req'd: info on 13 LED 6v dolphin torch to run from 2.1A USB/li-on battery.

Thread Starter

Poor old sod

Joined Jul 25, 2017
193
i hear the light srray depends on the battery interna resistance tolimit the current. i'm unsure how to proceed. i do not know the array drain,, mine may not work, as i tried to use 3x NiCd's and i don't know if i damaged it or i had it wrong.. thete was never any light from it. it's put away atm, but i'm thinking.
 

Alec_t

Joined Sep 17, 2013
14,408
Three NiCd cells in series will only give about 3.6V; hence why they gave no light if your torch requires 6V to work.
 

Thread Starter

Poor old sod

Joined Jul 25, 2017
193
the NiCd's are prob below threshold voltage,so led;s undamaged. any idea what total current draw should be? the leds are bright, and limiting the current isn't hard, if i know what it is. a const voltage source would be useful. partic if i used pwm and parallel capacitor to regulate the average voltage and a limiting series resistor.
 

LesJones

Joined Jan 8, 2017
4,226
It is very bad practice to drive LEDs from a constant voltage source. If it is designed to work with 6 volts there will probably be a limiting resistor in series with each LED. It is just possible the LEDs are in series and a boost constant current current regulator is used t drive the LEDs in series. You will need to see how it is wired at the moment.

Les.
 

dl324

Joined Mar 30, 2015
17,125
Without more information on the flashlight...

You have a flashlight designed to operate from 6V and you're considering a li-ion battery (~3.7-4V)? You might get away with USB/5V (4.5-5.5V), but 3.7V doesn't seem reasonable.
 

Audioguru again

Joined Oct 21, 2019
6,782
I have seen Little AA size lithium-ion battery cells that produce regulated 1.5V and have a USB charging jack on them.
They are made "over there" by no name-brand companies and they are expensive.
Notice that they are rated in a high number mWh instead of lower number mAh.
Forget this because the Eveready Dolphin torch uses a huge 6V lantern battery module.
 

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Audioguru again

Joined Oct 21, 2019
6,782
Since a 6V lantern battery quickly drops to 4V, then an ordinary "power bank" product has all the parts to work. It has a USB charging jack, a 3.7V Lithium Polymer battery with a high capacity, a voltage stepup circuit and a regulated 5V output.

I saw some power banks sold on Black Friday and on Boxing Day for 67% off the normal selling price.
 
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