#### smorgasbord

##### Well-Known Member

- Region
- USA

There have been many a post about Battery SoC (State of Charge) read-outs. From @Court rightfully complaining in reviews when bikes have just 5 bars, to inaccurate voltage readings even those are available. Having worked in Automotive a bit, I know that even gas tank sensors are put through a look-up table to convert the level of non-uniform gas tanks into actual gallons. We need to do that with our eBike batteries, too - yet no-one does it! The Voltage to SoC charts posted here (I've even posted them) basically just divide the voltage difference at 100% and 0% into equal parts. But, voltage drop is not equal for equal watt-hours consumed.

We all know this when we see that we get far more miles going from 5 bars to 4 than when going from 2 bars to 1. It creates Range Anxiety.

To gather some data, I took a ride today. After a couple of miles, I reset the EggRider trip and rode 1.55 miles at PAS level 4 (of 9) at about 15MPH (Trip A).

Then I created a new trip and rode about 20 miles to drain the battery (and have some fun).

Back at the starting point, I reset the EggRider and did the same 1.55 miles at the same PAS level and trying to go the same speed (Trip B).

Starting Voltage: 57.7volts = 96%

Ending Voltage: 57.1volts = 89%

Delta Voltage = 0.6 volts or 7%

Delta time: 6:43

71.3 Watt-hours consumed

Starting Voltage: 54.1volts = 71%

Ending Voltage: 53.3volts = 66%

Delta Voltage = 0.8 volts or 5%

Delta time: 6:37 (OK, so I went 6 seconds faster)

67 Watt-hours consumed

Notice that even though I used less Watt-hours on the second trip, the voltage drop was greater (0.8 vs 0.6).

What surprised me was that apparently the EggRider already has some kind of non-linear table built-into it. With more voltage drop later in the day, the SoC% drop was smaller. Maybe there's some rounding going on.

Questions:

We all know this when we see that we get far more miles going from 5 bars to 4 than when going from 2 bars to 1. It creates Range Anxiety.

To gather some data, I took a ride today. After a couple of miles, I reset the EggRider trip and rode 1.55 miles at PAS level 4 (of 9) at about 15MPH (Trip A).

Then I created a new trip and rode about 20 miles to drain the battery (and have some fun).

Back at the starting point, I reset the EggRider and did the same 1.55 miles at the same PAS level and trying to go the same speed (Trip B).

**TripA:**Starting Voltage: 57.7volts = 96%

Ending Voltage: 57.1volts = 89%

Delta Voltage = 0.6 volts or 7%

Delta time: 6:43

71.3 Watt-hours consumed

**TripB:**Starting Voltage: 54.1volts = 71%

Ending Voltage: 53.3volts = 66%

Delta Voltage = 0.8 volts or 5%

Delta time: 6:37 (OK, so I went 6 seconds faster)

67 Watt-hours consumed

Notice that even though I used less Watt-hours on the second trip, the voltage drop was greater (0.8 vs 0.6).

What surprised me was that apparently the EggRider already has some kind of non-linear table built-into it. With more voltage drop later in the day, the SoC% drop was smaller. Maybe there's some rounding going on.

Questions:

- Does anyone know if the EggRider really has a battery voltage to battery SoC adjustment and so its SoC readout can actually be (more) trusted?
- Why don't all displays do this? Having a look-up table to convert voltage to SoC takes little memory and tiny CPU.
- Does anyone have good data on what the right battery voltage to SoC conversion table looks like? It would be easy, if time-consuming, to build.

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