How to recharge a dead LiPo battery?

Released on Apr. 28, 2022

How to recharge a dead LiPo battery?

Lithium polymer batteries follow in the footsteps of their predecessors, lithium ion and lithium metal batteries. Since the 1980s, a great deal of research has been conducted in this area. It wasn't until 1991 that Sony released the first commercially available cylindrical lithium-ion battery. This was the starting point for what has been achieved in this field since then.

Can you recover lithium polymer batteries?

Lithium polymer batteries require care. They are charged using what is called the CC/CV system. This stands for Constant Current/Constant Voltage system. In this system, the charger will keep the current "charge rate" constant until it reaches the peak voltage of the battery, which is usually (4.2v per cell in the battery pack). After that, it will maintain that voltage, and in the process, it will reduce the previously constant current. This is the only safe way to charge LiPo batteries, which is why it is important to have a LiPo-compatible charger.

Most LiPo batteries require slow charging compared to NiMH or NiCd batteries. LiPo batteries with a capacity of 3000 mAh should be charged at a rate of no more than 3 amps. For most LiPo batteries on the market, the charge rate is 1C (C represents the capacity of the battery in amps).

So if you have a 1000 mAh battery, it will equal 1A, so the safe charge rate is 1C. for another 3000 mAh battery, the safe charge rate is 3C. for a 45000 mAh battery, the safe charge rate is 4.5C. etc.

That said, there are already batteries on the market today with fast charging capabilities. This means that a 5000 mAh battery can be charged at a rate of 3C (15 amps). The maximum charge rate is determined by the battery manufacturer.

Always remember that if the charge rate becomes very high or for any other reason, LiPo batteries can catch fire while charging. This is the way charging LiPo batteries should never be left unattended.

Sometimes, when you connect the charger to a LiPo battery, it is not recognized. This happens when you over-discharge a lithium polymer battery. An over-discharged Li-polymer battery is when the battery voltage drops below 3V. The recommended practice is to replace an over-discharged LiPo battery. However, you can salvage an over-discharged battery.

It is important to remember that the longer you leave an over-discharged battery; the higher its internal resistance. This means that saving it will be more difficult and dangerous.

That being said, unless you are an expert, replace an over-discharged LiPo battery.

How do I charge a fully discharged LiPo battery?

When a given LiPo battery is over discharged, it oxidizes the cells in it. This oxidation of the cells is what makes them perform very poorly. As we mentioned before, the longer you leave your LiPo battery in a discharged state, the worse it gets. However, if you catch the battery quickly enough, you may be able to rescue it without causing any major damage to it.

To salvage an over-discharged battery, you will need the following.

- LiPo balance charger.

- A charger that supports NiMH.

Steps to rescue a fully discharged LiPo battery.

- Connect the main plug of the LiPo battery to the NiMH charger.

- Charge the battery at the lowest possible current, e.g. 0.1A.

- Set the charging voltage to the closest to the battery's nominal voltage.

- While the battery is charging, pay attention to the voltage number that appears on the charger screen; disconnect the battery as soon as the number reaches 3V.

- Test the battery with a standard LiPo charger and you will find that the charger recognizes it. This means the battery is no longer at an over-discharge rate.

- After that, you can use a balanced LiPo charger to fully charge the battery.

Important safety advice.

- Never leave the battery unattended during any of the above steps.

- If the battery begins to expand or change its shape in any way, stop the process immediately.

- When charging lithium polymer batteries, do so in a well-ventilated, fireproof location

- If you check the battery and find that it cannot be balanced, remove it immediately. An unbalanceable lithium polymer battery is at risk of catching fire.

Can you discharge a lithium polymer battery before charging?

The short answer is yes, you can discharge your LiPo battery before charging. However, you need to make sure of the following.

- Never discharge your LiPo battery below 3V per cell. discharging your LiPo battery below this point will permanently damage your battery.

- Always discharge your LiPo battery in a safe, fireproof and well-ventilated location.

- Use the discharge function in a compatible charger to discharge your LiPo battery. Using a different charger may result in an explosion.

If you want to completely discharge your LiPo battery and render it completely useless, you can do so by immersing the battery in a salt water bath. Consider that this process takes a long time, usually a day or two. When you immerse the battery in a salt water bath, you will find that the battery is completely depleted after a day or two.

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