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Project: Kindle battery not charging

The battery not charging is a common problem for a Kindle. 

There are a few possibilities I have come across so far that explain why a Kindle fails to charge:

  • Faulty Charging Port
  • Faulty Battery
  • Faulty Charging circuit resistor  

The Kindle I’m repairing in this post is an 8th Generation Amazon Kindle Basic 2, model SY69JL. The symptoms are it briefly flashes it’s led charge indicator green when the Micro USB charge cable is plugged in then shows nothing. It also reports Error-22 Battery Invalid. 

Initially I though this was a dead battery but changing it out did not resolve the issue. The next thing I tried was to replace the USB charging port, this also did not fix the issue. Finally I used a heat gun to reflow the solder on one of the charging circuit shunts (resistor) which resolved the charging problem. 

 Step 1: How to remove the case on a Kindle 8th Generation?

 To remove the case on a Kindle you need a Philips screwdriver and some sort of tool to pry off the case. Ideally you will use a mobile phone repair kit with a special plastic prying tool. Most Electronics Tool Kit sets will include a choice of pryer tools and screwdrivers, this one from Amazon (opens in a new window) is a good one.
 
If you don’t have a proper set you can use something like a guitar pick or I even used a zester tool form the kitchen once. Just be really careful with anything metal in case it damages the case or scratches the screen. 
 

There are some small differences between models of Kindle as to how the face plate comes off but basically they are glued on and need to be pried off. Once you get the tool in a crack between the face plate and the case just work your way around the outside edge to pry it off. If you are really struggling to get a pry tool in there you can also pry it off from the screen side, just be super careful not to scratch it. 

An 8th Gen has 2 faceplates, this is what it looks like when you have disassembled it: 

There are screws where I have marked red circles, these need to be removed. You can then lift the Kindle main board and screen out of the case. I’ve already soldered wires for a serial port to this one, yours won’t have the wires or tape. 

Step 2:  How to replace the battery on a Kindle 8th Gen?

Once you have the case off following the steps above swapping the battery is easy. You just disconnect the old one and connect the new one. 
 
For this repair the first thing I tried was changing out the battery. On this particular model the battery is glued down and it’s a bit of a pain to remove and then re-glue a new one so I just laid the battery on top for testing, disconnected the old one and connected the new one. A pair of small long nose pliers makes it easier to pinch the battery connector to remove it. 

To my surprise the new battery made no difference, it still would not charge. At this point I inspected the Charging port, it seemed a bit loose and looked as though one of the pins might have a solder break so I decided to replace it. 

With hindsight I would have moved straight to step 4, I will know for next time but it was a good exercise to complete as I haven’t replaced a Micro USB charging port before. 

Step 3: How to replace the USB charging port on a Kindle 8th Gen?

If you suspect the charging port is faulty, the most common issues are:
  • Dirt or hair in the port
  • Broken solder joints 
Before you swap out the port inspect it with a magnifying glass to confirm what the issue is. You can try to clear the port with compressed air, sometimes it’s just dust or dirt which will come loose. 
 
I found it a little difficult to find the right spare part for the Kindle’s port, the Electronics stores I tried carried slightly different ports than the one the Kindle uses. I don’t know if it’s specific to Kindles but I suspect it might be. The port for the Kindle has 4 legs and looks like this:
  • If you are in the UK or USA you can find these at Mouser, RS components or similar electronics stores. Here in Australia the delivery is way too expensive from the big sites so I got 10 pieces from AliExpress.com. I used this seller with no issues: (opens Aliexpress in a new window) 10pcs Replacement for Amazon Kindle Paperwhite mainly because the photo was good so I could see what I was getting:

 

This is the strip of 10 that arrived

Removing the USB port from the kindle is quite challenging for a beginner. 

You will need some supplies to tackle this job:

Essentials:

  • Magnification of some sort, either a Helping Hands tool with Magnifying, a separate magnifying glass, Mircroscope, mobile phone camera attached to a monitor or something along these lines. The important thing to realize is this job is microscopic and too hard to do with the naked eye.
  • Something to apply the flux, I used a wooden toothpick
  • Something to clean flux off with, I used a q-tip (cotton bud)
  • Isoproyl Alcohol to clean the flux off with
 
Nice to Have:
  • Heat resistant mat
  • “Helping Hands” tool

Removing the USB port is the most difficult part of the job, getting the solder joints hot enough to pull the pins from the joints was a challenge with a small soldering iron. If I was doing it again I would use a much bigger tip on the soldering iron to transfer more heat to the joint. The anchor points are quite large so it takes a lot of heat to get the solder to liquidize.  

While I was researching how to do this it was suggested to use a product called Chip Quick (opens Amazon in a new tab) which is an alloy with a low melting point. This can help melt the solder quicker and make for easier desoldering, unfortunately I couldn’t find it in Australia but if you can source it where you are then I’d give it a go. Let me know what you think of it in the comments below if you have experience using Chip Quick or an alternative, I’d be keen to hear if it’s worth it.

 The factory solder joins have been done with lead-free solder which has a higher melting point than leaded solder so much more difficult to melt and de-solder. This is what the factory solder joins look like: 

 

The 5 joins in the middle are the most common place for solder breaks in the charging port, they can be hard to see. 

To remove the port add some flux to all the solder joins and heat them with the iron. If you have a heat gun it makes things easier, you can warm up all the joints at the same time. Once they are hot enough and you see the solder begin to melt apply gentle pressure to lift the port away from the joins. Make sure the solder is hot enough or you’ll risk tearing the pads off the board. 

 

Once you have the port removed you can see in the photo there is a lot of solder left behind in the anchor holes. This is where the copper braid comes in handy. Copper and Solder are best friends, the copper braid will attract the solder and pull it out of the holes. 

I found this desoldering the most challenging part of the whole operation. I looked into several different methods including using a solder pump and adding low melting point solder paste. In the end the copper braid was the best way to remove it but you need a large soldering iron tip with a lot of heat to get the join hot enough for the copper braid to soak it all up. I thin kthis would have been a lot easier if I’d had access to the Chip Quick I mentioned earlier. 

As this was my first go I used up heaps of desoldering wick! I would know better for next time. 

The port was pretty messy with flux by the time I finished, I cleaned it off with a q-tip and some isopropyl alcohol. Thh q-tip left behind some fibres that you can’t see with the human eye but the camera picked up. I did a little research and the recommendation is a hogs hair brush for cleaning this up, I have picked one up for next time. 

 

After removing the old port and cleaning up the solder and flux it’s time to solder in the new port. 

I researched whether to solder the anchors first or the pins first. You can do it either way, the anchors first made sense to me, you just need to make sure you get the joins level and the port close to the board so the pins touch the pads.  You want to make sure the whole thing is level so that you get strong solder joints and a good connection. This port will be used a lot so the joins need to be solid. This is also the reason for using leaded solder in an 63/37 ratio if you can get it. You can use the more common 60/40 it’s just not as strong.

I chose to do the anchors first and the pins after as they are more fiddly and I didn’t want the port moving around while I was working on them.

Apply some flux and solder the anchors. Try to get a decent amount of solder in the anchors but don’t worry too much, once this side is finished you can fill in the anchors from the other side. 

 

Not the most beautiful soldering ever but effective and after all it was my first attempt at this! 

Now turn the board over, if your solder didn’t flow all the way through (like mine) then add more flux and fill in the anchor holes with solder. 

 

Clean up the excess flux and you’re done! 

Check your work, I bought a charging cable with a built-in LED display to check the charge rates on e-readers I repair. WIth a Kindle as long as you get a solid Orange light then you’re fine and it’s charging. 

Unfortunately in this case the USB charging port swap did not resolve the problem, afterwards it was still not charging. 

After some more research and advice from another repairer, I decided to examine the charging circuit…

Step 4: How to reflow a shunt or resistor on a Kindle 8th Gen?

The charging circuit for this model has some components near the battery. I was advised that if your Kindle is reporting Error-22 and won’t charge it is usually one of the shunts (resistors) that’s the problem. 

The charging circuit is marked with a red square around it below, with the problem resistor circled on the right. 

This is a tiny resistor and looked like a very challenging soldering operation but I had heard replacing it fixed the issue. The larger chip further down the charging circuit turned out to be a BD71815AGW. The data sheet for that chip is here (opens in new window): https://www.rohm.com/datasheet/BD71815AGW. The data sheet mentions the following:

Embedded Coulomb Counter for Battery Fuel
Gauging
– 15-bit ΔΣ-ADC with External Current Sense
Resistor (10 mΩ, ±1% or 30mΩ, ±1%)
– 1-sec cycle, 28-bit accumulation

– Coulomb count while charging/discharging

and also  

15-bit ΔΣ-ADC measures the battery’s charge and discharge current by means of an external current sense resistor
(10mΩ, ±1% or 30mΩ, ±1%).

These indicate the 30 Ohm resistor is what the chip is referencing to measure charging. If the resistor is faulty it will be giving false readings to the chip and hence Kindle not charging properly. 

 I bought some replacements from Ebay here (opens in new Window): MCS1632R030FER – Ohmite – Current Sense Resistor they were a lot more expensive than I expected. When they arrived they were also a lot more tiny than I expected! 

I did attempt to desolder the R030 from the board, it was very difficult and I was not successful. In the meantime I heard from another repairer that he’d had success simply heating the resistor up with a heat gun and the Kindle had started charging afterwards. I looked up the recommended temperature for soldering the Resistor in it’s datasheet and used the mid point of that (240c) to warm it up using my heat gun. 

 

After letting it cool down for 10 mins or so I tried to charge the kindle again, it works! I got an Orange light so I left it overnight and came back to a green light the next morning, charging issue resolved! 

Unfortunately I think i damaged that tiny capacitor next to the resistor when I tried to desolder it so unfortunately this Kindle still displays the battery invalid. I heard from another repairer their’s was fixed simply by warming the resistor so if you are getting the same error give it a try and let me know in the comments if you are successful. 

If this is your first try at replacing a USB charging port, persevere you will get it eventually, took me a long time but was very satisfying in the end!