6v dc./sla. down to 3v dc to power a 1w.Duracell led flashlight that normally runs on 2 aa batteries or 12v to 3v.

this set up is for a bike light, I have access to a 6v sla. batt. that came from a larger flood light that was useless because of the power sucking halogen bulb,approx 15 min. run time.it also has its own charging circuit and a separate circuit for a single led night light.I tried looking up resistor values,but get confused cause i'm getting different answers from different sites ! LOOSING MY MIND ! HELP ! thanks oh..I use the night light circuit to power a red led flashing bike light for the rear.

Can you get two flashlights ?
Put them in series, connect to 6V, no resistor needed.
Otherwise, we don't have enough information. YOu need to measure the running current of the flashlight to work out the resistor value - and then you'll be blowing away half of the energy in the battery.
robin67 (author)  steveastrouk6 years ago
not sure of the current draw of the flashlight,going to try to find it online,but wouldn't a double a flashlight with 1 watt led draw close to 500ma,if I can't find that answer I might just go with two in series,now, would that work with a 6v or 12v supply.thanks guys,I really appreciate the help !
It'd work fine on 6V.

seandogue6 years ago
If I knew that you were an electronics geek, I'd simply suggest that you run a variable duty cycle clock (555) running at ~500Hz-1KHz (or thereabouts) into a power mosfet like a HexFet to create a 50% duty cycle PWM driver for the LED (might need a small inductor and cap to smooth things out a bit and dampen the 6V spikes). Total cost ~$5-6 + your time, circuit size...~1"x1.5" (2.5mm x 4 mm)

For a moderately powerful LED, this could appreciably reduce the wasted energy lost as a result of using a load resistor to burn off the excess energy, and you could also provide a user control of the lamp as well

As Steve noted, some idea of the current would be helpful to ascertain specifics. (for instance, a 500mA load at 3V represents a 6 ohm load, so testing and tuning of the circuit could be done with a 6ohm, 5W resistor without impacting the LED itself prior to insertion...)