# EV runs out juice in mid drive... **URL:** \ **Category:** Factual Questions\ **Created:** [February 3, 2020, 8:37pm UTC](https://boards.straightdope.com/t/ev-runs-out-juice-in-mid-drive/847442 "2020-02-03T20:37:35Z")\ **Posts on this page:** 20\ **Page:** 2
**Author:** ![breezman](https://avatars.discourse-cdn.com/v4/letter/b/4491bb/32.png) [@breezman](https://boards.straightdope.com/u/breezman)\ **Post date:** [February 3, 2020, 11:00pm UTC](https://boards.straightdope.com/t/ev-runs-out-juice-in-mid-drive/847442/21 "2020-02-03T23:00:20Z")
> [@Johnny\_L.A](#): > > Perhaps they can design cars with an internal combustion engine that charges the battery pack, and/or provides propulsion on its own in case the battery is drained. Oh, wait… 😛 I know you’re joking, but that’s a thing. BMW makes a variation of the i3 with a small engine that recharges the battery. This was also the original plan for the Chevy Volt. Diesel-electric locomotives (and maybe some busses?) work the same way. It may seem silly, but it has the advantages that the internal combustion engine can operate at whichever RPM they gives peak power or efficiency, and the electric motor can deliver full torque at startup. ---
**Author:** ![Dr.Strangelove](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/dr.strangelove/32/6613_2.png) [@Dr.Strangelove](https://boards.straightdope.com/u/Dr.Strangelove)\ **Post date:** [February 3, 2020, 11:01pm UTC](https://boards.straightdope.com/t/ev-runs-out-juice-in-mid-drive/847442/22 "2020-02-03T23:01:49Z")
> [@Joey\_P](#): > > As for swapping batteries, as it stands, that’s not an option. Replacing the battery on a Tesla involves removing the entire body. Not true. For the Model S (the skateboard in your linked picture), Tesla demonstrated a 5-minute semi-automated battery swap. The pack is held in by bolts accessible from the bottom, and the pack can be dropped down and exchanged. It’s no longer possible with the Model 3, though the pack can still be removed (it requires peeling up the carpeting to get at the bolts). Not good enough for a swap but it doesn’t require removing the body. Tesla closed their (one) battery swap station because nobody really wanted it. EV drivers spend almost no time at charging stations, so there’s just not much value in reducing that further. 20 minutes every few hours of driving is good enough for the occasional road trip, and the rest of the time (commuting, errands, short trips) they just charge at home. ---
**Author:** ![Marvin\_the\_Martian](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/marvin_the_martian/32/2898_2.png) [@Marvin\_the\_Martian](https://boards.straightdope.com/u/Marvin_the_Martian)\ **Post date:** [February 3, 2020, 11:37pm UTC](https://boards.straightdope.com/t/ev-runs-out-juice-in-mid-drive/847442/23 "2020-02-03T23:37:33Z")
> [@breezman](#): > > I know you’re joking, but that’s a thing. BMW makes a variation of the i3 with a small engine that recharges the battery. This was also the original plan for the Chevy Volt. > > Diesel-electric locomotives (and maybe some busses?) work the same way. It may seem silly, but it has the advantages that the internal combustion engine can operate at whichever RPM they gives peak power or efficiency, and the electric motor can deliver full torque at startup. When I first read about hybrid cars (probably in Popular Mechanics back in the 70s) this is what was described - an electric car that carried a gas powered generator. The gas engine would run at a constant speed (or constant torque, or whatever mode is most efficient) to charge up the battery, while the electric motor would handle propelling the car. I was very disappointed when the Insight and Prius came out that they did not operate this way. I still think this would make for a kick-ass 4WD vehicle - put the motors in the wheels and get tons of low speed torque while getting rid of the drivetrain. Put the engine/generator and battery high up in the vehicle and get tons of ground clearance. ---
**Author:** ![Joey\_P](https://avatars.discourse-cdn.com/v4/letter/j/919ad9/32.png) [@Joey\_P](https://boards.straightdope.com/u/Joey_P)\ **Post date:** [February 4, 2020, 12:23am UTC](https://boards.straightdope.com/t/ev-runs-out-juice-in-mid-drive/847442/24 "2020-02-04T00:23:43Z")
> [@Dr.Strangelove](#): > > Not true. For the Model S (the skateboard in your linked picture), Tesla demonstrated a 5-minute semi-automated battery swap. The pack is held in by bolts accessible from the bottom, and the pack can be dropped down and exchanged. I didn’t know that. My knowledge is limited to two videos I saw years ago. Even still, it’s not like you can do it on the side of the road. I think a lot of people envision something more along the lines of [this](https://n.b5z.net/i/u/6149217/i/battery_rack02.jpg). I mean it’s not a terrible guess. The current form factor of the Tesla batteries is odd. Clever, but odd. With that, I imagine a lot of those people not realizing this isn’t something you can swap on the side of the road. It probably doesn’t help that the battery for a hybrid vehicle is typically just under/near the back seat ---
**Author:** ![Joey\_P](https://avatars.discourse-cdn.com/v4/letter/j/919ad9/32.png) [@Joey\_P](https://boards.straightdope.com/u/Joey_P)\ **Post date:** [February 4, 2020, 12:28am UTC](https://boards.straightdope.com/t/ev-runs-out-juice-in-mid-drive/847442/25 "2020-02-04T00:28:53Z")
> [@Marvin\_the\_Martian](#): > > When I first read about hybrid cars (probably in Popular Mechanics back in the 70s) this is what was described - an electric car that carried a gas powered generator. The gas engine would run at a constant speed (or constant torque, or whatever mode is most efficient) to charge up the battery, while the electric motor would handle propelling the car. I was very disappointed when the Insight and Prius came out that they did not operate this way. Something else of note, the Insight and Prius, while having the same body, are totally different. The Insight never runs on battery alone, ever. If your foot isn’t on the brake pedal, the engine is running. To me anyway, that was the big difference. I don’t know enough about the Prius to comment on other differences. I still don’t know why Honda decided to use a nearly identical body. I’m sure I’m not the only Insight owner that stopped correcting people when they’d ask about their ‘Prius’. ---
**Author:** ![kanicbird](https://avatars.discourse-cdn.com/v4/letter/k/5f8ce5/32.png) [@kanicbird](https://boards.straightdope.com/u/kanicbird)\ **Post date:** [February 4, 2020, 12:39am UTC](https://boards.straightdope.com/t/ev-runs-out-juice-in-mid-drive/847442/26 "2020-02-04T00:39:25Z")
> [@Marvin\_the\_Martian](#): > > … > > I still think this would make for a kick-ass 4WD vehicle - put the motors in the wheels and get tons of low speed torque while getting rid of the drivetrain. Put the engine/generator and battery high up in the vehicle and get tons of ground clearance. Your adding quite a bit of unsprung mass which is not good for handling by putting the motors in the wheels. ---
**Author:** ![Johnny\_L.A](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/johnny_l.a/32/1084_2.png) [@Johnny\_L.A](https://boards.straightdope.com/u/Johnny_L.A)\ **Post date:** [February 4, 2020, 12:54am UTC](https://boards.straightdope.com/t/ev-runs-out-juice-in-mid-drive/847442/27 "2020-02-04T00:54:01Z")
> [@breezman](#): > > I know you’re joking… I was thinking about my Prius. 😉 ---
**Author:** ![Heracles](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/heracles/32/487_2.png) [@Heracles](https://boards.straightdope.com/u/Heracles)\ **Post date:** [February 4, 2020, 1:36am UTC](https://boards.straightdope.com/t/ev-runs-out-juice-in-mid-drive/847442/28 "2020-02-04T01:36:33Z")
> [@engineer\_comp\_geek](#): > > I have seen a couple of pictures of exactly that, so they are in use somewhere (no idea how common they are yet). > > Usually it’s been a diesel generator on a small trailer being pulled by a pickup truck. There was this [pilot project](https://www.auto123.com/en/news/caa-quebec-mobile-car-charging-pilot-project/65197/) in Québec about a year ago. Don’t know if it’s still ongoing. It appears to be just a big battery with level 3 output, not a petrol-powered generator. ---
**Author:** ![Ethilrist](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/ethilrist/32/4604_2.png) [@Ethilrist](https://boards.straightdope.com/u/Ethilrist)\ **Post date:** [February 4, 2020, 1:55am UTC](https://boards.straightdope.com/t/ev-runs-out-juice-in-mid-drive/847442/29 "2020-02-04T01:55:44Z")
> [@Marvin\_the\_Martian](#): > > When I first read about hybrid cars (probably in Popular Mechanics back in the 70s) this is what was described - an electric car that carried a gas powered generator. The gas engine would run at a constant speed (or constant torque, or whatever mode is most efficient) to charge up the battery, while the electric motor would handle propelling the car. I was very disappointed when the Insight and Prius came out that they did not operate this way. > > I still think this would make for a kick-ass 4WD vehicle - put the motors in the wheels and get tons of low speed torque while getting rid of the drivetrain. Put the engine/generator and battery high up in the vehicle and get tons of ground clearance. The people at [Zero South](http://www.zerosouth.com/) would seem to agree with you, although they just went with dual drivetrain front & back rather than one in each wheel. Diesel motor generating electricity for electric motors driving the vehicle. Pulling a modified Airstream on a sled. To the South Pole. Probably not too practical for most drivers, though. ---
**Author:** ![yo\_han\_go](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/yo_han_go/32/130_2.png) [@yo\_han\_go](https://boards.straightdope.com/u/yo_han_go)\ **Post date:** [February 4, 2020, 8:41am UTC](https://boards.straightdope.com/t/ev-runs-out-juice-in-mid-drive/847442/30 "2020-02-04T08:41:01Z")
[We drove these electric cars until they DIED!](https://www.youtube.com/watch?time_continue=12&v=ZH7V2tU3iFc&feature=emb_logo) Last minutes vary from car to car. But when they die, die. You can push some manually, but not all. ---
**Author:** ![Heracles](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/heracles/32/487_2.png) [@Heracles](https://boards.straightdope.com/u/Heracles)\ **Post date:** [February 4, 2020, 11:46am UTC](https://boards.straightdope.com/t/ev-runs-out-juice-in-mid-drive/847442/31 "2020-02-04T11:46:07Z")
> [@Marvin\_the\_Martian](#): > > When I first read about hybrid cars (probably in Popular Mechanics back in the 70s) this is what was described - an electric car that carried a gas powered generator. The gas engine would run at a constant speed (or constant torque, or whatever mode is most efficient) to charge up the battery, while the electric motor would handle propelling the car. I was very disappointed when the Insight and Prius came out that they did not operate this way. In practice, for a car at constant highway speeds, it’s often more efficient to use a petroleum engine linked to the wheels instead of using it to generate electricity to rotate a motor that drives the wheels. Or using it to generate electricity to charge a battery that rotates a motor that drives the wheels. See [this thread from 2017](https://boards.straightdope.com/sdmb/showthread.php?t=827443) about series hybrids. ---
**Author:** ![kanicbird](https://avatars.discourse-cdn.com/v4/letter/k/5f8ce5/32.png) [@kanicbird](https://boards.straightdope.com/u/kanicbird)\ **Post date:** [February 4, 2020, 12:58pm UTC](https://boards.straightdope.com/t/ev-runs-out-juice-in-mid-drive/847442/32 "2020-02-04T12:58:59Z")
Instead of a generator what about a battery pack? A generator would require a new redesigned truck with a PTO to the generator and those tow trucks most likely already have the PTO already occupied which makes it difficult to install another device. What about a battery pack? Something like a suitcase that has a inverter (or could somehow be hooked up direct dc to dc), and could provide that boost to get you to a nearby charging station? The tow truck driver could wait for the recharge or arrange to have them leave it after recharge. If the distance is too far to make it to a recharger then the car would have to be towed. ---
**Author:** ![kferr](https://avatars.discourse-cdn.com/v4/letter/k/71e660/32.png) [@kferr](https://boards.straightdope.com/u/kferr)\ **Post date:** [February 4, 2020, 1:24pm UTC](https://boards.straightdope.com/t/ev-runs-out-juice-in-mid-drive/847442/33 "2020-02-04T13:24:45Z")
I checked a couple of the big UK breakdown services. The AA will tow you to the nearest fuel station/charging point if you run out of fuel/charge. The RAC calls running out of fuel/charge a “driver-induced fault” and doesn’t cover it. ---
**Author:** ![YamatoTwinkie](https://avatars.discourse-cdn.com/v4/letter/y/cc9497/32.png) [@YamatoTwinkie](https://boards.straightdope.com/u/YamatoTwinkie)\ **Post date:** [February 4, 2020, 1:56pm UTC](https://boards.straightdope.com/t/ev-runs-out-juice-in-mid-drive/847442/34 "2020-02-04T13:56:13Z")
> [@kanicbird](#): > > Instead of a generator what about a battery pack? > > A generator would require a new redesigned truck with a PTO to the generator and those tow trucks most likely already have the PTO already occupied which makes it difficult to install another device. > > What about a battery pack? Something like a suitcase that has a inverter (or could somehow be hooked up direct dc to dc), and could provide that boost to get you to a nearby charging station? The tow truck driver could wait for the recharge or arrange to have them leave it after recharge. If the distance is too far to make it to a recharger then the car would have to be towed. Something like a [Tesla Powerwall](https://www.tesla.com/sites/default/files/pdfs/powerwall/Powerwall%202_AC_Datasheet_en_northamerica.pdf) (home battery with a build-in inverter) has a 13.5 kWh capacity, 5 kW output, and costs around $6500, which would be roughly 3X the cost of a portable gas generator with an equivalent output. ---
**Author:** ![kanicbird](https://avatars.discourse-cdn.com/v4/letter/k/5f8ce5/32.png) [@kanicbird](https://boards.straightdope.com/u/kanicbird)\ **Post date:** [February 4, 2020, 2:31pm UTC](https://boards.straightdope.com/t/ev-runs-out-juice-in-mid-drive/847442/35 "2020-02-04T14:31:16Z")
> [@YamatoTwinkie](#): > > Something like a [Tesla Powerwall](https://www.tesla.com/sites/default/files/pdfs/powerwall/Powerwall%202_AC_Datasheet_en_northamerica.pdf) (home battery with a build-in inverter) has a 13.5 kWh capacity, 5 kW output, and costs around $6500, which would be roughly 3X the cost of a portable gas generator with an equivalent output. We would need level 2 charging to be practical over towing, which would require 20 kWh. Level 2 gets you 25 miles/hour, Level 1 charging would only get you 5 miles per hour, before you have enough to go 5 miles with L1, the truck can have you at a L2 charging station. ---
**Author:** ![YamatoTwinkie](https://avatars.discourse-cdn.com/v4/letter/y/cc9497/32.png) [@YamatoTwinkie](https://boards.straightdope.com/u/YamatoTwinkie)\ **Post date:** [February 4, 2020, 3:14pm UTC](https://boards.straightdope.com/t/ev-runs-out-juice-in-mid-drive/847442/36 "2020-02-04T15:14:33Z")
> [@kanicbird](#): > > We would need level 2 charging to be practical over towing, which would require 20 kWh. Level 2 gets you 25 miles/hour, Level 1 charging would only get you 5 miles per hour, before you have enough to go 5 miles with L1, the truck can have you at a L2 charging station. I believe anything outputting 240VAC and is more than the Level 1 max of 1.9 kW qualifies as “Level 2”, but yes, ideally you’d want to have a charger that can output the Level 2 max of 19.2kW (4 Powerwalls hooked up in parallel). However, this is probably overkill for most EVs, since on board charging from AC sources is limited to 11.5 kW (at least this is the case for Tesla vehicles), which is good for 44 mi/hr on a Model 3. So lets just call it 3 Powerwalls (750 lbs total, ~$20k). ---
**Author:** ![scr4](https://avatars.discourse-cdn.com/v4/letter/s/59ef9b/32.png) [@scr4](https://boards.straightdope.com/u/scr4)\ **Post date:** [February 4, 2020, 3:21pm UTC](https://boards.straightdope.com/t/ev-runs-out-juice-in-mid-drive/847442/37 "2020-02-04T15:21:41Z")
AAA does operate [emergency charging trucks](https://electrek.co/2016/09/06/aaa-ev-emergency-charging-truck/) with level-2 chargers. ---
**Author:** ![kanicbird](https://avatars.discourse-cdn.com/v4/letter/k/5f8ce5/32.png) [@kanicbird](https://boards.straightdope.com/u/kanicbird)\ **Post date:** [February 4, 2020, 4:24pm UTC](https://boards.straightdope.com/t/ev-runs-out-juice-in-mid-drive/847442/38 "2020-02-04T16:24:48Z")
> [@scr4](#): > > AAA does operate [emergency charging trucks](https://electrek.co/2016/09/06/aaa-ev-emergency-charging-truck/) with level-2 chargers. As pointed out above, that is no more: [Bolt, Leaf, and Tesla Owners Take Note: AAA Temporarily Suspends Emergency Battery Electric Vehicle Charging Program | Torque News](https://www.torquenews.com/1083/aaa-temporarily-stops-emergency-battery-electric-vehicle-charging-program-hopes-return-better-service) ---
**Author:** ![eldowan](https://avatars.discourse-cdn.com/v4/letter/e/848f3c/32.png) [@eldowan](https://boards.straightdope.com/u/eldowan)\ **Post date:** [February 4, 2020, 4:34pm UTC](https://boards.straightdope.com/t/ev-runs-out-juice-in-mid-drive/847442/39 "2020-02-04T16:34:19Z")
Engineering explained tested towing a tesla with a Ford truck and ran some numbers on efficiency, etc. I can’t remember the results, but here’s the video for those inclined [![](https://img.youtube.com/vi/RaGVoB4Zn-Y/maxresdefault.jpg "Can You Charge A Tesla By Towing It? (With Ford Raptor)") ](https://www.youtube.com/watch?v=RaGVoB4Zn-Y) Sent from my SM-N975U using Tapatalk ---
**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:** [February 4, 2020, 4:34pm UTC](https://boards.straightdope.com/t/ev-runs-out-juice-in-mid-drive/847442/40 "2020-02-04T16:34:32Z")
> [@scr4](#): > > AAA does operate [emergency charging trucks](https://electrek.co/2016/09/06/aaa-ev-emergency-charging-truck/) with level-2 chargers. EVs are a fraction of vehicles on the road, yet > [@](#): > > **The service, which is only offered in a few of AAA’s markets** , aimed at addressing the often talked about issues with “range anxiety”, but as most EV drivers know, range anxiety doesn’t really exist with vigilant power management. Nonetheless, **the service has seen “thousands” of service calls** according to AAA. [Previous page](https://boards.straightdope.com/t/ev-runs-out-juice-in-mid-drive/847442.md?page=1) [Next page](https://boards.straightdope.com/t/ev-runs-out-juice-in-mid-drive/847442.md?page=3)