Lithium polymer batteries are expensive. How you handle yours will have a big effect on how long they last. Therefore, it is worth taking the time to learn about proper charging procedures.
Lets say you just finished using your lithium polymer battery. It can be charged again without delay, as long as it isn’t hot. If it is hot, you will need to wait until it has cooled down; preferably to below 35° Celsius (95° Fahrenheit).
Your battery isn’t hot, so let the charging begin. The first steps are to power up your charger and connect your battery charge cable to the charger. You should plug in the charge cable before connecting it to the battery, because charge cables usually terminate in exposed bullet / banana connectors, which are easy to short to each other directly or via anything metal (i.e. the charger). Now you can connect the battery to the charger via the charge cable.
It’s time to set the charger’s settings. Whatever the input method, there are two important settings: charge voltage and current. The correct voltage setting is determined by the lithium polymer battery you are charging. Most batteries say their nominal voltage, with the common ones being 7.4V and 11.1V. This number is calculated as
Correct Voltage Setting = 3.7V * Number of Cells in Series
On small to medium sized lithium polymer batteries, the number of cells in series is simply the number of cells in the battery. However, on large batteries, some of the cells are wired in parallel and as such do not contribute to the correct voltage setting. The standard for writing the number of cells in series is Xs. For a small battery, like the Thunder Power Pro Lite 3s 1320mAh, we see that X=3. For this battery, correct voltage setting = 3.7V * 3 = 11.1 V.
Correct voltage setting now determined, all that remains is current setting. Current setting is largely up to the user. The most common and always correct setting is:
Standard Current Setting = Battery Capacity / 1h
Continuing with the above example, the battery capacity is 1320mAh. Therefore, standard current setting = 1320mAh / 1h = 1320mA = 1.32A. This is known as a 1C charge, because C is defined as 1 / 1h.
Some like to charge slower than 1C to be gentle with their batteries. However, there is no scientific evidence of slower charging leading to longer battery life. There are also a few chargers that charge faster than 1C to save time, such as the Thunder Power 1010C. These chargers are usually very specific about when this fast charging is safe; please follow the instructions and warnings they come with.
With those two settings set, you are ready to start the charge. Once the charging process has started, the charger takes care of everything. It will end the charge when the battery is full, at which time you can use it again. There is no need to wait between the end of a charge and the start of a discharge.
There are two ways of increasing the safety of your charges. One is to use a balancer, such as the Thunder Power 205V or 210V. The balancer will fight cell imbalance, and provide some a warning if the cells are dangerously imbalanced. The other is to place your battery somewhere nonflammable. Ask yourself, if this battery ignites, will anything nearby ignite as well? Leaving the battery on a wood counter or in a wood airplane is more risky than isolating it on a bare cement floor.
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