Lithium Polymer (LiPo) batteries are a newer type of rechargeable batteries that have become popular in modern consumer electronics and devices. They have also been widely used in the radio control industry in the last couple of years, and are now some of the superior choices for people looking for high power and long run times.
LiPo batteries have several benefits over conventional batteries, and drawbacks as well. As such, each user needs to decide whether the benefits outweigh their drawbacks, and for many people, they do. Nonetheless, there’s nothing to fear about LiPo batteries as long as you treat them with the care and respect they deserve, and follow the rules.
Charging your LiPo battery correctly, especially for the first time is critical to your safety, and the lifespan of the battery pack. The first and foremost thing is to make sure that you use a LiPo compatible charger for your LiPo battery. As we have seen in the intro, LiPo batteries need specialized care. They use a Constant Current/Constant Voltage (CC/CV) system for charging. In simpler terms, the charger maintains the same charge rate or current constant, until the battery has reached its peak voltage, which is 4.2v per cell. The voltage is then kept constant, while the current is reduced.
On the contrary, NiCd and NiMH batteries usually charge best with a pulse charging method. However, charging a LiPo battery this way could damage the pack, and that’s why it’s imperative to have a charger compatible with LiPo batteries. Another reason for using a LiPo compatible charger has to do with balancing. It’s a term used to describe the process of equalizing the voltage of every cell in the pack. Balancing ensures that every cell discharges at the same rate. This usually helps with the battery performance, and is crucial for safety reasons.
Although there are many different standalone balancers in the market, it’s smarter to buy a lipo battery charger that has built in balancing capabilities. This helps to simplify the process of balancing, and only requires you to purchase one less thing. The prices of balancing capable chargers are at very reasonable levels, so there’s ideally no reason why you wouldn’t want to simplify your charging setup.
Getting a good computerized charger that has a built-in balance circuitry also lets you confirm the correct cell count of your pack, and even alter the charge and balance the rates. When balancing in the charge cycle actually occurs, it ensures a safe charge/balance cycle that will easily extend the useful cycle of your LiPo pack.
In fact, this is one of the safest way to charge higher capacity multi-cell LiPo packs, and it even opens up new channels that allow for advanced charging methods such as via a multiple pack parallel charging.
Choosing the correct charge current is vital when charging a LiPo battery, and the general rule of thumb here is to never charge a LiPo (or even LiFe, or LiIon) pack more than 1 times its capacity. This means that if you have a 200 mAh pack, then it should be charged at a current of 2.0 Amps or 2000 mA. Using a higher current will shorten its lifespan, and if the charge rate is significantly higher than its capacity, the battery could heat up to a point of puffing up.
According to LiPo experts, you can safely charge quality packs at 2C or 3C, provided they have a discharge rating of at least 20C or more and low internal resistances. However, this will reduce the lifespan of your pack significantly. It all boils down to your budget, and speed vs lifespan. For those that don’t mind taking some life out of their LiPo packs and prefer getting back on the track or air ASAP, charging at higher C rates could be a convenient compromise to suit your needs. However, as a precaution, never charge over 1C when the ambient temperature is over 90F (30 degrees Celsius).
Since there’s always the potential of fire with LiPo batteries, despite the low likelihood, you should undertake certain precautions to stay safe. Even the best lipo battery will need to be handled with a lot of care. Always keep a fire extinguisher nearby; though it won’t put the LiPo fire out as it’s a chemical reaction, it will contain the fire to keep it from spreading. A CO2 extinguisher is recommended, as it will remove the oxygen from the site, and cold down the battery.
Since there’s always the potential of fire with LiPo batteries, despite the low likelihood, you should undertake certain precautions to stay safe. Always keep a fire extinguisher nearby; though it won’t put the LiPo fire out as it’s a chemical reaction, it will contain the fire to keep it from spreading. A CO2 extinguisher is recommended, as it will remove the oxygen from the site, and cold down the battery. Investing in a good lipo battery monitor and tester is always a good idea, and you would want to use only recommended connectors.
Also, never leave your battery unattended when charging it. You would always want to put the batteries inside a lipo battery bag while charging. If anything does go wrong, there might be no one around to react promptly should the battery catch fire. If you don’t have the time to sit around the charging station to keep a keen eye on your packs as they charge, installing an inexpensive smoke detector above your charging area and storage chest is a useful precaution. This ensures that you are alerted in the unlikely even a battery bursts while charging or in storage.