I never thought of the CA as just modulating throttle signal. Are wattage and current just calculated? How are they limited?
The CA v3 info page and it's manual has a fair bit of detailed info on how the CA works, how each thing is measured, calculated, etc, but in general:
The CA reads the battery current via whatever shunt it is connected to (the current is calculated based on the shunt resistance calibration setting in the CA, which you must set for whatever shunt the system has, it needs to be fairly precise to get reliable readings and correct operation).
Watts are then calculated from that based on the CA-measured voltage at the battery input to the CA.
Then the CA counts PAS pulses and timing, and measures throttle voltage, temperature sensor, torque sensor, ebrake input, etc.
Then it processes all of those via the settings you've chosen in all the menus, and outputs a throttle signal to the controller based on all of those.
There is a screen with lower cap letters that go CAP when limited. a/A for amps, s/S for speed, etc. I did look at this screen during my troubleshooting process and noted no limiting by the CA. That’s what initially led me to believe the issue had to be the motor controller?
If there is no limiting happening in the CA, then the next step is to look at the Vmin recorded by the CA during an event. That will show if there is any voltage drop occuring, and how far it drops.
If there is no voltage drop occuring, or not enough to engage the LVC of the controller, then the battery is not causing the problem.
That then typically leaves the controller. For instances where a problem starts after a settings change, it can be software or settings doing it, but when no settings changes in the controller have occured, it's usually hardware failure. When the problem is gradually increasing in frequency or effect, it's usually a part that ages or gradually fails, like oxidizing connections or aging capacitors or vibration slowly fracturing solder joints or wires (at the point they connect to something).
Lastly, when I balanced the low cell group yesterday, the BMS app reflected a balanced battery pack.
A balanced battery just means all the cells are at the same voltage at the point they are measured to be equal. It does not mean the battery is working correctly.
Rebalancing a pack with an imbalance (especially a severe one) does not fix the pack, it only makes all the cells the same voltage, and makes it possible to use more of the available capacity of the pack than ohterwise.
To actually fix a pack that has an imbalance, the cell(s) that are causing the problem(s) would have to be replaced with ones that are identical to the rest of the cells in the pack that still match each other in capacity, internal resistance, etc. Without doing that, the imbalance will simply recur over time, and grow worse with aging as the cells that are already different in characteristics become more different.
On the CA, I changed the max Amps from 40.0a to 99.0a to ensure no limiting. Shortly there after, the BMS led’s went out. Interestingly, the CA still reflected 57.6v and the drive system still operated. Only after I disconnected the battery did it not come back to life.
If the system still operated but the BMS's status lights that indicate it is working are no longer lit, the BMS could have failed but left the FETs turned on, or the FETs actually failed (which is usually in the stuck-on condition). In either case, once disconnected from the load, etc., the output of the BMS might have finished failing in the totally disconnected state (assuming you read 0V on the output), or the FETs might have turned off.
Or some other type of failure of the BMS itself with the equivalent results.
If a cell failed or dropped below the BMS LVC, the BMS should shut off the output (it might also shut itself down completely to prevent recharge of the potentially-damaged cell), but if the FETs are damaged from something they would still let current flow (and thus be unable to protect the cells, ever).
I created a diagram for balancing my batteries on the bench. Can you take a look at it? I want to verify connections to charge the 14th cell group. Do I have it correct? Thanks.
The first three on the left and top appear correct, but the lower right will probably destroy your balance charger and short out your pack, because you are connecting it both backwards (reverse polarity, with the positive charger lead on the more negative side of the pack than the negative charger lead), and across multiple cells, creating a much higher voltage across the charger input than it can output, which even if it were not connected backwards would still force a high current thru it's output stage.
Since the output stage is usually a fairly low resistance, it will also short across all those cells.
To charge any cell group you must connect across the cell group in question exactly like you did with the other three.
Connecting the negative charger lead to cell 13's positive, and the positive charger lead to cell 1's positive, doesn't allow charging any cell group. May I ask what your thought process / reasoning was for connecting this way?
On the CA, I changed the max Amps from 40.0a to 99.0a to ensure no limiting. Shortly there after, the BMS led’s went out. Interestingly, the CA still reflected 57.6v and the drive system still operated. Only after I disconnected the battery did it not come back to life.
