@tine
Rick had mentioned that the cell wires should be equal length.
I plan to use 18 AWG wire (0.8 mm2), which is 21 milliohms per foot.
If I don't try to make the wires equal length, the difference between my longest and shortest cell wires will be about 10 feet, or about 0.21 ohm differential.
Given my nominal LTO cell voltage of 2.3V, the balance current might be on the order of 0.6 amp. At this current, the differential voltage drop on the cell wires, longest vs shortest, would be about 120 mV. I'm guessing you don't depend on measuring cell voltage while the balance current is flowing; but how critical is this cell wire resistance?
Is it worth going to the effort of making all cell wires equal within 1 foot? Within 1 inch? What errors are introduced if there is a 0.21-ohm difference between longest and shortest cell wires? What do you consider "best practices"?
Do not worry. We stop balancing for measurement. Keep the wires 90° to the power line so you minimize the EMI. Keep the loops as small as possible. @ Rick I just finnished writing the code for serial connetion. Please send me the Master BMS serial so I can add it to the firmware.
@tine Thank you tine; that is good to know.
When you say "power line", do you refer to any nearby 120/240-volt AC line? Or do you refer to any nearby high-current DC power cable?
Also thank you for finishing the serial-connect firmware update so quickly!
The power line that continues from sub-pack to sub-pack from batt- to bat+
@tine In my system the distance from the plane where I'd like to run the BMS cell wires, to the surface of the inter-cell bus bar, is about 45mm. Is that close enough to cause an EMI problem? The inter-cell bus bars are 10mm-thick by 50mm-wide copper straps (that is, they are not round wire).
If 45mm is too close, I can find a way to move them farther back, in which case there will be a 3-mm-thick aluminum frame channel between the BMS cell wires and the inter-cell bus bars. I suppose that would be the best solution.
