How longCan you rest a fully charged LIPO battery before it goes bad?whyDoes a LiPo battery break?
Most people in the RC hobby know not to leave their LIPO batteries fully charged.LIPO batteries are very sensitive., they don't want to be discharged, charged or discharged too quickly, they don't want to sit still either fully discharged or fully charged.
In this article I want to take a look at why this is the case and see the various phenomena you may be familiar with from your LiPo batteries and why they occur.
ALi-Po-AkkuIt consists of one or more individual cells, which are usually connected in series. However, they can also be connected in parallel or in series and in parallel. In the quadrocopter hobby, you usually only find those that are connected in series with each other. I like4S und 6S, meaning they have4 or in the latter case 6 cells connected in seriesmutual
A single cell consists of an anode, a cathode (the positive and negative terminals of the battery), and a separator in between. These layers are very thin (less than 100 microns each). The three layers are rolled tightly around a core and then placed in an aluminum foil bag, usually made of thermoformed aluminum foil. This film is then laminated on three sides. After rolling, the packaged roll is dried under vacuum with complete exclusion of moisture. After drying, the electrolyte is injected and the cell sealed. The electrolyte allows ions to flow between the anode and cathode. At this point the cell is fully discharged and must be activated by initial charging; That canExpand cell by up to 10%.
If you want to learn more about chemical processes, I encourage you to do soArticle about LiPo batteriesIt explains everything in great detail.
Why does my LiPo battery smell sweet?
If your battery smells sweet, smell the electrolyte, it just smells sweet. This means that the seal of one or more cells is broken. shoulddispose of this battery safelyand no longer use under any circumstances.
Why do LiPos swell?
There are several reasons why a LiPo might swell, let's look at them in more detail.
If a LiPo battery is mishandled, such as being discharged above its C rating or being over-discharged, the electrolyte in the cell will begin to evaporate. This will happen over time even if you take good care of your batteries, but it will happen more quickly if you treat them poorly.
This process is calledelectrolyte depletion. As the electrolyte decomposes, the electrolyte becomesbreaks down into lithium and oxygenand oxygen is the main reason why the battery swells. Oxygen also makes a swollen battery dangerous as it burns easily and is difficult to extinguish once on fire as it oxygenates itself.
The decomposition of the electrolyte is also the reason that the internal resistance of the battery increases. The high internal resistance is the reason for the sag.
Another reason for swelling is contamination during cell assembly. The contaminant could be water or some other substance that could cause oxidation of the lithium in the cell.
A swollen battery doesn't automatically mean it will catch fire while charging, but the risk is definitely higher. A swollen battery is another reason not to charge unattended.
Depending on the extent of the swelling, I would recommend disposing of a swollen battery safely, or at least using it for low-discharge applications, but only in cases where it's not overly swollen.
Can I fix a swollen battery?
There are some articles and videos online that claim it can fix a swollen battery, howeveryou just can't.
It may sound harsh, thoughLiPo are consumablesIn the RC hobby, they can break in an accident, you can reach the limit of the cycle, or they can swell. Anything, in a momentyou will be dead- So is it worth risking a fire and burning down your house just to get a few more cycles out of an already dying battery? look at thatBloated liposuction gone wrong list.
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After all this preamble, I still haven't answered the questionhow long. Actually the answer is quite simple:as short as possible.
Leaving a fully charged LiPo will drain the battery and the battery will weaken and even swell over time. High temperatures make matters worse.A fully charged battery at room temperature loses about 20% of its capacity in a year. A battery loses 40% of its capacity in just 3 months at 60 degrees Celsius.
And it all adds up, the more times you leave your LiPo battery fully charged, the worse it gets. It's not something that shows up after a few days of battery dormancy, but it will eventually add up.
It is best to discharge batteries to storage voltage if you do not intend to use them for the next few days. When I come back from a session with fully charged batteries, I usually discharge them if I don't want to use them the next day.
Safe disposal of LiPo batteries
In order to dispose of your LiPo batteries safely, you must first discharge them completely. There are several ways to do this. I would like to take a closer look at two of them.
discharge with load
Probably the safest way is to discharge your LiPo with one charge. A 12V, 20W halogen bulb or taillight bulb will work fine for up to four cells. It discharges slowly and after a few hours your battery will be dead.
Check again with a multimeter if your battery is really empty. With more than 4 cells, you can simply connect another lamp in series.
If you want to go fancy, you can get one tooLiposuction Killer- This is a simple circuit that will discharge your LiPo battery for you. The good thing is that you can also use it to discharge your batteries to storage voltage.
discharge in salt water
Another possibility is discharge into salt water. Just fill a bucket with water, mix in salt, throw in your battery andlet it rest for a few days. This method is especially good when you need to discharge multiple batteries at once. After placing the batteries in the salt water, you should see bubbles coming out of the battery posts, indicating that they are discharging. Also with this method, use a multimeter to check if the batteries are dead.
After discharging them by your preferred method, take them to a battery recycling facility. They can often be found in supermarkets or electronic markets. Your local hobby store may also accept them.
Some interesting videos about LiPo manufacturing: