Joined

·
843 Posts

Is the Ioniq EV traction battery level gauge linear, or weighted?

It is my view that in my previous Outlander, the battery gauge was linear in that it showed the battery charge remaining as determined by voltage. This meant that if I had travelled 12 miles and still had 50% charge remaining, I would have somewhat less than another 12 miles remaining.

This is because Lithium Polymer batteries have a fairly linear discharge curve in that the voltage steadily decreases as the cell discharges.

I use Lithium Polymer batteries in my hobby (Radio Controlled aircraft), and with the packs I use, the nominal voltage of each cell is 3.7v and a fully charged cell is 4.2V. I can utilise their capacity down to around 3.4v, but do not consider the cell to be fully discharged (to a safe level) until 3.2v

In terms of useable energy, it is the Amps (electron flow) that does the work. We measure the power of this work (when working with DC current) in Watts (volts x amps).

Now say we have a 370V Lithium Polymer vehicle traction battery, the fully charged voltage should be 420V, and if we need to pull 60kW, (60,000 Watts) from a fully charged condition, we would need around 143A (143A x 420V = 60.06kW)

As we use up the capacity the voltage drops, so by the time we get down to the nominal voltage of 370V we now need 162A to achieve the same 60kW (162A x 370V = 59.94kW). Pulling 162A is obviously going to use up the available charge much more quickly.

Ultimately then, it follows that a 50% charged battery will deplete more quickly than a 100% charged battery when presented with the same power demand.

So the question remains, is the charge level gauge weighted to represent actual useable power? or simply charge level remaining?

I have not yet gone below 3 bars of charge used in order to make a valid observation myself.