How to charge a car battery with a laptop power supply

If you need to charge a car battery, but the charger is not at hand, then a laptop power supply can easily replace it. Typically, such units produce 18-19 Volts with a maximum load of 3-4 Amperes. This will be enough for us to “refresh” or fully charge the battery.

Will need

Alligator clips (You can do without them by making loops from wire).
55 W halogen lamp (If you don’t have one, you can take two 21 W lamps and connect them in parallel).
Wires with a cross-section of at least 1.5 sq. mm.
Multimeter.
Laptop power supply.

We charge the battery with a laptop unit

The battery is standard 12V, 60 A/h. We measure the initial voltage on the battery.

About 8 Volts, which means a deep, even complete discharge. To facilitate the release of gas, unscrew all filler plugs.
We take a halogen lamp and screw the wires to its contacts.

We find the plus and minus in the contacts of the block from the laptop. We connect the source to the battery, and turn on a halogen incandescent lamp in the gap. It will play the role of a quenching resistor.

We connect the block to the network. We check the charging process with a multimeter.

Charging is proceeding correctly, the battery has begun to gain charge.
We translate multimeter into the current measurement and connect it to the open circuit.

The charging current was more than 2 amperes. Which, in turn, is not enough for the capacity of such a battery, so you will have to increase the charging time.
After a day, the current decreased. We check the density of the charged battery using a hydrometer.

The electrolyte density is completely normal. The battery is fully charged, as indicated by a voltage of 14.4 Volts. Disconnect the homemade charger. Screw in the plugs of the filler neck compartments.

Conclusion

The battery was fully charged after one day. The power supply from a laptop can be used not only as a temporary charger, but also as a permanent one.
So taking your laptop with you on trips is a great idea.