Understanding LiPo Battery Cells

Despite their popularity, most people probably couldn’t tell you the difference between a traditional lithium-ion and a lithium-polymer battery cell. Batteries are one of the world’s most used items and are the heart of hundreds of millions of electronic devices. Although we know how to replace them, most consumers know very little about the various batteries. For some, how and what makes them work remains a mystery.

Lithium-polymer, otherwise called LiPo, batteries are a rechargeable battery type and is fairly common. They’re very similar to lithium-ion batteries except lithium-polymer batteries use a semisolid form of polymer electrolyte instead of a liquid electrolyte. The high conductivity of the polymer gel inside provides more energy than other lithium battery types. These types of batteries tend to be used in applications where weight is a factor. You can find these batteries in devices like cellphones, tablets, and even electric r/c airplanes for example.

Our goal here is to educate you on lithium-polymer batteries so that you know how to properly pick the correct battery size and how to safely use them. We’ll also cover how properly store LiPo batteries, and how to deal with potential configuration connection issues.

Size of LiPo Battery Cell

When it comes to sizes involving LiPo batteries, the size can vary greatly depending on their intended use. These batteries can range from a single-cell pack up to multi-cell packs used for large scale electronic devices. In order to understand LiPo battery sizing, you need to first understand voltage and capacity. You can think of voltage as the strength or power of the battery and capacity as the energy or stamina.

It’s important to know that every single LiPo battery cell has an output nominally of 3.7 volts. Despite this constant, the capacity of LiPo batteries can vary depending on the configuration of the connection. For LiPo batteries, there are two ways that you can configure them in order to increase their voltage or capacity. One method configures the batteries in series and the other method configures the batteries in parallel. Each method of configuration has its pros and cons.

To configure LiPo batteries in series you connect the top of one battery to the bottom of another and so on and so forth. For each battery that you continue to add to the battery chain, you increase output voltage by 3.7 volts. However, the capacity of the combined batteries is still 2100mAh, or the equivalent of a single LiPo battery cell. To increase the capacity you’ll want to connect the batteries so every single battery cell’s negative and positive leads have their own connection. These single-cell connections then all join at a central point, connecting all individual cells together. This method of configuration of battery cells is called parallel. Similar to voltage, capacity is determined by adding 2100mAh for every cell placed in parallel. The more battery cells in parallel, the higher the capacity output, however, this does not affect voltage.

Storage Methods of LiPo Battery Cell

We often use batteries until they are dead and recharge them, if rechargeable. If batteries are incapable of recharging they end up in the trash or recycle bin. For rechargeable LiPo batteries, once they die, they should not be left in this state. If you plan on storing LiPo batteries, you don’t want to store them when they are fully charged. Storing them fully discharged just as bad as well. To get the longest life out of the battery, store them at room temperature and at 3.8 volts per battery cell. The batteries have a storage function to help extend the battery life. Modern chargers are capable of charging or discharging batteries to meet the 3.8-volt storage requirement.

Anytime that you are not going to use the batteries for an extended time, you should place the batteries in storage mode. The best way to extend battery life is by using the LiPo battery storage function after each use. You can create good habits for maintaining your batteries this way. Although it is rare, you can damage your LiPo batteries by storing them fully charged. This can happen in as little as a week’s worth of time. Again to drive the point home, proper storage of LiPo batteries is essential to extending the battery’s life.

Dealing With LiPo Battery Cell Connection Errors

LiPo batteries are capable of incredible amounts of power, however, having a bad connector or bad connections can drastically lower the battery’s effectiveness. By having bad connectors you can increase the resistance. if this happens you can prevent all the battery’s power from being used efficiently. There are many different types and style of connectors from numerous different vendors on the market.

LiPo battery connectors are only as good as the connections between each battery cell. If there is a problem with one of your cells, your entire battery configuration can fail. There are a few ways to check to make sure that all your LiPo battery cells are working properly. After all, just because the battery pack may be new does not mean it was connected properly.

If your LiPo shows signs of damage or swelling, you should place the battery in a safe area and contact the seller. Most often they will happily replace the battery pack for you. Low voltage is another problem you may encounter. If purchasing a battery pack, all LiPo batteries should not be more than .03 volts off from one another or from approx. 3.85-volts. If a battery cell falls below this range, it has a flaw. The lower voltage is a result of a tiny short between the plates that bleed off voltage slowly. Even if you recharge the flawed cell to appropriate levels the pack will never be as good as a balanced and properly charged battery pack.

If you are having issues with connections in your LiPo battery pack, there are steps you can take to try to remedy the problem. The first thing to do is to physically check the battery for loose wires, puffed cells, and damaged packaging. Next, with a multimeter, check the battery and individual cell voltages. If the cells don’t add up then you know its a cell problem and if they do then you know its a problem at the charging connector. Otherwise, if everything checks out but you still are having issues, it may require more investigation or a new battery pack.