Hi, I've read your story on instructables and I tend to think differently on the third pin usage. From engineering point of view, having full BMS on battery and not using it - it's just crazy and I simply refuse to accept that in Makita works some bad designer ;) And yes, "the star" Makita batteries have full BMS inside with ability to do the transistor cut off the power under every condition. So those batteries have under/over voltage, over current and over temperature protection (experienced all of those conditions with my set of tools). I've create a video with chines knock-off of the Makita battery (it had no any kind of protection, despite what it advertised) and also did BMS replacement for proper one with all protections (yes, they are available in china also) - but never posted it - so I could have a good look what is inside of all those original and not batteries inside. Anyway, the third pin I would call a grace notification for the tool that battery is close to be depleted. I assume that some kind of tools are better to shutoff itself, then been suddenly left without the power. So the device can shutdown itself properly finishing in known state (best analogy would be shutdown of the computer on power outage with UPS - UPS devices also give computer know, when they are close to be depleted, and if the devices won't shutdown itself - it will be cut off later anyway). And finally, yes the cutoff voltage on Makita BMS is extremely low - but those are professional tools and battery are not expected to last long, and what is more important, under heavy load the voltage read would be much lower then actual (not in my test - my load I would call mediocre) - so cutting it at 12V would be pointless as the capacity would be still there. You can just check how big voltage drop is on battery when you discharge it 150-200W and then check when you disable the load - I bet those would be few volts. ps. but yes, I agree those type of tests are not healthy for batteries - that's why some guys do those and post on YT - so others don't have to do it again ;)

@@sauronmakes...956 I know where you coming from and I did not intend to question your intentions or skills. I only go by the facts and honestly nobody can tell for sure why Makita is doing it this way. One thing we should take into the consideration is the fact that we are talking ONLY about the battery by itself. For Makita it's not only about the battery but the entire application. We don't know about Makita's business policies, governmental regulations, future products etc. Maybe Makita is doing the same thing what Tesla does, means programing the BMS the way it keeps the real capacity between 20-80% for longevity and battery health. In this case you would be right and discharging to 8V will probably not damage the battery! I am not an engineer, but I think by doing the Tesla trick you could over discharge your battery without damaging them since you are not completely depleting them! We just don't know and because we don't know I would go by facts and e.g. not discharge bellow Lithium's 2.8-2.9 per cell or at least Makita's STAR specification of 12V per pack (3. pin). We only would have certainty if somebody would take his brand new Makita battery and charge/discharge it completely as shown in your video, let's say for 500 times and then compare it to a normal STAR abused Makita battery. I am definitely not going to do that 😉 However, I appreciate your video and your response and hope to see more videos and tests in this regard. Take care and thanks again👍

@@sauronmakes...956 I found this video, so i could decide whether or how to use my makita batteries with other electronics safely, and I'm not yet fully conviced if the batteries themselves has LVP/Low Voltage Protection. People on the internet seems to disagree alot on this matter, is it in the batteries, in the tools, or is it a combination of the two. It wouldn't surprise me, if the LVP is in the tools, or a sort of handshake between the two, but as you say, it would be stupid to not have it in the batteries, I say no. Not from a business standpoint. Makita(probably) doesn't want consumers and hobbyists to make their own adapters for other tools or electronics. They can and will only vouch for their own ecosystem, so you'll buy more of their products. They think only about money in the end. For my own DIY electronics, I might end up using a bought LVP-board, and set cutoff artificially high, to protect my batteries :) TL/DR: I liked your video, and I hope we all find an ultimate solution to this discussion :)

Hello @BingoBongoMan (and I guess @magnuswf). It turns out you are both right, but also both wrong. The confusion comes from Makita LXT being different not just in time (star and non-star, and every other smaller modification they've made), but also by battery. The cheaper batteries (1.5 & 3Ah) don't seem to have stand-alone protection with a mosfet in the battery that can cut the power independently of the tool. The 5Ah and 6Ah do have this and will cut out usually at 12.5V, but at ~8V if the current is less than 5A. Where you are right is that Makita doesn't really use this cutoff mosfet and instead relies on pulling the 3rd pin low to stop the tool. If the tool stops within 500ms, then the mosfet stays on. kzfaq.info/get/bejne/qJekhNqgxqnIcnU.html

@@toolscientist ‘tool scientist’ knows !!!!!!!!!!!!!!!!!!!!!!!!!!!!!

They where charged and discharge in Makita device - so yes, they where used before test. But this "believe" about charging/discharging before reaching full capacity has no confirm in battery chemistry, it could be more to scale fresh BMS for battery then do anything with LiIon cells.

Nope, it doesn't (in general - for newer tools) - that's why Makita introduced batteries with "star" sign - that should be protected on it's own.

@@sauronmakes...956 You are wrong, battery protection is implemented in the tool, read the patents Makita.

@@user-mu3jx6hk6i There is absolutely tons of misinformation online about this, including from uniformed Makita staff. As you say, the protection mechanisms don't just sit within the battery but also within the tools/chargers. I wish that Makita would publish openly the circuits/schematics behind their batteries and charger/tool electronic protection but I figure they consider it valuable as trade secrets to prevent clones.

@@beardedchimp I've done some testing and mostly figured out what's going on. 1.5Ah and 3Ah don't have stand-alone protection and rely on the tool stopping when the 3rd pin is pulled low. 5Ah and 6Ah packs do have stand-alone protection, which is usually 12.5V, but is ~8V when discharge current is under 5A. I don't know where the 4Ah sits or if things are different in newer 3Ah packs (mine is 2017) or older 5Ah packs (mine are 2020 and 2022). kzfaq.info/get/bejne/qJekhNqgxqnIcnU.html

Capacity is one thing, performance is the other - more Ah batteries can provide more current, and this can sometimes be a game changer. But if you only need capacity, it's probably better (cheaper) to buy more 5Ah batteries (like 3x5Ah instead of 2x6Ah).

@@sauronmakes...956 5ah batteries are 80 euros and i found before christmas 2×6ah for 150 euros. So i bought 2×6. But it seems they were laying a lot since they are not with same power and duration. I bought it for duc353 and one always starts blinking before another one

And what discharge current did you use?

@@sauronmakes...956 about 5amps from memory

cutoff voltage seems to change with current. Less than 5A gives the 8V cutoff seen here. Over 5A gives 12.5V. 1.5Ah and 3Ah packs don't have stand-alone cutoff and rely on the tool to stop when the battery pulls the 3rd pin low.

New batteries (with "star") does have built in discharge protection, older batteries (without "star") did not. That's why some tools claim they are not compatible with older batteries. Third pin is for temperature. Other pins (small connector) are used during charging only.

@@sauronmakes...956 Maybe you could monitor the third pin and see if it does indeed switch off at a reasonable cutoff voltage. The batteries definitely have a microcontroller so there's no reason they can't signal the tool to switch of under many conditions (per cell under voltage, per cell over voltage, under temp, over temp for example). Just a little more reverse engineering is in order since unfortunately the behavior of that pin is not very well documented publicly. I can easily imagine that initially the third pin was only used to monitor temperature but as battery tech improved makita started using it to signal other issues as well.

A while back I researched how power tool battery under-voltage protection works, focussing on Makita. I remember reading that the reason the third pin is used as opposed to the battery having under-volt circuitry directly on the pins is that it would increase the internal resistance and result in a lower max wattage and higher wasted energy. This means that some of the knock-off batteries in pursuit of cheapness set the third pin as on and rely on low voltage cut-off. This can let the cells discharge not only below what is damaging but also far below what is safe, allowing the potential for internal shorts.

It's both. Protection is primarily via the battery signalling the tool to stop. Some newer batteries like the 5Ah and 6Ah have an additional layer of protection with internal cutoff mosfets that will switch off if the stop signal doesn't work. The mosfet cutoff voltage is normally 12.5V, but if discharge current is