Optimization issue with charging times

[irwinr]

Description: Route planner wastes time by asking you to charge unnecessarily high to reach the next charging station.

Type: Website

Link to Plan: https://abetterrouteplanner.com/?plan_uuid=bc54b4f8-6046-43c9-8776-88b7d490d9e0

Replication Steps:

1. Plan route from Orlando FL to Gulfport, MS using Kia Niro EV 64kWh

 

Notice that it asks you to spend 42 minutes at the "Kimco Village Commons" EA station to get up to 82% battery charge. Then it has you arriving at the next station in Chipley Florida with 40% battery.

 

Wouldn't it be far more efficient to only charge at Kimco Village to 52% and arrive at Chipley with 10%? I have my minimim charger arrival set to 10% and all of the other stops it has me arriving at 10%. Why is this stop having me waste so much time charging to 80+% so that I can arrive at Chipley with 40%?

 

See screenshot:

[CBenson]

I'm new to all this, having just bought an EV.  So I'm just guessing.  But my guess is that since you are down to 10% at your final destination, then should you arrive at Chipley with only 10% you'll just have to charge longer there.  It looks to me like Kimco Village has 350 kW chargers, while Chipley only has 50 kW.  So I'm guessing you'll waste less time charging at Kimco Village than at Chipley.  

Edited October 18, 2020 by CBenson

[Bo-ABRP]

Spot on! Chipley only has 50 kW chargers, and that means that the charger limits power instead of your battery up to a certain SoC. Most chargers are built so that they actually do not limit power but instead current, in this case 125A. Your battery will have slightly higher voltage at higher SoC and voltage x current = power so charging with a fixed current at higher SoC will actually give you more power. 

In these cases the difference is probably on the order of seconds or at most a minute, but the planner does not care - it looks for the fastest trip.

[irwinr]

Hmm. This does explain why it would ask me to charge higher than usual (52%)... But it doesn't explain why I'd want to charge all the way to 82%. In this case the ideal departure time would be the instant the charge tapers to a power level lower than what I would get at Chipley. At a 50 kW station like Chipley the Niro EV pulls down around 47-48kW (50kW stations are typically 125 amps.) So I would think I'd want to depart as soon as my charge tapers below 47kW...

At around 70% SoC the Niro EV will have tapered down to less than 47 kW of charging power (usually drops to about 38 KW) which matches the graphs you have posted on your blog. So if at 70% my charging power drops to 38 kW... and then it drops again to only 25kW at 78% SoC... Why would I sit and continue charging at 38kW and 24kW up to 82% when I could go ahead and depart and would get 47-48kW at Chipley?

Wouldn't it make the most sense to depart Kimco Village at whatever SoC the taper drops below 47kW (Which would be around 70-72%)?

[irwinr]

Well I can't reproduce this now because the Chipley EA station is down and now the route planner is avoiding it entirely... But another piece of evidence that suggests something else is going on here is when I changed my "Charger arrival SoC) from 10% to 5% I noticed the route planner had me charging at Kimco to 77% and arriving at Chipley with 35%. If it really was faster to keep charging to 82%, then why would lowering the "Charger arrival SoC" cause it to choose to charge to a lower percentage?

It almost seems it's somehow *adding* the "Charger arrival SoC" to the ideal arrival SoC rather than treating it as a minimum. In other words: It seems like the ideal situation would be to charge to around 72% and arrive at Chipley with 30%. But somehow the charger arrival SoC of 10% is being added to that 30% to get 40%.

[Leyline]

I know this is about a year too late maybe, but like the setting for charger arrival SOC there is a final destination arrival SOC.

You can even set it at each stop, so if you wanted to customize that it may allow you to skip a final charge, or charge lower at the last charger.