Limit car battery current

Discussion in 'Power Electronics' started by pidja105, Jan 28, 2016.

1. pidja105

106
1
Oct 16, 2015
Hello,
I have a question,
can I use R = V / I formula
to calculate resistor for 41 amps and 12 volts?

2. shrtrnd

3,827
520
Jan 15, 2010
Yes, but what the heck is running at 41 amps in your 12V car?
Are we talking about starter amperage when you crank the engine, or is this another issue?

3. pidja105

106
1
Oct 16, 2015
No,
it is for my electronics projects.

4. Alec_t

2,998
813
Jul 7, 2015
So which project requires 41A?

5. BobK

7,682
1,688
Jan 5, 2010
Ohms law will tell you what resistor would draw 41A if placed across a 12V source that is capable of that current. This is not very useful. Tell us what you are trying to do.

Bob

6. shrtrnd

3,827
520
Jan 15, 2010
BobK is right. Trying to draw 41A for an extended period of time from a 12V car battery is not going to last very long.

7. Gryd3

4,098
875
Jun 25, 2014
Please note that this problem can be looked at one of two ways:

If your device is meant to pull 40 Amps, then it will only pull 40 Amps. You don't need to limit this, just hook it up if the device is rated for 12V.
Otherwise, if you are building a switch mode power supply, current/voltage limiting should be done on that circuit.
Finally. If you are concerned with 'Anything' taking more than 40Amps. Use a fuse. It won't dynamically turn down the voltage to stop you from pulling more than 40A, but it will still stop you from pulling more than 40A for any more than a second xD

Tha fios agaibh likes this.
8. hevans1944Hop - AC8NS

4,630
2,159
Jun 21, 2012
Sure. I'll even plug and chug the numbers for you: R = 12/41 = 0.29268292682926829268292682926829 Ω
How's that for service?