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Significant Range Drop on 2017 Model S 75D - Battery Health Concerns?

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Mike T. · rep 0 · May 25, 4:02 AM · 1 replies · solved · Question

Vehicle: 2017 Tesla Model S 75D

Hey everyone, I'm a bit concerned about my 2017 Tesla Model S 75D. I've noticed a pretty significant drop in its estimated range over the last few months. I used to get around 230-240 miles on a full charge (rated), but now it's struggling to hit 200 miles, even with careful driving. The battery percentage also seems to drop faster than usual, especially in the middle range (e.g., 60% to 40%).

I mostly charge to 80-90% and only full charge for trips, and I avoid letting it sit at very low or very high states of charge for long. I'm wondering if this is just normal battery degradation for a car of this age and mileage (around 80k miles), or if it could indicate a more serious issue with the battery pack or its management system.

Has anyone with an older Model S experienced such a pronounced drop? Is there anything I can do to 'recalibrate' the battery or check its health more accurately? I'm trying to avoid a costly service visit if it's just normal wear.

✓ Accepted solution

ClearTheCode Admin

ClearTheCode Team · rep 0 · May 25, 4:02 AM

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ClearTheCode admin answer:

It's understandable to be concerned about a noticeable drop in range on your 2017 Model S 75D. Battery degradation is a natural part of an EV's life cycle, but a sudden or significant drop can sometimes indicate other underlying issues with the battery pack or its management system.

Here's what could be happening:

  1. Normal Degradation: At 80k miles and being a 2017 model, some battery degradation is expected. Tesla batteries are designed for longevity, but an 8-15% reduction in usable capacity over 6-7 years is not uncommon, depending on charging habits and climate. Your current observed range drop might fall within this normal window.
  2. Battery Management System (BMS) Calibration: The BMS estimates range based on various factors. Sometimes, the BMS can get out of sync, leading to inaccurate range predictions. A common method to attempt recalibration (though not guaranteed) is to:
    • Drive the car until the battery is very low (below 10%, ideally 5%).
    • Charge it to 100% and leave it plugged in for several hours after it reaches 100% (e.g., overnight). This allows the BMS to balance the cells.
    • Repeat this cycle a couple of times. Note: This should not be done regularly, as frequent 100% charging can accelerate degradation.
  3. Cell Imbalance or Failure: More serious issues can include individual battery cells or modules within the pack becoming imbalanced or failing. This can lead to a disproportionate drop in range and can affect power delivery. Your observation of faster drops in the middle range could be a symptom of this.
  4. Temperature Effects: Cold weather significantly impacts battery performance and range. Ensure your observations aren't primarily during colder months without sufficient battery preconditioning.

When to see a shop:

If the range drop is severe (e.g., >20% within a short period), or if you're experiencing other symptoms like unexpected power limitations, charging issues, or persistent internal diagnostic codes related to the battery (e.g., BMS_w001 - Battery Module Fault, or BMS_w002 - Battery Voltage Imbalance), it's crucial to schedule a service appointment with Tesla. They can run detailed diagnostics on the battery pack, assess cell health, and determine if a repair or replacement is necessary under warranty (if applicable).

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