Charging a car battery question.

  • #1
perplexabot
Gold Member
329
5
Hey. Was jump starting and charging a car battery a couple of days ago for the first time. I connected the positive of the bad battery to the positive of the good battery, then connected the negative of the good battery to a solid metallic, non-painted part of the engine on the bad car, or the body frame.

My question is: How is this a closed circuit? Is the negative terminal of the bad car's battery connected to its "solid metallic parts/body frame?"
 

Answers and Replies

  • #2
marcusl
Science Advisor
Gold Member
2,768
418
Yes, the negative is grounded just as you said.
 
  • #3
perplexabot
Gold Member
329
5
Yes, the negative is grounded just as you said.

Thank you for the quick reply. My mind is now at ease.
 
  • #4
perplexabot
Gold Member
329
5
Ok now a follow up question if you don't mind. Why then not connect the good battery's negative directly to the bad battery's negative?
 
  • #5
marcusl
Science Advisor
Gold Member
2,768
418
Batteries produce hydrogen gas bubbles as they charge, and this can be vigorous for a fully discharged battery. Connecting to chassis ground keeps any sparks away from the battery and flammable gas.
 
Last edited:
  • #6
perplexabot
Gold Member
329
5
Thank you.
 
  • #7
jim hardy
Science Advisor
Gold Member
Dearly Missed
9,847
4,883
Follow your battery wires.
Most GM cars have a positive post near the battery for jump-starting. It'll be underneath a red plastic pop-up cover.
Sure easier than trying to grab that battery side-post terminal, and safer too as marcusi pointed out.

I like to connect negative to a substabntial piece of metal on the engine. I figure starter is bolted to engine block, so starter's heavy current doesn't have to flow through a potentially weak frame wire on its way back to my jumping battery's negative..
 

Related Threads on Charging a car battery question.

  • Last Post
4
Replies
77
Views
5K
Replies
21
Views
2K
Replies
1
Views
2K
  • Last Post
Replies
4
Views
2K
  • Last Post
Replies
10
Views
4K
  • Last Post
Replies
13
Views
12K
  • Last Post
Replies
3
Views
2K
  • Last Post
Replies
1
Views
1K
  • Last Post
Replies
8
Views
1K
  • Last Post
Replies
4
Views
1K
Top