Keep all sources of flame or sparks well away from the battery. The battery produces hydrogen gas, which can explode if exposed to flame or spark. Do not attempt to start the engine if the discharged battery is frozen or if the electrolyte level is low, the battery may rupture or explode.
Sequence of starting the engine from the battery of another car:
1. Make sure the booster battery has 12V and that its negative terminal is grounded.
2. Check the electrolyte level in each cell of the battery.
3. If the booster battery is in another vehicle, do not allow the vehicles to touch.
This article is based on information from the website [hyundaibook.ru]
4. Turn off all unnecessary electrical consumers.
5. Connect all cables in the exact sequence shown in Fig. 120. First connect one end of a cable to the positive (+) terminal of the discharged battery, then the other end of the same cable to the positive (+) terminal of the booster battery. Next connect one end of the second cable to the negative (–) terminal of the booster battery, and then the other end to a solid, stationary metal point (such as an engine mount) other than the battery. Do not connect the cable to or near moving parts, as they may be damaged during starting. Do not connect the cable from the negative (–) terminal of the booster battery to the negative (–) terminal of the discharged battery. Do not allow the cables to touch anything except the corresponding battery terminals or a proper ground. Do not lean over the battery when connecting the cables.
The sequence of connecting cables when starting the engine from the battery of another car.
6. Start the car engine with the booster battery and let it run at 2000 rpm⁻¹. Then start the car engine with the discharged battery.
If the cause of your battery discharge is not obvious, such as the headlights being left on accidentally, you should have your vehicle inspected by an authorized Hyundai dealer.