Replacing Kobo Touch Battery

Intro

Over the course of a couple of months the battery life of my Kobo Touch started to deteriorate noticeably. Until it suddenly wouldn't start or charge anymore at all. Connecting it to the computer produced some response from the light, it would seem like the Kobo tried to start but then failed due to insufficient battery capacity or something. The screen never even flickered and my computer would not recognize the Kobo as being connected.

As I was sure no mechanical harm had happened to the device (I hadn't taken it anywhere in months), I figured it had to be that battery that gave out. So I set out trying to find out how to replace it, and figuring this out turned out to be a lot harder than expected. Googling just yields a lot of forum threads complaining about the bad practice of not putting user-replaceable batteries in devices like this (the term 'planned obsolence' comes along very often). I found one (Dutch) forum thread on someone dealing with the same problem I had, in the end he mentioned he just ordered a generic three-lead battery from 'the internet' but never responded to my question which battery this was. In reply to him, someone mentioned that he was lucky that the third lead on the battery he found matched up to what the kobo expected, and that it was a safer bet to just stick a new battery on the old battery's connection board. So this is what I did, and to save you the pain of figuring this all out yourself I will show you what I've done here in my first Instructable ever.

What you'll need

Soldering iron. I think any soldering iron will do, I got one of the cheapest ones available on Aliexpress, and it came including a stand, tweezers, soldering tin. Search for one yourself, or get the on I got here. The tweezers aren't a must

Soldering skills. Optional. No really, this project is the first time I've held a soldering iron since I was 14. You just need to know which end of the soldering iron gets hot, and then hold that end against whatever you want to (de)solder. The connections you'll be working with are pretty big, so it's easy work. If you want to, you can probably find tutorials on YouTube.

Desoldering braid. You can use this copper braid to suck op soldering tin when you want to desolder a connection. You cut off a piece of the braid, put in on the connection you want to desolder, then press it with your hot soldering iron until you feel the solder melting and being sucked up by the braid. I used this.

New battery. You'll need a new battery (duh!). More importantly, you'll need a LiPo battery of the same size as the one that's in your Kobo right now. I first tried to do this by measuring the size of the battery holder, and ordering a battery based on those measurements. That failed as, even though my Kindle now worked, I couldn't replace the back cover anymore. Then I figured out that the numbered code on the battery (see picture, I had unfortunately torn of the wrapper from the battery before making a picture) isn't just a product number, it's the size of the battery. In this case the numbers are 404252, meaning that this battery is 4.0 mm thick and 42 by 52 mm long/wide. And just this number code turned out the best way to find a new battery of exactly the right size, in the end I ordered this one and it works great. Check the number on your old battery to be sure!

Opening up the Kobo Touch is pretty easy. Looking at the picture that I took from TechCrunch's review on this device, you can see a crack running around the backside. Pressing on this crack and prying a nail behind the back cover, you can separate the back cover from the bezel and the internals. Look at this YouTube video to see someone doing this.

This will give you a view of the main PCB board, and will clearly show you the battery and the connector connecting the battery with the board. The battery is glued in the holder, so you will need some force to remove it, do this as follows:

• Start by disconnecting the battery. In the image, the connector is marked. Disconnect it by taking hold of the wires right where they leave the connector and gently pull them away from the board. In this case "away from the board" means that, assuming your Kobo is lying screen-down on a table, you'll pull gently upwards (away from the table). This will disconnect the battery, but it's still glued to the battery holder. The best way to get the battery out is to take a screwdriver, or anything else that can function as a lever, pry it below the edge of the battery and carefully try to lever it out, using the edge of the battery holder as a pivot point for your screwdriver. Do this in multiple locations and never apply a lot of force (you don't want to damage the screen below) and the battery should come out eventually.

Time to 'unwrap' your battery. Take off at least the top part of the black wrapping around your battery. This should be easy and will reveal a metallic battery cell with black isolating tape around the top edge (where the wires come out). This tape needs to come off as well, but be carefull not to damage the small board beneath it, we'll need it later.

The small board contains two connections for the positive and negative battery terminals, it also contains an NTC. Probably, this serves to measure battery temperature to prevent the battery from overheating. And presumably, this is what the third wire in the connector is for. This means that the Kobo expects the NTC to be at the other end of this wire, so in replacing the battery you have two options: either find a general LiPo battery and stick this connection board on it, or find another three-wire LiPo battery that also has an NTC. I failed finding another three-wire battery (not counting the one that cost $25 plus $90 shipping costs), so I went with sticking this board on a new battery.

To retrieve the board from the battery, take off the isolating foam strip. This will reveal the battery terminals, desolder the connections between the battery and the board.

My new battery came looking like this, it has its own connection board with just two connection wires (and no NTC). This board needs to come off. So: take off the tape, straighten out the battery terminals (they were folded in my case), and desolder the connections between the battery terminals and the connection board. Keep in which terminal was connected to B+ and B- on the board, as you'll need to connect them to the same places on the board that came from your Kobo.

Solder the Kobo connection board to this new battery. In my case, the battery terminals and the connections on the Kobo connection board weren't evenly spaced. This meant that I had to ben one of the battery terminals slightly to make it line up. This introduced a new problem though, due to this misalignment, part of the terminal would contact the connections of the the wires to the board, causing a short-circuit. To prevent this, I used some electrical tape to insulate the battery terminal, solving this problem.

Put the new battery in the battery holder, it will probably stick slightly to the glue residues that are still in there. Make sure the connection board fits in there as well, and has the connection cables on the side of the recess in the battery holder.

Reconnect the battery connection cable. Replace the back cover. Success!

Note: In my case, the e-reader initially wouldn't turn on. However, after connecting it to a computer it turned on almost straight away. After that, turning it on, off or in standby is no problem and starts again every time without having to connect it to a computer first.