This is a stupid idea because you’d have to make fasteners and high voltage interfaces that can survive an order of magnitude more cycles than they have to for a fixed pack. It would also be significantly more difficult to use the pack as a stressed member of the car structure. It’s better to just have less batteries and use them more efficiently through weight savings.
Do you realize that one of the reasons for the swappable batteries on various Thinkpads is so that you can hot swap batteries without powering down or rebooting?
I've never had an issue with the connectors for the batteries of the ThinkPad, and being able to swap in a spare fully charged battery has been very helpful many times when out doing field working all day long. What is an issue are the little plastic tabs on the batteries that break off over time. However, usually the batteries have already lost a lot of their lifespan by the time that happens, and since the batteries are removable they can be replaced without opening up the system or melting glue with heat as is the case on most modern cell phones. Seems like a win to me!
My point is that hot swappable battery packs have benefits that outweigh the cost of the connectors for the people that have a use case that needs them, as the grandparent referred to in Thinkpads. Not everyone fits in the constraints of design space chosen for a given product. There's a reason virtually every modern computer has a means of adding expansion devices.
Making a high voltage connector is well understood problem space. Every electrical engineer knows how to deal with ramping up current when a power supply is plugged in or turned on (inrush current specifications are most definitely a thing), and the entire electric grid is based on sizing, insulating, spacing and switching conductors appropriately for the voltage and current being used. Moreover, high voltage battery packs tend to have switches / contactors on the battery pack that keep the high voltage off until the connection is securely made and enabled, hence why even Telsas require a functioning low voltage battery to start the system.
There are also certain use-cases that are likely best served by putting battery packs in a trailer. Take the trucking industry: going by the charging requirements of a Tesla semi (1MW for 30 minutes), replicating your typical truck stop turns into a huge problem for the grid -- you'd need upwards of 50MW of charging capacity to replicate the flow of diesel coming out of a bank of 10 fuel pumps (sorry, I ran the thought experiment on that one back when specs were first released). Having a battery pack attached to the trailer that gets charged at a more leisurely rate at the warehouse while it is unloaded and re-loaded over a couple of hours is far more scalable than charging the truck in a few minutes at a truck stop. Charging overnight while the driver sleeps is fine, but getting the 8-12 hours of runtime for a workday in a semi is a heck of a lot of battery.
The dangers can be mitigated -- that's the entire raison d'etre of the electrical engineering discipline! Otherwise you wouldn't be able to safely charge an electric car at a 350kW rate these days at charging stations all over the world with a connector that is deemed safe to be handled by random humans. It's not like the software industry where we throw half baked shit at the wall and see what sticks when users encounter it by running an A / B test in production....
> Moreover, high voltage battery packs tend to have switches / contactors on the battery pack that keep the high voltage off until the connection is securely made and enabled, hence why even Telsas require a functioning low voltage battery to start the system.
These are little bit different than than what a swappable system would entail, aren't they?
> Otherwise you wouldn't be able to safely charge an electric car at a 350kW rate these days at charging stations all over the world with a connector that is deemed safe to be handled by random humans.
Okay maybe I miss read the initial premise but I took it as a home user swapping in-and-out modules themselves.
That would appear to me to be a significantly different engineering challenge and safety issue than what's currently deployed in consumer market EVs...
I'm not even sure the small upside here would justify the added costs and complexity either.
> These are little bit different than than what a swappable system would entail, aren't they?
From an electrical point of view, swapping batteries is fundamentally the same general problem regardless of whether they are large or small: you want to avoid arcing when the connector is plugged in, and you need to avoid exposing the user to stray voltage. Sure, there's added complexity to achieve that in a safe and cost effective manner when high voltages are involved, but it's a solved problem as the charge port does exactly this today.
> Okay maybe I miss read the initial premise but I took it as a home user swapping in-and-out modules themselves.
Current EVs on the market suffer from decreased maintainability compared to traditional ICE vehicles. The battery swapping skill set needs to be more widely available so that we don't see EV owners being dinged $40k for a battery swap. There are videos on Youtube showing people doing a battery swap themselves, and while it is challenging, it's not all that hard to do safely when the battery is not damaged given that the battery packs don't expose high voltage on the connectors when not enabled. Of course a damaged battery pack means that all bets are off on the safety front depending on the nature of the damage.
> That would appear to me to be a significantly different engineering challenge and safety issue than what's currently deployed in consumer market EVs...
> I'm not even sure the small upside here would justify the added costs and complexity either.
It a solved problem!!! Just put the charge port at the back of the vehicle and then use it for the add-on battery pack like the existing signal light connectors for trailers. You're done. The only added design constraints on the EV are on the location of the port and verification that it works while the vehicle is being driven. The F150 Lightning fails this today since the charge port is just in front of the driver side door, but relocating the charge port is not exactly rocket science.
Many EVs have already taken the step of making the charge port bidirectional so that the expensive battery in an EV can be used to provide power during an outage or to balance the load on the grid, and that is a far, far more complicated problem than accepting power from an external battery pack through the charge port while the vehicle is operating.
> From an electrical point of view, swapping batteries is fundamentally the same general problem regardless of whether they are large or small: you want to avoid arcing when the connector is plugged in, and you need to avoid exposing the user to stray voltage. Sure, there's added complexity to achieve that in a safe and cost effective manner when high voltages are involved, but it's a solved problem as the charge port does exactly this today.
The arcing is the problem AND generally when handling battery packs/modules requires high voltage safety equipment and precautions.
The charge port uses a low-voltage connection to "handshake" as I understand it before the high voltage is being supplied.
You can't, without a good bit more complexity to the battery module itself do that as the batteries terminals will just have the voltage of the battery itself (depends on their state of charge).
Plus the bus bar the module is connecting to also will have a voltage if there's existing modules connected to it.
You're down to having contactors and BDUs at every individual module.
> Current EVs on the market suffer from decreased maintainability compared to traditional ICE vehicles. The battery swapping skill set needs to be more widely available so that we don't see EV owners being dinged $40k for a battery swap. There are videos on Youtube showing people doing a battery swap themselves, and while it is challenging, it's not all that hard to do safely when the battery is not damaged given that the battery packs don't expose high voltage on the connectors when not enabled. Of course a damaged battery pack means that all bets are off on the safety front depending on the nature of the damage.
I'm not saying it can't be done. I am saying it's harder to make it actually safe for the average normal consumer to do as simply as plugging a battery into a power drill for example. In part because of the higher voltages involved.
> It a solved problem!!! Just put the charge port at the back of the vehicle and then use it for the add-on battery pack like the existing signal light connectors for trailers. You're done. The only added design constraints on the EV are on the location of the port and verification that it works while the vehicle is being driven. The F150 Lightning fails this today since the charge port is just in front of the driver side door, but relocating the charge port is not exactly rocket science.
This is a different concept than adding/swapping individual modules in the vehicle itself.
But regarding the concept of a trailer, I suspect that the high cost for the product for the minimum gain it not justifiable for the average consumer. That is you're trying to solve a problem in an inefficient and not profitable manner. (Who wants a trailer of batteries parked in their garage 99% of the time just to have a slightly lighter car?)
> Many EVs have already taken the step of making the charge port bidirectional so that the expensive battery in an EV can be used to provide power during an outage or to balance the load on the grid, and that is a far, far more complicated problem than accepting power from an external battery pack through the charge port while the vehicle is operating.
I understand that, but either you want a trailer or you want internal swappable/addable modules which both economically in my opinion seem of little benefit over engineering better cars with newer/better battery technology and stronger/lighter material.
Additionally, I didn't even mention the annoyance of engineering integrating the heating & cooling system for the modules themselves.
Better energy density batteries & better materials (or smarter manufacturing) make more sense to me than trying to make individual modules for a car swappable or asking people to drive around with a trailer they would use so infrequently that it would not justify the cost to them (not to mention most people don't know how to drive with one properly anyways).
Speed limits for towing smaller trailers mostly derive from safety concerns about overloaded or imbalanced trailers being unstable at high speeds. A battery-only trailer with little or no cargo space, designed and certified in conjunction with specific tow vehicles, could easily be safe enough to operate at highway speeds.
I think the main reason why we don't see anyone seriously pursuing the battery trailer idea is that it would be an expensive niche product. It would have to be mostly a rental-only product, and offer few advantages over simply renting a more suitable vehicle.
Obviously a trailer would not be a clever idea, but Nio already has cars with swappable batteries, for short distances you could just install a battery pack which is maybe 20% battery and 80% empty space
It’s enough of a pain in the ass to swap summer and winter tires, and that’s something that (some) people only do twice a year. I can’t imagine people wanting to swap battery packs (either themself or by making an appointment at a service center) before and after every long trip.
Ideally they could just come to my home or workplace and swap the batteries out there while I am doing something else (if it is going to take longer than 30 mins)
Both upthread replies seem to evidence approximately the same level of effort to me; "It won't be faster" isn't wildly less effort than "what if it will be faster?"
Nio has fewer Nio battery swap stations operating in the entire world than just the state of New Jersey has filling stations (not dispensers, entire stations).
Nothing in the video above made me think "oh wow, that looks like that process will be a lot faster than filling up!" and several segments made it seem like there would be more time involved in just getting the car into and out of the battery replacement service bay than filling up takes. (Nio's claim of a 2.5-3 minute battery swap seems to be measuring only the swap time while the car is stopped in the bay.)
That's all before we consider the travel time to one of the stations (which is unlikely to be as close to your trip as a typical filling station because of the rarity of stations), time waiting for the car [or cars] in front of you to complete their swap (which if Nios ever became popular would likely be longer than waiting for one of the typically eight or more dispensers to free up at a filling station), nor to account for the "all long range batteries are out of stock at this location, because it's the Friday before Christmas and everyone is road tripping to visit family" NACKs that are liable to occur in a Nio-only battery swap system.
For me the killer line in the video that will make it hard for Nio to solve all of these is at https://www.youtube.com/watch?v=hNZy603as5w&t=270s : "Building these stations is incredibly expensive and it's no secret that Nio is losing a staggering amount of money right now..."
My point is, it may be interesting if it’s faster than filing up. Now, is it likely? Not at the moment, as you correctly pointed out.
Can I guarantee it will never happen? No. Hence my comment. It was not about stating what will happen or not, I don’t feel this type of prediction has any reliability. Millions of people smarter than me get it wrong every day, especially the very long term ones are almost always wrong.
Having done a long trip in an EV, in a very inhospitable location (the USA, without access to Tesla chargers), I'm not convinced there is an EV range/charge time problem. I think it's mostly in the minds of the public. Hence I'm skeptical that the changeable battery pack is a solution to any problem.
My experience was that you end up stopping to charge a bit more often than you'd stop to fill up gas, but factoring in stops for bathroom and food, it's really not a significant difference. There just needs to be more chargers (to avoid queuing for an open one), and chargers that are more closely spaced (every 50 miles like gas stations instead of every 100+ miles). Then today's EVs will be just fine for long trips. Not completely perfect, but perfectly adequate, to the point that it won't be worthwhile buying an ICE vehicle just to have it for long trips.
It surprises me how much people are determined to use the "car" form factor when it's clearly not a good design for weight reduction and efficient transport.
If instead people consider EVs that are non-car-shaped then we get things like e-bikes and e-scooters. Both can feature easily swappable batteries as the batteries are so much smaller due to the reduced weight of the vehicle. Also, the problems around congestion can pretty much disappear when you get enough people to use an e-bike/e-scooter instead of a car. The tyre wear/pollution is minimised due to the reduction in weight and similarly the brakes.
I imagine semiautonomous trailers that would just tag along in the slipstream within cable range for distances beyond your daily. With computer-fast reaction to brake and steering inputs of the lead car. Those would universally be rentals that you change like the horses in pre-rail post networks.
NIO does battery swaps in minutes, in China and Europe. I believe you can also perhaps get different ranges but if not, would be great to swap between a 50kwh pack for normal use and say 100+kwh for your road trip.
Then again battery charging/weight tech is getting pretty good pretty fast.
Like the Thinkpads with the "bigger battery" humps: https://sm.pcmag.com/t/pcmag_ap/photo/l/lenovo-thi/lenovo-th...