Within the hobby community, the two most common batteries used for remote controlled planes, drones and cars are NiMH (nickel-metal hydride) and LiPo (lithium-ion polymer). While NiMH batteries were the industry mainstay for a long time, developments in battery technology over the past few decades have led to a dramatic increase in the popularity and affordability of LiPo batteries.
While LiPo batteries offer a range of benefits over NiMH batteries, they do come with some significant downsides, which are important to consider if you’re thinking about upgrading your batteries. So let’s have a look at some of the pros and cons of LiPo batteries.
So, here it is: LiPo batteries deliver much more power and a longer charge than other batteries, while being significantly lighter. All these factors are hugely important for RC enthusiasts.
LiPo batteries have significantly higher energy density, up to 3-4 times higher, than other commonly used batteries like NiMH and nickel-cadmium. Energy density refers to the amount of energy that can be stored in a given system, in this case, a battery. It’s often measured as the amount of energy it contains in proportion to its weight. Of course, battery weight is an important consideration for RC vehicles, especially RC planes. Ideally, you want the lightest possible battery containing the highest energy density.
Lightweight and compact
LiPos are the most lightweight and compact battery option. They don’t take up a significant amount of space in the RC vehicle or weigh it down unnecessarily. They are also pliable and versatile and are available in a range of sizes and shapes to suit specific types of RC planes, cars or drones.
A single LiPo battery can have three times the voltage of similar NiMH and nickel-cadmium batteries. This means that LiPo batteries can carry a significantly higher power while weighing much less than other batteries, which is particularly beneficial for RC planes or drones.
Higher voltage batteries should also have a higher discharge rate making them appropriate for equipment that requires a large power output within a short window of time, like high powered RC cars or planes.
No memory effect
Repeated charging and discharging of batteries can reduce their capacity over time. This is known as the memory effect. When properly charged, discharged and stored, LiPo batteries experience no discharge effect meaning that they maintain their capacity and peak performance over the life of the battery.
Despite the many benefits of LiPo batteries, they also come with some serious downsides.
Shorter cycle life
Cycle life is the number of charge and discharge cycles that a battery can perform before starting to see a measurable dip in performance. Under optimal conditions, LiPo batteries can reach around 500 charge and discharge cycles. NiMH batteries, on the other hand, can generate up to 1,000 cycles.
Can be dangerous
If not properly handled, LiPos can be much more dangerous than other batteries. Their sensitive battery chemistry means that they can cause fires if punctured, improperly charged or stored.
LiPo batteries contain lithium, which can react with water and combust. When heated, lithium can also react with oxygen and combusts. So if punctured or overheated, a chemical reaction can take place causing the battery to catch fire.
Over time, lithium-oxide (basically lithium rust) can build up inside the battery. This can increase battery resistance, causing the battery to heat up during use. The increased heat can lead to more oxygen building up, causing the LiPo pack to start swelling. This is a clear sign that the battery has reached the end of its life. Never use a LiPo battery that has been damaged or is bloated or swollen.
Requires care when charging and discharging
Over-charging or discharging can damage LiPo batteries and render them inoperable. They require specific LiPo-compatible chargers. These chargers keep the current, or charge rate, constant until the battery reaches its peak voltage. They also balance the battery. Balancing equalises the voltage of each cell in a battery pack to ensure that they discharge at the same rate.
Discharging a LiPo below the optimal voltage can also permanently degrade the battery. This means that you need to use a low voltage cutoff on your speed controller. This ensures that the system will cut out once the battery reaches its low voltage cutoff. Using the battery below this cutoff will discharge below its safety point and do permanent damage.
Requires careful storage
With NiMH batteries you can just throw them on the shelf, charged or discharged, once you’re finished using them. However, LiPo batteries should never be stored charged or discharged. Instead, they need to be charged to what is known as “storage mode”. Storage mode ensures that all battery cells are balanced and charged to the appropriate storage voltage to minimise the risk of damage to the battery. Failing to properly store the battery means that it can leak charge while not in use and if it falls below its voltage safety point it can be permanently damaged.
While it’s rare, LiPos can also combust if improperly stored. To mitigate this risk, however unlikely, storing them in a fireproof bag or box is recommended.
Finally, as newer and more delicate technology, LiPo batteries are significantly more expensive than NiMH batteries. Their cost, combined with the care required when charging or storing them, means that they are not recommended for amateur hobbyists.
Besides the battery itself, you may also need to pay a little extra for an appropriate LiPo-compatible charger and a speed controller with a low voltage cutoff, if you don’t have one already.
LiPo batteries are a no-brainer if you’re looking for a powerful battery with a long run time, which is something all RC hobbyists love. However, given the costs and complexities involved with upgrading to LiPo, it’s vital that you do your research and understand what is involved to minimise the risk of injury or damage.