If you want to make a DIY battery charger or more commonly known as power banks, you will surely need a battery pack. There are many type of batteries such as venerable AA or 9V cell. This batteries are great for making into larger multi battery packs. They can carry plenty of charge and also at cheap cost. But if you want your batteries to also be rechargeable and want to save money for longer term, you will need rechargeable lithium polymer batteries.
What is Lithium-Polymer Batteries
Lithium Polymer batteries are the latest type of battery which are now commonly used in many consumer electronic devices. The latest device such as power banks also use power bank to store extra charge. Lithium batteries have been gaining in popularity in the radio control industry over the last few years, and are now the most popular choice for anyone looking for long run times and high power.
Lithium polymer batteries offer more benefits than other alkaline or common Nickel Metal Hydride batteries and Nickel Cadmium batteries.
- Lithium polymer batteries are much lighter weight, and can be made in almost any size or shape.
- Lithium polymer batteries offer much higher capacities, allowing them to hold much more power.
- Lithium polymer batteries offer much higher discharge rates, meaning they pack more punch
Lithium Ion batteries tend to be rectangular or sometimes cylindrical. They are hard shelled with a robust casing. Lithium batteries are more heavier and come with larger capacity compare to other battery types. They are also sturdy and not easy to puncture. These batteries are often used in top power banks in India and laptops.
Why Lithium Polymer Batteries in Power Banks
Lithium Polymer batteries offer a wide array of benefits. But each user must decide if the benefits outweigh the drawbacks. For more and more people, they do. In my personal opinion, there is nothing to fear from LiPo batteries, so long as you follow the rules and treat the batteries with the respect they deserve.
These benefits are important in any RC model, but for airplanes and helicopters they are the reason electric flight has become so popular. Face it, electric cars and boats have been around for decades, it wasn’t till LiPo battery technology arrived on the scene, that electric planes and helicopters started showing up and are now surpassing
nitro power in terms of performance.
Lithium Polymer Battery Features
High Energy Density: For their weight, Lithium Polymer batteries are capable of storing a proportionately high amount of energy compared to older technologies such as those found in NiCd and NiMH batteries. In many cases, they offer over 4 times the energy capacity for the weight.
Cell equalization: Because a Lithium battery cannot be overcharged, there is no natural mechanism for cell equalization. Therefore, an alternative method must be employed.
Flat Voltage Curve: Lithium Polymer cells are fully charged at 4.2 volts and are considered fully
discharged at 3.0 volts. This allows for a relatively flat voltage discharge curve, providing solid performance throughout the discharge cycle.
High Capacity: Lithium Polymer cells with reduced capacity or high internal impedance tend to have large voltage swings when charging and discharging. For HEV applications, it is necessary to cell balance lithium chemistry because of this over voltage potential.
No Memory Effect: Lithium Polymer cells do not develop a memory effect from being only partially discharged and then charged again (such as that experienced by NiCd cells). The cells may be partially charged and discharged without damaging their performance so long as they are kept within their normal operating voltage parameters.
Differences in Lithium Ion and Lithium Polymer Batteries
Many people get confused between Lithium-Ion and Lithium-Polymer batteries. Though they have many similar features, but they also differ in key points. Lithium-Ion and Lithium-Polymer batteries have essentially the same chemical make up and are cared for in the same way; the differences are in how the cells are packaged and the type of electrolyte that is used.
These batteries use an organic liquid solvent as the electrolyte. This electrolyte is responsible for the ion exchange between the positive anode and negative cathode just like any batteries. This organic solvent based electrolyte is highly flammable and the reason why Lithium-Ion batteries are more volatile and can catch fire or explode if mistreated.They are also usually encased in a hard metal can adding weight and not allowing many different options as far as shape and size.
A true Lithium Polymer battery doesn’t use a liquid electrolyte but instead uses a dry electrolyte polymer that resembles a thin plastic film. This film is sandwiched between the positive anode and negative cathode of the battery allowing for ion exchange thus the name lithium polymer. This method allows for a very thin and wide range of shapes and sizes of cells.
Lithium Polymer Battery Specifications
As we discussed above about the similarity and difference between the Lithium Ion and Lithium Polymer batteries, You should always treat them somewhat similarly and consider them two different versions of the same kind of battery. Below we will discuss its specification.
Depending upon the design of your lithium polymer battery, you may find them in different nominal voltages. For example, most lithium polymer batteries are in the range of 3.7V to 4.2V batteries. What this means is that the maximum voltage of the cell is 4.2V and that the average voltage is 3.7V. As you use the Lithium Polymer batter, the voltage will get lowe and lower, until the maximum voltage becomes 3.1 V.
The capacity of a Lithium polymer battery is basically a measure of how much power the battery can hold. Think of it as the size of your fuel tank. The unit of measure here is milliamp hours (mAh). This is saying how much drain can be put on the battery to discharge it in one hour. The capacity of the battery suppose is 5000mAh. This means that a load of 5000mAh (or 5A) would drain the battery completely in one hour. We use this information on charging as well, because it works in the opposite way as well. If we charge the above battery at 5 Amps, it will be completely charged in about an hour. Physics is a bit fickle, and there is energy lost along the way, so it won’t be an hour on the dot, but it’s a good ballpark time.
How To Prolong The Life of Your Lithium Polymer Batteries
Good quality cells like ours, although cost more in initially will easily out perform and outlast the cheaper cells and therefore cost you less in the long term. Good quality cells are also safer in operation then the cheaper far east cells. As with all things in life, you get what you pay for.
- Purchase good quality battery packs. Cheap far east cells are a bad investment with regards to life, performance and safety.
- Do not charge your lithium polymer batteries above their max safe voltage.
- Do not discharge your lithium polymer batteries below their safe minimum voltage
- Purchase a good quality charger designed specifically for charging Lithium Polymer cells. Make sure the charger has a display that will show the amount of energy that is put back into your packs in terms of “mAh” and one that shows the voltage of the individual cells being charged. This is essential to monitoring and therefore adapting your use and charging of your batteries.
- Lithium polymer batteries offer plenty of power and run time for us radio control enthusiasts. But that power and run time comes at a price. These batteries are capable of catching fire if not used properly
- Purchase a digital voltmeter. We can supply these for as little as £6.99 and is an essential tool for checking your
- For the longest life of the batteries, Lithium batteries should be stored at room temperature at 3.8V per cell. Most modern computerize d chargers have a LiPo Storage function that will either charge the batteries up to that voltage, or discharge them down to that voltage, whichever is necessary.
Electric vehicle applications can benefit from cell-balancing devices, especially for lithium-based battery chemistries. Since battery pack charging is limited by any one single cell reaching its end-of-charge voltage (4.1 V to 4.3 V), it is useful to control high voltage cells until the lower voltage cells catch up. This way, each cell can be charged to its end-of-charge voltage.
So there you have it now you know most of what you need to know about Lithium Polymer batteries. I make no claims that this article teaches you everything there is to know about LiPos, but hopefully it helps give you some insight into how these batteries work. LiPo batteries have the potential to overtake NiMH batteries in general use in the next few years, quicker than any battery in history. It is certainly an exciting time for the hobby, and things are changing on a frequent basis. Just remember to have fun, and ask questions! The only dumb question is the one you don’t ask!