50W Led torch with out driver

Hello,
i have this led 50w floodlight 30-35vdc input which i installed on an old broken dive light.Now i need to use a driver but iam thinking to connect it directly on the batteries.I will use 8 or maybe 9 sony 18650 3.7V 2900ma in series.This theoretical will give around 2,5 to 3 hours which is more than enough for diving purposes(my needs is 2hours)

My questions is: what is the disadvantages or dangers if i don't use a driver? The only thing i can think of is the constant light output.

Are you sure the floodlight doesn't have in integrated driver already ?


Some LED's have been known to draw a bit too much current and heat up faster without the use of a driver. Not sure, I vaguely recall reading about something like that.

At it's most basic of function, a Driver will typically throttle the amount of current that is fed to the LED.
Constant light output is not a feature of all drivers. That's an advantage known to be more a feature of the buck style driver and some boost models.

In your case, you'd neither be bucking nor boosting.

Idealy, you'd want to find out the current draw specs of your floodlight, and compare them to the measured current draw you get from your setup.

There is a very good chance you can run direct drive if you want.

You would want to use 8 cells and not 9.
You're going to want to judge your cell count based on 4.2v a cell not 3.7 as 4.2 is their max working voltage fresh off the charger.
9 cells would be 37.8v

The only danger I can think of is lack of low voltage protection.
This is important when running li-ion batteries.
If you buy protected cells then they will have it build in.
If you are getting raw cells to build a pack, you will need some sort of low voltage protection, especially in an LED which can still shine bright even when the batteries are exhausted giving you no heads up that your batteries are starting to get upset.

UNless someone chimes in with a better recommendation, there is a CPF user that makes the JM-PH-D1 regulator.
It's a PWM FET regulator designed to run incandescent bulbs, but I have tested it in direct drive LED applications before.
If it fits in your system, it's rated for up to 40v, would give you low voltage protection, and the ability to throttle some current if you find you LED is running too hot.