Charging lithium-ion cell from a current limited voltage source

In summary, the SEPIC controller from National Semiconductor can be used to provide a PWM output to control the charging of a lithium ion battery. However, because this controller is designed for use with LED drivers, it may not be the best option for charging a lithium ion battery.
  • #1
gnurf
370
8
I want to charge a single lithium-ion cell from a current-limited voltage source. My "black box" (or rather, it's white -- with a question mark inside) has inputs of ~250mA @ [3.7V to 5.4V], and target output (i.e., the lithium-ion cell) of 3.2V to Vch = 4.2V. Which means: I can't charge the battery at the low end of the input voltage range with a simple linear or buck type charger, and a boost type of charger will not work at the high end of the input range.

Since the output voltage range can be greater or less than the input, I've thought about building a SEPIC converter which could be controlled with a PWM driver and, e.g., a uC. However, I have little experience (and time..) with the ins and outs of SMPS, so I wonder if I would be shooting myself in the foot with this idea.

Ideally, there would be a lonely IC sitting out there somewhere waiting for me to find it, but I've had no such luck in my searches yet.

Any ideas?
 
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  • #2
gnurf said:
I want to charge a single lithium-ion cell from a current-limited voltage source. My "black box" (or rather, it's white -- with a question mark inside) has inputs of ~250mA @ [3.7V to 5.4V], and target output (i.e., the lithium-ion cell) of 3.2V to Vch = 4.2V. Which means: I can't charge the battery at the low end of the input voltage range with a simple linear or buck type charger, and a boost type of charger will not work at the high end of the input range.

Since the output voltage range can be greater or less than the input, I've thought about building a SEPIC converter which could be controlled with a PWM driver and, e.g., a uC. However, I have little experience (and time..) with the ins and outs of SMPS, so I wonder if I would be shooting myself in the foot with this idea.

Ideally, there would be a lonely IC sitting out there somewhere waiting for me to find it, but I've had no such luck in my searches yet.

Any ideas?

National Semiconductor makes several SEPIC controller ICs. I'm familiar with the LED drive versions, but they have straight voltage source versions as well:

http://www.national.com/cat/index.cgi?i=i//318

.
 
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  • #3
Try this lithium battery charger (lonely) IC from National just waiting for you to find it:
http://www.national.com/mpf/LM/LM3622.html#Overview
Bob S
 
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Related to Charging lithium-ion cell from a current limited voltage source

1. How does a current limited voltage source affect the charging of a lithium-ion cell?

A current limited voltage source limits the amount of current that can flow into the lithium-ion cell during charging. This helps prevent the cell from overheating and potentially causing damage.

2. Can a lithium-ion cell be charged from a current limited voltage source?

Yes, a lithium-ion cell can be safely charged from a current limited voltage source. However, it is important to use a voltage source with appropriate current limiting capabilities to avoid damaging the cell.

3. What is the recommended charging current for a lithium-ion cell from a current limited voltage source?

The recommended charging current for a lithium-ion cell depends on the cell's capacity and manufacturer's specifications. It is generally recommended to use a charging current that is 1/10th of the cell's capacity. For example, a 2000mAh cell should be charged at a maximum current of 200mA.

4. How long does it take to charge a lithium-ion cell from a current limited voltage source?

The charging time for a lithium-ion cell from a current limited voltage source also depends on the cell's capacity and the charging current. Generally, it takes about 3-4 hours to fully charge a lithium-ion cell with a 1/10th charging current. However, it is important to follow the manufacturer's recommended charging time to avoid overcharging the cell.

5. Can a current limited voltage source damage a lithium-ion cell?

If used correctly, a current limited voltage source should not damage a lithium-ion cell. However, using a voltage source with inadequate current limiting capabilities or not following the recommended charging time can lead to overcharging and potential damage to the cell. It is important to always use a voltage source that is compatible with the cell and follow the manufacturer's guidelines for safe charging.

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