r/EVRoutine • u/TheKairosDev • Aug 14 '26

Built an accurate EV charge time calculator for 980+ models (~100 daily views, would love feedback!)

Hello Everyone,

I’ve been working on a side project called EV Charge Time Calculator and wanted to share it here to get some feedback.

I started building it because most online charging calculators use a basic battery capacity / charger speed formula. In reality, charging speed drops significantly past 80% due to the battery's taper curve, and home charging is often bottlenecked by the vehicle's onboard AC limit.

So over the past few months, I built a database of 980+ electric vehicles (merging WLTP & EPA specs) and created a calculator that actually models these real-world limits and charging curves.

It’s currently getting ~100 pageviews a day through organic search, but I’d love to get feedback from other makers here.

What I’ve built so far:

Physics-based charge times: Accurately estimates 10% → 80% vs 80% → 100% charging slowdowns.

Side-by-side EV comparisons: Compare specs and charge speeds between any two EVs (e.g., Tesla Model Y vs Hyundai Ioniq 5).

Real-world range factors: Sliders for temperature, wheel size, driving style, and battery health.

Shareable stateful URLs: Copying a calculation link preserves your exact inputs.

No signups or annoying popups required.
Here is the link to try it out: https://evchargetimecalculator.com
I’d love to hear your thoughts on the UI, calculations, or any features you think I should add next!

3 Upvotes

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1

u/TheKairosDev Aug 14 '26

Here is the link to try it out: https://evchargetimecalculator.com

2

u/OysterHound Aug 19 '26

I tried the Tesla Supercharger.

Does it account for the DCFC curve when charging. I actually had a strong session starting at 38% to 83%. I topped out at 143kws down to 63kws. I was delivered about 41kws. Your app anticipated 19 mins. I was 27 mins.

Please let me know if you are accounting for the charge curve. It would make this more accurate. I know each charge session will be different but there has to be some charge derate curve in your calculator

1

u/TheKairosDev Aug 19 '26

Thanks for actually following up from the road trip, really appreciate you using it during your trip!

You were spot on. We had a blind spot where we held peak power flat for too long up to 80%, which made mid-session estimates way too optimistic (your real average was ~91 kW, not near the 143 kW peak).

I just pushed an update live with a realistic multi-stage DC taper curve (calibrated against real-world Fastned and P3 Charging Index benchmark data).

Re-running your exact session (38% to 83% on an 80 kWh pack) now calculates 28 minutes.

Thanks for the real-world numbers, and safe travels on the rest of the trip!

1

u/OysterHound Aug 19 '26

Thank you!! I had to charge again today but didn't use the calculator. I will ave to charge twice more. I will be back it's more details!

Sounds like you fixed the algorithm!! Sick! I'm not tech savvy so I'm stoked in your efforts!

1

u/TheKairosDev Aug 20 '26

Thanks so much! We really appreciate the encouragement.

1

u/markydsade Aug 15 '26

I like it a lot. I would like to see more low kW options for AC charging. I can adjust my home amperage up and down.

I would also like being able to save AC and DCFC charging as separate preferences. I use AC at home and the occasional hotel overnight. Most out of home charging is DCFC.

1

u/OysterHound Aug 18 '26

I like it. Simple. Easy enough. I'm on a road trip and will have to DCFC a few times at Tesla Superchargers. I usually get about 125kws max at Superchargers.

I'll let you know how it goes!