Car to car charging

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New member
Sep 28, 2017
Bedford, UK
The ability to transfer charge from one i3 to another with a Type 2 double ended cable, such as when there are two i3 cars in a household and one runs flat before getting home so that the other can come to its rescue and replenish it with some of the state of charge in the ‘rescue’ car. You can perhaps see the origins of this idea.
Alternatively, a domestic plug socket in the boot into which a home charger could be plugged. I am sure I saw this idea depicted by BMW as a future proposal yet I cannot find any reference to it online no matter how hard I search.
The type 2 plug accepts acv. THat gets converted in the car to dcv to charge the batteries. To do what you suggest would require the car to have a significant acv inverter to convert the batteries' dcv back to acv. While possible, it would likely require a fairly large, expensive module.

Now, it might be possible to do a dc-dc charging session, but to actually charge a battery, the supplier must be higher than the destination, so, depending on the initial charge states of each, it may not transfer much at all.

A relatively low powered ac inverter is a possibility, and is available in some evs today, but charging would be slow, and may not get you all that much. TO get significant power, the module needs to be fairly large, and the efficiency isn't always all that great.

One thing that is coming, sometime, is V2G vehicle to grid where upon demand and permission, a car can provide the grid some power, acting like a buffer to handle peak loads. So, once that is implemented, it MIGHT be possible to do this, but the implementation could be messy.
V2V perhaps , could be added to the Level III - DCFC Protocol . It might be complicated by the fact that voltages differ by vehicle . Maybe a V2V device would simply connect both DC lines and communication lines of the 2 vehicles . They could communicate their information and then base their action on which vehicle has the lower SOC .
I'd be very interested in Vehicle to Home charging. An EV essentially becomes a battery, owners can use solar to charge the car during the day and use the car's battery to power the home after sunset.
BMW demonstrated a prototype home power storage unit using battery pack(s) from decommissioned i3s. This is not from a working vehicle, but after a battery pack was removed, giving it a second life. So, there is a commercial use for the battery packs, even when they no longer meet the vehicle's needs. Now, whether that will ever make it into a commercial product you can buy, don't know. With the large depreciation on i3 vehicles, it might almost make sense to just take the battery pack out and plug it into a storage unit, if BMW, or someone else made the interface for it, to integrate it into a residence.