emmebrusa
commented
5 months ago The E7 overcurrent error has been present since version 4-update-3 for 860C, and has now been added to the stock display version as well. Overcurrent control is important. In some versions of OSF there were cases of burnt mosfets, one hypothesis was a bug breaking the motor control loop, so a current control was added in the main loop too. During one ride I had an accident, on a very steep climb, I made a risky gear change, the chain fell, got stuck and broke. The motor was at maximum power and consequently the blue gear was also damaged, but the E7 error appeared and this was enlightening. I understood that the current had reached 23A (overcurrent limit at the time, the battery limit was 17A) and that this control could also be used to protect the blue gear. The E7 control time was every 100 ms, so I reduced it to 25 ms. Subsequently the same accident happened to me, the chain fell and got stuck, it didn't break, the motor stopped due to the intervention of E7. Turned it off and on again, no damage to the blue gear. I also had confirmation of this from another episode, on a path there was a very high root, I should have got off the bike, but instead I pushed hard on the pedals to overcome it, I got stuck. E7 intervened and I got out without harm. How can an overcurrent occur? Is the question I asked myself. The answer is simple, motor control does not limit the current, the rule! If the acceleration is very fast, at maximum power the limit is exceeded. Only after exceeding it does the current decrease, following the deceleration ramp, until it stabilizes at the maximum limit. While with the intervention of E7 the interruption of the power is immediate and it is then necessary to turn the display off and on again. The current peak may be false, due to noise on the ADC input. To have immediate intervention, the instantaneous value of the ADC is controlled without filters. Applying a software filter would decrease the effectiveness of the function. Now the E7 trip point is 8A above the maximum battery current (in the 860C version it is 6A). It's in main.h, #define ADC_10_BIT_BATTERY_EXTRACURRENT 50. I increased it after a report like yours of unwanted interventions. However, the user did not solve the problem by increasing the limit, he instead solved it by decreasing the acceleration ramp. See if it works for you too. Otherwise we need to understand the cause.
dzid26
Sometimes it enters E07 when pedaling and stays there until restart.
There is fairly large amount of complexity around Battery maximum power. But this shouldn't even exist. Max Battery power is a marketing term and not physical limitation. Current is always the limit. (And why would we allow more current at lower voltage??).
If anything, battery max power could be converted to (secondary) battery current limit only once! - based on rated battery voltage (cells x 3.6V) - not startup voltage readings.
I am not sure if the problem is there, but it's likely. If I have a high battery voltage after charging, the limit will be low. That would explain why at the end of the ride I was not getting the error anymore.
I may try setting battery power higher so it doesn't have a influence.