Non static main battery location
 

I posted this "futuristic" topic on another forum, but it got little traction, pun intended:

So not exactly in the vein of structural battery utilization, maybe heading the alternative direction?

My thinking, here out loud, batteries are a large part of vehicle mass with electrics, beyond the motor itself. It seems it needs to be always considered the battery has a useful limited lifespan, and replacement at least once will be required. Because of its mass and density, its placement on the vehicle is always a consideration, lower, and more centered being normal goals. It also is likely somewhat conformable in final shape, ie, doesn't need to need to be a single unit/mass.

So with new electric PU's on the horizon, which will need greater battery capacity (meaning size/weight) than many current typical auto offerings, and the fact most PU's have higher ground clearance, and my observations most PU operate at effectively zero load carry at 50% of the time ( this number is just my guess), leads me to the following questions/idea;

Would an underslung, relatively flat, single unit battery pack, be a significant advantage in ride, handling, aero, replacement, safety, etc, if it was was dynamically moveable to optimise the COG for varying load and/or driving conditions? My thinking in beginning development, the battery movement would be very slow, but if found later to be real world effective, speed of movement of the battery could be increased, almost like a side rider on motorcycle racing sidecar. As electrical technology is improved in capacity/density, using another electrical motor for main battery movement would be an easy adaption. It seems active suspension could address many of the above concerns, with greater complexity, but not as well in the end, as an optimized COG is hard to mimic?"

Another commented COG could also be altered by moving axles locations, and manufacturers don't consider it worthwhile, my reply:

"Yes it would have an effect, but my thinking much less effect, be much more complicated, and would directly effect the drivers perception of turning, overhang clearances, aero balance etc, and I suspect for the average driver, be a potential driving hazard. Regarding no manufacturers not feeling its a worthwhile goal currently, at one time, nobody felt streamlining an outside mirror was worthwhile.

I like the unconventional thinking.

My thought is they would have implemented such a system with fuel tanks if the benefits outweighed the costs.

Packaging is extremely important in vehicle design, so no volume is wasted. That means no dead spaces where weight can actively shift.

The main issue is that it's not needed. By my observation, 90% of drivers are afraid to take a corner fast enough to even feel lateral G forces (the bane of my existence). If people are already too uncomfortable to drive their vehicles anywhere approaching the limits, why would they value a higher performing vehicle?

Active suspension has more versatility because it can deal with shifting CG as well as uneven terrain.

A moving battery introduces safety and reliability challenges. If it can move, then how will it survive in a collision vs being rigidly contained. How about the stress of the wires and coolant hoses that must articulate to accommodate the battery position.

Finally, it would be tricky to implement as the shifts need to occur prior to cornering. If the shift occurs during cornering it simply places more force on the tires.

This sounds like an application for one of my new favorite things the planetary screw. duckduckgo.com/?q=planetary+screw

Load balancing would not require fast reaction. Countering corner forces would.

I'm reminded of Bucky Fuller's Omnidirectional Transporter. It had a two-piece (later three-) frame so that when the two front wheels were hammered the Ford V-8 bounced up and down, but the passenger cabin rode in the rocking chair.

Even with the biggest massive battery I can conceive, you're looking at most 1,000 lbs including the holding structure. My volt battery is 88 lbs of battery and 300 ish pounds of holder.

I see a lot of yahoos in my 'hood putting 2000 pounds of construction materials into their Toyota pickups. You can tell they are that heavy because the tires in the back partially disappear, and I know what a pallet of concrete block weighs. Moving the battery around is going to solve that?

Interesting concept indeed.
However the additional weight and space requirements of such a system would cancel out any potential benefits and let's not ignore the cost and reliability issues associetad with such a system.

Maybe I wasn't clear enough, my idea was to initially improve load balancing, with a 50/50 weight bias being the ultimate goal. I was thinking if the idea took hold, then the battery might become more of a solution to improve handling/cornering by more active movement, but regardless, a 50/50 weight bias loaded to unloaded, is nearly always ideal in every situation, and I thought worthy, but mainly thinking PU and thier loads. I personally don't see it a complex effort for requiring flexible wiring/coolant lines, ie we have had 4 wheel hydraulic brakes for many decades reliably.

Thanks for the reasoned replies.

My ignorance makes it hard to understand the reasoning behind the above numbers. Is the battery encased in a 2" thick Ti tub or something, or is this just unique to a Volt for some reason?

Factory says the assembly weighs 480 lbs. Huge and heavy metal back bone and nosecone with 88 metal retaining clips and attaching nuts, bolts washers and spacers, 2 gallons coolant, 30 estimated pounds of plastic battery case, 20lbs control electronics, 10lbs wiring and 40lbs plastic waterproofing cover and way over engineered assembly with even more attaching hardware. The 88 lbs is reported by "Yabert" over on DIYELECTRICCAR when he disassembled his volt pack back 6 years ago.

I don't speculate what a tesla skateboard weighs.

I like this idea! I don't know how practical it would be, but I like the idea.

One area where it would help is in 2WD winter traction. Ideally you want a huge weight difference at slow speeds. Cars that I've driven with nearly a 70:30 weight ratio (more weight over drive wheels, whether RWD or FWD) can pull out of sticky situations nearly as well as an AWD vehicle. But once going down the road that weight bias becomes a problem since it contributes to oversteer and understeer. So being able to change that weight on the fly would be nice. Right now the only way to do that is manually moving around heavy objects like sand bags. It's kind of hard to put them over the hood though when you need the weight up front.

:D:thumbup:

non-static location
 

* it complicates the design, construction.
* it weakens the chassis, requiring additional reinforcement for torsional stiffness, crashworthiness.
* adding weight.
* wasting otherwise needed materials.
* if it fails-dangerous, the driver and passengers may be imperiled, with asymmetrical weight distribution, tire overloading, polar moment instability, loss of directional stability, rollover, spinal cord injury if not traumatic death.
* I don't see any upside.
* current lateral g-forces for production cars already exceed what most drivers are comfortable experiencing.

One thing I would like to point out is that it would probably be more practical to add an adjustable ride height. Keeping weight down low will improve stability. But it seems the majority of people like a higher ride height. So maybe have a system that lowers the vehicle the faster it goes. Usually when you're going 75mph you're not getting in or out of your vehicle nor are you driving over potholes.

I wonder how many here actually drive PU's.

And know the real F/R weight bias range, loaded and unloaded, and then can give a real world realistic estimate how much drive distance is in each category.

Meaning, a PU is a horrible solution for any optimal COG goal, It always has been, with the new use of large batteries in electric PU's, we have an opportunity to improve, if not rectify the problem.

How this is complicated, has no upside, etc, is IMO, only a failure of imagination and will.
Selling the driving public on the solution seems to me, to be the biggest hurdle, kinda like here?:D

I get what you're saying. If anyone who isn't Elon Musk or Henry Ford suggests a new idea, it's automatically called out as snake oil.

For a few examples:

• Solar panels on cars: "The weight and aerodynamic drag will get you less range." "Most people might get 3 inches a week of range from them." "It's 500% cheaper, easier, more effective and more practical to just stick them on your roof."
• NEV's: "People have to have at least 300 miles of range and go at least 90mph for it to be practical." "I get on the freeway to work for about 1/4 of a mile and going around at 25mph would add 5 minutes to my drive, which is way too long." "How am I supposed to fit a sofa in one?"
• Aerodynamic cars: "Cars may be over 10 times less aerodynamic than they could be, but they're still ultra aerodynamic." "I want to drive a car that looks like a car, I mean, SUV that looks like an SUV."

Instead of snake oil, contemplate the net cargo weight and center of mass, vs the mass of the battery pack and how far it can practically be moved.

As a 'first approximation' I'd venture that if the battery has half the weight of the maximum cargo variation, it would have to move half the wheelbase of the vehicle. For more than partial compensation.

This may be possible with planetary screws and segmented cable stays. But it eliminates the possibility of structural batteries.

I do. Either the diesel F250 or the electric ranger.

The 250 with a full 3/4 ton load is 50/50, empty the front axle weighs 5000 ish pounds so it's really front biased maybe 63/37, worse when I drive. It's so nose heavy that it burns through front brake assemblies in any configuration. It does close to 800 miles per tank of fuel

The ranger is missing the engine which was replaced by the Kostov so it lost 200 lbs but it has 600lbs related battery hardware in the bed. Not sure about F/R BIAS perhaps 45/55 but it's weirder than anything else I've driven. Gets really twitchy on the freeway above 55. @18kwh, you get 40 ish calculated, I chicken out at 30

F/R
 

Spirit of EcoModder.com was almost 50-50 weight distribution as raced at Bonneville. And at a travel weight of 4,220-pounds indicated virtually zero-lift in the wind tunnel ( 33-lb front downforce and 22-lb rear lift @ 135-mph )
The National Highway Traffic Safety Administration testing failed to tip over the Tesla Model S. It can't be done!
When Cybertruck finally bows, at it's lowest suspension setting, the NHTSA may be just as challenged to get it's COG to work against it.
I'll be pleased when Tesla builds school buses. They have a horrible rollover track record.

The 250 numbers you note I believe support my original contention rather well, but can you also comment how often percentage wise you are driving at those load conditions?

Not sure how the Ranger applies here, is it still functionally a load carrying vehicle in the electric configuration?

Well I'm contemplating, being PU's have usually a generous WB, and the fact without the conventional powered under carriage impediments/drivetrain obstructions with an under slung battery mount, the battery could move a considerable distance, would it achieve the ideal? 50/50, likely not, could it make a big improvement, my thinking is yes, especially a lot of other mass in a EV is also changed, and additionally no varying fuel tank weight consideration.

Not sure how the "structural battery" figures in here, as a movable battery would not add, as I see it, any structural aspects to the moveable battery application.

99% of 250 is empty with just me (shudder) mostly to charge battery or exercise engine. About 4-6 months between 10 gallon refills.

The ranger has a 500 lb available, but its hard to find something that will still fit around the battery. Primary city vehicle for 2 people perhaps 4 times weekly.

Thanks, that supports my original thinking, an unfavorable F/R weight 99% of the time, all including way over rated rear spring rates? for a solution for 1% of the time. My PU might be a 90/10% spread.

Well the 250's main purpose was to tow a 5ton camping trailer with seating for 2 kids long distance (600 miles) comfortably.

Dont have the kids, they grew up, sold the trailer, but the truck is paid for and is still extremely reliable.