Car Battery Current: Questions & Answers

  • Thread starter Thread starter jearls74
  • Start date Start date
  • Tags Tags
    Battery Current
Click For Summary

Discussion Overview

The discussion revolves around the current output of a 12-volt car battery, particularly in relation to connecting various devices, such as a transistor. Participants explore the implications of connecting devices with different current ratings and the factors that influence the current supplied by the battery.

Discussion Character

  • Exploratory, Technical explanation, Debate/contested

Main Points Raised

  • One participant inquires about the current output from a car battery and whether connecting a 15 amp 20 volt transistor would short it out, indicating a lack of clear information found online.
  • Another participant suggests that the current supplied by the battery depends on what is connected to it and recommends reviewing Ohm's law.
  • A different participant explains that the current limit from a battery is influenced by its internal resistance, noting that pulling high currents can lead to voltage drops and potential damage to the battery.
  • Concerns are raised about safety when connecting devices to a car battery, emphasizing the risks associated with battery acid and potential explosions, suggesting that beginners should use current-limited power supplies instead.
  • One participant reiterates that the current from the battery is dependent on the load connected and mentions the amp-hour rating of the battery.

Areas of Agreement / Disagreement

Participants generally agree that the current output from a battery is dependent on the connected load, but there are differing views on the safety and appropriateness of connecting certain devices without further knowledge.

Contextual Notes

Participants mention factors such as internal resistance, temperature effects, and safety concerns, which may not be fully addressed or resolved in the discussion.

Who May Find This Useful

Individuals interested in electrical engineering, automotive technology, or those learning about battery systems may find this discussion relevant.

jearls74
Messages
53
Reaction score
1
im trying to figue out how much current comes from a 12 volt car battery? i know that the starter pulls atleast 200 amps so does that mean anything that is hooked to it will get a very high current ? what would happen if i hooked up a 15 amp 20 volt transistor to it? would it short out the transistor? I've search the internet and can't find anything that answers this question. any answers would be a big help. thanks
 
Engineering news on Phys.org
What you connect to the battery determines the current supplied by a battery.
Try reading up on ohms law.

Depends on how you hook the transitor up.
 
The limit for the current you can pull from a bettery depends on the internal resistance of the battery.
Picture it as a perfect 12V source with a series resistor inside.
Typical internal resistance for a lead acid battery is a few 10mR, so if you pull 200amps you will lose at least 2V across the internal resistor. Once you lose all 12V across the internal resistor you can't get any more current out and will damage the battery.

In reality it also depends on how quickly you take the current and for how long since the internal resistance depends on temperature andtaking current heats the battery.
 
No offense, but, maybe you should study the fundamentals before connecting anything to a battery. A car battery contains sulfuric acid which, if the battery should explode, could result in severe burns and even blindness. If one is in the learning stage, they should use current-limited bench top power supplies. I'm just looking out for you.
 
Jearls74, the current that comes form it is dependent on the consumer that you attach to it. That's why it says on it a number of Ah.
What would happen to the transistor would depend on the way you connect it.
 

Similar threads

  • · Replies 23 ·
Replies
23
Views
18K
  • · Replies 3 ·
Replies
3
Views
3K
  • · Replies 36 ·
2
Replies
36
Views
5K
  • · Replies 10 ·
Replies
10
Views
2K
  • · Replies 28 ·
Replies
28
Views
46K
Replies
22
Views
4K
  • · Replies 2 ·
Replies
2
Views
2K
Replies
3
Views
2K
  • · Replies 7 ·
Replies
7
Views
2K
Replies
1
Views
4K