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
