Makita 18V Battery Has Big Problem!

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In this video I was solving the biggest Makita 18V battery problem once and for all. No more faulty dead cells inside and prolonged lifespan.

Used components and more:

18V Li-ion Makita Battery Protect Circuit Board:

Battery case for 9Ah battery:

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looks like you should change title to after-market "makita" batteries have huge problem..

izoyt
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I bought Makita first gen LXT lithium cordless tools in 2007. Quite a few of those batteries died within 5 years. Makita learned that battery lifespan is important to construction professionals. They rolled out second gen lithium batteries, gave me two on goodwill warranty. I bought many more. Have only managed to kill one of those over ten years. My fault, too.

wallacegrommet
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Funny thing, I came up with exactly same situation about 5 years ago. I got a bucket full of discarded Makita batteries. Some were ok, just low voltage. Some had 1 phase dead, others fine. Makita's charger would not charge them since battery circuits have low voltage memory.
I did exactly same solution. I didn't have 3d printer so I made the adapter out of plywood. Also I didn't use epoxy for connector attachment (I think I wil do it now). Still use it today to charge them with hobby charger. Great video!

SamiMarjeta
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The clone battery does not have any balancing leads. the leads which are connected are a measuring wire to check the first cell. This is used to do the fuel gauge and the internal electronics, which are much easier to drive from 3.5V-4.2V and not the full pack voltage.
The original board is deactivating the charging, not only with unbalanced cells, but also with low-voltage cells. Which could be charged but are very likely to fail soon and are not capable any more to deliver the currents needed. Therefore makita is deactivating the battery.

I dont really like this from a sustainability point of view, but as a manufacturer which have to garanty the current and power delivery for these battery it makes sense.

kayakerk
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Discovered this issue a few years ago, specifically on the 14.4 battery packs, (because these were the ones we were using).
On the early batteries the battery management board is permanently powered from the first pair of cells, resulting in the first pair of cells always being slightly more discharged than the rest of the cells. This issue builds up, especially if the batteries are stored for a long period. When the battery is used with the drill the first pair of cells eventually get slightly over discharged, which degrades them faster than the rest of the pack and reduces their effective capacity. I believe there is some natural cell balancing when the battery is repeatedly discharged and charged, however if the battery is stored this does not appear to be enough and the first pair of cells dies first.
It feels like a design fault/money saving exercise/intentional battery lifetime limiting feature, which makita have decided is acceptable because it doesn't normally kill the batteries before the 1000 charges in continuous professional use of the 4-5 years of DIY use.
As a side note, The battery management board on the early batteries communicates with the charger and appears to count charges and disable the battery if the number if charges exceeds a number, I have guessed at 1000 charges, remember putting a full battery onto the charger to see if it is full counts as a charge... I expect this is a 'safety feature' which the marketing department wet themselves over.

BitTwisted
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You can get the DIY kit cases with the larger balancing board too.

drsquirrel
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It is good to mention that original Makita 18V battery does not include low voltage and over voltage protection. A MOSFET is inside every Makita tool. Important if you use the battery for purposes other than Makita.
That's why I added a whole new BMS to the battery that has over and under voltage protection MOSFET included.

Eratas
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Goes to show you get what you pay for. Cheap aftermarket generic batteries are cheaper for a reason and this video shows why. It was a bit poor that the video didn’t clearly state the battery with the problem was a clone copy and not a genuine Maikta battery.

julesgraham
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Cells will become unbalanced with age, it's a normal part of the degradation process. When charging it with a RC charger like this, you're top balancing them and you might find at some point that you need to do this more and more often and maybe even with every charge, because they will not stay in balance. This might cause problems with the low voltage protection, because the individual cells aren't monitored during discharge and you rely on the low voltage protection that only checks the pack voltage. With the same modifications shown in the video, you could also bottom balance the cells. You discharge all cells individually to, for example, 3.0V. For optimal efficiency, you match this voltage times five with the low voltage protection of the power tool or the battery protection circuit.
Then, you charge the pack, but without balancing the cells (much like the original charger would do, or the RC charger does without the balance wires connected or the balance charge option selected). While charging, you monitor the individual cell voltages through your newly fitted balance connector. Towards the end of the charge, the cell voltages will drift and become unbalanced at the top of their charge cycle. You wait until the first cell reaches your desired end of charge voltage. Could be 4.20V, but you could also consider a slightly lower voltage, like 4.1V or 4.0V, which will increase the longevity of the cells. At that point, all the other cells will have a different voltage. You then take note of the pack voltage. This is your new end of charge voltage for the entire pack. You can then discharge the pack by using it in your power tools and the cells will be balanced at the bottom, just like you've set it up at the start. And then you can charge them again without balancing, using the RC charger or a lab bench power supply with adjustable voltage, set to your determined end of charge voltage.
By doing that, you make sure that all the cells, even though they're different because their different states of degradation, are in balance at the bottom of their voltage range. This is a bit more work at the start compared to top balancing, but there are two advantages. The first, you make sure that the low voltage protection still works properly. The second, charging will be quicker, because a top balance charge will take longer than just a normal charge.

christiano.
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You are completely wrong. It's not Makita batteries that have a problem, but the counterfeit cheap clones. Your headline is not serious.

-Prozent-MICHAEL
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I'm glad it's just the counterfeits that have this problem. I feel like it would be a massive safety risk if genuine makita batteries did not have active cell balancing.

RCHobbyist
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Where's the balanced board battery fix you mentioned for 2nd half of the video?

Iamsuccesspro
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Just checked my own 5 makita battery's but they all have the big pcb. Even the oldest one still works fine after 4 years.

peterdevreter
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The aftermarket battery is junk, that’s not last a year, my older original battery 10 years still going strong

cryingeva
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Great stuff. You should take a look at the dewalt flexvolt batteries. I suspect they have the same problem. Would like to see you do a mod to those.

davideyres
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Sir, if you wipe the tip of your solder iron on a wet sponge every time you pick it up you will achieve factory spec soldering. thanks for your video

michaeljettershank
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Good idea, but the OPEN PINS of the jst-xh connector are a safety issue. They are way too easy to short circuit.

izemanevobike
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IT'S A FAKE MAKITA! Use original Batteries!

TheOnlyDominik
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Praise God. My makita battery does not charge and 0 volts already for few months. Today, I jump start it by connecting a 20 volt well battery (same type of voltage) to the positive ang negative side of the damage battery. In just 2 minutes it becomes too hot and i stop it (pls stop if hotter-i did it with opened casing), then check the voltage of 4 volts. I let it cool and I charge it but it doesnt charge. I did it again in front of a fan for 1.5 minutes (It becomes hot then i stop it before its realy hot). I let it cool and voltage is about 8volts. I charge it and praise God it charges slowly up to full charge for some time. Thank you Lord. I ordered a makita 5-battery pcb board, but i cancelled it. Wow praise. I really want to take video to help others but i did not expect it will work. Just be careful in repairing. Pray always.😊

saved
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I have many Makita 18V tools.. and no problems with the batteries !

grafslo