Structural batteries in electric vehicles

[Isaac Zachary]

Ya, swapping would only make sense if some far superior chemistry for range comes out that takes a long time to charge.

Either that or a cheaper battery that has a lower life expectancy. To fix the changing range problem it could have a fixed kWh made available that's lower (say 70%) of the total battery capacity. When the capacity degrades to that available amount the battery is considered out-of-service.

[freebeard]

I don't want... I don't want ....

Nobody is holding your feet to the fire.

The swappable battery has established a business model on the low end. Tesla tried and abandoned passenger vehicle battery swapping.

I suspect the opportunity is on the high end, trucking and fleet vehicles.

[redpoint5]

Originally Posted by freebeard

Nobody is holding your feet to the fire.

The swappable battery has established a business model on the low end. Tesla tried and abandoned passenger vehicle battery swapping.

I suspect the opportunity is on the high end, trucking and fleet vehicles.

The context was passenger vehicles, so that's what my response was in reference to.

I've speculated in other threads before that battery swapping would make sense in certain applications. The most interesting to me is autonomous farm tractors. Once they become automated to the point of not requiring a dedicated operator, they could swap packs as needed to continue working while the spent pack is recharged.

There's an interesting case for it in trucking too.

There's no profitable model for passenger vehicles though. Even an autonomous taxi fleet would probably be better served by simply having more vehicles than having swappable batteries.

[oil pan 4]

Hot battery swapping batteries is stupid. Like "coal being the safer choice over nuclear" level stupid.
But it is nice to be able to get the battery worked on or a full replacement so the whole vehicle isn't junk because of a bad cell or to repurpose the battery from a wrecked car.
Structural battery vehicle a bad battery or wrecked vehicle means the whole assembly is trash.
When the car gets crushed at the junk yard they just going to let the battery explode and just let the car burn?

[Xist]

Sawzall.

[JSH]

Originally Posted by Isaac Zachary

Now compare that to a full sized EV battery. The 24kWh OEM Nissan Leaf battery costs some $8,000 and has only gone up in price even before COVID-19. We have yet to see if cheaper-per-kWh aftermarket solutions will actually last.

On one hand the Nissan Leaf is a poor example as they are the only company that I know of that went cheap and put an air-cooled battery in an EV. That is why they have some many failure in hot climates.

However, they are also a good example as their design failure also makes them the first large manufacturer that has needed to offer replacement battery packs on a somewhat large scale.

So let say I have a Leaf and the battery fails at 8 years / 100K miles right when the warranty expires. I then buy another new battery from Nissan with another 8 year / 100K mile warranty. If it also fails right at the warranty it will have cost me $1000K a year / $83 a month or 8 cents per mile. Add another 3 cents per mile for electricity to charge the battery and the "fuel" for my EV has cost me $11 cents per mile. That is the equivalent of a gas car getting 33 mpg with gas at $3.50 a gallon. So worst case I'm coming out ahead of buying the typical gas car in the USA. (Currently 24.9 mpg)

Originally Posted by Isaac Zachary

Then add to that the structural aspect we're talking about. There have been a few Tesla owners who have had a single battery module go out and Tesla now won't replace just the module. Thankfully some have figured out how to do it and have saved themselves the cost of a whole new battery. There are similar stories with Prii and Leafs. But with a structurally battery the whole thing is one module! Now what?! Replacing just the bad cells will be very prohibitive.

Tesla is the oddball when it comes to battery design. Both that they use small cylindrical cells and that they glue their battery together. If you look at designs from traditional automakers they are using much larger pouch or prism cells that are in pack and modules that are mechanically fastened together. This not only makes them easier to repair but also easier to repurpose and recycle at the end of life in the original vehicle.

You can make a battery pack a stressed member in the chassis without gluing it in place. Engines are stressed members in motorcycle frames and they are still bolted in place and can come out for service.

[Isaac Zachary]

Originally Posted by JSH

So let say I have a Leaf and the battery fails at 8 years / 100K miles right when the warranty expires. I then buy another new battery from Nissan with another 8 year / 100K mile warranty. If it also fails right at the warranty it will have cost me $1000K a year / $83 a month or 8 cents per mile. Add another 3 cents per mile for electricity to charge the battery and the "fuel" for my EV has cost me $11 cents per mile. That is the equivalent of a gas car getting 33 mpg with gas at $3.50 a gallon. So worst case I'm coming out ahead of buying the typical gas car in the USA. (Currently 24.9 mpg)

Good points. And it's something a lot of people don't understand. They are willing to pay $1 or two for an ice cream cone but fell $4 is too much for a whole box of ice cream...

On the other hand, putting a lot of money all at once in a car that's worth less than that puts a person in a difficult situation if an accident were to occur. If the next day your car is totaled and according to the insurance company worth only $5,000, there's an extremely small chance you'd be able to get both your $5,000 plus the $8,000 you just spent on your battery. So you wouldn't be able to go and buy another $5,000 Leaf, just like yours, and put in a new battery, just like you had done.

Also, depending on where you live you could be paying as much as 30 cents per kWh. Add it all together and you'd be paying much more than a small gasser.

Originally Posted by JSH

You can make a battery pack a stressed member in the chassis without gluing it in place. Engines are stressed members in motorcycle frames and they are still bolted in place and can come out for service.

Of course this is all speculation. From what I understand a lot of car companies are against right to repair. So they could care less how easy they make their batteries to come apart, especially if the have the excuse "it's a structural member." But in the end, we really don't know what the end result will be for car owners.

[redpoint5]

It was Sandy Monroe who most famously suggested that Tesla make the battery into a structural member because he noticed the frame was made stronger/heavier than necessary.

Originally Posted by Isaac Zachary

If the next day your car is totaled and according to the insurance company worth only $5,000, there's an extremely small chance you'd be able to get both your $5,000 plus the $8,000 you just spent on your battery. So you wouldn't be able to go and buy another $5,000 Leaf, just like yours, and put in a new battery, just like you had done.

Good point. I wonder how an insurance company would appraise that scenario. They don't cover stuff the owner installs like expensive stereo systems or custom rims, so I wonder how they would treat the battery. It's not exactly custom gear, as it's essential to the operation of the vehicle.

I once argued with an adjuster for a couple months about their valuation of my Subaru. They argued it wasn't worth much because there wasn't a straight piece of bodywork and it had 220,000 miles on it. I argued it ran perfectly, and I valued it for the utility and not for picking up babes. Comps for vehicles that ran perfectly were much higher; it's not my fault they hadn't used up the bodywork as much as me. I ended up negotiating 2.5x their initial offer.

A similar problem will occur where an old EV will have a new battery, and there will be no comps to base replacement price off of. Then it becomes a matter of who is more stubborn on which value is settled on.

[JSH]

Originally Posted by Isaac Zachary

On the other hand, putting a lot of money all at once in a car that's worth less than that puts a person in a difficult situation if an accident were to occur. If the next day your car is totaled and according to the insurance company worth only $5,000, there's an extremely small chance you'd be able to get both your $5,000 plus the $8,000 you just spent on your battery. So you wouldn't be able to go and buy another $5,000 Leaf, just like yours, and put in a new battery, just like you had done.

Sure it is a risk. No different than if you put a new engine in an old gas car.

Originally Posted by Isaac Zachary

Also, depending on where you live you could be paying as much as 30 cents per kWh. Add it all together and you'd be paying much more than a small gasser.

At 30 cents a kWh that would come out to 7 cents per mile + 8 for the battery = 15 cents (and you have a huge incentive to install solar) That is about the same as a gasser in the low 20 mpg range (for just the gas not including thousands in maintenance the years)

Originally Posted by Isaac Zachary

Of course this is all speculation. From what I understand a lot of car companies are against right to repair. So they could care less how easy they make their batteries to come apart, especially if the have the excuse "it's a structural member." But in the end, we really don't know what the end result will be for car owners.

Of course manufacturers care about how hard it is to repair their vehicles - we are on the hook for warranty repairs and recalls.

That is one reason that traditional automakers are taking a more conservative approached and forgoing the weight and cost savings that come from gluing together a battery pack. They have all experienced large recalls and understand the risk that comes from having a non-serviceable battery that would have to be replaced as a unit. Image the effect on Tesla if a 5 cent component buried deep in a Model 3 battery failed and Tesla was forced to recall every Model 3 and replace the entire battery pack.

[Isaac Zachary]

Originally Posted by JSH

Sure it is a risk. No different than if you put a new engine in an old gas car.

Does it cost $8,000 to install a new engine in a car???

What about the costs and benefits of rebuilding an engine compared to rebuilding a battery that has low range?

I don't recall spending anywhere near $8,000 to rebuild the 1972 Super Beetle engine. It was more like $1,500 and I sold the car for $5,000 IIRC. But even if it were worth only the $1,500 I put into the engine at least I'd come out even at the moment. But $8,000 in a car worth $5,000 then I'd be $3,000 in the hole, at the moment.

And that's talking about a 10 year old car, not a 30 or 40 year old car. What if the EV is worth only $3,000 or $1,500 30 or 40 years from now. Then an $8,000 new battery would be pretty much out of the question. Throw away the car and buy a new one.

But rebuilding the battery compared to rebuilding an engine... I guess we'll have to find out how that compares. Or how long the batteries will last in the long run.