can a battery charge power a car

[LeTheo]

Yes, a typical 12-volt car battery cannot "charge" a car by itself, but a portable jump starter or power station can use its stored energy to jump-start a car with a dead battery. These devices are essentially high-capacity, powerful batteries designed to deliver the large burst of current (measured in cold cranking amps, or CCA) needed to turn the engine over. However, they are not meant for recharging a completely dead battery; their primary function is to provide enough power to start the engine, after which the car's alternator takes over to recharge the battery while driving.

For electric vehicles (EVs), the term "charge" is different. You cannot use a small portable power station to significantly recharge a depleted EV battery due to the massive energy capacity required. An EV's battery pack is measured in kilowatt-hours (kWh), far exceeding the capacity of even the largest consumer power stations. The only practical way to recharge an EV is through a dedicated EV charger (Level 1, Level 2, or DC fast charger) connected to the electrical grid or a large stationary power source.

The following table compares the energy capabilities of different power sources versus what's needed to start or charge a car:

Power Source	Typical Capacity	Primary Function for a Car	Feasibility & Notes
Standard Car Battery	40-60 Ah (Amp-hours)	Start the engine, power electronics	Cannot charge itself or another battery.
Portable Jump Starter	10,000-30,000 mAh	Jump-start a car with a dead battery	Effective for starting. Provides a high-amp jolt.
Large Power Station	1-2 kWh	Jump-start, potentially slow 12V charge	Can start a car and may slowly recharge a 12V battery over hours.
EV Battery Pack	60-200 kWh	Propel the vehicle	A small power station cannot meaningfully recharge an EV.
Level 2 EV Charger	Connected to Grid	Recharge an EV battery	Standard method, delivering 6-12 kW to fully recharge an EV in hours.

In summary, while you can't use a standard car battery to charge another car, dedicated battery-powered devices are excellent emergency tools for starting a combustion engine car. For electric vehicles, recharging requires a much more substantial power supply.

[OAlan]

Absolutely, but only for a jump-start, not a full recharge. I keep a compact lithium jump starter in my glove box. It's saved me twice when my old sedan's battery died in a cold parking lot. You just connect the clamps, wait a minute for it to transfer some juice, and turn the key. It’s not about charging the dead battery; it’s about giving it just enough life to start the engine. Once the car is running, the alternator does the actual charging as you drive.

[Sousa]

Technically, a larger battery can transfer energy to a smaller or depleted one, but it's inefficient and not recommended for a standard car battery. The primary goal is starting the engine, not recharging. A portable jump starter is designed specifically for this task—it delivers a controlled, high-current burst to crank the engine. After a successful jump-start, you must drive the vehicle for a substantial time (at least 30 minutes) to allow the alternator to properly recharge the battery. Relying on another car's battery alone is a temporary fix.