Recharging Battery

J

Thread Starter

Jason1998

How does a battery recharge and also give output to a circuit? I'm wondering about smaller batteries like those for game consoles, headphones, etc.
 
Battery is a chemical process. By combining chemicals you can make electricity, and by adding electricity you can break back apart chemicals.
There are rechargeable batteries in AA and AAA size.
Many of the rechargeable batteries use different chemicals. Watch out for 1.25 Volt batteries. Some consoles will work at 1.5 volt but not at 1.2V. There are 1.5V rechargeable. You need to read the fine print.
 
Ideal batteries have constant voltage. This is not the case with practical batteries. In reality, the battery voltage is a function of the battery capacity. The shown curve is for lithium ion battery. The exponential region is from Vfull (4.2V) to Vexp (4.6V). In this region, the battery voltage drops qucikly. So in matter of minutes the battery voltage will drop from 4.6V to 4.2 V. Then you have the nominal region from Vexp(4.2V) to Vnom (4V). This is the operating voltage. Commonly, when you're using a battery this is the voltage that you will see. Then, you have the last region from Vnom (4V) to Vend (2.6V). When the voltage reaches 2.6 V, the battery is considered empty and must be disconnected and charged. If the battery falls below 2.6 V, the battery cannot be charged with high current, which means that it takes long time to get out of this region. So, you should never get the battery below Vend.

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Depending on the current battery voltage the charging rate is determined. There are several methods for battery charging the most common is CCCV (const current const voltage charging). There are 4 stages in charging

Trickle charging (from Vend to Vcutoff): This is applied if the voltage dropped below the Vend (2.6V). The battery is charged with 0.01C until the battery is 2.6V (if a battery capacity is 1000 mAh , then charge with 0.01 * 1000 = 10 mA)

Pre-charge: The battery is charged with 0.1C from 2.6V to 3 V (0.1 * 1000 = 100 mA)

Constant current: The battery is charged with constant current equal to 1C from 3V until 4.5V

Why not until full charge V ? so that the high current does not damage the battery

Constant voltage: A constant voltage equal to the battery full charge voltage (4.6V) is applied until the battery is fully charged.


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The current control is achieved using a DC-DC converter buck converter and any microcontroller with a voltage and current measurement sensors.
 
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