Makita batteries info

[rks96]

Has anyone probed Makita 18v tool (yellow) connector? Most I got was 0.2v across a couple of connectors with multimeter. When googling, I found mostly speculation and that's it! I don't have an oscilloscope!
Second question: What is Makita battery pack max current output? Most sources I found say 20A. I could look at used cell max current rating, but that doesn't mean that it is same as max power that the tools actually use. In other words: Same batteries are used across multiple tools, what would be maximum power to support all of them @18V?
Thanks for reading.

[Kleinstein]

The small connector is used by the charger. The machines use the outer large ones for power and one more as a kind of power good signal. So the electronic in the battery pack can turn off the machine if the battery gets too hot or votlage too low. I would not assume much inteligence in the Machines. AFAIR there is a small µC inside the battery pack.  Some machines can use quite a lot of power for a short time. Nominally 20 A sounds reasonable, but short time current is very likely higher.

Chances are the circular saw and angle grinder would use about the maximum power they can get. Small angle grinders can use an awfull lot of power.

[mikeselectricstuff]

So the electronic in the battery pack can turn off the machine if the battery gets too hot or votlage too low.

The battery has no internal switching of the output - they rely on the tool's speed controller to cut out when battery voltage goes too low. From memory the battery has 2 parallel fuses - I think they were something like 25A  each

[janekivi]

There are many types of 18v battery and there are some videos about testing.
For example

I have one beeping BL1820 here probably 10 years old because of timestamp.
I can turn it's output ON and OFF. If I swipe over TH and AS and then short temp sensor it shuts OFF.
If I connect it to the charger it turns output ON again. Switching side is negative battery connection.

So some of them have internal switching of the output.

[janekivi]

There are two IRF7739 mosfets for switching and some chips.
TH goes probably to the fuse (15A FRC5) and it has connection to the positive battery pack pin.
AS goes to top of that marked 100 Ohm resistor below that fuse and then... only BigClive may figure more of that out.
BL1820 AS is 5.0V below battery back (it's beeping and it's faulty may be) and BL1840 NEWAS is 0.58V.
Last picture is from my working 2015 BL1840 where are no those mosfets and AS signal is now NEWAS (old was AS new is NEWAS) : )