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# How many white LEDs can a 6V lead-acid battery drive at a time and for how long- for a emergency lamp Answered

I want to make am empergency lamp (power outages are frequent) using maybe a 6V lead-acid battery. How many white LEDs can it drive at a time and for how long?.The lamp should hv enough juice to light up a 12x12 room.. all suggestions are welcome.

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I am doing a school project. I am charging 4 aa batteries(Ni-Mh 800mAh) with a solar panel.
I want to lit 3mm white LED with the battery. how many LED I can connect to this batteries and did I need to use a resistance?

all u need to do is to know the ampere-hour rating of your battery. white LED can glow for a current of 20mA at 4V. therefore for brighter light connect the LEDs in parallel but you can use a series resistor to reduce the voltage across the LED to avoid damaging it. you can power as much as 30(to the best of my knowledge) for as long as 5hr using a 4.5A-hr lead acid battery. from Nnonyleu Chibuzo

for a 7.2ah 6v sla battery...

45leds = 1.1amp = about 5 hours
leds in parallel with series 12ohom each you can have up to about 300 leds but the battery will probably only last 20-30mins and will be blindingly bright and expensive.
use as many leds as you want
or even have a switch to control how many you have on.

You will need to find the current rating of battery. If it is A amperes then power provided by batter would be 6*A Watts. A white LED requires about 250 mA of current. Most probable you lead acid batter is 6 A i.e 6000 mA so it would be enough to run 24 LEDs. I recommend to connect them in parallel if possible. If you connect them in parallel, you will not need to add any extra resistor if they are 24 LEDs. If you connect them in series you will need to add a resistor of about 30 ohms. Check the current of your battery and tell me. Regarding the time, time will depend on the discharging factor of your battery. It should run the LEDs atleast for 3 hrs.

A lot, for quite a while. But to do the maths you need to know a few things: What is the capacity of the battery in (milli)Amp-Hours? What current do the LEDs require, and what voltage? What is the light-output for each LED (lumens) and what do you need or have at the moment for lighting the 12x12 room? L