Reverse-engineering The Milwaukee M18 Redlink Protocol

In an excellent world, each single battery pack for energy instruments would use the identical bodily interface and converse a clearly documented protocol with chargers. Since we dwell in a decidedly less-than-ideal world, we get to benefit from the enjoyable pastime of reverse-engineering the interfaces and protocols of mentioned battery packs.

Hooking up a logic analyzer to a M18 battery and charger.

A current video from the [Tool Scientist] goes over what’s already identified in regards to the Milwaukee M18 Redlink protocol, used with the producer’s M18-series of batteries, earlier than diving into some prodding and poking of those packs’ delicate elements to see what comes out of their interface.

Beforehand, [Buy It Fix It] shared their findings on Reddit, protecting the essential protocol, together with the checksum methodology, however with out an in-depth evaluation of all the charging protocol. In the meantime [Quagmire Repair] carried out an in-depth teardown and reverse-engineering of the M18 {hardware}, together with the circuitry of the BMS.

Placing these two issues collectively, [Tool Scientist] was in a position to shortly get a few of his M18 packs strapped down into the evaluation chair for each passive evaluation, in addition to the impact of overvoltage, undervoltage, overheating and freezing the battery pack on the output reported by the battery’s BMS.

One of the lists of commands and response messages obtained by [Tool Scientist] on YouTube.
One of many lists of instructions and response messages obtained by [Tool Scientist] on YouTube.

The result’s a somewhat complete checklist of directions obtained beneath these numerous situations, together with a fault situation (05) returned by the BMS of 1 pack indicating its doubtless demise. Total, it doesn’t seem like a very particular (or well-designed) protocol, nevertheless it does make for an excellent reverse-engineering goal, whereas including to the physique of collective data on these extensively accessible battery packs.

Hopefully the identical inertia that stops individuals from transferring outdoors the designated energy software ecosystem as a result of incompatible battery packs may also be certain that this degree of  data will stay related for the foreseeable future, particularly for the reason that producers of knock-off battery packs appear somewhat unwilling to share the outcomes of their very own reverse-engineering efforts.

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