Thanks for this thread
@nz_lifer it's been very informative to me. I'm a coder but historically haven't been able to stop myself from getting seduced by power electronics. As I currently have a ton of 18650 packs on hand to disassemble and make something of, it was only a matter of time until I found myself here contemplating what a purpose-built (but DIY) cell testing system would look like, and boy did you deliver. The schematic you posted showing the different circuits gated by mosfets controlled by your arduino is really like what I had been envisioning and I'm so glad to see that it really is as simple as I hoped it could be.
I'm curious if you have any thoughts about simplifying some of this. So I take it the floating voltage (4.2v) is shared and utilized by all the cells once they are "charged", yes? So that's circuitry that does not need to be duplicated (like your discharge and charge circuitry must be for each cell). Well, what about temperature sensing? I wonder if there's a way to run thermistors over to each cell, but mux a single temperature IC to them somehow. Or I guess if you're gonna use something like LM35 it would not be as complicated? But what mechanism will you use to mux them?
Thanks dc443 for the interest
Yes it is that simple once you know the basics.
And keyboard warrior friendly too since we don't have to manually place those microscopic components. My eyes and hands are not what they used to be. Still have to manually route all those interconnecting traces.
Float voltage device is 1x device shared per 16 cell board. It could be shared across the whole system as the power draw is not that much.
Temperature sensing is per cell, TEMP_1.
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All inputs are mux'ed to an onboard adc.
Full schematic here also.
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I put the adc onboard as my current design (pictured) has a ±0.003v error in use.
Due to the long run back to the adc, 200-500mm. 8"-20".
And poor onboard routing.
Chasing those millivolt unicorns
is not for everyone or required but I wanted to give it a go.
Tested floating above batch of cells.
Using this dc buck converter I had on hand.
Look at those starting voltages. Come here little unicron.
I will finalize the design and start routing the board in the next week.