Sunday, 31 March 2013

Fusible Link Repair






18v LXT Battery Repair – Chip Reset
By Ryan Flint – April 2013

Introduction
The Makita range of battery power tools are undoubtedly the best tools on the market, with the range and availability unparalleled by any other brand.  Unfortunately in the 18v LXT range for the general user the batteries have a tendency to fail and become useless.  As an Electrician/Engineer I thought there would be plenty of solutions to this problem….. 

I have searched the internet in hope that I could find a solution to my faulty batteries, I have contacted Makita agents and supposed repair centres all giving me the same advice.  Throwing them away and buy new ones...
I decided to ignore their advice and to have a play around with them and think I have a solution to some of the problems.  Please note that this solution is not for all problems and that this will void all warranty.  If your battery is less than 12 months old and you have a proof of purchase I advise you to go through the proper channels and have your battery replaced by Makita.

The common red/green flashing fault on the 18v Makita Charger

Some basic electronic skills and tools such as a soldering iron, multi-meter and basic hand tools are required for this procedure.   

Opening the battery
To open the battery you will require a small flat head screw driver and a T10 long torx bit.  Firstly you will notice a white tamper proof bung in one of the screw holes.  Flick this out with a screw driver and toss it, this will no longer be required.  The 4 screws are all that hold the top of the battery in place.  Remove the top and the white clip (Be careful of the spring under the clip, it could cause a possible short).  You now should see a similar view to Figure 1.

Figure 1

Testing the Cells
To test the voltage of each cell use a multi meter and test the voltage between the 6 points shown in Figure 2.  Each cell when fully charged should have close to 4 volts in it (point 1 to 2) but in most cases we will see much less.  Check between points to make sure none of the cells have gone to zero.  If one of the cells has gone to zero, the cell will need to be replaced before any further repair can be done.  You may have several batteries with a faulty cell and my advice is to create a battery from the spares. (Example: make 3 from 4)

Figure 2

Removing the Circuit Board
To remove the board several joints need to be un-soldered and parts removed.  Listed below are the items that need attention.
                                  1.       Positive Terminal - unsolder from the board 
                                       2.       Negative Terminal – unsolder from the board
                                       3.       Temp Sensor – glued in (need to lever out, be careful not to damage)
                                       4.       Ribbon Cable – remove
                                 5.       Screw – removed

Once these parts have been attended to the board should be able to be removed from the battery pack.  The temperature sensor (point 3 in Figure 3) is glued into place and becomes the hardest part to remove, be careful not to snap the probe from the board.  The ribbon cable (point 4) is very delicate and also needs careful attention.  At all times be careful not to short any parts of the board or cell pack while removing the board.

Figure 3

Repairing the Fusible Link
The fusible link being blown has been the cause of the problem on three of my batteries to date.  I have not been able to find any circuit diagrams online to actually understand what the fuse supplies but I assume it is the supply to the chip itself. 
The fusible link has a black cap (noted F03 on my board) that can be flicked off with a screwdriver showing the metal parts.  A solder blob was the applied to the top of the chip to bridge out the blown section.  This should have hopefully of fixed the problem.   
By bypassing the fuse (shown in Figure 6) we have supplied the chip with power again and in my case it solved the problem.  However as you are bypassing a fuse the next time such fault occurs there will probably be irreversible damage to the electronics, so far all is running well in the repaired battery!



Figure 4 - Underneath the board
Figure 5 - Cap flicked off
Figure 6 - Soldered repair of the fuse

Re-Installing the board
The board can now be reinstalled into the cell pack and the pack put back together and placed into a charger.  A handy hint on reinstalling the circuit board is installing the ribbon cable first as it is quite difficult once soldered and screwed back in.  Hopefully your battery pack comes back up to full voltage and runs for many more cycles giving the Makita tools the customer satisfaction they deserve!



Ryan Flint 31/03/2013






20 comments:

  1. HI!

    nice article! What about a full rebuild of the battery pack with brand new 18650 cells??

    ReplyDelete
  2. Have some cells on order and will let you know! The hardest thing will be joining them together without an expensive spot welder. I have soldered them together but they can get bulky.

    ReplyDelete
  3. Hey Ryan!

    I have the spot welder here in my small lab and I'm about to perform the same test as you. Have you figured out how to reset that chip on the PCB?

    I have spent many hours searching for info about that PCB/Chip reset and find nothing yet!

    ReplyDelete
    Replies
    1. See my new post for the updated chip reset! I dont think the "chip reset" is possible without spending serious dollars!

      Delete
  4. What kind of cells did you ordered for you rebuild??

    ReplyDelete
    Replies
    1. Hi, i used the cheap ebay special cells for this pack build as i was trying to keep the cost right down. Think they were about $25 bucks! I will test them out and get back to you!

      Delete
    2. The way to go is use the spare batteries from other makita packs! That way the cells are all the same!

      Delete
    3. Recently I found a website cordless drill battery (USA) store many power tools batteries, and most of them cheaper than ebay.
      You can visit use this link

      Delete
  5. hey guys.
    i just disassembled a batterpack.
    charged the single cells to have a normal voltage (now17,5)
    but the charger blinks again red and green...i think the chip is locked.

    i didn't found anything to unlock it BUT on alibaba are some companies that sell PCB for BL1830 - maybe there we can buy some fully assembled! i will try my best!

    ReplyDelete
  6. bad news, some negative feedback... they only make PCB's but they need files etc.

    ReplyDelete
  7. On older battery the MCU used is a FreeScale MC908JK3E witch is based on the Motorola 68HC908
    Tips : people playing with cars ECU have a need to "unlock" the said chip. Search for UPA-USB Programmer, its looks like their programmer can defeat the security bit present in the MCU allowing us to dump the firmware.
    On Newer battery the freescale was replaced by a NEC 78k0 (F0513S).
    On the same path as before some people playing with car IMMO module need to unlock differents flavor of 78k0 chips. Hints : search for NEC Dash Programmer.
    It worth a try...
    If i has more time on my hands i would try to power glitch the 78k0 as it seems from some research paper that those chip would be good candidate. NEC has a 10bytes password and FreeScale has a 8bytes one so bruteforcing the whole nspace isnt an option.Power analysis on good response VS bad response while trying the password might reduce the space to search.

    ReplyDelete
  8. I bought a couple replacement boards through alibaba. There's a slight mechanical mismatch to installing in place of the original (newer NEC version) board, but cutting one plastic alignment pin allows it to fit.
    It has an F9222 chip. They're definitely not identical.
    After installation in place of the old, I confirmed that it will not talk to the charger as supplied. The charger becomes unresponsive once the battery is installed. I've written the supplier for assistance. I presume this is the board that they use in the half price ($50) replacements also available through alibaba or ebay.

    ReplyDelete
  9. The F9222 is a SMPS management chip it has noting to do with the 'locking' problem. The chip that lock the battery is a MCU usually a NEC based 78k0 or a FreeScale based 68HC08.

    ReplyDelete
  10. If the supplier can supply all the components it mean either they got their hand on the firmware (illegally dumping it) OR they wrote a new firmware to simulate the Makita's one and is probably not very safe to use unless they wrote a complete BMS system. If they can supply all the parts let me know i would order some board to play with...

    ReplyDelete
  11. I haven't heard back from the supplier yet, but I've attached front and back pictures of the original board (in white on left) and replacement board (in green on right) for your review. See here: http://postimg.org/gallery/8etbc01m/74f7417c/
    I have a spare replacement board for $12 if you'd like it.

    ReplyDelete
  12. Thanks, judging by the pictures i was wrong. They replaced the F0513S by a F2222T both are 8bits MCU made by Renesas. The clone one is a 78K0S/KA1+ exactly a NEC (now Renesas) μPD78F9222. So they either dumped the original firmware and adapted it to their board (its not exactly the same circuit) or they wrote their own BMS firmware. One good news tough is the clone MCU can easily be dumped ie : read but im not sure how useful this could be. Yes, i would like to buy your spare :) you can reach me at skaos0110(at)gmail.com. I will give you my address to calculate shipping

    ReplyDelete
  13. Lililunou, did you receive my email from last week... just wanted to make sure the communication was successful.

    ReplyDelete
  14. This comment has been removed by the author.

    ReplyDelete
  15. I'll definitely be subscribing to your site. Keep up the good posts.Makita

    ReplyDelete