How to keep the 18650 batteries for a long life and maintain capacity rating?

The 18650 batteries have become so popular that so many companies have gone for competition to take a big market share. Customers also have advantage when using the best 18650 batteries including low cost, multi uses, long using time, so many options to choose models, manufactures.

All batteries including 18650 batteries have one thing in common: they function for a while, need recharging, progressively weaken after each cycle of recharging and discharging, and need replacement. Because replacing batteries costs, method of improving batteries life now gets appropriate attention.

Ways to keep 18650 batteries for a long life and maintain capacity rating is presented below.

The Solution for a long life of 18650 batteries

The first to do thing is to read carefully the instruction from the manufacture. Every battery model has the different purpose and working condition.

Before put the battery into equipment, you should read specification of the equipment carefully to make sure the battery is suitable for the equipment.

The main physical effects on the longevity and the rated capacity and the solution

1.1. The temperature

Two factors affect the battery usage are time and temperature. Every 10 degree rises in temperature makes rate of chemical proceed double and the t1/2 relationship demonstrate how internal resistance of battery change with time t. The graph below illustrates this relation.

The chemical reaction in battery is driven by voltage and temperature. The hotter battery, the faster chemical reaction occurs. So, higher temperature will improve performance of battery. But, according to higher temperature, unwanted chemical reaction is also stronger, it results loss in battery life.

1.2. The pressure

Increasing internal pressure within a cell is the consequence of increased temperature. Several reasons can play a part in raising pressure and temperature in cell. Overcharging is one factor not only to make temperature rise but also cause the release of gas, according to this event, the pressure will go up. The increased pressure may magnify the effect of high temperature by increasing rate of chemical reaction in cells. Extreme pressure can also cause defection of chemical reaction within cells such as short circuit between some parts. These may reduce the potential life of cells.

1.3. The Voltage and the Cut off Voltage

Each 18650 batteries has its own characteristic working voltage range, it depends on particular cell chemistry formula. When all active chemical components have transform into composition according to full charged condition, charging more electrical energy into it will cause heat rise and to start unwanted reaction between chemical components can break them down into form which cannot be combined. Charging the cell with voltage which is beyond the voltage limit of cell can lead to irreversible chemical reaction which can damage the cell. Increase temperature and pressure in cell could be dangerous; sometime these events lead to explosion or fire. Some protection circuit has been designed to make sure cells working in recommended working voltage range. For example, if we over-discharge NiMH cell 0.2 V, it can damage the cell 40% cycle life.

The best way to recharge energy for 18650 batteries.

2.1. Cycle Life

At the same condition, the amount of chemical components is proportional to the depth of discharge. Cycle life of 18650 batteries is inversely proportional to depth of discharge. Battery life depends on total energy that active chemical component can tolerate. Ignoring the aging effect, energy of one cycle of 100% depth of discharge approximately equal 2 cycle of 50% depth of discharge and equals 10 cycles of 10%% depth of discharge. You can improve battery life when charging battery before it completely discharges. If you charge cells when energy is only 20 to 30%, It can make cell life 5 to 6 times longer when you discharge it completely every cycle.

2.2. Charging Level

Cycle life of 18650 batteries can increase by decrease the charging cut off voltage. By reducing cut off voltage 0.1 V, you can have more 200 cycles of battery charging and discharging.

2.3. Charging Rate

Charging rate also influences number of cycle life of 18650 batteries a lot. The capacity loss in high current discharge mode occurs because the transformation of active chemicals componet can not correspond to the current extracted. Trying force too much current into batteries can lead to irreversible loss.

The Conclusion

Reading the manufacture’s manual or instruction is very necessary. You also must remember to not let the capacity of 18650 batteries drop too low.

Choosing the right equipment to charge battery is undeniably essential, the manufacture often give a list of charging device that is compatible with batteries that they produce. So, don’t forget to choose the right one for you.

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