18650 Battery Charger

The car has no charging circuit in it. The cells come out of the holder and go into a charger, and that charger is what stops them at 4.2V before they become a problem.

What a proper Li-ion charger does

It charges at a constant current until the cell reaches 4.2V, then holds 4.2V while the current tails off, then stops. That last part — stopping — is the whole reason you cannot use a generic supply. A lithium cell held above 4.2V does not simply refuse the extra charge; it degrades, then it vents.

A dual-bay charger has one of these circuits per slot, so the two cells charge independently and it does not matter that one is flatter than the other.

Reading the lights

• Red — charging.
• Green or blue — done. Colours vary between makes; the only thing that is consistent is that the colour changes.
• Light never changes, or flickers between the two — the cell is not making contact, or it is too flat to start, or it is dead.

How long it takes

Most of these chargers push about 500 mA per slot, so a flat 2000 mAh cell takes somewhere around four to five hours, and a 3000 mAh cell more like six. A charge that finishes in under an hour means the cell was not flat, or the charger is not really doing constant-current charging.

Charging habits worth having

• Charge on a hard, non-flammable surface. Not on the sofa, not on a bed, not on paper.
• Do not leave it charging overnight or while the house is empty.
• Unplug the charger when it is finished. Many of them keep trickling.
• Charge the pair together so they stay at a similar state of charge. Cells in series drain as a pair and behave best when they are matched.
• For long storage, leave the cells at about half charge rather than full or empty.

Every part of the car

Arduino Uno R3: pins, power and limits Brain L298N motor driver for an Arduino car Motion HC-06 Bluetooth module for Arduino Control Chassis, Wheels and Gear Motors Motion Buzzer Sound 18650 Lithium-Ion Batteries Power 18650 Battery Holder Power 18650 Battery Charger You are here Jumper Wires and Circuit Wire Wiring Transparent Enclosure Box Housing