Improvement to Battery SOC
On current version of firmware, there are 2 different ways for calculating the battery SOC: 1. based on battery voltage and 2. based on Coulomb counting (counting the used watts from the battery).
Method 1. is not very precise and 2. is very good for my experience as also from the feedback from users, so, I decided to remove the 1.
2. has the disadvantage that user needs to configure the right value for his battery Wh, but nowadays it is the most well know technical characteristics of ebike batteries because of range. Also the user can very easily use the display to measure the real value of his own battery.
Also, I decided to improve the 2., by considering the power loss on the battery internal resistance (this includes the cables), here an example how this power loss on the battery is relevant:
1. my battery has 350Wh (3.6V each cell * 3.5 amps/h each cell * 14 series (52V) * 2 paralel = 3.6*3.5*14*2 = 350Wh
2. my battery has internal resistance of 250 milli ohms (I did adjusted this value on the display until the voltage keep mostly stable while riding with motor pulling max current)
Let's say I am driving with motor pulling like 15 amps from the battery, the power loss is: P = R * I * I = 0.25 * 15 * 15 = 56 watts.
Since my battery has 350Wh, 56 watts of power means a 16% loss on the battery internals!! This means this value should be considered so the SOC can be more accurate.
Also, I decied to show on the battery configuration screen the battery power loss value, this is important for debug but mainly to educate the users that want to learn more about all this and maybe optimize their battery builds and/or the amount assistance power asked from the motor.
I also changed the battery icon on SW102 to be similar to the one on the 850C.
Here some pictures, in this case on SW102 but the 850C is similar: