Makita 18v LXT Lithium-ion Battery Repair

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About: An IT Professio​nal from the West Midlands, with an interest in history, food, wine and all things technical​.

I have been a big fan of the Makita 18v LXT cordless tools for several years now. In most cases I rarely if ever use the corded tools they replaced, despite this there does seem to be a major week point, the batteries. Out of the eight batteries I have purchased over the years four have failed out side of the warranty period, plus two failed within or just after the end of the warranty and were replaced at no charge by Makita.

It seems there are two main failure causes, number one over heating and the second is the first two cells fail due to them being used to power the battery management chip and slowly discharging over an extended idol period. This causes the battery to be unbalanced. Once you get the red / green flashing lights three times on the charger your battery control board locks the battery from being recharge again.

I will be concentrating on replacing the battery control board as frequently this is all you need to do to get things up and running, although if you do require new cells these can be changed pretty easily. Makita seem to use the Sony Konion LiMn cells and these are available online for between fire and ten pounds each or you can frequently pick up failed batteries on ebay and cannibalise these for parts. If you do need to replace cells spot welding to the cells is the best way to go, as if you solder you risk overheating. Battery tab spot welders do come up on ebay from time to time or its something an electronics hobbyist could make themselves.

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Step 1: Dismantling & Inspection

Before we start with the dismantling, remember that even if your batteries do not work anymore they most likely still contain a significant amount of energy. Be careful in how you handle them and above all make sure you do not short them out.

So the first step is to get the cover off. This is held on by four T10 Anti Tamper screws, on newer models there may be a white Anti Tamper plug covering one of the screws. I have found that the easiest way to remove it is to drive in a small wood screw and pull it out with a pair of pliers. Once you have the battery open being careful that the retaining clip spring does not fly away or short out the control board you should be able to see if there are any obvious major issues. The first time I open one of these batteries up I was surprised how much dust had made its way into the batteries, I soon learned to keep my charger away from dust and never to charge them on the floor!

If on opening you seen any visibly damaged cells you are going to have to replace them which is outside of the scope of this write up.

Step 2: Testing the Batteries.

I had four failed batteries, and checked the voltages of the batteries and cell pairs individually. I found the following:

  • Battery One: Fails to charge with a over temperature alert. Also the plastic at the side of the release button has bubbled. It is showing 7.99v across the whole battery which is way to low and 0.04v, 0v, 3.96v, 0.04v and 3.97v across each of the cell pairs respectively. Upon opening up the battery there is obvious damage to the second pair of cells.
  • Battery Two: Fails to charge with classic red / green flashing lights. It is 12.84v across the battery and 3.2v, 0v, 3.22v, 3.22v & 3.21v across each of the cell pairs respectively.
  • Battery Three: Fails to charge with classic red / green flashing lights. It is 15.54v across the battery and 0v, 3.89v, 3.89v, 3.89v & 3.89v across each of the cell pairs respectively.
  • Battery Four: Fails to charge with classic red / green flashing lights. It is 18.15v across the battery and 3.62v, 3.63v,3.6, 3.63 &3.62v across each of the cell pairs respectively.

By way of comparison a known good battery seems to measure around 20v when freshly charged.

So I decided that my best option to end up with an extra working battery was to change the board on Battery Four as its cells were all pretty close on voltage suggesting it was fairly evenly charged. Up until recently replacement circuit board were not available so once you had seen the red / green flashing lights three times your battery was bricked. However recently they have become available for a round £10 which is certainly much cheaper than a replacement battery.

Fixing the other batteries is going to be a little more challenging. Whist it is possible to solder cells together the heat required to solder them risks damaging the cells. Having investigated purchasing a battery tab spot welder I feel that is out of my budget but I may have a go at making a capacitor discharge one.

Step 3: Replacing the Control Board.

The control board came with ok instructions on how to fit but they don't explain everything, this may be because it can be used with all of the models of 18v LXT battery Makita have made. Providing you have a bit of common sense you should be ok.

So apart from the soldering you might expect you also have to cut away a lot plastic and that's assuming you are lucky like me and don't need to replace any cells. If you do spot welding to the cells is the best way to go, as if you solder you risk overheating.As I had previously got the battery pack out of the case the first thing to do was remove the existing pcb and cut away the plastic pcb support etc as per the instruction. I opted to cut the nickel contacts instead of desoldering. Fitting the pcb and soldering the wires to the contacts was simple although I had to break out my larger soldering iron. By far the hardest part was getting the covers back on this took a little fettling of the plastic to get it to fit.

Step 4: Putting It to the Test!

Next came the moment of truth, I put the battery on a charger and it charged. I then fully discharged the battery and once again recharged the battery and that also worked. Eight month on the battery is still preforming perfectly.

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    40 Discussions

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    Snoopy2022

    2 months ago

    Please everybody : Beware of circuit boards with only two connections (+18V , 0V) to the cells.
    In order to protect your battery, the BMS must absolutely be able to measure the voltages of all the 5 series blocks, as the makita BMS does. If not, overvoltage will happen, and if the temperature sensor isn't close to the cells overvolting, the battery will catch on fire.

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    WBHenry

    Question 1 year ago on Introduction

    I bought new Makita 18v 5.0ah batteries that fit fine on my charger but don't fit on my drill.
    Is there a fix?

    2 answers
    0
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    ArronS10WBHenry

    Answer 7 months ago

    Just grab a sharp stanley knife, and trim
    Plastic on battery.

    0
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    High Voltage FunWBHenry

    Answer 1 year ago

    Sorry, I dont think so. I would be interested in a work around if you know of one.

    0
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    WBHenry

    Question 1 year ago

    I bought new Makita 18v 5.0ah batteries that fit fine on my charger but don't fit on my BHP451 drill.
    Is there a fix?

    4 answers
    1
    None
    ChrisJ301WBHenry

    Answer 10 months ago

    Yep you'll find there's a little plastic stopper (about 5mm x 12mm long) on the battery slide of your drill. I shaved mine off with a sharp 10mm chisel. Supposed to stop old tools being used with new batteries or vice versa but I've had no issues in 3 years of using them daily since.

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    darryl1940ChrisJ301

    Reply 7 months ago

    I had the same problem with mycordless angle grinder cut off the tabs Bingo works well I suppose makita would prefer you purchase the correct batteries

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    Robertwb70ChrisJ301

    Reply 9 months ago

    Did the same to mine, no problems yet (been about 2 yrs now).

    0
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    High Voltage FunWBHenry

    Answer 1 year ago

    Sorry, I dont think so. I would be interested in a work around if you know of one.

    0
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    darryl1940

    Question 7 months ago on Step 1

    where can I get a circuit board in Australia to suit a makita Li battery

    thanks Darryl

    0
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    JózsefP

    Question 9 months ago

    I will change the panel of my Makita 18V 3 A battery pack.
    I bought panel on E-Bay from China. But this panel is so as in Your pictures, and in my battery pack is other type. I think it's never.
    My question: in panel of Your pictures ( old panel ? ), where to solder the 4 cell outlets ( B1, B2, B3, B4 )
    Thanks!
    Jozef

    1 answer
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    High Voltage FunJózsefP

    Answer 9 months ago

    Hi Jozef,

    I am not exactly sure what you want to know. But if your battery is a latter generation battery you will will need a different control board.

    Cheers
    Stuart

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    jnissen

    1 year ago

    II recently fixed my Makita DC18RA charger fan by using a 5015 type squirrel cage blower with three wires (black -, red +, and yellow tachometer). EBAY had a ball bearing unit that was a perfect fit. I only had to exchange the plug end that snaps into the board. Snipped off old connector and spliced into new fan. Was $8.00 vs. $20+ from Makita.

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    YehudaB1

    Question 1 year ago on Step 1

    Does anyone know the manufacturer and part number for the yellow connector on the Makita LXT batteries? Those things snap off like nothing if you throw a battery in your toolbox.

    1 answer
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    High Voltage FunYehudaB1

    Answer 1 year ago

    Sorry I never had to replace one, you can normally get a failed battery for next to nothing, which you could harvest a connector from.

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    NguyenH189

    1 year ago

    pls help ! I dont have makita batterry thats why I ask for help, except red wire and black wire, there is a small red wire connect to the third connector, some one tell me how many volt this connector supply for the speed controller ? thanks alot

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    masoon

    2 years ago

    I like how Makita reversed their guarantee of 1000 charges or replacement.

    3 replies
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    High Voltage Funmasoon

    Reply 2 years ago

    To be fair to them its was never an official policy, just soemthing they often agreed to. On the plus side the later generations of batteries seem to be a lot more reliable.

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    rbbiggsHigh Voltage Fun

    Reply 2 years ago

    A class action suit was filed against Makita USA in 2015 for this premature battery problem. I believe part of the suit was Makita had to replace battery packs. So yeah, it is a policy now. Attornys had to twist Makita's arms to make it one.

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    masoonrbbiggs

    Reply 2 years ago

    So they do have to replace them? I saw some articles about the suit, but not the outcome. Do you remember where you saw that info? Thanks