How to Fix a Dead 18650 Battery? 3 Useful Methods

Lithium-ion 18650 batteries are extremely common these days. You’ll find them powering everything from laptops and power tools to electric vehicles and energy storage systems.

However, these batteries don’t last forever. After hundreds or even thousands of charge/discharge cycles, they eventually wear out.

You might think that a “dead” 18650 battery is useless and ready for recycling. But in some cases, it may be possible to bring an 18650 battery back from the dead.

In this post, as a professional 18650 battery pack manufacturer, I will share 3 useful methods for fixing a dead 18650 battery.

What Makes an 18650 Battery Die?

First, let’s take a quick look at the reasons why an 18650 might fail in the first place. That way, you’ll know what to look for when trying to revive one.

The most common causes of 18650 battery failure include:

• Over-discharging – Discharging a lithium-ion battery below 2.5 volts can damage the cathode material. This is why protected 18650 cells have built-in protection circuits to disconnect the battery when voltage gets too low.
• Internal short circuit – Defects in the separator material can allow the cathode and anode to make contact. This leads to a rapid loss of energy and overheating.
• Dendrite formation – Tiny metal filaments (dendrites) grow through the separator over time, eventually causing an internal short. This process accelerates at higher temperatures.
• Chemical breakdown – The electrolyte and cathode materials slowly degrade during repeated charge/discharge cycles and exposure to high temperatures. After hundreds of cycles, the battery’s capacity fades.

Any of those failure mechanisms can render a lithium-ion battery unusable. Fortunately, the built-in protection circuits of protected cells minimize catastrophic failures. However, after sitting unused for months or years, an 18650 may be “dead” due to over-discharge or dendrites.

How to Fix a Dead 18650 Battery?

Method #1: Use a Charger with Recovery Mode

The easiest way to attempt to revive a dead lithium-ion battery is to use an intelligent battery charger with a dedicated “battery recovery” mode.

These advanced chargers, like the LiitoKala Lii-500, can apply a very small current to an over-discharged battery. If the voltage responds and climbs above 2.5-3.0 volts, indicating the protection circuit has reset, the charger will resume normal charging.

Battery recovery process:

1. Connect the seemingly “dead” 18650 battery to the charger.
2. Select the battery recovery mode, if available. Or choose lithium-ion battery with the correct nominal voltage (3.6/3.7v).
3. Set the charge current to around 0.1-0.5 amps, or whatever the lowest current setting is.
4. Closely monitor the battery voltage and temperature as current is applied. Stop charging if you observe abnormal behavior.
5. Continue charging slowly until the battery voltage exceeds the cut-off threshold (around 2.5-3.0v). If successful, the protection circuit will reset.
6. The charger will now detect a viable battery and resume normal CC/CV charging to 4.2v.

Not all “dead” batteries can be recovered this way. If there’s a hard internal short or severe cathode damage, the cell is likely too far gone. A very slow charge rate minimizes risks while attempting to revive a deeply discharged 18650.

While convenient, not everyone has access to a charger with this specialized recovery feature. DIYers can also build their own recovery circuits to wake “sleeping” batteries.

Method #2: Use a Power Supply with Current Limiting

With some basic electronics supplies, you can rig up a simple 18650 recovery station:

Supplies needed:

• Adjustable DC power supply
• Alligator clip test leads
• 18650 battery holder
• Multimeter

Follow these steps to revive an apparently dead battery:

1. Set the power supply voltage between 3-4.5 volts. This keeps things below the maximum charge voltage of 4.2v.
2. Set the current limit as low as possible, around 50-100mA. Some power supplies may only allow adjusting in larger increments, e.g. 0.5A.
3. Carefully monitor the battery voltage and temperature as current starts flowing. Watch for swelling, smoke, sparks or extreme heat. Immediately stop the process if there are any concerning observations.
4. If the battery voltage begins climbing above 0v, continue charging slowly up to a maximum of 4.2v. Reduce current if temperature rises.
5. When voltage exceeds 2.5-3.0v, indicating the protection circuit has reset, you can attempt normal charging. But there may still be some internal damage.

Essentially, you’re just trying to “jump start” the dead 18650 battery by applying a tiny trickle current. This small jolt of energy may be enough to get a battery voltage response. But extreme caution is necessary, given the risk of short circuits and overheating.

For the best chance of success, start revival efforts soon after the apparent failure. Leaving batteries sit at very low voltages for weeks or months makes recovery much less likely. Still, with some patience and careful observation, there’s a possibility of bringing dead cells back to life.

Method #3: “Shock” the Protection Circuit

In some cases, protected li-ion batteries appear dead due to tripped protection circuits, not because the cells are physically damaged. A sharp mechanical “shock” to the positive terminal can sometimes reset the circuit:

Supplies needed:

• Insulated pliers
• Non-conductive stick or rod
• Multimeter

To attempt a reset:

1. Use the pliers to grip the positive (+) end of the 18650 battery. Avoid contacting the body of the cell.
2. With light force, use the non-conductive stick to quickly press on the small indentation near the center of the (+) terminal.
3. Check if battery voltage has been restored with a multimeter. If successful, proceed with careful charging.

By pressing on the protection circuit “button”, you may be able to re-close the electrical connection inside a protected li-ion battery. However, this method has risks:

• Repeated protection circuit triggers indicate something is wrong internally. So while you can reset it, that battery is probably damaged.
• Forcing the positive contact could bend it or break internal welds. This could expose fresh lithium metal to air, creating a dangerous situation.
• Applying too much mechanical shock can rupture the thin battery wrapper, again allowing moisture infiltration.

Tread carefully if attempting a protection circuit reset. Thoroughly check for damage afterward. And don’t expect revived batteries to have normal capacity or lifespan at this point.

Disposal of Unrecoverable Cells

If the above revival methods don’t show promising results, it’s best to retire those batteries to prevent unsafe conditions:

• Remove any protective case sleeve, and wrap bare cells in electrical tape or duct tape
• Place taped cells in a fireproof lipo safety bag or metal container
• Follow regional laws and guidelines regarding lithium battery disposal
• DO NOT throw dead li-ion cells in the normal trash

Even if they won’t take a charge, dead lithium cells still contain reactive cathode and anode materials. These can get extremely hot and even catch fire if crushed or punctured. Treat end-of-life batteries as hazardous materials.

Most areas have recycling programs to handle consumer electronics and batteries. Proper disposal keeps those reactive materials out of landfills and waterways.

While it takes some effort, reviving a dead 18650 isn’t impossible. Just be sure to take the proper safety precautions. And don’t try to push a battery too far beyond its limits. With responsible handling and realistic expectations, you may be able to squeeze a bit more life out of retired li-ion cells headed for the recycling bin.