Each readout increases "dumb" charge count

[lukaskuzmiak]

Hey! Thanks for all the work that went into this.

I started playing with it and noticed each readout increased the "dumb" charge count by one - I am assuming this is just because some handshake needs to take place and battery remembers that as a communication with a charger and thus increases the count?

Not sure if anything can be done about it.

[mnh-jansson]

I'm unable to replicate that. Are you sure it's just not when you plug in the serial adapter? If you plug in the serial adapter without first starting the Python script, the TX would be high (making J2 high), causing the battery to go into dumb charge mode.

[lukaskuzmiak]

Yes, @mnh-jansson, this is indeed the issue, I am sorry, I was unaware of the battery's behavior. Thanks for clarifying that. I ended up watching [004] Reverse-engineering the Milwaukee M18 Redlink Protocol and have a better idea of the protocol now.

I think this would be best fixed in hardware to have a software-controlled pull-up for the J2 line and only starting it when the software decides to do that and initiate the communication. I happy to give this a go if you guys think it makes sense. I am not a big fan of introducing charge cycles by mistake 🙂

Are there other requirements for the communication? I am assuming you are trying to keep the components very simple so people are able to build this from random stuff laying around?

[mnh-jansson]

I've placed an order for a custom PCB with a fix for this. In this design i have DTR controlling TX through a N-channel mosfet. This will invert the DTR behaviour and should give the wanted effect.

Should be available soon.

[lukaskuzmiak]

Ok, cool. I've got a bunch of different M18 batteries and would like to inventorize them and see how old/bad some are. Happy to submit all that as well. But would wanna make sure I don't screw up the stats by introducing charge cycles. Already gutted an older charger to make a "diagnostic box". So if that ends up working pls keep me posted.

Btw, the voltage level is supposed to be BAT+ or 12V? Not sure what batteries that made it under 12V do.

[mnh-jansson]

Will do. The voltage needs to be higher than 8V, so down to roughly 10V VBAT will be ok. I think this is acceptable

[lukaskuzmiak]

Hi @mnh-jansson, how's it going with the custom interface? I'd be curious to pick this back up on my end - did you guys get anywhere or have some "latest prototype"?