Hmp10
Well-Known Member
- Joined
- Mar 7, 2019
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- 629
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- Location
- Naples, FL
- Vehicles
- 2015 Tesla Model S P90D; 2018 Honda Odyssey
My point is very simple. Regenerative braking will not "automatically kick in" when an EV starts to coast or has its brakes applied. EV motors will not just go into and out of regeneration mode based on whether the EV is being towed, whether it is being braked, whether it is going up or down hill, or what a towing vehicle is doing.
You can disengage the electric motors for towing and use only the friction braking to assist with braking the tow vehicle, as you could with towing an ICE vehicle.
However, if you're going to recharge an EV by towing it -- which is the point around which this discussion began -- the motors have to be switched into regeneration mode. Once they are, if the EV is being towed on flat terrain the regeneration drag will increase the burden on the towing vehicle, as stated in the article Cappyjax cited. It was your claim that the author was inaccurate and that a vehicle could be towed for recharge without increasing the burden on the towing vehicle as long as it "was done right" that raised this question.
Exactly what has to be "done right" to recharge an EV when towing without increasing the burden on the towing vehicle? The only way to have the towed EV not add drag to the towing vehicle is for the EV motors to be taken out of regeneration mode. It is simply impossible for an EV to be charged by towing without adding drag to the tow vehicle. This drag may be desirable when going downhill, which is where the concept of "free energy" comes in, as you are essentially converting the force of gravity into electrical current via the motors-cum-generators. It also may be desirable when braking the tow vehicle, as you're also getting "free energy" from converting the potential energy of the two cars' forward motion into electricity. But when towing on flat terrain or uphill, that added drag of the EV being recharged is overcome not by gravity, but by the increased output of the ICE engine in the tow vehicle. And that energy is not free. If you want to pay that penalty to charge the EV because of the lack of charging infrastructure where you are going, that's fine. But there will be that penalty.
If you want to use flat towing to recharge an EV and do so without increasing the burden on the tow vehicle, my question remains how do you do that? What sensors, devices, or programming are in the towed vehicle to take the motors out of regeneration mode on flat terrain when there is no driver in the car and you do not want the added drag of flat towing the vehicle in regeneration mode?
You can disengage the electric motors for towing and use only the friction braking to assist with braking the tow vehicle, as you could with towing an ICE vehicle.
However, if you're going to recharge an EV by towing it -- which is the point around which this discussion began -- the motors have to be switched into regeneration mode. Once they are, if the EV is being towed on flat terrain the regeneration drag will increase the burden on the towing vehicle, as stated in the article Cappyjax cited. It was your claim that the author was inaccurate and that a vehicle could be towed for recharge without increasing the burden on the towing vehicle as long as it "was done right" that raised this question.
Exactly what has to be "done right" to recharge an EV when towing without increasing the burden on the towing vehicle? The only way to have the towed EV not add drag to the towing vehicle is for the EV motors to be taken out of regeneration mode. It is simply impossible for an EV to be charged by towing without adding drag to the tow vehicle. This drag may be desirable when going downhill, which is where the concept of "free energy" comes in, as you are essentially converting the force of gravity into electrical current via the motors-cum-generators. It also may be desirable when braking the tow vehicle, as you're also getting "free energy" from converting the potential energy of the two cars' forward motion into electricity. But when towing on flat terrain or uphill, that added drag of the EV being recharged is overcome not by gravity, but by the increased output of the ICE engine in the tow vehicle. And that energy is not free. If you want to pay that penalty to charge the EV because of the lack of charging infrastructure where you are going, that's fine. But there will be that penalty.
If you want to use flat towing to recharge an EV and do so without increasing the burden on the tow vehicle, my question remains how do you do that? What sensors, devices, or programming are in the towed vehicle to take the motors out of regeneration mode on flat terrain when there is no driver in the car and you do not want the added drag of flat towing the vehicle in regeneration mode?
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