Tips on extending the lifespan of your LiPo battery
Although LiPo batteries will inevitably deteriorate to a point where they can no longer be used, there are a couple of things that you can do to delay their expiration. The following are some of the best practices for the handling, charging, and storage of LiPo batteries that can prolong their lifespan.
1. Store in a cool place
A LiPo battery continues to age and deteriorate even while it is kept in storage. However, the deterioration process becomes accelerated when the battery is kept in high temperatures. A study showed that the capacity of a LiPo battery kept at 60 degrees C for 3 months has declined to only about 75% of its original capacity. Another battery held for a similar period at 25 degrees C also deteriorated but to a much less degree: it was able to retain 96% of its original capacity. It is even possible to store LiPo batteries in near-freezing temperatures, and this has been shown to preserve its capacity better.
2. Store at about 40% to 50% battery capacity
In a study comparing how batteries stored at different capacities behaved in terms of deterioration, it was shown that storing at around 40% capacity only resulted in about 4% capacity loss after 1 year of storage. Another battery stored in similar conditions but was fully-charged deteriorated by as much as 20%. At its fully charged state, the accumulation of ions in the anode leads to the faster accumulation of the restrictive SEI layer.
On the flip side, storing a battery that is completely drained runs the risk of the battery’s protective circuit failing. This means that a battery that goes into a “deep discharge” state might not be able to hold a charge at all.
As a rule of thumb, it is best to store LiPo batteries at 3.6 V to 3.8 V. This is applicable for standard LiPo batteries that hold 4.2 V per cell when fully charged. Charging a LiPo battery to full capacity should be fine as long as you use or discharge it within 2 or 3 days.
3. Do not over-charge or over-discharge
Another big no-no for LiPo batteries is leaving them plugged in even when they are already fully charged. This will lead to “trickle charging,” or the process where the battery recharges with the smallest drop in battery voltage. Aside from accelerating the deterioration of the battery, leaving it plugged in also tends to result in overheating. As we have mentioned, heat is a major weakness of LiPo batteries.
It is also not a good idea to use a LiPo battery until it is completely empty. For a 4.2V LiPo battery, discharging to 3.0 V is discouraged. By letting a battery go into “deep discharge”, you are allowing some of the anode material to dissolve into the electrolyte solution. Typically, batteries have built-in voltage thresholds that prevent it from going into deep discharge. However, a drained battery that is stored for a long time will continue to discharge and can go below the threshold voltage value.
4. Use only official chargers
If you stumble upon a deal that offers $5 chargers for your LiPo battery, chances are you’ll end up spending more on replacing those batteries soon. Cheap chargers may not be rated for your specific battery model which may result in overcharging or overheating your LiPo battery.
Multi-cell LiPo batteries are especially prone to getting unbalanced when using cheap chargers. An unbalanced LiPo battery has cells that have different voltage values and therefore provides power at uneven rates. This means that individual cells can easily get over-charged or over-discharged. In fact, an unbalanced LiPo battery can be very dangerous and will probably need to be disposed of.
If you care about keeping your LiPo batteries safe and functional, then you need to invest in a high-quality balancing charger.
How long can I expect my LiPo battery to last?
Most LiPo batteries are not rated to last longer than 300 charge cycles. A whole charge cycle in this context is defined as a full battery being drained to empty and charged to full capacity again. However, measuring a LiPo battery’s lifespan may not be practical, as batteries go through varying depths of discharge when they are used.
Many manufacturers have stated that their LiPo batteries will last 2 or 3 years. This is a somewhat realistic approximation for a scenario where a battery is regularly used and charged around 2 or 3 times a week. However, battery replacement based on a date stamp might not apply to all scenarios, as it does not take into account the level of usage.
In any case, a LiPo battery is considered to start “aging” the first day that it is activated. This is applicable whether the battery is under regular use or is stored for a more extended period. How a LiPo battery’s performance deteriorates during storage is determined by its storage conditions, as we shall cover in more detail later.
In conclusion, a realistic approximation of a LiPo battery’s lifespan should consider both its number of charge cycles and its age. In any case, a LiPo battery is deemed to be past its useful lifespan when its capacity has declined to about 80% of its original capacity.
20°C/68°F is considered a normal ambient temperature. If the temperature of the environment rises above this value, battery lifespan will decrease.
What happens when a LiPo battery is past its lifespan?
Fortunately, a LiPo battery does not necessarily undergo catastrophic failure when it is past its lifespan. As mentioned, a LiPo battery that can only hold 80% of its original capacity is considered past its prime. This is an irreversible process, so this battery will just continue to deteriorate until it can no longer hold a charge.
Realistically speaking, an old LiPo battery will probably show signs of swelling or puffing as it nears its expiration point. Swelling of LiPo batteries happens due to the gas generated by the decomposition of the battery’s electrolytic solution. Aside from having significantly reduced performance, a swollen LiPo battery also has a much higher chance of catching fire when it overheats. Thus, you probably will not want to wait until a LiPo battery can no longer hold a charge – it becomes dangerous to continue using it before it reaches this point.
How can I tell when a battery no longer works?