We populated a prototype BMS board today:
A big thank you to the kind people at Electronics Innovations for allowing us to use their hot air gun, microtip soldering iron, and for their sage advice on how to mount surface mount parts, and how to repair the inevitable stuff-ups.
As you can see, BatchPCB redid our boards and this time they came out correctly. Unfortunately, they could not tell us what was different this time. One thing Weber noticed is that the slot for the opto isolator (which we know they can't route) was missing even from the silk screen overlay.
Only one of the four bypass resistors was installed, and on long leads, so we could still access the parts underneath.
We found only one stuffup: the push-button switch was wired the wrong way around, so it was always closed. As a result, the error latch didn't latch. I managed to bodgy the switch on at 90° so that it worked. We also noted the need for slotted terminal holes, so that it will work on both SE cells (60 mm) and Thunder Sky cells (64 mm). They are so close, and yet... irritating.
The rest of the board worked fine, although the temperature threshold was a bit high at 76°C, and the bypassing was at about 3.60 V, compared to the designed 3.57 V. (Edit: had bypass and overvoltage confused; overvoltage was also a little high at 3.65 V). We'll have to see if that's due to the design or due to component tolerances. The error latch reset was also up a bit at about 3.95 V, due to the voltage drop across the 330 ohm resistor that we neglected in the calculation. That will hopefully prevent some nuisance resetting. (Edit: was nuisance tripping.)
The LEDs are surprisingly bright, especially in subdued light:
With the bypass resistors installed, the board isn't as impressive:
One surprise is that the ceramic beads end up on the outside of the pigtails, not centred on the donut:
Note how one of the beads is touching R6. We can just move the donuts for the resistors in a few millimetres.
There is room under the bypass resistors for real 1W resistors (the ones we got are supposed to be 1W, but I don't think they'll take the voltage). Another thing to fix.
Another slight problem, more difficult to solve, is that there isn't much clearance over the wires to the daisy chain and monitor wires:
Edit: replaced last two blurry photos with sharper ones
Nissan Leaf 2012 with new battery May 2019.
5650 W solar, 2xPIP-4048MS inverters, 16 kWh battery.
1.4 kW solar with 1.2 kW Latronics inverter and FIT.
160 W solar, 2.5 kWh 24 V battery for lights.
Patching PIP-4048/5048 inverter-chargers.