Whats inside an iLuv i601 Battery

Here are a few photos of the contents of an iLuv i601 external battery pack intended for a first generation Apple iPod Nano.

This is an interesting device as within its very slender enclosure it contains: -

• a li-poly (lithium polymer) battery with a few hundred mAh of capacity,
• integrated charging and protection circuit for above,
• 5V regulated boost converter circuit with output drive capability of a few hundred mA.

This array of functions makes it an ideal donor for little projects which need a nicely regulated uninterruptable power supply, e.g. a digital alarm clock.

The battery comes as part of a kit which includes a handy multi input voltage mains adaptor with a regulated 5V 2A DC output via a standard USB type A connector. This will undoubtably come in handy for other things, especially charging other USB equipped stuff while traveling.

I got mine for a bargain £5.00 at my local branch TK Maxx. (It didn't fit the iPod I bought it for as the connector is positioned to suit only the first generation iPod Nanos. I didn't notice if this was mentioned on the outer packaging, but that's probably why they are cheap.)

Disassembly

Being so compact, this was unsuprisingly a bit of a bugger to get into. The white plastic case is welded shut at the seams and the delicate foil body of the li-poly battery is fixed to both halves with extremely tenacious sticky foam pads.

I tackled it by cracking the lower edge of the seam with a small flat blade screwdriver and working a little way around the corners up the body, but stopping once I could see the location of the battery. Putting a screwdriver through the soft foil of the lithium cell would be a sure way to cause unpleasantness such as hot gasses escaping or small exlopsions.

I managed to get the back off by running some alchohol down the inside of the case. I use whiteboard cleaner as there's a ready supply of it in the office stationary cupboard. I found the sticky residue isn't really dissolved by this stuff but it is enough to loosen the foam pad it adheres to.

After a few minutes softening, the back can gently be prised off the battery by inserting a soft and wide plastic blade (e.g. a credit card) in the gap.

Inside, the charging and output PSU circuits are all contained on a single PCB, which helpfully has "In", "Out" and "GND" marked in the silkscreen. Almost made for hacking!

I actually went a little further and removed the battery from the other half of the case. I wouldn't recommend it as the operation is quite precarious and isn't necessary unless the bulge at the end makes the unit too large to fit your project's enclosure, or if having redundant hardware really bothers you.

Underneath the main board are a couple of little PCBs with the audio circuitry and connectors on. These are joined to the main PCB via wires soldered to the three pads marked as described above on the reverse of the PCB.

Reuse as a Project Power Supply

The PSU output is quite smart in that it appears to need to see a load before it is enabled. This load can apparently be as small as 1mA (I didn't try any less).

The output it latched into either on or off state, depending on whether the load was present while the input voltage was present. Therefore if this is being used for an uninterruptable supply for some TTL logic or a microcontroller, the PSU would just always be powered up until the battery runs flat.

I guess as per the iPod itself, the input needs to be a regulated 5V. When the input supply is present, the output voltage seems to match the input.

(Whilst charging, an onboard bicolour LED illuminates red. It turns green once the bettery is fully charged.)

With a small load (such as a 4K7 resistor), the output will go to 5V once the input supply is removed.

It appears that once latched on, the load can be removed completely and the PSU stays on indefinitely (until the battery dies).