electric car to car charging?

As electric cars become more and more common, someone will be by the side of the road with a flat battery. Now what?

While none of these ideas would currently work, the theory seems sound with the right software and cords.

So your car (car A) is dead, but your buddies car (B) has 3/4 of a charge:

 1. Plug the 2 cars together and let B charge A enough to get to the next charge point.

2. Plug the cars together and let the battery from B run both cars. The cord becomes sort of a tow rope/umbilical.

3. Call AAA or similar. They bring out a truck with a large battery or genset and charge the car onsite.

Could this be the future of roadside assistance and GRM ideas?

I think certain phones can share their charge with each other, so yeah...could be possible.

The roadside assist portable generator already exists in Europe. It is on a trailer that is brought to the stuck car.

You have to think about the logistics...

Most EVs on a standard level 1 charger take  several hours to charge, not feasible along the side of the road.

Car to car is not workable as most charging ports are meant to have AC voltage applied to them and they are only meant for AC voltage to go into the EV.  This may change if vehicle to grid takes hold.

Even DC fast charge systems will need a high amperage DC output from the car that is still charged... not very safe.

I wish I wasn't intrigued by EV's.  (Stupid open mindedness)

In reply to Gearheadotaku :

Wouldn't a little portable camping sized gas powered generator carried in the trunk of the car act like a spare?  Run flat out of charge someplace, pop open the trunk,  lift it to the ground and plug it into outlet? 15-20 minutes later, less time than calling for help and you're back on your way.  To a proper charging station. 
 Of course careless,  thoughtless, people run out of gas all the time  most people don't. 

In reply to frenchyd :

Thats why hybrids seem to makes so much sense to me. You take the generator along with you already!

The last time I ran out of fuel, I was stuck on the side of the road for three hours, and the trip ended with a flatbed tow.
  I don't see EVs being any less inconvenient.

In reply to triumph7 :

Agreed.  I would be surprised if there wasn't a diode in the system to prevent back-feeding the charging port with battery power.

I'm sure there is a way to do car-to-car charge sharing, but it would require some additional hardware and probably some programming.

frenchyd said:

In reply to Gearheadotaku :

Wouldn't a little portable camping sized gas powered generator carried in the trunk of the car act like a spare?  Run flat out of charge someplace, pop open the trunk,  lift it to the ground and plug it into outlet? 15-20 minutes later, less time than calling for help and you're back on your way.  To a proper charging station. 
 Of course careless,  thoughtless, people run out of gas all the time  most people don't. 

I'm not careless.  I just have an overabundance of optimism. And a flakey fuel gauge.

In reply to frenchyd :

Camping generators are rated in the 3000 to 5000 watt range and most EVs consume that much per mile.  On a level 2 charger (220V) our vans take 4-6 hours for a full charge (90-120 miles) and on a level 1 charger 9+ hours.  Average EV uses about 3 kW per mile, assuming 100% efficiency and the ability to keep the generators circuit breaker from blowing you will be on the side of the road for a long time just to get a couple miles.

triumph7 said:

In reply to frenchyd :

Camping generators are rated in the 3000 to 5000 watt range and most EVs consume that much per mile.  On a level 2 charger (220V) our vans take 4-6 hours for a full charge (90-120 miles) and on a level 1 charger 9+ hours.  Average EV uses about 3 kW per mile, assuming 100% efficiency and the ability to keep the generators circuit breaker from blowing you will be on the side of the road for a long time just to get a couple miles.

You may want to check your units- 3kW is a power unit, now the amount of energy used per mile.  3kWhr per mile would make more sense, although a far less confusing unit to use would be Joules, and 3-5kWhr would be about 10MJ/mi.  And since a gallon of gas is roughly 117MJ, that would be just under 1/10 gal per mile, or 10mpg.  Which seems REALLY high usage.

Last I checked, EV's are roughly 100mpge, or about 117MJ/100mi, or 1.1MJ/mi which is roughly 0.3kW-hr.  Which means a 1kW generator should be capable of charging a car to move three mile in about an hour.

Probably easiest to flat-tow it to a charging station - an EV will provide extra rolling resistance to keep the rope tight and charge the battery through regeneration.

chaparral said:

Probably easiest to flat-tow it to a charging station - an EV will provide extra rolling resistance to keep the rope tight and charge the battery through regeneration.

I'd love to see the EV manufacturer's recommendations regarding flat-towing.  Your statement sounds logical. 

I doubt flat towing will be suggested by EV maker. Except to move a vehicle from a dangerous place, I think it's likely illegal to tow with a strap /rope/chain/cable. A dedicated towing contraption would be vehicle specific so that's not gonna happen. 

As posted by others a roll back is the answer, just as it is now for combustion engined cars.

There have been guys screwing around with the "tow to recharge" technique, but it's mostly just geeks playing with cool toys. The correct answer is "drag the car to a gas station". The infrastructure is in place, it gets the car out of danger ASAP and it's the most efficient option from the point of use of the tow vehicle.

As for efficiency - the Tesla reports in Wh/mi. Normal usage is in the range of 285 Wh/mi, or 0.285 KWh/mi.

Knurled. said:

The last time I ran out of fuel, I was stuck on the side of the road for three hours, and the trip ended with a flatbed tow.
  I don't see EVs being any less inconvenient.

Same thing happened to me the last time I ran out of Subaru bearings.