Supercapacitor as small LiPo replacement

Hi Forum,

I’m looking to replace the battery in my Sandisk clip+ with a Supercapacitor.

My thoughts so far:

–DISCHARGING–

Original Battery with 290mAh @ 3.7V nominal Voltage. ==> 1.073 Wh
-Provides up to 15h of playback.

Replacement ~250F Capacitor @ 2.7V ((0.5CV^2)/3600) ==> 0.2531 Wh
-Theoretically 3:45h of playback.

Since the Voltage range of a LiPo battery will go from 4.2V fully charged to 3.0V empty I would guess it is safe to run the mp3 player at 3V and minimize conversion loss.

So I need a step-up converter ideally from 0V to 3V.

–CHARGING–

Simple enough a step-down converter from ~5V to 2.7V.

I guess it should be current-limited to ~500mAh not short out a USB port.

What are your thoughts on this? Did I miss anything?

Hi,
You need to look at the discharge characteristic of the capacitor.

It is not like a battery that for most of its life has relatively constant output voltage then drops off.

A capacitor has a decreasing output voltage over its discharge range, there is no constant output voltage.

Tom.... :slight_smile: