Makita Power Tool Battery Charger

As I mentioned before, along with the BL1850 and BL1860 batteries, I also received a charger for them. At first, I hadn't even planned to review it, but I tested it while checking the batteries, took it apart, and decided it was probably worth writing about after all.

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To get ahead of myself, I liked the charger, although, as always, there are a few caveats, which I'll get to at the end of the review.
The charger costs $16.80, but unfortunately the shipping cost spoils the deal: it's about $10.50, bringing the total to around $27.
This is the third review in the series. I previously wrote about the BL1850 and BL1860 batteries.

It comes in a neat little box with no printing. The package includes a power cable and a manual. Several plug types are available, and naturally I chose the European one.


To be honest, when I ordered it, I thought it would be a bit smaller, and I was surprised by its size when I unpacked it.


In the middle are a couple of LEDs indicating the operating modes, and... that's it.


On the left and right are some explanations about the sound signals, various melodies and so on, but when I tested it, it turned out to just beep. I love these ordinary beeping devices, with no melodies, light shows, etc.
In practice, I heard only two types of sound signals: a single beep when plugged into the mains, and a triple beep at the start and end of charging. That's it.


There are lots of possible operating-mode indicators, but I saw only a few:
1. flashing green - no battery installed
2. steady red - charging
3. steady red+green - supposedly indicates 80% charge
4. steady green - fully charged

I don't know how it determines the third mode, but in reality, if anything, only 1-2 minutes pass between the third and fourth modes.


On top are a sliding protective cover, the power contacts, and the system connector.


The power cable socket and a label with basic specifications. The stated charging current is 3 A.


There's nothing else interesting on the outside, so we'll continue our search inside. We remove the four self-tapping screws and lift off the top cover. By the way, it's quite conveniently designed: I didn't even have to disconnect the battery while measuring temperatures.


The first thing I noticed was the neatly routed cables. The wiring harness is neatly bundled with a cable tie so it doesn't flop around.


The circuit board is white. That doesn't affect anything, of course, but it looks neat. The board layout is very open, which should help with cooling.


1. The input has a full filter, with a fuse, thermistor, and varistor—in short, everything as it should be.
2. The input capacitor is 100 µF, which is more than enough for the stated power of 63 W.
3, 4. The high-voltage transistor and output diode assembly are mounted on heatsinks.


And this, as I understand it, communicates with the battery controller and actually manages the charging modes, since the charger is designed for batteries with different voltages.


The underside of the board is clean and neat. I'm always amazed by how many components there are in modern chargers. It made me think of the old chargers: a transformer, a bridge rectifier, a handful of components, and that's it.
Actually, yes, I don't quite understand why they have to be so complicated. Surely all this could be done more simply? It seems to me that some chargers are gradually approaching the complexity of a decent bench power supply.


PWM controller
Op-amp, presumably amplifying the shunt signal
Some transistors, I think for disconnecting the battery when charging is complete.


Here are a few photos of other chargers for comparison.
First, an older version of the original charger. I couldn't find its rated current, but it's claimed to charge a 3 Ah battery in 45 minutes, which means the current is around 5 A.


A newer version, with charging current up to 9 A. By the way, this one and the previous one both have a fan, but it's for cooling the battery, not the charger. The batteries I showed also have ventilation holes, incidentally.
Personally, I think 9 A is quite a lot, and it will only work properly (with airflow) with 3P batteries. Though I don't know, maybe it automatically reduces the current for smaller batteries.


And for comparison, here's the inside of a cheap Chinese charger, the kind with an LCD screen. I think many of you have seen these already.


In the review, I mentioned that both the battery and the charger have a system connector. I've been asked several times whether the battery balancing contacts are brought out there. No, they aren't. Enthusiasts have looked into this, and even tried to figure out the protocol, though they were actually trying to solve the battery lockout problem. In the end, some concluded that it was easier to buy a Chinese board.



As I already mentioned, the green LED flashes when there's no battery, and it stays red while charging. By the way, when I took the charger apart, I immediately stuck a piece of electrical tape over the buzzer so it wouldn't beep so loudly. It's much better now: you can still hear it, but it doesn't get in the way.

I didn't measure the charging current, because during the battery tests I found that:
1. It charges a 5 Ah battery in 1 hour 35 minutes
2. It charges a 6 Ah battery in 1 hour 55 minutes
And since the battery capacities are known, we can see that the claimed 3 A is there.

I also found that during a normal charging cycle, it charges the battery to 20.9–21.0 V. If you remove and reinsert the battery after charging is complete, it charges it to about 21.2 V. The difference in capacity is around 80–90 mAh, so I recommend using the normal procedure: insert it, charge it, remove it.
For example, after balancing, I topped up the battery—in other words, I tried to charge an already charged battery—and got 4809 mAh.


Then I charged it again, but in a single session, without topping it up, and got 4714 mAh. Without balancing, the battery delivered 4708 mAh in the same test, which, incidentally, indicates that it was in pretty good shape to begin with.
As I mentioned, I only found this out near the end of the tests, so there's some measurement error, since I'm used to my battery testers always charging the same way.



The battery is held in the charger by the standard latch, so it's hard to remove without pressing it. And yes, it could use rubber feet; that would make it more convenient.



While it was charging, I took a few thermal images. I shot them near the end of the charge, when the current was still at its full value but the voltage was close to the maximum—or, more accurately, right at the end of the CC phase.


It was hotter inside, of course. You can see that most of the heat is concentrated around the output diode assembly.
1. Overall view
2. High-voltage transistor
3. Output diode assembly.

The transformer was at around 80 °C, so the temperatures are perfectly reasonable, especially since this isn't a power supply that might run in this mode for days or weeks on end.


Then I thought: I have a DIY battery pack, after all. It doesn't look quite as nice anymore, but I haven't used it all that much.


It cost me over $45 at the time, if I remember correctly: 10 VTC6 cells at €3 each, plus a case with a board for about $12, plus shipping. The cells were new, high-quality ones from NKON.


I thought, why not measure its capacity? But I ended up doing two experiments.
The first was a self-discharge test. The last time I charged this battery was either in July (8 months ago) or at the end of March (almost a year ago). I thought I’d put it on charge, then run a test and measure its capacity. But in less than half a minute, the charger beeped to say everything was OK, deciding the battery was fully charged.
The second test was for capacity.
I connected it to the tester, set the discharge current to 1C, and got 5873 mAh before the cutoff at 12.5 V, or 5741 mAh with the cutoff set to 13.74 V.
Yes, this battery is almost a complete copy of the original, right down to the lack of a power protection circuit against over-discharge. This is exactly what I talked about in my battery reviews: using a battery like this with a “Makita-compatible” tool that has only two contacts is unsafe for the battery. For example, both of my screwdrivers have only two contacts, while my angle grinder has three, so in this case the battery can send a command to the tool.

But that’s not the point. Here’s an example of a battery with genuine, high-quality cells that still doesn’t deliver the expected 6 Ah.


By the way, this battery’s charge indicator lights up while it’s charging, which is very convenient.



And now for the conclusions.
As for the charger, all I can say is that I’m completely satisfied with it. Some people may like lots of indicators or a fancy musical accompaniment, but I didn’t need any of that. Two LEDs and a buzzer are perfectly fine: put the battery in and let it charge until it beeps three times.
I have no complaints about the charging current, or the charging itself, really. If you charge it in one go (without topping it up afterward), it leaves the battery slightly undercharged, which is perfectly fine too: the battery will last longer, and the difference in capacity is minimal.

Whether to buy one is a tricky question. On the secondhand market, you can sometimes get a genuine one for a similar price. They’re sold by people who buy tool kits, leaving them with a spare charger. But there are a few things to watch out for: sometimes you can end up with a 100–115 V version that you’ll have to modify, so be careful. I ordered the one reviewed here simply because it was sent to me as a bonus, and honestly, it’s more than good enough for me.

So far, it has fully charged the battery about 25 times and is still working fine. Looking at how it’s put together, I think it’ll keep working. At least it’s definitely better than the chargers “with a little screen,” though not as good as the genuine ones that can cool the battery while charging. Then again, the charging current here isn’t high enough to heat the battery noticeably, so it may even last longer with this charger.

That’s it for batteries and chargers for now. I’ve had a new board lying around for ages to convert a power supply into a UPS, so I’m off to solder it :)