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LiPo batteries under the microscope
LiPo batteries under the microscope

LiPo batteries under the microscope

The vape and LiPo accus

In the electronic vaporizer, the most dangerous element remains the source of energy, which is why it is important to know your "enemy" well.

So far, for the vape, we mainly used Li-ion batteries (tubular metal battery of different diameter and more commonly 18650 batteries). Some boxes are equipped with LiPo accumulator. Often these are not interchangeable but just refillable and remain quite limited in the electronic vaporizer market.

Yet, more and more these LiPo batteries are starting to appear in our boxes, sometimes with extravagant powers (up to 1000 Watts and more!), In small formats that can retreat from their homes to be charged. The big advantage of these batteries is undeniably their size and weight which are reduced, to offer more power than that which is conventionally with Li-Ion batteries.

This tutorial is for you to understand how such a battery is built, the risks, the benefits of using it, and many other useful tips and knowledge.

A Li Po battery is a battery based on lithium in the polymer state (the electrolyte is in the form of a gel). These batteries maintain a stable and durable power over time. They also have the advantage of being lighter than Li-Ion batteries, which are electrochemical accumulators (the reaction is based on lithium but not in the ionic state), by the absence of the metal tubular packaging. that we know.

LiPo (for lithium polymer) consist of one or more elements called cells. Each cell has a nominal voltage of 3,7V per element.

An element loaded to 100% will have a voltage of 4,20V, as for our classics Li-Ion, value that must not be exceeded under pain of destruction. For the discharge, do not go down below 2,8V /3V per element. The destruction voltage is at 2,5V, at this level, your accumulator will be good to throw.

Voltage according to the% of the load

Constitution of a LiPo battery

Understanding the packaging of LiPo batteries
  • In the picture above, the internal constitution is that of a battery 2S2P, So there is 2 elements in Serie and 2 elements in Parallèle
  • Its capacity is noted in big, it is the potential of the battery which is of 5700mAh
  • For the intensity that can provide the battery, there are two values: the continuous and the crest, which are 285A for the first and 570A for the second, knowing that a peak lasts two seconds maximum
  • The discharge rate of this battery is 50C, which means that it can give 50 times its capacity which is here of 5700 mAh. We can therefore check the given discharge current by doing the calculation: 50 x 5700 = 285000mA, 285A continuously.

When an accumulator is equipped with several cells, the elements can be organized in different ways, this is called cell coupling, in series or in parallel (or both at the same time).

When identical cells are in series (therefore of the same value), the voltage of the two adds up, while the capacity remains that of a single cell.

In parallel, when identical cells are coupled, the voltage remains that of a single cell while the capacity of the two is added.

In our example, each separate element provides a voltage of 3.7V with a capacity of 2850mAh. Serial / Parallel association offers potential of (2 2 series elements x 3.7 =) 7.4V and (2 parallel elements 2 x 2850mah =) 5700mah

To stay in the example of this 2S2P constitution battery, we have 4 cells organized as follows:

Each cell being 3.7V and 2850mAh, we have a battery with two identical cells in series of (3.7 X 2) = 7.4V and 2850mAh, in parallel with the same two cells for a total value of 7,4V and (2850 x2) = 5700mAh.

This type of battery, consisting of several cells, requires that each cell has the same value, it's a bit like when you insert several Li-ion batteries in a box, each element must be loaded together and have the same properties, charge, discharge, voltage ...

This is what is called balancing between the various cells.

What is balancing?

Balancing allows each cell in the same pack to be charged at the same voltage. Because, in manufacturing, the value of their internal resistance may vary slightly, which has the effect of increasing this gap (as small as it is) over time between charge and discharge. Thus, there is a risk of having one element that will be more stressed than another, which will lead to premature wear of your battery or to malfunctions.

That is why it is preferable, with the purchase of your charger, to opt for a charger having the balancing function and at the time of the reloading, you will have to connect the two cards: power and balancing (or balance)

It is possible to find other configurations for your batteries with for example serial elements of the type 3S1P:

It is also possible to measure the voltages between the different elements using a multimeter. The diagram below will help you to position your cables for this control.

How to charge this type of battery

A lithium battery is charged at constant voltage, it should not exceed the 4.2V per item under penalty of deterioration of the battery. But, if you use a charger suitable for LiPo batteries, it manages only this threshold.

Most LiPo batteries charge 1C, it's the slowest but also the safest charge. Indeed, some LiPo batteries accept faster loads of 2, 3 or even 4C, but this mode of recharging, if accepted, uses your batteries early. It's a bit like with your Li-Ion batteries when you're doing loads of 500mAh or 1000mAh.

Example: if you load a 2S 2000 mAh battery with its charger with integrated balancing function:

- We turn on its charger and select on its charger a "lipo" load / balance program

- One plugs the 2 plugs of the battery: charge / discharge (the big 2 son) and balancing (the small with full of son, here in the example she has 3 son because 2 elements)

- We program its charger:

- battery 2S => 2 elements => one indicates on its charger "2S" or number of elements = 2 (so for info 2 * 4.2 = 8.4V)

- 2000 accu mah => it makes a capacity of the 2Ah battery => it is indicated on its charge a charging current from 2A

- the load is started.

Important: After using a LiPo battery with high power (very low resistance), it is possible that the battery is more or less hot. It is therefore very important to let a lipo battery rest for 2 or 3 hours before recharging. NEVER recharge a LiPo battery when it is hot (unstable)

Balancing:

Since this type of battery consists of several elements, it is imperative that each cell remains in a voltage range between 3.3 and 4.2V.

Also, if one of the cells is unbalanced, with one element at 3.2V and the other at 4V, it is possible that your loader overloads the 4V element to a value greater than 4.2V to compensate for the loss of the element to 3.2V in order to obtain a global load of 4.2V. That's why it's important to do the balancing. The first visible risk is the swelling of the pack with a possible explosion at the key.

To know :
  • Never discharge a battery under the 3V (risk of battery irretrievable)
  • A lipo battery has a life time. About 2 to 3 years. Even if we do not use it. In general, it is about 100 charge / discharge cycles with maximum performance.
  • A lipo battery works poorly when it is very cold, the temperature range where it is at the top is around 45 ° C
  • A drilled battery is a dead battery, you must get rid of it (a tape will not change anything).
  • Never charge a hot, pierced or inflated battery
  • If you no longer use your batteries, as for Li-Ion batteries, store the pack at mid-charge (ie around 3.8V, see charging table above)
  • With a new battery, during first uses it is important not to climb with too high vape power (break-in), it will take longer
  • Do not expose your batteries in places where the temperature could rise to more than 60 ° C (car in summer)
  • If a battery seems hot, immediately disconnect the battery and wait a few minutes while moving away, cool down. Finally check that it is not damaged.

In summary, Li-Po batteries are neither more dangerous nor less than Li-Ion batteries, they are just more fragile and require strict adherence to basic instructions. On the other hand, they allow to go up to very high powers by associating the tensions, the capacities and the intensity in a reduced volume by a flexible and light packaging.

We thank the site http://blog.patrickmodelisme.com/post/qu-est-ce-qu-une-batterie-lipo which has served us as a source of information and which we advise you to read if you are passionate about model making and / or energy.

Sylvie.I

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