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Charging a low capacity lithium polymer battery

Mehdi Rahman
Intellectual 555 points
Other Parts Discussed in Thread: TPS61221

Hello all,

In my current design I am using a single NiMH AAA battery as my main power source to power a 3.3V boost converter (TPS61221).  I need to a small rechargeable energy source to power a load of 30 mA for approximately 1 minute (a little less would be fine) while the NiMH battery is removed for replacement.  

After doing some research, I came across this part the GMB031009: http://www.gmbattery.com/product/showproduct.php?lang=en&id=31 .  It is a rechargeable lithium polymer battery that comes in a small form factor but allows ~70 mA of continuous discharge current .  

The high C version would allow for the discharge currents I am looking for.  I talked with the vendor, and it turns out that they are no longer selling the version of the battery that comes with the protection circuitry, so I would have to put the protection in my PCB.

Now this is an exception to a normal lithium polymer charging situation, as standard charging is 0.2C and takes 8 hours, which makes the charging current very small (1.6 mA) compared to most other cases.  Additionally, my available charging voltage is 3.3V from a boost converter.  

Are there any specialized ICs that someone would recommend for this purpose?

Sincerely,

Mehdi

  • 0
    TI__Genius 13700 points

    Hello Mehdi,

    You could also look into a super capacitor solution which has a far simpler charging requirement and when combined with the boost converter can be just as functional and probably end up being similar in size.

    Another possibility would be to use a non-rechargeable primary lithium cell such as a coin cell. Know is capacity you can determine how many battery servicing it can support which should be quite a few since it only needs to work for a minute every time the batteries are changed.