What do all the pins on a Bosch 18V battery pack actually do?

[Thomas Martinez]

The Bosch 18V pinout is one of those things that's kinda scattered around the forums so I put it all in one place for you all to see if this is accurate or not.
The obvious ones are minus, plus, tool, charger pin for the tool to identify the battery, NTC for temperature indication so that the tool know if the battery is getting too hot, and then the C1-C4 pins for balancing the cells during charging.
I'm not sure if the tool or the charger uses the other pins for identification though. I'd think Bosch would be smarter than to just use resistors for identification. I'm guessing the tool wouldn't use the C1-C4 pins during charging.
Has anyone actualy taken one of these open to see if the identification pins are just simple resistors to ground?

 

[Apa]

on the procore packs there is definately more going on, theres a small mcu in there that talks to the charger. The older 4ah and 5ah ones with the round style are pretty much just resistor ID though.

 

[European Met]

C1-C4 are tap points for the cell groups, only the charger pulls on them. Tool side ignore them completely. If you measure between minus and C1 you'll get the voltage of a single cell group. Between minus and C2 you get two groups at around the same voltage.

 

[Double Sta]

C1-C4 are tap points for the cell groups, only the charger pulls on them. Tool side ignore them completely. If you measure between minus and C1 you'll get the voltage of a single cell group. Between minus and C2 you get two groups at around the same voltage.

wait so if I read like 3.6v between minus and C1 that means just the bottom cell group is at 3.6? what if I get 0v on one of them does that mean a dead group?

 

[European Met]

wait so if I read like 3.6v between minus and C1 that means just the bottom cell group is at 3.6? what if I get 0v on one of them does that mean a dead group?

Yeah pretty much. 0v on one of those indicates either a dead group on that side or a wire break to that group. Pull the shrink to inspect though, the spot welds on those nickel strips sometimes fails.

 

[Inquisitive Iguana]

the T pin (tool) on most bosch packs is just an NTC reference, the tool reads their thermistor through it. ID is a different pin. You mixed those up i think

 

[Save Yourself]

Nah dewalt is better

 

[Courageous Cat]

I tore one of the 6ah procore packs open last winter when the BMS bricked it after a deep discharge. There's a small PCB with what looks like a dedicated BMS IC and a tiny microcontroller. The identification pin into the tool isnt just a resistor on those packs. I had to scope it to find out that it actually pulses when actuating the tool's trigger. The older bare round packs on the other hand were just a thermistor and resistor identification on the tool.

 

[Double Sta]

I tore one of the 6ah procore packs open last winter when the BMS bricked it after a deep discharge. There's a small PCB with what looks like a dedicated BMS IC and a tiny microcontroller. The identification pin into the tool isnt just a resistor on those packs. I had to scope it…

so does that mean if you swap the bms board between two procore packs they wont work? like is the mcu paired to the cells somehow

 

[Courageous Cat]

so does that mean if you swap the bms board between two procore packs they wont work? like is the mcu paired to the cells somehow

Not in any cryptographic sense. The number of cells in the pack is reflected in the firmware on the MCU though. A bms from a 4ah pack probably wouldn't play nice with an 8ah, at least not without some reprogramming. Might be interesting to try it out with two packs of the same size though.

 

[British Un]

why do they even need a separate charger ID and tool ID? cant one resistor just do both jobs

 

[Apa]

why do they even need a separate charger ID and tool ID? cant one resistor just do both jobs

because the charger uses the ID to determine the chemistry and capacity of the battery. The tool just needs to know that there is a tool connected to the battery.

 

[A Boy and His Jackham]

you wrote that NTC is for the charger and probably the tool. Its DEFINITELY both. The tool absolutely throttles on temperature, ive had a gde18v shut off in the middle of a cut in the summer when it was hot outside, it was the battery's temperature, not the motor.