# Supplemental Battery Pack

#### meep

Well you're way off on the weight and the range. The problem with stacking all the batteries in the trunk is the center of gravity. There's a reason that the battery packs are on the floor in the center of the car. If you want 6 battery packs weighing 40 pounds, that's 240 pounds in the trunk, throws off the driving dynamics although 240 isn't that much, if it was 1200, it'd be a lot. 240 pounds of lithium batteries won't get you very far is the problem. The model 3 battery pack is 1060 pounds and good for 310 miles but EPA claims 272 miles. At 1/4 of that in power, you're now at about 75 miles. So you'd be swapping battery packs every hour or two depending on how fast you're going.

Can you imagine the workout you'd get for swapping out 6 40 pound battery packs? That's not a simple single propane tank exchange. If you want to do the full battery pack on a Tesla, that would be 26.5 40 pound packs or more. Not too many people out there would want to move 40 pound packs a few feet 26.5 times. People on average are way too out of shape for that. Also keep in mind that Blue Rhino puts in 15 pounds on a propane tank so a full propane from them is about 32 pounds instead of 37 with a real full 20 pound tank.
Good math! With you.

#### y_p_w

Basically none of the math works. You can't tow a generator because the amount of power you'd need would have to make it a pretty big generator, not some small few hundred dollar one. Same with the battery pack, probably at least 10k for a pack you could tow.

Also swapping battery packs can be tricky because the entire battery pack in a Tesla is in the 1200 pound range. So it's pretty heavy. Plus as you drive the car, the battery pack ages and you lose performance, maybe 1-2% a year and up to 20% or more if you're driving 100k so who wants to get suck with a weaker battery pack on an exchange?

The talk about the short range electric powered planes is that they do a battery swap, but that's an aircraft with dedicated equipment to do that.

#### PandaBear

The thought occurred to me why don’t they design EV’s so they could tow a small trailer that has a supplemental battery pack? That way the car could have a smaller 150-200 mile range for day-to-day driving and then the few times a year you go on a long trip, you rent a battery trailer so you have 500 mile range and can recharge car and trailer battery at the same time. What would be the drawbacks? Safety?
I'm sure it will come sooner or later like the battery bank for cell phones, but it didn't happen for cell phone until there's enough volume and economy of scale to make.

Who wants to be limited to 55 or 60 mph on vacation?
The people who went on vacation with RVs or a kayak / surfboard on the roof, and people who don't want to stop at super chargers for lunches and dinners.

And when the trailer isn’t being used for transportation, it could balance the power grid.
Not really a good idea. Do you really want a sudden "shut down" on power grid because all the load balancing battery got decommissioned? The only way for this to work is some cheap batteries with low cycle life is sitting as cold spare, charged only when there's negative or zero cost (surplus wind and solar in moderate days), then to be used for Thanksgiving / Lunar New Year / Christmas road trips. So basically 4x a year and then just sit there for the rest of the year.

As we can see here, a standardized swappable battery is really the better choice. You can swap into regular car, no extra trailer needed (but you can put them there if you want and swap them at the rest stop or camp site), and most of them can be along highway with frequent travelers, and they can be used all throughout the years instead of 3x a year, and they don't need to be oversized or undersized as they can swap more or less frequently if desired.

Maybe we'll see a trailer with battery storage compartment once the size is standardized. Maybe we'll also see RVs and Camper powered by these batteries instead of diesel / alternator / inverter, you can live off grid and just swap some batteries out when you go to grocery stores.

I don’t know. Driving around with the weight of a built in generator (and all associated maintenance) for 10% of your driving in a car the is used less than 5% of the time seems like a waste. Better to borrow it.
I remember back in the 90s our analysis in a hybrid lab is we only need 30hp to coast at highway speed, but we buy vehicles with 150-200lb/ft of torque to accelerate and climb hills, which means we really are driving around with about 70% of our power unused.

The only way around is to have multiple vehicles in a family and different sizes and types: commuter EV, long distance traveler vehicles, toys and tool vehicles, etc. We need to think what is our priority. I know mine is a 1.8L Prius V with lots of cargo space and some old beaters for now, and when the old beaters wear out maybe an EV with 150 miles range that will last about 15 years.

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#### Cujet

In the Tesla world, each 10KW of battery power adds roughly 100 pounds to the car. The above 1200 pound battery pack weight is for the older 85kwh pack. The 90 and 100kwh batteries are heavier and contain more cells.

One reason Tesla owners are strongly discouraged from installing the 100kwh pack is that the p85 is not configured to carry the extra weight, either structurally or suspension-wise.

#### PandaBear

Well you're way off on the weight and the range. The problem with stacking all the batteries in the trunk is the center of gravity. There's a reason that the battery packs are on the floor in the center of the car. If you want 6 battery packs weighing 40 pounds, that's 240 pounds in the trunk, throws off the driving dynamics although 240 isn't that much, if it was 1200, it'd be a lot. 240 pounds of lithium batteries won't get you very far is the problem. The model 3 battery pack is 1060 pounds and good for 310 miles but EPA claims 272 miles. At 1/4 of that in power, you're now at about 75 miles. So you'd be swapping battery packs every hour or two depending on how fast you're going.

Can you imagine the workout you'd get for swapping out 6 40 pound battery packs? That's not a simple single propane tank exchange. If you want to do the full battery pack on a Tesla, that would be 26.5 40 pound packs or more. Not too many people out there would want to move 40 pound packs a few feet 26.5 times. People on average are way too out of shape for that. Also keep in mind that Blue Rhino puts in 15 pounds on a propane tank so a full propane from them is about 32 pounds instead of 37 with a real full 20 pound tank.

I think, that if your car has a normal range of 250 miles, and you are on a road trip, that you can plug in the trunk an extension battery for 75 miles, you should be able to go 325 miles to reach a charger that you can quickly top off maybe 100 miles in 20 mins, plus swapping 75 miles every one hour to top off that amount if you do not want to stop for too long (say 5 mins). It sucks for sure but it beats not able to make it to the destination.

Yes it would be a lot of workout to swap if you are going that far, and it is the wrong vehicle to use if you want to drive an EV that far. It helps extend the range and it is not something we can build overnight, just like the gasoline and diesel infrastructure was not build overnight to work for Thanksgiving and Christmas holiday rush. People didn't always go back home driving that far back then and they also don't drive 2000 miles during the holiday either, they fly.

I think the transition to EV if all ICE vehicles are no longer produced would be "interesting", and people would really change their behavior then. Maybe flying more often, maybe doing multi day drive with resting while charging, or maybe there'll be all sorts of generator trailer using gasoline or diesel that we are laughing at now, or we will really see whole pack battery swap station and people just rent battery from manufacturer / gas station / investment banks + retirement fund / electric companies in the future, I don't know.

Swapping or not, there is no way around storage of energy whether it is liquid fuel for combustion or battery that you over build just to sit around for holiday rush. There is only so much money to be spend on overbuilding battery capacity until flying + rental car at destination (EV if you must) is cheaper.

#### Burt

You guys aren’t thinking out of the box. You’re trying to say the EV has to match the the IC. It doesn’t. The problem with widespread acceptance of EVs in the US is still first cost. You still pay a premium for EVs, granted you might save some on fuel and maintenance but the average Joe borrows the money. Will banks say they’ll lend more to somebody because their car has lower operating costs?

If you put a smaller battery for urban use, costs come down, weight goes down and range, relatively goes up. Then you hitch a battery trailer when you need it.

What’s missing from your comments is an appreciation of how much lower cost the car would be. Maybe you personally don’t like it but millennials think cars are just appliances.

You say people won’t like renting a trailer but Elon thinks when self driving cars are a reality, Tesla will buy them back and rent them like taxis and it’ll be too cheap to justify owning.

Using EVs to manage the grid is already happening in places like Austin. It just adds another valuable tool for the grid operator.

#### JeffKeryk

You guys aren’t thinking out of the box. You’re trying to say the EV has to match the the IC. It doesn’t.
Think outside the box, collapse the box, and take a xxxxxxx sharp knife to it.”
Banksy. Or maybe Elon?

#### Cujet

You guys aren’t thinking out of the box. You’re trying to say the EV has to match the the IC. It doesn’t.
I really like the fact that homeowners can charge at home. That single issue is flat-out glorious! Not to mention the EPIC performance of a well designed EV, for guys like me who are HP junkies!!!!

But I disagree that EV's don't have to match conventional vehicles. They absolutely do. My job requires massive travel, and driving as much as 10,000 miles per month. The interstates are chock-a-block full of long haul travelers. And no, renting is not a viable option. \$1000 per week is now a normal rental cost, with \$750-\$1500 drop off fees, YIKES!! Along with very poor vehicle availability.

I drove a Jeep Compass to Sav from PBI last week, with a Model 3 tagging along. We both traveled at my normal rate of speed, north of 80mph. He was off and charging by Vero Beach (about 1/3d the way) . I made it non stop. We can sugar coat this all we want, but until range and charging times improve markedly, EV's will not gain full acceptance.

Consider the base model, \$60,000 F150 lightning with it's 70-100 miles of boat/RV towing range. Even a trip from Jupiter, FL to Key West would be an exercise in utter frustration. 5 hours, 250 miles, well within normal pickup towing range. I predict boat/RV owners will choose more conventional vehicles. Nobody in their right mind is going to spend 4+ hours charging each way for that trip.

It should be self evident that bigger batteries take longer to charge. Even with the eventual implementation of 350KW chargers, we are still looking at very long charge times for these larger 140Kwh batteries. Remember, they taper the rate as the batteries "fill up"

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#### JeffKeryk

Not only do bigger batteries take longer to charge, they add weight. Efficiency is important.

#### Burt

I really like the fact that homeowners can charge at home. That single issue is flat-out glorious! Not to mention the EPIC performance of a well designed EV, for guys like me who are HP junkies!!!!

But I disagree that EV's don't have to match conventional vehicles. They absolutely do. My job requires massive travel, and driving as much as 10,000 miles per month. The interstates are chock-a-block full of long haul travelers. And no, renting is not a viable option. \$1000 per week is now a normal rental cost, with \$750-\$1500 drop off fees, YIKES!! Along with very poor vehicle availability.

I drove a Jeep Compass to Sav from PBI last week, with a Model 3 tagging along. We both traveled at my normal rate of speed, north of 80mph. He was off and charging by Vero Beach (about 1/3d the way) . I made it non stop. We can sugar coat this all we want, but until range and charging times improve markedly, EV's will not gain full acceptance.

Consider the base model, \$60,000 F150 lightning with it's 70-100 miles of boat/RV towing range. Even a trip from Jupiter, FL to Key West would be an exercise in utter frustration. 5 hours, 250 miles, well within normal pickup towing range. I predict boat/RV owners will choose more conventional vehicles. Nobody in their right mind is going to spend 4+ hours charging each way for that trip.

It should be self evident that bigger batteries take longer to charge. Even with the eventual implementation of 350KW chargers, we are still looking at very long charge times for these larger 140Kwh batteries. Remember, they taper the rate as the batteries "fill up"

Sorry but it will be many decades before they design a passenger vehicle good for 10,000 miles a month. That’s 10 hours a day plus charging time. They need to design cars for the masses that drive 1,000 miles a month.

#### PandaBear

I really like the fact that homeowners can charge at home. That single issue is flat-out glorious! Not to mention the EPIC performance of a well designed EV, for guys like me who are HP junkies!!!!

But I disagree that EV's don't have to match conventional vehicles. They absolutely do. My job requires massive travel, and driving as much as 10,000 miles per month. The interstates are chock-a-block full of long haul travelers. And no, renting is not a viable option. \$1000 per week is now a normal rental cost, with \$750-\$1500 drop off fees, YIKES!! Along with very poor vehicle availability.

I drove a Jeep Compass to Sav from PBI last week, with a Model 3 tagging along. We both traveled at my normal rate of speed, north of 80mph. He was off and charging by Vero Beach (about 1/3d the way) . I made it non stop. We can sugar coat this all we want, but until range and charging times improve markedly, EV's will not gain full acceptance.

Consider the base model, \$60,000 F150 lightning with it's 70-100 miles of boat/RV towing range. Even a trip from Jupiter, FL to Key West would be an exercise in utter frustration. 5 hours, 250 miles, well within normal pickup towing range. I predict boat/RV owners will choose more conventional vehicles. Nobody in their right mind is going to spend 4+ hours charging each way for that trip.

It should be self evident that bigger batteries take longer to charge. Even with the eventual implementation of 350KW chargers, we are still looking at very long charge times for these larger 140Kwh batteries. Remember, they taper the rate as the batteries "fill up"

Does every vehicle of your household have to match the "best" feature of every other vehicle? They all have their places and that's why we typically don't buy 2 of the same vehicles in the same household.

Say you have a F150 to tow a boat and a Prius with 55mpg, you are not going to complain that the Prius cannot tow nor your F150 cannot get 55mpg. What you are expecting from an EV should be it beats a Prius in cost of ownership or a Mercedes in comfort, not that it cannot tow for 250miles, nor that it cannot be used to drive 10k miles a month (way outside of a typical commuter range in the US which is about 15k a year).

#### philipp10

It' be an expensive trailer for sure.

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