can you charge a car battery using both terminals

[HectorFitz]

Yes, you can and should connect jumper cables to both terminals when charging a car battery, but the sequence of connections is critical for safety. The correct order is designed to minimize the risk of a dangerous spark near the battery, which can emit explosive hydrogen gas.

The safe procedure is to connect the cables in this specific sequence:

1. Connect the positive (+) red clamp to the dead battery's positive terminal.
2. Connect the other positive (+) red clamp to the good battery's positive terminal.
3. Connect the negative (-) black clamp to the good battery's negative terminal.
4. Connect the final negative (-) black clamp to an unpainted metal surface on the dead car's engine block or chassis, not to the dead battery's negative terminal.

This final step grounds the circuit away from the battery, preventing a spark from igniting any gas. Once connected, start the car with the good battery, let it run for a few minutes, then attempt to start the dead car. Disconnect the cables in the reverse order.

The following table outlines the risks and correct procedures based on industry standards from sources like the National Highway Traffic Safety Administration (NHTSA).

Risk/Factor	Incorrect Method (Connecting to Neg Terminal)	Correct Method (Grounding to Chassis)
Primary Hazard	Spark ignites hydrogen gas, causing battery explosion.	Spark occurs away from battery, eliminating explosion risk.
Battery Damage Risk	High risk of damaging the battery and vehicle's electrical system.	Significantly lower risk of damage to electronic components.
Standard Procedure	Not recommended by any major automotive authority.	Officially recommended by AAA, JDP, and vehicle manufacturers.
Safety Priority	Focuses on convenience, compromising safety.	Prioritizes operator and vehicle safety above all else.
Ease of Reversal	Common mistake, especially for those in a hurry.	Requires a moment of extra thought but becomes habit with practice.

[VonGabriela]

Look, I've been tinkering with cars for decades. The rule is simple: always hook up the positives first. Then, for the negatives, you clamp the good battery's negative, but for the dead car, you find a bare metal bolt on the engine. That last connection will spark, and you don't want that spark anywhere near the battery itself. It’s a one-minute job that can go wrong in a second if you get lazy. Just find a solid piece of unpainted metal; it’s your safest bet.

[McAddyson]

Safety is the absolute priority here. While you are connecting to both terminals in the sense of completing the circuit, the final negative connection must be made to the car's chassis, not the battery's negative post. This is because a lead-acid battery releases flammable hydrogen gas, especially when depleted or being charged. A single spark from connecting the clamp directly to the terminal can cause a severe explosion. Grounding to the chassis safely dissipates any spark away from the battery, protecting you from acid and shrapnel.

[HarrisonRose]

For a DIYer, it's all about making a solid connection without the boom. You're creating a giant circuit. Positives to positives, that's straightforward. The key is the last black clamp. Don't just attach it to the dead battery's negative. Scout around for a good grounding point—a sturdy bracket, a clean bolt on the engine block, anything unpainted and metal. You'll see a spark when you clamp it, and that's fine; it's just happening far from the battery gases. It’s a small step that makes a huge difference in doing the job safely and correctly.

[TylerLee]

Yes, but be very careful. Connect the red clips to the positive terminals on both batteries. Then, connect one black clip to the good battery's negative terminal. For the last black clip, attach it to a shiny metal part of the dead car's engine, not the battery. This keeps any sparks away from the battery. After the dead car starts, disconnect the cables in the exact opposite order. It’s not hard, but doing it right prevents a scary and dangerous accident.