# Why can't you rent towable aux batteries for electric cars? **URL:** \ **Category:** In My Humble Opinion\ **Created:** [October 30, 2021, 1:47pm UTC](https://boards.straightdope.com/t/why-cant-you-rent-towable-aux-batteries-for-electric-cars/953519 "2021-10-30T13:47:50Z")\ **Posts on this page:** 20\ **Page:** 2
**Author:** ![Spiderman](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/spiderman/32/230_2.png) [@Spiderman](https://boards.straightdope.com/u/Spiderman)\ **Post date:** [November 1, 2021, 2:02pm UTC](https://boards.straightdope.com/t/why-cant-you-rent-towable-aux-batteries-for-electric-cars/953519/21 "2021-11-01T14:02:42Z")
> [@Shalmanese](#): > > > [@Spiderman](#): > > > > for many people this could be much, much longer because it involves precise backing to get the ball over the hitch > > You could engineer the swap stations so your car just has to be in approximately the right position and the trailer would use computer vision to automatically drop onto the hitch. Hitch isn’t the same height on every vehicle, you may have raised it high enough to get your car out but my model has a higher ball; I can’t drive under because the trailer isn’t high enough. Does that precise enough backing exist now, or is that more development? I know existing tech won’t hit something like a curb or a bumper, but in this case you also need precise alignment. > [@Spiderman](#): > > People _will_ forget that their vehicle is longer; this _will_ cause accidents when they go to change lanes & don’t remember that they need to leave extra room because their normal short car is suddenly longer. > [@Shalmanese](#): > > You could engineer it so that the trailer has backup cameras that get automatically piped into the car for changing lanes. Also, self driving is pretty good for highways these days and the self driving system could know when you have a trailer and account for that, leaving you not having to worry about the driving portion. A longer, heavier vehicle handles differently when you’re driving, not all driving will be on the highway & in self driving mode. Also, Self-driving isn’t perfect. & not all driving is highway driving. I’m used to two-lane roads that add an occassional passing/slow lane in the hills/mountains. > [@Spiderman](#): > > - If a rental, I’d assume it’s like a car rental company > [@Shalmanese](#): > > No, they’d be fully automated, like charging stations are now. You pull in, hit a button on a mobile app and it tells you what bay to drive into to drop off/pick up. What happens when it’s cold out, or raining, or you’re late & don’t plug it in for the next guy? People are a-holes & won’t treat rental equipment with the same loving care they (don’t) treat what they own. Who’s doing the inspection for damage when you drop it off? What happens if it needs maintenance, like the tires &/or brakes (if it’s big enough to require them) are wearing down? > [@Spiderman](#): > > (personally, most of my trips aren’t city-to-city, but suburbs-to-rural) > [@Shalmanese](#): > > Unless your suburb to rural trip is more than 60 miles long, just use your normal battery, these are designed for 300 - 1000 mile long trips, where you’d pick up your trailer at a highway offramp. Not every off-ramp will have one of these stations, & even if there was one at my off-ramp, that would mean my destination is within 30 miles (60 round trip). I don’t think you understand what rural means. > [@Spiderman](#): > > Logistical issues with the rental company distributing their supply back to where it’s needed; > [@Shalmanese](#): > > You have a pair of them on either side of of a highway and, under normal circumstances, the flow is balanced. If the flow isn’t balanced, you can use discounts or even paying people to hook up a trailer and tow it to the next swap station down the road. City-dwellers going to their mountain/beach house for the weekend NCAA football fans going to the game Fri eve/Sat morn & all returning on Sat afternoon are just two examples that come to mind of unequal distribution > [@Shalmanese](#): > > You could save ~$10K and ~15% on your fill up costs if you slimmed it down to a 80 mile battery and used an aux battery whenever you needed 400+ miles of range. There’s a _huge_ world between 80-400 miles; I’m SoL at a 45-50 mile round trip (something which is common for me) > [@Shalmanese](#): > > The criticism I’m hearing that I feel has the most legitimacy is that driving with a trailer is significantly more difficult than driving without one. What if instead of a loose trailer, it was more like a truck bed with rigid mounting points to the back? It would effectively turn your Nissan Leaf into a Ford F150 for the duration of the trip, then you could go back to your normal economy sized car at the end of the trip. True, driving a trailer is harder. How much storage does one lose with that. Can’t fit clothes & toys for that trip to Grandmother’s house if the cargo area is now a battery. If externally mounted, who is lifting it into place & ensuring it’s mounted & strapped/bolted down properly so as to not become a hazard when driving? ---
**Author:** ![LivingGhost371](https://avatars.discourse-cdn.com/v4/letter/l/b9e5f3/32.png) [@LivingGhost371](https://boards.straightdope.com/u/LivingGhost371)\ **Post date:** [November 1, 2021, 8:30pm UTC](https://boards.straightdope.com/t/why-cant-you-rent-towable-aux-batteries-for-electric-cars/953519/22 "2021-11-01T20:30:50Z")
If you have the enormous hassle of renting something every time you want to take a road trip, why not just rent the entire vehicle that’s suitable for for the trip? Then you’re not pulling a trailer everywhere. There’s a reason people own pickup trucks instead of owing a sedan and then renting a trailer or a different car for the weekend- you want one vehicle that can fulfill all your needs without having to rent. Also, you’re asking people to mess around with high current electrical lines that would be exposed in the event of a crash. As far as the suggestions of putting a module in the trunk- OK, now your trunk space is all gone for your road trip and your vehicle is extremely top-heavy. ---
**Author:** ![digs](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/digs/32/14889_2.png) [@digs](https://boards.straightdope.com/u/digs)\ **Post date:** [November 1, 2021, 10:37pm UTC](https://boards.straightdope.com/t/why-cant-you-rent-towable-aux-batteries-for-electric-cars/953519/23 "2021-11-01T22:37:00Z")
I’d consider an EV if I could just carry even a small “Emergency 50-mile Battery Pack” in the back. Like I do for my iPhone; I carry a small battery and cords in my bag. Oh, it’d be as if I were carrying two gallon gas can in the back of my Subaru. But less smelly! ---
**Author:** ![Ranch\_Dip](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/ranch_dip/32/5238_2.png) [@Ranch\_Dip](https://boards.straightdope.com/u/Ranch_Dip)\ **Post date:** [November 1, 2021, 11:02pm UTC](https://boards.straightdope.com/t/why-cant-you-rent-towable-aux-batteries-for-electric-cars/953519/24 "2021-11-01T23:02:05Z")
> [@ShadowFacts](#): > > I would love there to be a small emergency battery that I could carry on longer trips, with like 20 miles of range on it, just so I could be sure never to be stranded. My Prius Prime has the best of both worlds. I can drive fully electric, hybrid, or traditional gasoline. My travel distance on one tank of gas is just shy of 500 miles. I’m not getting stranded anywhere. I filled my tank on Aug 15. I finally filled it again on Oct 30. ---
**Author:** ![kanicbird](https://avatars.discourse-cdn.com/v4/letter/k/5f8ce5/32.png) [@kanicbird](https://boards.straightdope.com/u/kanicbird)\ **Post date:** [November 2, 2021, 12:10pm UTC](https://boards.straightdope.com/t/why-cant-you-rent-towable-aux-batteries-for-electric-cars/953519/25 "2021-11-02T12:10:58Z")
This may be possible one day with Al-air batteries, which are non-rechargable. But the issues is how to get them to not degrade in storage, and the are not ready for primetime. But like gas powered cars, carrying extra fuel really is not a viable/practical or necessary option for most people. I had a small jug of ‘emergency fuel’ which I bought back in the early 90’s some sort of super stabilized synthetic gas alternative, that would get you perhaps 10 miles. Carried it for decades, never needed to use it, and finally about 20 years after I finally just added it to the tank to get rid of it. What you do want is the ability to walk to a nearby ‘gas station’ and be able to buy a cheap ‘gas tank’ and fill it with ‘gas’ and walk it back to your stranded vehicle. This can be done with batteries, or super capacitors that you most likely would have to drive back to the place you got them from, more of a rental situation. ---
**Author:** ![dtilque](https://avatars.discourse-cdn.com/v4/letter/d/d6d6ee/32.png) [@dtilque](https://boards.straightdope.com/u/dtilque)\ **Post date:** [November 2, 2021, 1:47pm UTC](https://boards.straightdope.com/t/why-cant-you-rent-towable-aux-batteries-for-electric-cars/953519/26 "2021-11-02T13:47:45Z")
There are range extenders for EVs. The F-150 Lightning is supposed to have one as an option. They’re basically small gas generators. I don’t think there’s going to be a big market for auxilliary batteries for EVs, so most likely these range extenders will fill the small market for that need. ---
**Author:** ![JRDelirious](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/jrdelirious/32/9531_2.png) [@JRDelirious](https://boards.straightdope.com/u/JRDelirious)\ **Post date:** [November 2, 2021, 4:44pm UTC](https://boards.straightdope.com/t/why-cant-you-rent-towable-aux-batteries-for-electric-cars/953519/27 "2021-11-02T16:44:54Z")
Y’know, myself not planning to be crossing the desert in any kind of vehicle any time in the foreseeable future, at first it was kind of amusing the concern among many about fuel or charge range. Just plan your route and top off no later than when you get to half, right? …But then it hits me that the real issue is not range per se but (a) availability of recharging points and (b) the fact that with gas/diesel I can fill up with 300 miles of range in _minutes_, with trivial effort, at any station coast to coast in every podunk town, but not so for an EV. The big issue is the time cost of having to be plugged in anywhere from the best part of an hour to overnight depending on type of charger and car, and now having to consider the contingency of needing to have to split the trip and _overnight_ at the rest point when you could have just made the trip in one long day of driving. ---
**Author:** ![Dewey\_Finn](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/dewey_finn/32/4222_2.png) [@Dewey\_Finn](https://boards.straightdope.com/u/Dewey_Finn)\ **Post date:** [November 2, 2021, 4:46pm UTC](https://boards.straightdope.com/t/why-cant-you-rent-towable-aux-batteries-for-electric-cars/953519/28 "2021-11-02T16:46:28Z")
> [@JRDelirious](#): > > But then it hits me that the real issue is not range per se but (a) availability of recharging points and (b) the fact that with gas/diesel I can fill up with 300 miles of range in _minutes_ , with trivial effort, at any station coast to coast in every podunk town, but not so for an EV. On the other hand, an EV can recharge (albeit not necessarily quickly) anywhere an electrical outlet is available. ---
**Author:** ![JRDelirious](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/jrdelirious/32/9531_2.png) [@JRDelirious](https://boards.straightdope.com/u/JRDelirious)\ **Post date:** [November 2, 2021, 4:53pm UTC](https://boards.straightdope.com/t/why-cant-you-rent-towable-aux-batteries-for-electric-cars/953519/29 "2021-11-02T16:53:04Z")
Which is why I emphasized the “in minutes” part. ---
**Author:** ![Capn\_Carl](https://avatars.discourse-cdn.com/v4/letter/c/838e76/32.png) [@Capn\_Carl](https://boards.straightdope.com/u/Capn_Carl)\ **Post date:** [November 3, 2021, 1:00am UTC](https://boards.straightdope.com/t/why-cant-you-rent-towable-aux-batteries-for-electric-cars/953519/30 "2021-11-03T01:00:55Z")
This doesn’t match my EV road trip experience at all. A 500 mile trip across the desert involves 3 stops of under 20 minutes each. ---
**Author:** ![commasense](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/commasense/32/3017_2.png) [@commasense](https://boards.straightdope.com/u/commasense)\ **Post date:** [November 3, 2021, 1:39pm UTC](https://boards.straightdope.com/t/why-cant-you-rent-towable-aux-batteries-for-electric-cars/953519/31 "2021-11-03T13:39:30Z")
I’m surprised no one has mentioned [Better Place](https://qz.com/88871/better-place-shai-agassi-swappable-electric-car-batteries/), a company that proposed swappable batteries for electric cars more than ten years ago. Israeli founder Shai Agassi proposed > the swapping station—a network of automated pitstops that, in a mere three minutes, or about the same time required to fill up a car with gasoline, would replace an exhausted battery with a charged one. In one fell swoop, a large new generation of drivers would be corralled into quiet, clean electric cars, now equipped with the allure of effectively limitless distance. The idea seemed especially well-suited for compact countries such as Israel and Denmark, along with dense cities in the US and Australia. Although the plan seemed very promising, and he raised a lot of capital and got the cooperation of Nissan chair Carlos Ghosn, various entrenched interests in Israel hampered the plan, and the company went bankrupt. Since then one of the main obstacles that Agassi was trying to overcome, underpowered batteries and concomitant low range, has largely been fixed, so the need for such a system is no longer as great. ---
**Author:** ![Dewey\_Finn](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/dewey_finn/32/4222_2.png) [@Dewey\_Finn](https://boards.straightdope.com/u/Dewey_Finn)\ **Post date:** [November 3, 2021, 1:52pm UTC](https://boards.straightdope.com/t/why-cant-you-rent-towable-aux-batteries-for-electric-cars/953519/32 "2021-11-03T13:52:55Z")
Also, eight years ago Tesla demonstrated ([YouTube video here](https://www.youtube.com/watch?v=H5V0vL3nnHY)) how quickly it was possible to swap the batteries in a Tesla Model S but they seem to have dropped the idea since then and I don’t know if the batteries in their newer cars are still as easily swapped. ---
**Author:** ![dtilque](https://avatars.discourse-cdn.com/v4/letter/d/d6d6ee/32.png) [@dtilque](https://boards.straightdope.com/u/dtilque)\ **Post date:** [November 3, 2021, 1:55pm UTC](https://boards.straightdope.com/t/why-cant-you-rent-towable-aux-batteries-for-electric-cars/953519/33 "2021-11-03T13:55:26Z")
More recently, Chinese companies are working on battery swapping: > **[China's Geely to set up 5,000 battery swapping stations by 2025](https://www.reuters.com/business/autos-transportation/chinas-geely-set-up-5000-battery-swapping-stations-by-2025-2021-09-26/)** > > China's Geely (GEELY.UL) aims to set up 5,000 battery swapping stations for electric vehicles (EV) globally by 2025, as sales grow in the world's biggest vehicle market, the automaker said in a statement on Sunday. As far as Tesla, their current plans are to change to a battery that’s a structural part of the car, so battery swapping is right out for them. ---
**Author:** ![bump](https://avatars.discourse-cdn.com/v4/letter/b/7c8e57/32.png) [@bump](https://boards.straightdope.com/u/bump)\ **Post date:** [November 3, 2021, 2:50pm UTC](https://boards.straightdope.com/t/why-cant-you-rent-towable-aux-batteries-for-electric-cars/953519/34 "2021-11-03T14:50:05Z")
There are a lot of factors- traffic, wind, road construction detours, and so on, that might well consume more battery than someone might plan on during a trip. And if charging stations are few and far between like they are today, that might well mean running out before you get to your destination. Same thing happens with ICE vehicles- people generally don’t run out of gas, but it does happen despite people’s best interests and planning. So having some sort of reserve might well be a good idea- I would think maybe some sort of disposable fuel cell might be the way to go on something like that- batteries will lose charge over time, but a cylinder of some kind of gaseous fuel probably won’t. ---
**Author:** ![Dewey\_Finn](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/dewey_finn/32/4222_2.png) [@Dewey\_Finn](https://boards.straightdope.com/u/Dewey_Finn)\ **Post date:** [November 3, 2021, 2:51pm UTC](https://boards.straightdope.com/t/why-cant-you-rent-towable-aux-batteries-for-electric-cars/953519/35 "2021-11-03T14:51:29Z")
There are systems using either generators or batteries that allow for a tow truck to provide an emergency recharge for an electric cars. ---
**Author:** ![bump](https://avatars.discourse-cdn.com/v4/letter/b/7c8e57/32.png) [@bump](https://boards.straightdope.com/u/bump)\ **Post date:** [November 3, 2021, 2:59pm UTC](https://boards.straightdope.com/t/why-cant-you-rent-towable-aux-batteries-for-electric-cars/953519/36 "2021-11-03T14:59:10Z")
Why is that better than just having a small emergency charging battery-type device in your trunk? I don’t know about you, but dealing with tow trucks is always expensive and slow, and doubly so when I haven’t been in the midst of an urban area. ---
**Author:** ![Dewey\_Finn](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/dewey_finn/32/4222_2.png) [@Dewey\_Finn](https://boards.straightdope.com/u/Dewey_Finn)\ **Post date:** [November 3, 2021, 3:04pm UTC](https://boards.straightdope.com/t/why-cant-you-rent-towable-aux-batteries-for-electric-cars/953519/37 "2021-11-03T15:04:32Z")
If the “small emergency charging battery-type device” really is small and light enough that it doesn’t take much space in your trunk, sure it’s not a bad idea. But what I found on Googling this, is that if such things are small enough not to be a hassle, they’re only going to give you five or ten miles of range and if they’re big enough to give you substantial range, they’re going to take up a lot of room and be heavy. And how often are EV owners going on trips through places with no charging options, keeping in mind that the car or your phone will have apps to identify the nearest charger? ---
**Author:** ![Dewey\_Finn](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/dewey_finn/32/4222_2.png) [@Dewey\_Finn](https://boards.straightdope.com/u/Dewey_Finn)\ **Post date:** [November 3, 2021, 3:42pm UTC](https://boards.straightdope.com/t/why-cant-you-rent-towable-aux-batteries-for-electric-cars/953519/38 "2021-11-03T15:42:43Z")
FYI, the [Edmunds website recently tested various EVs](https://www.edmunds.com/car-news/testing-teslas-range-anxiety.html) to see how many miles they would go even after the car indicates zero miles available and all would go at least five miles or more. ---
**Author:** ![Mangetout](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/mangetout/32/19_2.png) [@Mangetout](https://boards.straightdope.com/u/Mangetout)\ **Post date:** [November 3, 2021, 3:49pm UTC](https://boards.straightdope.com/t/why-cant-you-rent-towable-aux-batteries-for-electric-cars/953519/39 "2021-11-03T15:49:33Z")
Yeah, carrying around an extra battery that you intend to never use seems like an awful idea for a few reasons such as efficiency and the utility life of that battery itself. It would be better to build that capacity into the main battery and have use of it, and take notice of the remaining charge indicator. But then, I’m not one of those people who sets all their clocks deliberately fast in order to try to trick themselves into not being late. ---
**Author:** ![dtilque](https://avatars.discourse-cdn.com/v4/letter/d/d6d6ee/32.png) [@dtilque](https://boards.straightdope.com/u/dtilque)\ **Post date:** [November 3, 2021, 4:48pm UTC](https://boards.straightdope.com/t/why-cant-you-rent-towable-aux-batteries-for-electric-cars/953519/40 "2021-11-03T16:48:41Z")
> [@bump](#): > > I would think maybe some sort of disposable fuel cell might be the way to go on something like that- batteries will lose charge over time, but a cylinder of some kind of gaseous fuel probably won’t. Maybe there’s some kind of fuel cell that uses a gas other than hydrogen. If so, then maybe that’s a good idea. But hydrogen is such a small molecule that it leaks out of every kind of container. Some containers can hold it for a while, but they tend to be thick and heavy. So you’re not saving or gaining anything by keeping one of those in the car. [Previous page](https://boards.straightdope.com/t/why-cant-you-rent-towable-aux-batteries-for-electric-cars/953519.md?page=1) [Next page](https://boards.straightdope.com/t/why-cant-you-rent-towable-aux-batteries-for-electric-cars/953519.md?page=3)