Charging a car battery question.

In summary, when jump starting a car battery, it is important to first connect the positive terminals of the good and bad batteries, and then connect the negative of the good battery to a solid metallic part of the bad car's engine or body frame. This creates a closed circuit and allows the flow of electricity from the good battery to the bad battery. It is important to ground the negative of the bad battery to avoid sparks and potential hazards from hydrogen gas bubbles produced during charging. Additionally, connecting to a substantial piece of metal on the engine can provide a more efficient flow of current.
  • #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?"
 
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  • #2
Yes, the negative is grounded just as you said.
 
  • #3
marcusl said:
Yes, the negative is grounded just as you said.

Thank you for the quick reply. My mind is now at ease.
 
  • #4
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
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
Thank you.
 
  • #7
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..
 

1. How long does it take to charge a car battery?

The time it takes to charge a car battery depends on several factors, including the size and type of battery, the level of charge when you start, and the charging method used. On average, it can take anywhere from 4-24 hours to fully charge a car battery.

2. Can I charge a car battery while the engine is running?

No, it is not recommended to charge a car battery while the engine is running. This can cause damage to the battery and other electrical components in the vehicle.

3. Can I use a regular household outlet to charge my car battery?

No, most car batteries require a higher voltage than a regular household outlet can provide. It is recommended to use a dedicated car battery charger or a jump starter with a built-in charging function.

4. How do I know when my car battery is fully charged?

You can use a battery charger with a built-in voltage meter to monitor the charge level. Once the voltage reaches the recommended level for a full charge, the battery is fully charged. You can also use a multimeter to measure the voltage directly on the battery terminals.

5. Can I overcharge my car battery?

Yes, it is possible to overcharge a car battery, which can lead to damage and reduce its lifespan. It is important to follow the recommended charging time and voltage for your specific battery to avoid overcharging.

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