How to Restore Your Damaged Lithium Polymers Batteries' From Start

"Within the confines of their compact and unassuming frame, LiPo batteries harness a hidden power that propels innovation to soaring heights and electrifies our world with a discreet intensity." BUT If use unproperly they can be extremely dangerous.

It's always challenging for us RC hobbyists to manage our LiPOs. We generally don't have as much time to care for our batteries as we enjoy flying with planes, racing with fast cars, or diving underwater with our subs, and we end up in a scenario where our batteries are below the level of discharged or may be damaged during our fun-filled excitement.

Many people throw away their LiPOs Just because they think they are dangerous and now of no use to them, however, I don't. I restored them.

Supplies

To Restore your Old or damaged batteries you need the following or if you don't have the required supplies just follow the precautions as mentioned in this Instructables step by step.

A Smart Lithium Polymer Battery Charger.
Lipo Safe Charge Bags
Fire extinguishers ( OPTIONAL)
Battery Volt meter
A Safe place for charging

If you don't have a smart charger Here are some links for smart chargers -

http://electricrcaircraftguy.com/2013/02/thunder-ac680-computer-data-logging.html
http://www.hobbyking.com/hobbyking/store/uh_viewitem.asp?idproduct=7028&aff=281904
http://www.hobbyking.com/hobbyking/store/__216__408__Chargers_Accessories-Battery_Chargers.html

Step 1: Warnings & Cautions

Before we start off, you should be aware that LiPos are usually regarded as "unpredictable and "dangerous." This is due to the fact that overused LiPo batteries are known to occasionally catch fire, and some have burned down houses or cars, and a number of Radio Controlled airplanes have caught fire during crashes due to damaged LiPos.

LiPo batteries will not undergo combustion during a reasonable or gradual discharge, even if discharged completely to 0V per cell. The discharge phase itself does not pose a fire risk; it is the subsequent recharge phase that can lead to ignition. The reason behind this is that when a LiPo battery is brought below approximately 3.7V per cell, its internal resistance to accepting a charge begins to rise, with some of the increase being permanent.

Once the battery's voltage drops below approximately 3.0V per cell, the extent of the damage becomes significant enough to warrant concern. Recharging a LiPo battery below approximately 2.5V per cell is deemed too hazardous by most LiPo charger manufacturers. At this voltage level, the battery's internal resistance to charging has increased to a point where a standard recharge rate, such as 1C (1 time the battery's capacity), can generate potentially unsafe heat within the battery.

As the LiPo battery's voltage falls below approximately 2.0V per cell, the rate of permanent internal damage accelerates. This damage intensifies even further when the voltage drops below approximately 1.5V per cell, resulting in a greater permanent increase in internal resistance. The degradation process is non-linear and likely follows a power function or an exponential relationship with the battery's voltage. In any case, it is crucial to exercise extreme caution when dealing with such circumstances.

I have personally achieved the successful restoration of numerous batteries. Among the most severely discharged ones that I have continued to utilize, some had reached levels as low as approximately 1.0V per cell. Remarkably, I have even managed to recharge batteries that were as low as a few millivolts per cell, possibly around 10 millivolts per cell or 0.010V per cell. Nevertheless, these batteries proved to be ineffective as they quickly self-discharged back to approximately 0V per cell once removed from the charger.

Before proceeding, allow me to clarify the meaning of "restored" when referring to these LiPo batteries. By stating that I have "restored" them, I do not imply that I have repaired or reversed any damage they may have incurred. Additionally, I do not suggest that I have returned them to their original, pristine condition. Instead, what I mean is that I have merely recharged these batteries to a safe and functional level where they can continue to be utilized. That is the extent of the restoration process.

It is essential to be aware that the internal resistance of a battery increases as its voltage decreases, with a battery at 0.5V per cell having a significantly higher internal resistance compared to one at 1.0V per cell. Moreover, both of these cases exhibit higher internal resistances than a LiPo battery at 1.5V per cell. The relationship between voltage and internal resistance does not appear to follow a linear pattern.

It's crucial to note that high internal resistance is what contributes to heat buildup during the recharging process, which, if not carefully managed, can potentially lead to fires or other hazardous situations. Therefore, if you choose to undertake the restoration of over-discharged LiPo batteries, it is your responsibility to be fully aware of the risks involved and to exercise caution throughout the process.

Step 2: Using a Smart Charger for Charging

NOTE- It doesn't matter if you're using a smart charger and sitting on your couch watching your favorite TV show while the battery charges; it's important to realize that you must be attentive while charging these Lithium Batteries; you simply cannot leave them unattended.

You need to monitor them by touching them to ensure they do not get hot, and by sight touch to ensure they do not puff up (puffing is an indication of released gases due to internal heat build-up). For example, If you are restoring a 3-cell lipo the charge per cell will be almost 4.0V so try to check with your volt meter how much the volt per cell is in regular intervals.

If you think the battery getting hotter by a minute use a Lipo-safe bag to ensure the heat doesn't come out and if you don't have one try to stay away from it and use a fire extinguisher as well in case of emergency.

Step 3: Important Precautions While Charging

NOTE- That although some smart chargers can charge at currents as low as 0.05A, many cannot charge at a rate lower than 0.1A. If you cannot set your charger to charge at a current as low as you'd like, simply choose its lowest setting possible, and carefully monitor the battery during the charge.

To recharge a LiPo battery below 3.0V per cell, it may be necessary to utilize a NiMH or NiCad charger setting, as many smart chargers incorporate safety mechanisms that prevent charging LiPo batteries below 2.5V per cell due to the potential dangers associated with using a standard charge rate. Since the primary objective is to apply a low and safe constant charge current to raise the LiPo battery's voltage to a safe level, using a NiMH or NiCad setting is acceptable until the battery voltage exceeds 3.0V per cell.

However, it is crucial to never leave LiPo batteries unattended when using a NiMH or NiCad setting to bring the LiPos above 3.0V per cell. This caution arises from the fact that the end-of-charge detection method used for NiMH or NiCad batteries is not compatible with lithium-based batteries. If the LiPo battery is left on the charger until it reaches a full charge, the end-of-charge state will never be detected, leading to overcharging. Overcharging a LiPo battery can potentially result in a fire hazard, causing the battery to ignite and self-destruct.

Therefore, it is essential to exercise caution, closely monitor the charging process, and never leave LiPo batteries unattended when using a NiMH or NiCad setting, as the charging method is not specifically designed for LiPo batteries and lacks the necessary safeguards for their safe charging.

Step 4: Almost Done

Once the LiPo batteries have exceeded 3.0V per cell, there is an option to increase the charge rate to approximately 1/10 to 1/5 of the battery's capacity (C-rate) until they reach around 3.7V per cell or higher.

At this point, it is no longer necessary to constantly hold or monitor the battery's temperature. If desired, the LiPo battery can be placed inside a fireproof container or a LiPo-safe charge bag as an additional safety measure.

When the voltage of the LiPo batteries reaches the range of 3.7V to 4.2V per cell, there is an optional opportunity to further increase the charge rate to approximately 1/2 of the battery's capacity (C-rate) until the batteries are fully charged at 4.20V per cell.

Step 5: Using Our Lipo's

After recharging and restoring the LiPo batteries, they can be used as normal. However, it's important to note that the extent of permanent damage will vary based on how deeply the battery was discharged. If the battery functions properly when used, such as in flying an RC airplane, it is generally safe to assume that subsequent charges at 1C (1 time the battery's capacity) are acceptable.

It is advisable to closely monitor the battery over the next few charging and discharging cycles. Ensure that there are no signs of puffing during either the discharging or charging processes. Puffing can indicate that the internal resistance of the battery is still too high for normal use and standard 1C charge rates.

Nevertheless, due to the over-discharge experienced, it is possible to observe a permanent decrease in the battery's capacity (mAh) or maximum discharge rate. This may result in reduced power output and diminished overall performance, as the increased internal resistance of the battery leads to some irreversible damage. Furthermore, the longevity of the over-discharged LiPo battery, in terms of the number of cycles it can withstand, will likely be reduced.

Please remember to prioritize safety throughout this process, and let me know if you have any further questions or concerns. Stay safe!