How can I limit the amperage from an automotive battery without affecting the voltage?
KrazzyMan asked:
I need to limit the amps from an automotive battery to a max of 30 amps with out affecting the voltage, no matter how much amps a device wants to pull. what kind of circuit can I build, with details please. I would like to make it variable from 5 to 30 amps it’s for an electronic project.
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I need to limit the amps from an automotive battery to a max of 30 amps with out affecting the voltage, no matter how much amps a device wants to pull. what kind of circuit can I build, with details please. I would like to make it variable from 5 to 30 amps it’s for an electronic project.
June 5th, 2010 at 6:36 am
You need a current limiter for this.
The best place to look, if you’re thinking of constructing one yourself, is in schematics for battery chargers, where variable limiting current is more common.
Have a look here: HandyMan
June 6th, 2010 at 10:58 pm
You could do it with 2n3055 power transistor and a poteniometer. But I can’t draw you a schematic here, so you might need to search the web for one. sparky
June 9th, 2010 at 2:50 am
The amount of DC current a device (in your words) wants to pull is determined by the resistance of the device itself and the magnitude of the applied voltage. Since you have no control over the resistance of the device this means the only way you can control the current to the device is by controlling the magnitude of the voltage.that is applied to the device. (not the battery voltage)
An automobile battery`s voltage is fixed so this means you will have to design, build and place a circuit, (who`s resistance is variable and controlled by a sampling of the amount of current the device is drawing), in series with and in between the battery and the device. This circuit`s variable resistance will control the voltage applied to the device and thus control the amount of current the device will draw. The exact circuit is too complicated to tackle by e mail outside a lab. I would not care to tackle it anyway, but maybe the above will give you an idea of how to approach the project.
If you make it continuously variable from 5 to 30 amps that will make it even more complex. Making it variable in steps rather than continuous might simplify this part of the design by allowing you to switch in, a different but fixed value resistor for each step, in series with the variable resistance circuit.
Better yet you might find a circuit already designed along these lines and modify it to suit your application. Mr. Un-couth