New issue happening, soc % dropping upon departure, anyone else have this?

[lightspeed]

Here is a video involving Dr. Dahn that discusses how the accumulated errors that impacts the accuracy of SOC and thus GOM estimates can be eliminated with LFP batteries by taking them to 100% weekly to reestablish the SOC accurate readings without reducing battery life.

We have NMC batteries btw, so this doesn't apply to our batteries.

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[jthiesse13]

I didn't realize the issue in this thread was that it was dropping on both. I have the same issue with mine though. The truck will be charged to 85% and on the a/c charger overnight as soon as I unplug and turn the truck on before I even back out of the garage the display is saying 84% and before I get even a mile up the road it will be 83%.

I'm experiencing the same issue with my 23 Lariat ER where I charge it to 90%, and it drops to 89% before I leave the garage. It just started doing this a few weeks ago.

 

[ElectrifyingMe25]

Noticed this three days ago. Reached my target soc of 90% by 12am and by 12pm I unplugged, turned truck and a/c, 5 minutes later got in and took up and soc% dropped right away to 84.

Didn't think much of it since my target soc was reached 10 hrs prior to departure and I had the AC on for several minutes.

Yesterday I reached 90% couple hours before departure, got in and took off right away and soc dropped to 88%. No preconditioning in this trip.

I asked Reddit and Facebook, someone said to charge to 100% and see what happens. Got to 100% this morning and with no preconditioning I drove off and everything stayed constant. Got to work at 97% and 5 hrs layer left for lunch, almost immediately leaving work it dropped to 93%. No preconditions on this trip too.

I called my service shop who said the earliest they can get me in is Sept 24

Edit: I have a sr lightning and primarily level 1 charge. Did recently use level 3 once last week and couple times the week prior for a camping trip. But probably 95% of the time I'm charging level 1

Here is an answer to your question, compliments of X-AI (Grok-3). It's a great explanation and it makes sense:

Grok-3:
This question is about Ford F150 Lightning Trucks. Specially a 2023 XLT standard range battery truck. When I charge it to 90% and the get into my truck to drive it, within about 1 minute the percentage of charge on my battery goes to 87%. I know I can't be using that much power. Why does the state of charge fall so quickly then stabilize?

Answer:

Understanding the Quick State of Charge (SOC) Drop in Your 2023 Ford F-150 Lightning XLT (Standard Range Battery)It's frustrating to see that percentage drop so fast right after charging, especially when it feels like you're not using much power. This is a common experience among F-150 Lightning owners, particularly with the standard-range (SR) battery (98 kWh usable capacity), and it's not indicative of a major issue like excessive drain or a faulty battery. Instead, it's largely due to how the truck's Battery Management System (BMS) estimates and displays SOC. I'll break it down step by step, based on owner reports, Ford's technical details, and EV battery behavior.Why the SOC Drops Quickly (From ~90% to ~87%) Within 1 MinuteWhen you "charge to 90%," the BMS is estimating that level based on voltage readings during charging—when the battery cells are at their highest voltage after current flow stops. But once you unplug and start driving (or even just powering on the systems), a few things happen almost immediately:

1. Voltage Relaxation and BMS Recalibration:
   • Lithium-ion batteries (like the ones in your Lightning) experience a temporary voltage "sag" after charging ends. The cells were under charge current, which keeps voltage artificially high. When charging stops, internal resistance causes the voltage to drop slightly as ions redistribute evenly across the cells.
   • The BMS continuously monitors cell voltages, temperatures, and other data to refine its SOC estimate. In the first 30–60 seconds of driving (or system wake-up), it recalibrates to a more accurate "resting" SOC. This can result in a 2–5% apparent drop, especially near the top end of the charge (80–100%), where the BMS uses conservative buffers to protect battery health.
   • Why it stabilizes quickly: The recalibration settles once the BMS has fresh data from light driving or idling. After that initial adjustment, the SOC tracks actual energy use more linearly.
2. Battery Buffer and Usable Capacity Design:
   • Ford builds in a ~10% "buffer" at the top and bottom of the battery to prevent overcharging or deep discharge, which extends lifespan. So, your displayed "90%" is actually closer to ~80–82% of the true full capacity. When the BMS adjusts post-charge, it "reveals" this by lowering the display to reflect usable energy more precisely.
   • This is more noticeable on the SR battery because it's optimized for efficiency, and owners report similar drops (e.g., 3–4% in the first mile) when charging to 90%+.
3. Minor Power Draw from Startup Systems:
   • You're right—it's not "using that much power," but turning on the truck activates the high-voltage contactors, 12V battery top-up (from the main pack), infotainment, and possibly cabin preconditioning or sentry mode if enabled. This can sip ~0.5–1 kWh in the first minute (equivalent to ~1–2% SOC on your 98 kWh pack), but it's amplified by the recalibration above.
   • If it's cold (<40°F) or hot (>85°F) outside, the battery thermal management system (cooling/heating) kicks in briefly, adding a tiny extra draw. Ford recommends plugging in and using scheduled departure to precondition while plugged in—this draws from the wall, not the battery.

Is This Normal? Evidence from Owners and Ford

• Owner Reports: On forums like F150LightningForum.com and Reddit's r/F150Lightning, dozens of 2022–2023 XLT SR owners describe exact scenarios: Charging to 90%, unplugging, driving <1 mile, and seeing a 3–5% drop that stabilizes. Examples:
  • One owner: "Charged to 99%, drove 18 miles at 2.7 mi/kWh, arrived at 87%—initial drop was recalibration."
  • Another: "90% after charging, drops to 84–86% in the first few minutes of driving, then holds steady."
  • This is more common after Level 1/2 AC charging (like home setups) than DC fast charging, and on SR vs. extended-range batteries.
• Ford's Guidance: In the owner's manual and charging FAQs, Ford recommends 90% daily for longevity (vs. 100% for trips), noting that SOC displays are estimates and can fluctuate based on driving style, temperature, and load. Technical Service Bulletin (SSM) 53208 addresses similar "SOC drops from 100% to <90% within 60 seconds of driving" in 2022–2023 models, attributing it to BMS logic or rare cell imbalances (but no DTCs in your case, so likely normal).
• No Major Drain: If it were phantom drain (e.g., from software bugs), you'd see ongoing loss over hours, not just a quick initial drop. Your stabilization confirms it's not that.

Tips to Minimize or Work Around the Drop

• Set a Slightly Higher Target: Charge to 92–95% if you need a "stable" 90% post-drop. The buffer makes this safe for daily use.
• Precondition While Plugged In: Use the FordPass app or truck settings to schedule departure. This warms/cools the battery and cabin using wall power, reducing startup draw.
• Monitor with OBD Tool (Optional): If curious, an app like Car Scanner Pro via OBD-II can show real-time cell voltages and "energy to empty" (kWh remaining). This reveals if the drop is just display vs. actual energy (often it is).
• Temperature Management: Park in a garage or use a Level 2 charger (e.g., Ford Charge Station Pro) to keep the battery at ideal temps (59–77°F).
• When to Check Further: If the drop exceeds 5–7%, happens consistently below 80% SOC, or you see reduced range overall, visit a dealer for a BMS reset or module check (covered under 8-year/100k-mile battery warranty). But based on your description, it's textbook behavior.

In short, that quick 3% dip is the BMS fine-tuning its estimate—think of it like your gas gauge settling after a fill-up. Your actual usable range (EPA ~230 miles at 90%) isn't changing; it's just the display catching up.

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