Ask Cardoktor I purchased a Tesla Model Y-How to charge the battery correctly?

[evlover]

Hi Battery Dr

I purchased a Tesla Model Y with an LFP battery. According to the Tesla manual, the high-voltage battery should be charged to 100% once a week. Furthermore, the manual states:
The most important way to preserve the high-voltage battery is to I LEAVE YOUR VEHICLE PLUGGED IN when not in use. This is especially important if you plan to not drive Model Y for several weeks.
In my case, charging once a week is sufficient, which means I need to fully charge the battery to 100% every time. I understand that LFP batteries can handle being charged to 100% better than other types, but it is still generally recommended to keep the battery at around 50%.
How should I charge my Tesla Model Y if I want to preserve the battery and maintain it in the best possible condition for the longest time?

Thank you, Evlover

 

[Car Doktor]

Thank you for your question, Evlover

One of the most persistent and unfortunately still widespread myths is that fully charging or deeply discharging lithium batteries harms them, and they should always stay at around 50%. I don’t know who promotes this idea, but it’s simply not true! Please, don’t believe it for a second.
In lithium batteries, a lithium-ion migrates through a semi-permeable membrane and, when charged, nests comfortably in the gaps of a graphite lattice. When discharged, it becomes part of a compound complex. It’s not like we’re pumping air into the battery, causing harm from overpressure; the lithium-ion simply moves from one place to another under a small electrical potential of just 3–4V. As such, fully charging or discharging does not harm any lithium battery.

For ternary cells, the operating range is typically 2.5–2.7V to 4.2V (for LFP cells, it’s 2.00V to 3.65V). This represents the total battery capacity physically built into the vehicle. However, for safety reasons, manufacturers cut off a portion of this range at both ends, so it’s common for cells to only operate between 3.35V and 4.16V (LFP: 2.8V to 3.6V), which is called the "net" or usable battery capacity.

In the case of the Hyundai Ioniq with a 28 kWh battery, there have already been reports of cars suffering reduced capacity because they were managed using the "smart" 20–80% strategy. Similarly, the Bolloré BlueCar models are regularly repaired due to the damage caused by this supposedly "battery-friendly" wisdom. Every day, the list of victims grows.
The Tesla Model Y with an LFP battery will be the next victim if you don’t follow Tesla's guidance and instead listen to internet "armchair experts." The LFP battery's characteristics are such that the cell voltage doesn’t increase noticeably until the charge level reaches 99%. At that point, the voltage suddenly jumps by as much as 0.25V in seconds. This leaves the BMS (Battery Management System) with insufficient time to balance the cells, as it can only adjust their voltage in the last 3–5 minutes of charging. This is why it’s crucial to always charge LFP battery vehicles to 100%, not just 80%.

Moreover, the fear of charging to 100% is baseless because the unique properties of LFP chemistry cause the cell voltage to drop back down by 0.25V within just 15 minutes of reaching 100%. This means that even when the battery is at 99% charge, the "voltage stress" on the cells is exactly the same as it would be at 20% charge.
The one part I disagree with is the recommendation to "leave your vehicle plugged in." This might work in the U.S., but for everyday use, there’s no need to leave it constantly plugged in. Charge it during the day as needed (it doesn’t always need to be charged to 100%), but when you get home in the evening, plug it in and let it charge fully to 100%. Once charging is complete (or the next morning), unplug it. There’s no point in recharging every night if you come home with, say, 60–80% charge and have enough range for the next day. Use the entire battery range, as you paid for the bottom of the battery too, not just the top!

Think of it like a gas-powered car: if you don’t have enough fuel for the next day, you fill up before heading home but you don’t detour to the gas station every night just to keep the tank full. Manufacturers optimize charging systems for typical usage patterns, not the pseudo-science of armchair experts.
If the car will be unused for several weeks or months, then it does make sense not to leave the battery at 100%. In such cases, there are specific steps to follow, which I’ve explained in previous answers. For your situation, charging to 100% once a week is sufficient.

Best,
Battery Doctor

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[John]

From my own long-term experience, I can fully confirm what Battery Doctor explained, especially regarding how LFP batteries behave in real use.

I’ve been driving a Tesla Model Y with an LFP battery for over a year now, following Tesla’s recommendations rather than the common internet advice. I charge it to 100% at least once a week and don’t try to keep it artificially locked in a 20–80% window. The displayed range has remained stable, there are no signs of capacity loss, and the BMS calibration is clearly more accurate when the car regularly sees full charges.

Earlier on, I made the mistake of listening to too many generic lithium-battery “rules” and avoided charging to 100%. The result was inconsistent range estimates and a battery that never seemed quite sure where it actually was. Once I returned to weekly full charges, those issues disappeared completely.
What many people underestimate is the voltage behavior of LFP cells. If you’ve ever monitored the charging curve, you can clearly see how flat it remains almost until the very end. This chemistry behaves fundamentally differently from NMC or NCA packs. The classic idea of “100% - high stress” simply doesn’t apply in the same way here.

I also share a similar view on the “always leave it plugged in” advice. It makes sense for long periods of inactivity, but for daily use there’s no reason to overthink it. I charge when needed, let it reach 100%, then unplug. Not because it would harm the battery to stay plugged in, but because there’s no practical benefit once charging is complete.
Overall, I think the biggest mistake with LFP batteries is trying to apply universal lithium rules to a chemistry that works differently by design. If you trust the manufacturer guidance and use the battery the way it was intended, you get exactly what LFP was chosen for in the first place: stability, longevity, and predictable behavior.
It’s refreshing to see this explained here based on actual battery physics and real-world experience rather than forum myths.

 

[Mike]

From my own long-term experience, I can fully confirm what Battery Doctor explained, especially regarding how LFP batteries behave in real use.

I’ve been driving a Tesla Model Y with an LFP battery for over a year now, following Tesla’s recommendations rather than the common internet advice. I charge it to 100% at least once a week and don’t try to keep it artificially locked in a 20–80% window. The displayed range has remained stable, there are no signs of capacity loss, and the BMS calibration is clearly more accurate when the car regularly sees full charges.
Earlier on, I made the mistake of listening to too many generic lithium-battery “rules” and avoided charging to 100%. The result was inconsistent range estimates and a battery that never seemed quite sure where it actually was. Once I returned to weekly full charges, those issues disappeared completely.
What many people underestimate is the voltage behavior of LFP cells. If you’ve ever monitored the charging curve, you can clearly see how flat it remains almost until the very end. This chemistry behaves fundamentally differently from NMC or NCA packs. The classic idea of “100% - high stress” simply doesn’t apply in the same way here.
I also share a similar view on the “always leave it plugged in” advice. It makes sense for long periods of inactivity, but for daily use there’s no reason to overthink it. I charge when needed, let it reach 100%, then unplug. Not because it would harm the battery to stay plugged in, but because there’s no practical benefit once charging is complete.
Overall, I think the biggest mistake with LFP batteries is trying to apply universal lithium rules to a chemistry that works differently by design. If you trust the manufacturer guidance and use the battery the way it was intended, you get exactly what LFP was chosen for in the first place: stability, longevity, and predictable behavior.
It’s refreshing to see this explained here based on actual battery physics and real-world experience rather than forum myths.

What both of you are describing matches pretty closely with what I’ve seen in practice, but there’s one detail that made a bigger difference for me than I expected.
It’s not just about charging to 100%, it’s about how often the car actually gets to sit near the top of the charge curve.
With LFP the flat voltage curve makes it hard for the BMS to stay accurate if you spend most of the time in the middle range. I noticed that when I was doing mostly short drives and only occasionally charging to 100%, the range estimation started drifting even though nothing was actually wrong with the battery.
What fixed it wasn’t just “charging to 100% once a week” in a strict sense, but making sure the car regularly completes a full charge cycle and has a bit of time at the top so the BMS can properly recalibrate.

After that the behavior became much more predictable again.

On the other hand, I also tested the “always plugged in” approach for a while and didn’t see any real advantage in day-to-day use. The car manages itself well either way, but once charging is done, leaving it connected didn’t improve anything measurable for me.
What seems to matter more is consistency rather than perfection. Regular full charges, using the battery across a wider range, and not over-optimizing every cycle.
I think a lot of confusion comes from people mixing LFP habits with NMC/NCA logic. They look similar on paper, but in real use they behave very differently.
One thing I’m still curious about: have either of you noticed any difference in long-term consumption or efficiency when the BMS is well-calibrated versus when it’s slightly off? It feels like the car becomes more predictable, but I’m not sure if there’s any measurable impact beyond that

 

[WarrenAutoLab]

I’ve been following the recommended charging habits for my Model Y, mostly keeping it around 80% for daily use and avoiding unnecessary supercharging. It’s helped the battery feel healthy and maintain range over time. One thing I found reassuring is that if any issues ever pop up, professional tesla battery repair options exist and can address problems quickly before they get worse. It’s nice to know there’s a solution that keeps the car running optimally without jumping straight to a full replacement.​

 

[Car Doktor]

I’ve been following the recommended charging habits for my Model Y, mostly keeping it around 80% for daily use and avoiding unnecessary supercharging. It’s helped the battery feel healthy and maintain range over time. One thing I found reassuring is that if any issues ever pop up, professional tesla battery repair options exist and can address problems quickly before they get worse. It’s nice to know there’s a solution that keeps the car running optimally without jumping straight to a full replacement.​

Thank you for your input, WarrenAutoLab!

You’ve touched on a crucial point: one of the biggest fears in the EV world is a total battery pack replacement, which often equates to a total financial loss. It is indeed reassuring that by 2026, professional Tesla battery repair (cell-level diagnostics and module replacement) has become a viable, cost-effective option, so owners aren't forced to scrap the entire unit over a few faulty cells.

However, as the "Car Doktor," I need to make an important clarification regarding your strategy to ensure you hopefully never need those repair services:

The LFP vs. 80% Rule: You mentioned keeping your Model Y at 80% for daily use. If your Model Y is equipped with an LFP (Lithium Iron Phosphate) battery (standard in many RWD models), the 80% limit is actually more harmful than helpful. LFP chemistry requires 100% charging to calibrate the BMS (Battery Management System). Without a weekly full charge, the car can "lose track" of its true state of charge, leading to unexpected shutdowns even when the screen shows 10-15%.
The Supercharging Myth: With modern thermal management, occasional Supercharging does not drastically degrade the battery. The most important factor for State of Health (SoH) is balanced usage.
Proactive Protection: While repair options are great "safety nets," the best protection is following the manufacturer's chemistry-specific guidance. If you have an LFP pack, don't fear the 100% mark!
In summary: It's great to know expert help is available if things go south, but a proper charging routine (100% for LFP, 80-90% for NMC/NCA) is your best bet to prevent ever needing to open that battery pack for a cell-fix.

WarrenAutoLab, do you monitor your degradation data (using apps like Tessie or SMT), or do you just rely on the displayed range to gauge your battery's health?

Best,

-Car Doktor