Battery

How Much Cell Imbalance Is Normal? 263 Days of Pack Data, and Why Regen Looks Worse Than a Supercharge

On 16 September my own monitoring flagged my own car’s battery pack.

It was wrong. Worse, when I went looking for the culprit I found the wrong one — I assumed the supercharge that afternoon had done it, and the data says the drive home was twice as bad.

Both of those are worth showing, because the mistake underneath them is the same one that makes owners panic at a cell-imbalance number read off an OBD app.

Tesla Battery Replacement Costs: The $40,000 Quote Was Two Quotes

“How many ‘Tesla battery replacement costs $40K’ articles are being written right now based on this misunderstanding?”

— r/TeslaModelS

That comment sits partway down a 267-comment thread. At the top of the thread is a photograph of a Tesla work order for a 2013 Model S, total just under $40,000, posted with the caption “Upgrading to a 90kw. Just under $40k out the door.”

The commenter was right to ask. That invoice is a large part of where the internet’s Tesla battery number comes from, and it is not a battery replacement price.

Your Tesla Battery Health Test Says 78%. OBD Says 73%. Which Is Right?

Here’s a question that comes up constantly in Tesla owner forums, almost word for word:

“Coming up on 200k km. Tesla’s battery health test says 78%, but the OBD data works out to about 73%. Where does the difference come from — and which one is right?”

It’s a good question, and the answer matters, because a five-point gap sounds like the difference between a healthy pack and one heading for trouble. So people panic. They shouldn’t — and the reason why is a nice illustration of the difference between a number and a measurement.

The Community-Verified Used Tesla Model S & X Buying Checklist (2026)

Two owners of the same car, same year, same spec:

“I have 42k miles on my 2017 X and in the last 6 months have paid about $4,000 in repairs… Car is turning into a pumpkin with such low miles.” — r/TeslaLounge

“Our 2017 with 125k on it has been perfect. Tires only.” — r/TeslaModelX

Both are telling the truth. A used Model S or X is not one gamble — it’s a stack of small, checkable facts, and almost every expensive surprise in the first story was visible before purchase if you knew where to look.

How to Check Your Tesla Battery Health in 2026

Your Tesla’s battery pack is the single most expensive component in the car — commonly $12,000–$22,000 to replace out of warranty. Yet the owner UI gives you almost no visibility into its long-term health.

This guide covers the four ways to actually check it, from free to fully automated — and, more usefully, what each metric reads on a real nine-year-old Model X we’ve tracked every day for 263 days, so you know what “healthy” is supposed to look like before you go hunting for problems.

Tesla Phantom Drain: Causes, Diagnosis, and How to Fix It

You wake up, check your Tesla app, and your car lost 8 miles of range overnight. It was parked in your garage, plugged in to nothing, doing… what exactly?

This is phantom drain — one of the most common Tesla owner complaints. Here’s what’s actually happening, how to diagnose it, and a measured example from our own car that shows why the app can’t be trusted to tell you.

What Is Phantom Drain?

Phantom drain (also called vampire drain) is the gradual loss of battery charge when your Tesla is parked and not in use. Every Tesla experiences some level of it — the car’s computers never fully shut down. But “normal” is 1–3 miles per day. Anything beyond that deserves investigation.

What's Normal Tesla Battery Degradation? Data from 100,000+ Vehicles

“My Tesla lost 15 miles of range in the first year — is that normal?”

This is probably the most common question in Tesla forums. The short answer: yes, probably. But let’s look at the data.

The figures in this article are drawn from published large-fleet degradation datasets — chiefly Geotab’s EV battery degradation study, Recurrent’s Tesla range reports, and Tesla’s own Impact Report — cross-referenced with owner-reported numbers on Tesla Motors Club and Reddit. They’re population averages: your individual pack depends on climate, charging habits, and configuration.