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Tesla's car batteries keep much of their capacity through 1500 cycles, but Apple's cell phone batteries only allow 500 cycles (300~500 cycles is also consistent with my experience and internet data from other cell phone makers).

So, is there some reason or technical trade-off causing cell phone batteries to wear out so quickly? It seems the Tesla technology could be scaled down to a typical cell phone battery priced below $10.

bobuhito
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    from your link: A normal battery is designed to retain up to 80% of its original capacity at 500 complete charge cycles when operating under normal conditions. That isn't "worn out." – Tiger Guy Oct 06 '21 at 14:55
  • cell phone batteries are only $10? – DKNguyen Oct 06 '21 at 15:04
  • @TigerGuy The 1500 is also for about 80%, so call it all "early wear out" if you want, but the comparison still is fair. – bobuhito Oct 06 '21 at 15:08
  • I'd love to see a 100-battery statistical study of different Li-Ion batteries with 20% to 80% recharge cycles until 80% capacity remains, but that's very difficult, so I don't expect to just find it. Anyway, I think my premise that Tesla batteries do 3x better would be true. It seems Tesla/Panasonic has optimized to give more cycles and their technology should now be ported to cell phones...or am I making some mistake? That's my question here. – bobuhito Oct 06 '21 at 15:20
  • Is the statement that tesla batteries can be scaled down your opinion? A pipe dream or established fact? If fact, what is the source? – Solar Mike Oct 06 '21 at 19:43
  • @SolarMike Tesla batteries contain a buttload (that's the ISO unit) of independent cells, each of which is rather small. However, the aspect ratio, compared with the super-thin "pancake" battery that cellphone mfrs require, is much more amenable to thermal management. – Carl Witthoft Oct 07 '21 at 13:34
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    @CarlWitthoft yes, was hoping the OP would be doing some research... – Solar Mike Oct 07 '21 at 13:36
  • Tesla batteries have a lot of over provisioning. A 60 kWh is actually 75 kWh. – Eric S Oct 07 '21 at 15:20

2 Answers2

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There are many factors that effect the longevity of a lithium ion battery.

  1. Running a battery harder reduces its longevity. Specifically, lithium ion batteries last much longer if not charged to their maximum voltage. The tradeoff is a reduction in capacity.

chart of battery capacity vs cycles for various charge voltages

A device which must be extremely compact might use a greater percentage of it's battery on a regular basis. This has a double hit on longevity, as a larger fraction of a cycle is used every day, and because the battery likely will need to be charged to a higher voltage (to maximize capacity), therefore the number of cycles it can withsand will also be decreased.

Modern devices like smartphones and EVs actively manage the battery charge level to reduce wear Here's a quote from apple:

With iOS 13 and later, Optimized Battery Charging is designed to reduce the wear on your battery and improve its lifespan by reducing the time your iPhone spends fully charged. When the feature is enabled, your iPhone will delay charging past 80% in certain situations. Your iPhone uses on-device machine learning to learn your daily charging routine so that Optimized Battery Charging activates only when your iPhone predicts it will be connected to a charger for an extended period of time. The algorithm aims to ensure that your iPhone is still fully charged when unplugged.

  1. Even with the same chemistries, battery cells can be constructed differently. With lead acid for example, you can make the plates thicker to improve the longevity of the battery, or thinner and more numerous to increase the current capacity (cold cranking amps). I don't know about lithium ion batteries specifically in this regard, but I assume there are similar design tradeoffs.
Drew
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  • As for my question with your #1 point, I don't see a Tesla as being charged less fully every cycle than an iPhone, so I can't apply your point. I think the key is in your #2 point, but you're basically restating my question without an answer. – bobuhito May 14 '23 at 11:36
  • Why don't you think #1 applies to these devices? It almost certainly does. – Drew May 15 '23 at 01:37
  • I don't have an iphone or a tesla, but I have an android phone and an E bike. Both of them have the capability to charge to less than 100%. If you can do that more often, the battery lasts more cycles, simple as. – Drew May 15 '23 at 01:39
  • I am saying #1 applies to both Tesla and to iPhones, so there should be no difference in battery performance between the two. I'm trying to understand the difference, why one battery is rated for 3x more cycles than the other. – bobuhito May 15 '23 at 03:21
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Something I learnt very recently is that there are massive differences in different types of Lithium rechargeable batteries. The number of charge discharge cycles in an LiFePO4 (LFP) battery - which are, I believe what Teslas 18650 cells are, have many, many more charge/discharge cycles then the Lithium Ion batteries I believe are used in Cellphones.

Lithium Ion has nominally about 500 charge/discharge cycles. Lithium Iron Phosphate batteries have nominally 2500 charge/discharge cycles [ Exact numbers vary, and depend on depth of charge/discharge, temp etc, but still, one is 5 times the other ]

Edit with some refs (per @Fred comment) -

  • Official Depth of Charge Recommendations for LiFePO4 from Victron Energy - 100% Dod - 2500 Cycles
  • PowerTech - 3000 cycles at 100% DoD for LiFePO4 batteries.
  • Figure one of this study shows the striking difference between LFP, NMC and NCA (all Lithium batteries) batteries
  • Here is another curve showing the number of cycles of Lithium Ion (NMC) cells. Note the conclusion - "NMC cells have a cycle life of 500-2000 cycles while LFP cells have a cycle life of 2000-5000 cycles depending on the cell form factor, charge-discharge C-Rating and operation temperature....
davidgo
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