Modular battery pack design

[MountainDad]

Design the battery system for maintainability/upgradeability.

Battery modules (groups of cells) should be individually replaceable and the entire battery pack should be designed to minimize the effort necessary to replace it.

This would ensure these vehicles will remain viable into their 2nd and beyond lives, and be able to leverage inevitable improvements in battery tech over time.

 

[pwrofgrayskull]

I like where you’re going with this. Great thoughts! Upvote added.

 

[InnerMogul]

Love this idea, especially if Scout intends for us to be able to work on our trucks in the driveway. We can then ship back the old batteries to Scout for recycling.

 

[J Alynn]

You guys realize how heavy battery packs are and just wondering who is going to ship a battery with all the chemical risk and flammability. We aren’t talking mower batteries. Even if smaller and modular there is significant weight. Quite frankly I don’t want any vehicle owners having access to the battery cells

 

[Rampy]

You guys realize how heavy battery packs are and just wondering who is going to ship a battery with all the chemical risk and flammability. We aren’t talking mower batteries. Even if smaller and modular there is significant weight. Quite frankly I don’t want any vehicle owners having access to the battery cells

Why not along the lines of the Tesla Semi’s where you pull up & have your empty battery replaced with a full one

Obviously not the same but have it easily replaced at a dealership or even in your driveway by a “dealership” service vehicle

 

[J Alynn]

Why not along the lines of the Tesla Semi’s where you pull up & have your empty battery replaced with a full one

Obviously not the same but have it easily replaced at a dealership or even in your driveway by a “dealership” service vehicle

There is some existing long running threads about this on the forum already and the discussions leave it as being very impractical considering all the processes involved as well as cost.

 

[R1TVT]

The cost alone to make batteries modular would be astronomical. The pack and all of its connections to cells (typically made with plates) need to be weatherproof / waterproof and are very complex systems. Safety is also critical, and liability would go way up for Scout. Once you start trying to make them modular and serviceable, you add weight, risk, cost and take up way more space, making for a much larger battery pack.

instead of making the pack modular, maybe the focus should be on making the pack itself (and its surrounding area) easier to access in the vent of a battery pack replacement at some future point in the battery pack's life.

I would suspect it is much more common for cell health to degenerate more uniformly across the pack, over time, also making this is a likely better approach. But I am not a chemist or a battery scientist.

 

[CarTechGeek]

Many packs are modular. I expect they would go this route anyway. I think most do outside of Tesla.

But doing so doesn't really make them user/easily serviceable. A 350 KW pack is going to weigh near a ton, that will need to be removed from the vehicle before it can be opened. Especially for a vehicle like the scout with water fording capability, the environment sealing needs to be EXTREMELY robust. You are going to want the best specialists working to ensure full environmental sealing is re-established after any pack repair.

There are two strategies out there. The each have pros and cons.

Module to Pack. Where you make modules and assemble them into packs. So you have building blocks, and you can replace a module instead of the whole pack,

Main Pro: Repairable.

Main Con: Less space/mass efficient.

Ford lightning modular pack:

Cell to Pack: This is exemplified by Tesla, in their current "structural" packs. These are completely unrepairable. Definitely not a fan of this.

Main Pro: More space/mass efficient, and serves as additional structure.

Main Con: Completely unrepairable packs. You need to replace the whole pack.

Check out this glued together mass that they had to destroy the cover to even see inside:

 

[R1TVT]

Rivian uses modules - 9 modules in total (containing a total of 7,777 individual cells) however using modules doesn't necessarily make them any easier to repair (by an owner). In the case of Rivian, this is mainly b/c the modules are all sealed inside the pack with wiring, cooling, etc. So, you would need to drop the entire battery pack (which weighs in at 1750lbs on my R1T), then you would need to split-out the modules from the battery pack frame, then you would need to crack open a module to replace an individual cell.

Good news is that SW and the BMS manage the health of the pack automatically to mitigate individual cell or module degradation. in the case of Rivian at least, and according to them "Rivian vehicles are built with an intelligent battery management system (BMS) that optimizes cell performance and extends the life of your battery. Our intelligent BMS continuously monitors the health and status of your battery to maximize your experience of available energy and sends and receives data in real time, continuously learning how you drive and charge."

I think the OP was referring to making the modules in such a way that they could be accessed, disconnected from wiring, disconnected from cooling, pulled and replaced without dropping the entire pack. I would estimate that the cost VS. benefit analysis for something like this would not be attractive, and the space required to accomplish this would also make this prohibitive. Since this is already one of the bigger cost centers, and since these systems with a solid BMS can have very long lifespans.

 

[MountainDad]

You guys realize how heavy battery packs are and just wondering who is going to ship a battery with all the chemical risk and flammability. We aren’t talking mower batteries. Even if smaller and modular there is significant weight. Quite frankly I don’t want any vehicle owners having access to the battery cells

Whole car batteries - yes, these are large and heavy.

Battery pack modules - much smaller. Like individual slices of bread vs the whole loaf.

Jaguar did this with their i-Pace batteries - an early attempt at making more serviceable battery packs and making them more sustainable. In the early days, if one group of cells in a whole pack went bad, you had to take out the whole pack and install a new one - this can cost more than $10,000 - either for the automaker in warranty, or for the driver beyond the warranty. Then you have the problem of what to do with the whole pack when only a few bad apples have ruined it.

Making individual modules within the whole pack replaceable, it would allow for a more sustainable and affordable replacement strategy over time.

Making the entire pack more easily maintainable would allow for cheaper upgrades, when the technology is there such as solid state batteries and better LiIon recycling.

You have to design for the future - it's called "Evergreen Engineering," and is an evolving strategy of systems engineering.

Note, I'm not necessarily talking about these being user-serviceable, but just being designed for serviceability, including by 3rd parties.

 

[MountainDad]

The cost alone to make batteries modular would be astronomical. The pack and all of its connections to cells (typically made with plates) need to be weatherproof / waterproof and are very complex systems. Safety is also critical, and liability would go way up for Scout. Once you start trying to make them modular and serviceable, you add weight, risk, cost and take up way more space, making for a much larger battery pack.

instead of making the pack modular, maybe the focus should be on making the pack itself (and its surrounding area) easier to access in the vent of a battery pack replacement at some future point in the battery pack's life.

I would suspect it is much more common for cell health to degenerate more uniformly across the pack, over time, also making this is a likely better approach. But I am not a chemist or a battery scientist.

Battery packs already are modular in that they aren't one giant battery, but they are either clusters of cylindrical cell batteries (like your trusty Duracell), prismatic cells (inherently structural but lots heavier and come with all kinds of fire and thermal risks), or pouch cells, which are flexible and can be made to confirm to specific spaces. Each has advantages and disadvantages.

Each of these types is already sold as modules, which are then assembled into a pack of appropriate size. Because most of these today come from one manufacturer in China, that's why you see common pack sizes clustering around 75, 80, 90, 100, 120, etc kWh - because you have to use their module design.

The thing is, these are generally hard-wired together such that while individual modules are isolated, they aren't generally designed to be separately replaced.

There would need to be new non-recurring engineering to be able to make individual modules "line replaceable" at an appropriately qualified workshop, such that there's no soldering, cutting, and the whole battery pack doesn't need to be taken out to be worked on.

 

[R1TVT]

There would need to be new non-recurring engineering to be able to make individual modules "line replaceable" at an appropriately qualified workshop, such that there's no soldering, cutting, and the whole battery pack doesn't need to be taken out to be worked on.

Yes, that is what I wrote in post #9, but you might have missed that entirely! LOL.

"I think the OP was referring to making the modules in such a way that they could be accessed, disconnected from wiring, disconnected from cooling, pulled and replaced without dropping the entire pack. I would estimate that the cost VS. benefit analysis for something like this would not be attractive, and the space required to accomplish this would also make this prohibitive. Since this is already one of the bigger cost centers, and since these systems with a solid BMS can have very long lifespans."

 

[shnngns]

The cost alone to make batteries modular would be astronomical. The pack and all of its connections to cells (typically made with plates) need to be weatherproof / waterproof and are very complex systems. Safety is also critical, and liability would go way up for Scout. Once you start trying to make them modular and serviceable, you add weight, risk, cost and take up way more space, making for a much larger battery pack.

instead of making the pack modular, maybe the focus should be on making the pack itself (and its surrounding area) easier to access in the vent of a battery pack replacement at some future point in the battery pack's life.

I would suspect it is much more common for cell health to degenerate more uniformly across the pack, over time, also making this is a likely better approach. But I am not a chemist or a battery scientist.

I don't think it's a good idea to have batteries serviceable by the owners, that sounds like a nightmare for anyone buying used later down the line for those reasons you mentioned, connections, cooling, waterproofing. No thanks.

Having the pack easily accessible by a SM service center (or even mobile service?) for replacement or repairs though is a different story and something I think should be done no doubt about it.

 

[Cranky Canuck]

While I think this is an interesting idea on the face of it I don't think it's actually needed or desirable.

Breaking the traction battery up into removable modules would me a decrease in energy density which is already pushing the limits. The housing and connections would take up valuable pack space in the vehicle and would introduce new points of failure or opportunities for water ingress.

As it is EV batteries already outlast the vehicles they're in by a wide margin so the ability to replace individual modules would be of limited benefit and only for those very few rare cases where there's an issue with an individual cell. It would benefit those looking to salvage packs for other uses but the owners of the vehicles would be unlikely to see any benefits and would suffer for all the compromises such a design would introduce.

While I think it's a neat idea and totally agree with your thinking about long term serviceability etc on it, in reality it would add more problems than it solves.

 

[CarTechGeek]

While I think this is an interesting idea on the face of it I don't think it's actually needed or desirable.

It depends one where you are in the ownership curve.

If you only buy new, and trade them while the still have a warranty, then a modular pack is mostly just disadvantages. It's just less efficient packaging.

OTOH, if you are buying used without a warranty (or a very short one), then a modular pack is a huge servicing advantage.

 

[MountainDad]

Yes, that is what I wrote in post #9, but you might have missed that entirely! LOL.

"I think the OP was referring to making the modules in such a way that they could be accessed, disconnected from wiring, disconnected from cooling, pulled and replaced without dropping the entire pack. I would estimate that the cost VS. benefit analysis for something like this would not be attractive, and the space required to accomplish this would also make this prohibitive. Since this is already one of the bigger cost centers, and since these systems with a solid BMS can have very long lifespans."

Hah LOLOL no, I didn't.

 

[Cranky Canuck]

It depends one where you are in the ownership curve.

If you only buy new, and trade them while the still have a warranty, then a modular pack is mostly just disadvantages. It's just less efficient packaging.

OTOH, if you are buying used without a warranty (or a very short one), then a modular pack is a huge servicing advantage.

Not really. I've owned old, used EVs with packs out of warranty. It's not the battery that is a concern, it's all the other little gizmos. The battery is designed to last longer than the vehicle, if it doesn't have an issue after a couple of years then it's good to go for decades. There aren't any moving parts in the packs so it's not like an older gas car. I'd buy a 15 year old EV over a 15 year old combustion car any day! They're WAY more reliable.

 

[ID_ENG]

I see where the OP is going with this and normally I'd be all for it. Bring back replacable phone batteries!!

But for a lot of what's been said already, the practicality starts to go out the door. I'd imagine the battery pack and compartment needs to be very precise to handle all the rough terrain these vehicles will handle. So making it more general may in fact start to have a safety risk involved.

I'd argue that the effort and research money should go into the actual recycling process than making it user swappable.

 

[CarTechGeek]

Not really. I've owned old, used EVs with packs out of warranty. It's not the battery that is a concern, it's all the other little gizmos. The battery is designed to last longer than the vehicle, if it doesn't have an issue after a couple of years then it's good to go for decades. There aren't any moving parts in the packs so it's not like an older gas car. I'd buy a 15 year old EV over a 15 year old combustion car any day! They're WAY more reliable.

Batteries aren't magic, they can and do fail. Cell don't just uniformly follow some kind of mapped out degradation. Individual cells can fail, and can take out the pack.

The other gizmos are relatively inexpensive to repair.

A whole battery packs is ~$20K, and essentially writes off the car.

 

[MountainDad]

It depends one where you are in the ownership curve.

If you only buy new, and trade them while the still have a warranty, then a modular pack is mostly just disadvantages. It's just less efficient packaging.

OTOH, if you are buying used without a warranty (or a very short one), then a modular pack is a huge servicing advantage.

Think of all the people today who are driving 40-year old Scouts. If you can't upgrade the batteries, there will never again be 40-year old Scouts.