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Does a joule thief consume power without a load? Answered

I want to add a joule thief to a battery so it always puts out 12 volts regardless of the charge level but i don't know if it will constantly drain the battery.

I am also wondering if anyone has ever used a joule thief with a wind generator to charge batteries.


Yes the if Will use a small amount of energy regardless of the load or not.

can you be more specific?
I'm not very experienced with electronics, but it seems to me like it will constantly drain the source at full power regardless of the load

A joule thief may give you more voltage but at a very reduced current. They are great for extending the battery life in an LED flashlight but won't do you any good as far as connecting it to a small wind generator and trying to charge a 12V battery. Once you connect it to the heavy load of a battery, if you don't burn out the circuit, the voltage output will drop to almost nothing. You need to be putting in more power then the battery is trying to put out to charge the battery.

From what i know about how these things work is the voltage will increase until it can complete the circuit. If this is true it will continually increase the voltage as it charges the battery, thus a cheap, adaptable charger.

The Joule thief isn't a particularly efficient device, just one that starts at a fairly low input voltage. There are much better supply designs


5 years ago

You can wire the joule thief so it only runs when the wind blows.

But, even the smallest wind generator will put out more power
then a joule thief !

The special feature of a joule thief  is can run on very low voltage,
less then the 1.5V of a single cell battery.
That is not what you need from a wind generator.


I intend to make a high-output version in the 5-15K watt range and want to know if anybody had tips on that sort of thing