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Old 05-24-2018, 05:08 PM   #37 (permalink)
Isaac Zackary
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Originally Posted by ldjessee00 View Post
I wanted to figure out a way to pull a trailer of batteries and/or small generator and charge our Leaf while out and about so we can do longer trips.
But, i would need to run high voltage lines from the front to the back...
Also, with the limited thermal management, would charging and discharging at the same time cause too much heat?
This is perfectly possible and has been done several times. Basically you connect the extra battery or generator to the main bus on the car and then match the voltage and then feed current into the main bus.

However, there is no such thing as charging and discharging at the same time. Either current is going into the battery or it is coming out. A river can only flow one way, and the same is true of electrical current. There's likely only one thing that would happen with an extra battery and three possibilities with a generator.
  1. If the motor is pulling X amount of current the current will be divided between all the batteries. For an example, if your trailer battery is twice the size of the Leaf's main battery then 1/3 of the current will come out of the main battery and 2/3 from the trailer battery. If the generator is small. less than 15kW, then you will normally be using some current from the main battery and some from the generator as the car goes down the road.
  2. If the generator puts out about 15kW or 20hp, then at highway speeds the battery may not be charged nor discharged while driving, except a little when going up or down small hills or when accelerating and decelerating. But overall, the battery's level of charge will stay roughly the same during the trip.
  3. If the generator is big enough, like 30kW or 40hp, then it will be able to both charge the battery and drive the car at the same time. Basically current from the generator will come to the main bus and split, part going to the motor and part going to the battery. Of course once the battery is full you'd have to turn down the power output of the generator so as to not overcharge the battery.

The effect of adding another battery or a generator will be a cooler main battery because it will be under less load.
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