by very low-cost asian manufacturers, so quality might be questionable.

By the way, switching regulators usually employ mosfets as high-speed switches.
 

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