Revived a “won’t charge” Kobo Libra Colour with a deeply discharged battery
I bought a Kobo Libra Colour (N428) on eBay listed as “won’t charge”. The screen was still showing the low-battery/“please charge” message, so I thought it was worth a gamble.
When it arrived I connected a USB cable via a diymore 240W USB-C power meter/tester (very cheap on Amazon) so I could see the voltage and current draw. With both an old 5V/0.8A charger and a PC USB port it would:
- light the white LED
- draw about 0.2A for a few seconds
- then the LED would go out and current would drop to 0A
If I immediately unplugged/replugged the USB cable current stayed at 0A.
I opened the back and measured the battery using a multimeter and it only read 2.50V. To do that I disconnected the battery and probed the contacts on the battery connector with a multimeter until I found the battery + and − terminals (the battery is an EVE188595QH btw). I then plugged the battery back in and tried charging again in the hope this might have unlocked the battery somehow. It hadn't but when I checked the battery voltage again it had gone up to 2.53V and stayed there after 10 mins. That suggested the battery was at least accepting and holding some charge, while some part of the battery/charging protection was aborting the charging attempt because the voltage was so low.
What eventually worked was repeating this cycle:
- Unplug the USB charger from the Kobo.
- Disconnect the battery from the motherboard.
- Leave the battery disconnected for about 20 seconds.
- Reconnect the battery.
- Plug the charger back into the Kobo's USB-C port.
- Let it do its brief ~0.2A charge attempt until it stopped.
- Repeat a lot! This wasn't two or three attempts — I had to repeat the cycle 40+ times before the battery voltage climbed enough.
During that process, the battery voltage gradually increased:
2.50V → 2.53V → 2.63V → 2.69V
At around 2.7-2.8V something changed (not 100% sure what voltage as I stopped checking it at 2.7V) and the Kobo finally began charging continuously instead of shutting down after a few seconds.
It initially charged at about 0.15A, then increased to around 0.8A (so maxed out the old USB charger). At that point I switched to a 5V/2A USB supply and the Kobo drew around 1.52A, as shown on the diymore meter.
A while later I noticed the screen had changed from the low-battery message to a book cover and said:
Sleeping — Charging 5%
I left it alone and it eventually reached 100%. It booted normally, I logged the previous owner out, and it successfully installed a firmware update.
So in my case there was nothing wrong with the USB-C port or motherboard. The battery had simply fallen to around 2.5V, and the Kobo's charging circuit wouldn't initially sustain a charge. Repeatedly disconnecting the battery for ~20 seconds and then letting the Kobo make another brief charging attempt eventually raised the battery voltage enough for normal continuous charging to start.
I'm now testing how well the battery holds charge before deciding whether it actually needs replacing.
Obviously, a deeply discharged Li-ion battery can be damaged, so I wouldn't assume this will work or be safe for every dead Kobo. I monitored the battery for heat/swelling throughout and used the Kobo's own charging circuitry rather than directly forcing current into the cell.