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Comment by rkangel | Hacker News Reader

There's no mention of battery degradation. That's what I'd be curious about. Has anyone got a Tesla with a load of miles on the clock?

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I got my car in March 2013 and have 75K miles on it. I haven't noticed any degradation.

I'm sure if I were really careful to measure, there's been a few % of degradation, but nothing on the level of what you might experience from a 3 year old mobile phone and I never look back longingly on the days when my car could go further. There's no trip I took 3 years ago that I wouldn't take now.

There's an 8 year, infinite mile warranty on the battery, but there have been differing reports on when it gets replaced. I have heard numbers ranging from 15-30% capacity loss, but I plan to drive it for another 5 years, so I'm sure I'll find out.

This is amazing sounding. Laptop and phone batteries degrade so fast it seems!

Does anyone have any thoughts on why the Tesla battery isn't like this?

Not universally. At our company we have a mix of Macbooks and Dells. Our 2010 17" Macbooks will still hold a charge for 3 or 4 hours depending on usage, and they spend the vast majority of their time plugged in too. Newer ones are even better. The Dells on the other hand barely manage 20 minutes after about a year in the field, and the HP's aren't any better.

For whatever reason the majority of PC manufacturers just suck at making batteries (or charging hardware, not sure which.)

> For whatever reason the majority of PC manufacturers just suck at making batteries

They just suck at making battery cooling systems (e.g. all-plastic cases) or neglect to include one altogether. If there is one thing those all-metal MacBooks are good at, it's dissipating heat.

And I, someone who sets these up for a living did not know a battery needed to be cooled.

TIL. But yeah, that does explain why Macbooks' batteries hold up so well.

The enemy of batteries is heat. Most laptop batteries that I have had degraded prematurely due to poor heat management.

Phones are kind of a different case. The phones that I have had with bad batteries to begin with (Galaxy S2, Nexus One, etc) were often recharged multiple times per day. 1000+ cycles per year for two or more years will degrade the battery a lot, as the degradation is largely based on the number of cycles.

The Tesla P85D has a ~300 mile battery. Unless you are driving 300 miles per day, you are unlikely to see 1000 cycles in a year. If you do cycle it 1000 times, you've put 300,000 miles on it.

That is really a completely different situation from the typical mobile phone or laptop usage scenario.

I expect the soon-to-be-released 100kW pack to be even more durable due to further reduced cycling.

Really interesting point.

Out of topic, but is it possible that is this why phone manufacturers are shying away from putting bigger batteries in their flagships? They want the batteries to degrade in the 2 or 3 years of daily power cycle, and most people choose to upgrade instead of replacing their non-user-replaceable battery. Does this make sense?

I have often wondered the same thing. It seems like batteries in phones sometimes actually get smaller for no reason that makes sense to me.

It might just be that the manufacturers think everyone wants a thinner device, though.

Tesla battery packs have active thermal management, and improper thermal loading is one of the greatest enemies of li-ion cells. You are also not likely to cycle the pack nearly as much as in typical cell phone or laptop usage scenarios, which are usually drained/charged nearly fully once per day.

Laptop battery dying isn't catastrophic to the image of the company.

Tesla having bad batteries would be a PR nightmare. Toyota has taken similar measures with their prius, never let the battery go anywhere near a deep discharge. Through over provisioning you can make sure that any given cell is always in its optimal range, and in a big car like a tesla, extra weight wont be that negative. Laptops "need" to be thin and light, so over provisioning the battery means less usable life per charge and/or bulk.

Way different chemistry, reserve capacity, active thermal management.

Of these, the chemistry should answer for most of the improvements. Electric cars as a rule do not use standard lithium ion batteries exactly because of the degradation. Instead, they get less energy density.

Actually Tesla batteries use the same chemistry as most notebook batteries, the ones that prioritize energy density. The real difference is the usage pattern. Notebooks are usually left for days or weeks with a 100% charge and then drained to 0% when the battery actually gets used. Electric cars are charged to 80-90% at the beginning of each day and then drained no lower than 10-20% barring extreme circumstances. Anyone who flies RC aircraft (which use the same battery chemistry) will tell you that the only thing worse for a lithium battery than storing it at 100% charge is draining it all the way to 0%.

Active cooling and far more time spent not fully charged or discharged.

Think about how a laptop battery spends it's day: probably at 110 degrees and plugged it at 100% SOC. That's a perfect storm of horror for a li-ion battery. Tesla batteries spend nearly their whole lives at 70 degrees and between 20 and 80 percent SOC. That's the good life for li-ion.

Laptop and phone makers have pretty much zero incentive to protect the batteries they install.

The key to keep LiIon from degrading is 1) never allow it to go 100% full 2) never have it go 100% empty 3) avoid high battery temperatures, cooling if necessary.

Now on 1) and 2), to do that you have to give up battery capacity. If you only ever discharge to 5% and charge to 95% you've just given up on 10% of battery capacity. This makes your laptop look bad on "battery life" benchmarks.

For 3), as batteries make up 80% of the physical space in phones and laptops, that makes it very difficult to cool them actively or otherwise effectively. At the same time manufacturers want to sell fast charging capability to customers, and that's perfectly fine with LiIon, most of them are capable of gulping up much more current than most chargers deliver, only this dramatically increases the heat buildup in the battery. That's fine for a Tesla as it has liquid cooling for individual cells, but phones or laptops have none of that.

I'm pretty sure the Tesla batteries are controlled to never actually go to 100% capacity when charging, and likely have a hard cutoff well before fully discharging as well. I wouldn't be surprised to hear that there are other active battery management techniques in place as well. IIRC, one of their options for higher power capacity is actually just a firmware setting on the same battery packs, which would also match up - pay more for higher capacity on the same hardware, with the extra $$ paying for the increased wear and tear on warrantied components.

One thing you can do with some laptops is adjust settings to extend battery lifespan. Lenovo ThinkPads have settings in the power management software to set the maximum charge level as well as a range where it won't start charging (this is also available in their Windows 10 Lenovo Settings app, though I believe it wasn't present for the first few months of Windows 10). I set ThinkPads to not charge above 85% and to not start charging unless the charge level is below 75%.

Some other Lenovo laptops (e.g. Yoga 2 Pro ultrabook) have a similar but less-functional setting called "conservation mode" that in my experience caps the battery charge at 55-65%. The chosen values on those seem too low to me since my reading indicated that most of the benefit from capped charges is at the very high end, but that's what you get with consumer-grade equipment.

I'm pretty sure I've seen similar battery control options on other laptops, but I couldn't tell you which manufacturers support it without research.

Edit: Samsung calls this "Battery Life Extender." Lenovo (Win7) has it in Power Manager, Advanced mode, Battery, Battery Maintenance. ThinkPads (Win10) have it in Lenovo Settings, Battery, Battery Charge Threshold. Non-ThinkPads (Win10) have it in the same place, but as Conservation Mode. Some Dells (at least under Win7) have an option in Dell Quickset to "Turn off battery charging" until the next power cycle, but that's a manual process and more to prevent lots of small power cycles.

Note: my thoughts on Tesla capacity were in fact way off - they are physically distinct units.

75k for 300 range is nothing.

Degradation is directly proportional to capacity and early model electric vehicles start seeing noticeable degradation after about 600 full range charge cycles as a rule of thumb (probably improved by 20-30% since then).

That's why you see a TON of stories about degradation on Nissan Leaves (60084 = 50,400 miles, easily doable in 2-3 years of heavy commuting) and almost none for Teslas (600 280 = 168,000).

As you can see, a person would have to drive almost 21,000/year, which most people don't and by that point you'd be outside the warranty period (unless I misread the warranty)

> That's why you see a TON of stories about degradation on Nissan Leaves

Mind you, you need to remove the 2011 Nissan "Leaves" from the dataset, they had bad chemistry that didn't survive much on hot climates. New batteries are better.

Hot climates? Like what? Atlanta (where tons of leaves were sold because of local tax rebates IIRC) is definitely well within the normal range for North America. Not a lot of leaf owners in the Southwest (big commuting distances).

Saying they didn't survive hot climates is kind of misleading. "The warm range of normal" is more accurate.

I was under the impression that Tesla deliberately de-rated the battery. Meaning that its true capacity is greater than the "full" capacity that is reported.

I'm sure they're doing some clever things with not charging the packs to 100% because the heat and stress decreases the lifetime.

I am not a battery expert, but I believe that these can extend the number of charge/discharge cycles considerably.

That was the first things I was looking for in this article... I wonder why they skipped this topic as this is the most important thing related to electric cars

Most EV batteries have a total capacity greater than the usable capacity as some is reserved for degradation - this means you shouldn't experience much (if any) capacity loss until 10years+ of usage. The one to look out for is the P90D which will likely suffer increased degradation in Ludicrous mode.

I'm interested in this as well. I was under the assumption that the range of the Model S goes down slightly with every charge.

I assume the batteries aren't under the warrenty?

Is it the case with some EV's that you never own the battery, you have a lifetime lease so the unit gets refreshed every so often?

I'm surprised that Tesla honors the consumer warranty with the car being used for commercial purposes. That's pretty unusual I think.

Do most cars have warranties that only apply to non commercial use? I've never heard of that and it would be interesting to see some examples.

Most everything does.

My lawnmower has a 3 year warranty. 30 days if commercial use.

My blender has a 2 year warranty. 0 days if commercial use.

I don't know about cars or not having the exclusion, but it wouldn't surprise me.

Aren't car warranties for time and mileage, whatever is reached first? That already takes care of commercial use, I'd think.

Kind of. City miles are harder than highway miles. A taxi is likely all city.

I believe they have 8 year warranty for 100,000 miles by default, and you can increase that to 8 year and "infinite miles", which is what the taxi driver wanted to do next:

https://www.tesla.com/blog/infinite-mile-warranty

EDIT: It seems to differ based on battery model and other things, and the basic warranty is just 4 years and 50,000 miles now:

https://www.tesla.com/sites/default/files/blog_attachments/m...

You never had to increase it. "the warranty extension will apply retroactively to all Model S vehicles ever produced"

The Tesla battery pack comes with an 8 year, infinite mile warranty on all cars. Some small amount of capacity loss is considered normal over time, but from what I've read it's generally been pretty minimal.

My own Model S is only about two years old with a bit over 20k miles on it, so I don't know how things will go once the car gets older, but so far it's lost <1% of its range.

The battery has an 8 year unlimited mile warranty. I believe that it is considered to have failed if it is at 70% capacity or below.

In general, one should expect to get at least 300k miles (482,000 kms) out of a battery like the one in the Tesla before it gets anywhere close to this level.

I think the chemistry of the batteries is such that fully charging or discharging it is the most detrimental thing for its life. Charging it from say, 20% to 80% might actually be the optimal case for battery life.

You are correct - the interesting question is whether or not the Tesla pack has enough extra but unreported cells to cover that drop over time so you don't see the losses.

From the driver down in the comments:

> It was 430 km, and now 400 km, I'm in Canada so its not miles, I made 161,306 km ;)

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