Revealed: the cost of the i3 lithium batteries

[TomMoloughney]

The i3's battery is comprised of 8 modules, each of which contain 12 cells. The pack has 96 large-format battery cells, not 8 cells as has been posted here.

As for Tesla, they use the the small 18650 cells that are commonly used in laptops. They can't just replace one though, they need to replace an entire module which has hundreds of them wired together.

The point I'm trying to make about Telsa is they can pull a defective subassembly, carry out maintenance at the service centre to replace a damaged cell. Or if it takes too long they can drop in a loaner pack whilst repairs are done elsewhere. Like they did with the squeaky or vibrating drive units.

Having smaller cells that can fail makes them easier (aka more cost effective) to replace. With the i3 approach - I'm not sure what can be fixed if one of the 96 get broken. Presumably stripping down and refurbing what is effectively a 234Wh cell (22.5kWh/96) doesn't sound like a job you can do on a bench at the dealership. But swapping a couple of 18650s and re-soldering is.

I say that having never seen the inside of a Telsa battery module, so I could be wrong. Obviously you can do the same to an i3 module... send it off for repairs, and slot in a loaner, but if it's totally defective that's a larger cost item to replace than 1 or 2 18650s.

I still think the i3 solution is more elegant, lighter and probably longer lasting, but don't quite get where the 20 odd years life expectancy comes from. That's news to me... I'm now thinking damn I should have waited till the packs were 50kWh as replacing a battery well before it's life expectancy is a bit silly. Unless they have a trade in programme later on. Like Telsa are doing on the Roadster (I sound like a stuck Telsa record now).

Is the refrigerant used in the same circuit to pre-warm the batteries in winter? I.e. it's basically a heat carrier?

PS - what's the warranty on the i3 battery, I never even thought to check this before! I presume something like 8 years 100,000 miles that Toyota introduced on the Prius.

BMW can swap a module just as quickly as Tesla can. That's what will happen if it is determined a module is bad. Neither Tesla or BMW will actually tear open a module and replace individual cells at a service center. An 85kW Model S has 16 modules, each have over 400 18650 cells. If a few cells are bad, you won't even notice it. If a significant amount fail or there is some other problem with the module, Tesla will just swap the module. BMW will do the same thing if one of the 8 modules in the i3 are bad. The job of swapping a module in an i3 can be done in less than a day at the dealership. I was able to have a private tour of the i3 technical training center at BMW headquarters in Woodcliff Lake NJ where I was shown how they would easily swap a module if it needs to be replaced. The module will then be sent to HQ where they will take it apart and decide whether to repair it or not. Service centers Tesla or BMW, aren't going to be tearing open modules and changing individual cells. ALl they will do is swap the module and send it to the mothership for analyzation and possible refurbishment.

There is a separate heating system for the battery pack, it doesn't use the refrigerant.

Yes, The i3's battery warranty is 8 years, 100,000 for defects, but it also guarantees at least 70% capacity for that term.

 

[ultraturtle]

...What is Tesla's definition of a failed battery pack? BMW is pretty straightforward about what it says it 'failed'.

Spot on.

There is a reason Tesla specifically declines any capacity warranty. From page 5 of the Tesla Model S Warranty document:

The Battery, like all lithium-ion batteries, will experience gradual energy or power loss with time and use. Loss of
Battery energy or power over time or due to or resulting from Battery usage, is NOT covered under this New Vehicle
Limited Warranty.

While the warranty covers the battery pack for unlimited miles, it does not cover much. As long as the battery can move the Tesla forward a few feet, replacement is technically not required. It is a smart move on Tesla's part, since they allow the owner full access to the battery bank's capacity in order to publish impressively high range numbers. Charging to full capacity and discharging to near zero capacity quickly degrades, and potentially damages lithium ion cells, so it would be financially irresponsible of Tesla to provide a capacity guarantee.

As we all know, BMW will replace or repair the battery pack if it drops below 70% state of health during the warranty period (which can be as high as 10 years and 150,000 miles in CARB states). In part to make this possible, BMW protects the battery bank from owner abuse by only allowing us access to ~87% of its capacity.

 

[user 1096]

Given the likely long life of the car, I'm wondering whether in the future, battery upgrades will offered. ....

Keep in mind, BMW is in the business of selling cars. Samsung will make the bulk of the $ from a battery upgrade and BMW can only take a cut.

I wouldn't be surprise if all the batteries are numbered and/or i3 has to reset from BMW's central control once a battery cell is replaced.

I have to comment: in 1971, with my first BMW, 2002, when the "Rochester Valve" went south, you could count on getting the same old GM rocker arm/valve cover anti=pollution valve at twice the price, but at least it had a blue and white roundel on the box, with a BMW part number. Living and driving a 175 miles east of Rochester (Delco research and plant), we were always amused...to a point.