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How to change 3v to 2v? Answered

I want to install some LED string lights in my garden. The package comes with a solar charger (2V 100mA), built in battery (600mAh) and 30 meters of wire and 300 LED bulbs. The problem is that I cannot use the solar charger this time of year. So I want to cut the wires and join them to a power supply.

The lowest voltage adapter i can find is 3V. Do I need to change the 3V to 2V? How?

13 Replies

Nematic! (author)2016-11-27

use stepdown module availabe on ebay for cheap

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Rajkumar2506 (author)2016-11-24

You can use voltage divider circuit to convert 3 to 2 volt.To know how i have attached you an image

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MartinaA5 (author)2016-11-15

Hello, thanks for the responses. It's true I don't know much about electronics, but i can find positive negative and i have a voltmeter.
This is the product. Do you think i can do it and what do i need to do to supply the correct power?


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iceng (author)MartinaA52016-11-16

So you already have the 300 LED version. Yes you can do it.

Take pictures before and after so we could help later.

Most solar lights turn off the light when charging the battery in the day time.

The solar cell must be disabled by covering or disconnecting one wire.

Measure the full charged battery voltage and IF your adapter is above that same voltage by about a volt or less. Then just place the adapter wires across the battery plus to + and - to minus. IF your adapter voltage is more than a volt above a charged battery just take out the battery..

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iceng (author)MartinaA52016-11-15

Reading https://www.amazon.co.uk/d/gha/GAXmi-Outdoor-Light...

Specifications of your lights appear to be true based on positive comments the 300 LEDs will work on a 600mah battery for a minimum of 8 hours, and flashing

14 hrs if_the_weather_be_good.

Assuming all 300 LEDs are on for a minimum of 8 hours the equation is

300 x ma x 8 = 600

solving for current ma = 600/(300 x 8) gives an astounding (possibly PWM)


I would by it in in an instant if the deal was available in the US...

Did you know they have a plug in 100 LED string at £9.90


you could buy three.

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Josehf Murchison (author)2016-11-15

How many mA is the adapter?

Is the solar charger one or more batteries?

Do you have a multi meter?

I wouldn't worry about it, although the specks say the solar cell is 2 V 100 mA it can be more.

If it is 2 VDC 1 volt isn't much but if you are worried just add a 100 ohm resistor.

What makes me wonder is a 100 mA solar cell is usually used to charge a 1000 mAh Ni-Cd battery for a 5 hour charge at a 1/10 charge rate.

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If you cut the wire at the box and connect the three volt adapter to the LED wires you will need all three volts.

Go to this Instructable.


See step 8.

By the way if you post a link hit enter and it will act like a link.

When someone clicks on it the link will send them to that page.

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Okay thanks!
Does it matter how much current the adapter supplies?
I can buy one that gives 1.0 Amp.
And will I blow the LED bulbs if I reverse the polarity by accident?

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If you connect the LEDs backwards they will block the current like a regular diode and just won't light.

Going by the battery 3 volt 250 mA adapter should be good enough so if you can get a 1.0 amp it should be plenty.

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iceng (author)2016-11-15

Don't cut just put a diode in series, you do not sound like you know electronics. Remember to observe polarity.. Disconnect the wires from the solar cell and Place the now two 2 volts across the where the soar cell was (observe polarity).


The above is based on what you told us. I find it hard to believe that 300 LEDs can run off of a 600mah battery because assume each LED uses a very very low 10ma times 300 LED gives a total current of 3000ma == 3Amperes..

Simple math to time the battery 600 ma hr / 3000 ma = 0.2 hr

each hour is 60 min 0.2 hr x 60 min / hr = ONLY 12 minutes of light time !!

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MartinaA5 (author)iceng2016-11-15

please see my reply above

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steveastrouk (author)2016-11-15

Get a diode, like 1n4001, put them in series, and connect them from your 3V supply. They'll drop around 700-900mV, and bring the output to where you need it.

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