Roadside assistance for electric cars

Tesla sold ~21,000 cars in August 2018 in the US.  All other manufacturers sold about 2,600 that month.  We can assume that there will be a lot of electric vehicles (EVs) on the road soon.  This note discusses requirements for roadside assistance for these cars.  Traditional Internal Combustion Engine (ICE) vehicles typically require the following services:

Many of these services simply do not apply to Electric Vehicles (EVs).  Clearly, EVs don't need gas, the keys they used are radically different.  EVs need a different set of services that are currently not addressed.  This note describes a roadside assistance service suitable for EVs.

Emergency Fuel

A big problem with EV cars is running out of juice.  The only real option today is to tow it to a recharging station.  Unlike traditional cars, they cannot be readily brought back to life with a couple of gallons of gas.  Some options for charging are described below. 

Assume a fully charged battery capacity of 75 KWH and a 300 mile range.  Two levels of roadside charging are considered: 30 mile recharge to get the vehicle to the nearest charging station, and a 100 mile dose that would allow the vehicle to complete the day's routine and get back home.   These two ranges correspond to 10% and 33% charges respectively.  Note that the charging times are not linear with the percentage. Charge times are typically quotes as RangeMiles/Hour.

1.      Super charging

This option is described only to compare it with all other options.  It is currently the fastest way to charge an EV.

Tesla Super-charging station can provide up to 135 KW of power.  Charging stations for other makes of cars (BMW, Chevy, etc) are being planned at 150 KW.  A 10% recharge would need 7.5 KWH and should take 7.5/135 hours, or about 5 mins.  A 33% charge should take 15 mins.

Long queues can be a potential problem with super-charging stations.  Once they start charging, most drivers opt to top up their vehicles.  Each vehicle would take about 30 mins.  The drivers would wander away and it could be another 5 mins for their return after they are notified that charging has completed.  Note: Tesla charges a premium if the car is not promptly unplugged after fully charging.

2.      Home charging with 240v

Again, this is not a real option for roadside charging, but is listed for timing comparison.

There is a range of options for home charging.  The most popular choice would be a 240V setup.  This uses 38A yielding a nominal 9 KW rate.  This is called Level 2 charging.  (Level 1 would be 120V.)  The times for 10% and 33% charges are shown in the table below.

3.      Portable generator

There is a wide range of portable generators.  They usually have integrated IC engines.  They could be carried on a recovery service truck, though they tend to be quite large and heavy.  They cost from $600 to $2000.  They weigh from 300 lbs to 1200 lbs, and would be inconvenient to carry around on a truck. 

These chargers have limited power generation capabilities, ranging from 3.5 KW to 10 KW.  The charge times would be inconveniently long for roadside assistance.  Lastly, this is an inelegant solution because it involves a duplicate ICE, fuel tank, battery, etc.

4.      Generator on tow truck "power take off"

Today's tow trucks are built on commercial diesel pickup trucks.  Some of these vehicles have ICEs with an option for "power take off".  This capability allows the truck's engine to directly drive a generator.  The engine would both propel the truck and power the generator.  Depending on the truck model, between 50 to 100 hp can be available to run the generator.  This corresponds to about 25 to 50 KW of charging capacity.

The problem here is that, for most trucks, the generator would have to be squeezed into the truck's engine bay.  This limits the size and the capacity of the generator.  Typically, we could expect this design to yield about 25 KW.  A larger generator could be placed in the rear, but the driver cab is usually between the engine and that area. 

5.      EV friendly service truck

A new generation of EV friendly tow trucks can be designed based on a cab forward truck.  This exposes the ICE & transmission behind the cab and allows a larger generator to be installed.  A 300 HP engine would be available.  A generator would fit within a 2' x 2' x 3' space and could generate 135 KW.  This would be equivalent to a Level 3 charger.

Chevy offers a "Low Cab Forward" model but the available transmission is capable of delivering only 45 HP.  This yields about 22 KW.  A new transmission that supports a "power split" would be needed.

There currently are several incompatible standards for fast charging, but they will be forced to converge.  Tesla will soon offer an adapter for CHAdeMO, the leading Japanese standard.  Europe supports CCS and apparently China has its own.

A nice alternative to having an ICE powered generator would be for the truck to carry a large bank of batteries.  It could be an electric vehicle itself.  Assuming that this bank delivers power at 0.1C, it would need to have a capacity of 1350 KWH.  Assuming a battery cost of $100/KWH, this would be an expensive $135K.  Also, the time to re-charge these batteries would be counted as "down" time for the truck, thus further affecting its economics.



10%, 30 miles

33%, 100 miles

Setup Cost

Tesla Super charging or DC Direct

135 KW

5 mins

15 mins


Home charging with 240v 50A (level 2)

9.6 KW

50 mins

2.5 hours


Small portable generator

4 KW

2 hours

6 hours


Large portable generator (level 2)

10 KW

45 mins

2.5 hours


Generator on tow truck "power take off"

24 KW

20 mins

1 hour


EV friendly service truck

135 KW

5 mins

15 mins



Tire Replacement

Many modern EVs do not carry a spare tire that can be used as an emergency replacement.  Nor do they have the necessary jack and associated tools.  Some owners carry a can of "Fix a Flat".  Run flat tires are an option, but the current technology is not popular.  Tesla offers a service where they send over a truck with the appropriate wheel.  Unfortunately, this service is available for free only for the first 4 years of ownership.

A roadside assistance vehicle should carry a few wheels that can be loaned to the disabled vehicle.  


Traditionally, drivers lost their keys and were locked out of their car.  Today's cars don't use keys, they can be opened with mobile apps and fobs.

Rather than being trained in lock-smithing, today's roadside technician must be familiar with the car's features.  The simplest way may be to call the EV manufacturer's support center and have them remotely unlock and enable the car.  Many drivers may not know how to do that. 

The Value Proposition

Having defined the problem, this section suggests a solution, and an opportunity.  It seems that the current Roadside Assistance business will be changing drastically.  Here are some new requirements for the recovery vehicle.


  1. 135 KW charging capability with configurable voltage & EV adapters for multiple models of EVs
  2. Room to carry about 12 regular spare wheels (rims + tires) for multiple models of EVs.
  3. Lightweight electric jack & tools to rapidly change wheels
  4. Mobile data connection to provide local WiFi service


The alternative to roadside charging would be to tow the car to a charging station.  Assume that this results in a 15 mile tow.  A typical tow for 15 miles in the USA costs about $120.  Ignoring the time taken for the assistance truck to arrive, it would take at least an hour to load the car, move 15 miles and unload the car.  Then there is the time taken to charge.  Assuming that it is a Level 2 charging station, which are most common, that adds another hour.  Further, the EV is now away from its planned route.  Say the time cost of 2 hours of hassle is at least $100.  Total cost of the tow is $220.  In comparison, an EV friendly assistance truck could give the vehicle a 30 mile recharge in 5 mins flat.  The driver would gladly pay a premium, say $150 or more.  Time is precious for someone who can afford a Tesla.

There are other ways to generate revenue with a roadside charger.  Electric semi trucks will soon be on the roads and they will need a powerful charger if they run out of charge on the road.  A roadside assistance vehicle as described here can help that market as well.

Some new services can be offered.  Given that charging an EV takes time, and busy people hate to wait at a charging station, a service could provide charging "delivery".  A busy executive could ask the service to come and charge the car where it is parked while they continued to work, or party.  Such a non-emergency recharge could cost less, but the provider would have flexibility in scheduling this service between other requests.  Of course, in the long run, the EV would decide it needs a charge and would drive itself to a suitable charging station.


AAA USA started a service to provide emergency roadside charging.  It claims to provide 3 to 15 miles of charge to allow the vehicle to go to the nearest charging station.  The charging speed is Level 2, same as Home charging, and it would take 30 mins to get the 15 mile recharge.  However, this service does not seem to be available widely though it was started several years ago.

Clearly, others will think through this issue.  However, most will opt for the middle option of portable generators.  They will likely not start with the premium option suggested here.

Can't find any other project to spec or build such a solution in the USA or Europe.  The biggest challenge competition would have is to build a generator capable of economically generating 135 KW.


Given that some re-engineering is required for the generator, it seems that we need a vendor that has a suitable platform, engineering capability and the hunger to succeed.

Mahindra's Furio truck looks like a potential starting point.  M&M's main attraction is that they have started trying to enter the US and European markets.  They also have a very successful Formula E team and would benefit enormously from the exposure.  Likely issues: do they have a left hand drive version?  Powerful enough engine (300 hp) ?

The goal would be to prototype a truck with the charging capacity in "carrier" mode.  (Carriers can load the disabled vehicle on a platform, while "wreckers" have a hook to lift one end of the EV off the ground and tow it.)  Carriers are preferred for the upper end.

There are many roadside assistance purveyors, like AAA, most EV manufacturers, most insurance companies, etc.  However, these large purveyors enlist smaller local truck services.  The goal would be to target both parties: the big purveyors and the local services.  For purveyors, offering this premium service to their subscribers would make their offering more valuable.   For local services, having this premium service allows them to charge more.

Sept 2018