Charging with rope in a jam?

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dangerHV

Well-known member
Joined
Sep 12, 2015
Messages
80
From my understanding, there is a continuous mechanical connection between the motor and wheels, regardless of "shifter" position, power on/off, etc. If I find myself nearly out of power - either my planning was off, or a charger was out of service - could I tie a rope to my Spark and maybe the trailer hitch of a passing truck. I'd put my car in low with power on and get towed for 10 - 20 minutes to regen enough power to get me to my destination?
I realize that technically this is illegal, but I'd be willing to take this chance in a jam if conditions were right. I wouldn't take this "ride" over 40 mph and I'd use the brake to keep the regen power at around 40 KW. (2c charge rate should be fine for the battery and motor)
This would reduce my range anxiety quite a bit. It would be like hitchhiking. If it worked, wouldn't it be a challenge to try to cross the country without plugging in?......Hmmmmm.....now my mind is racing again. Time for MORE COFFEE!

David
 
I'm thinking that a AAA tow would be faster and safer. Why put yourself and your vehicle at risk? I'd say the potential downside is not worth the cost savings.

But if you do do this, make sure to make a video for YouTube!
 
Long ago, these Dutch guys tow charged a Leaf:
http://www.autoblog.com/2011/05/25/is-the-quickest-way-to-charge-a-nissan-leaf-by-towing/ (turn on the English subtitles via the gear icon).

Here's "Supercharging" a Model S Russian style :mrgreen:
https://www.carthrottle.com/post/these-russians-recharged-their-tesla-model-s-by-getting-towed-behind-a-truck/ - you'll see what I mean at ~0:25
 
Well, I guess I'm NOT crazy after all! Not completely anyway. Thank you CW. I was thinking about this after my post and it's no different than going down a hill or mountain. Just for emergencies.

David
 
David,
I'm totally with you. 40kW is safe because when I'm on a DCFC I see 43kW for 10-15 minutes. Riding the brake pedal does not use friction brakes until regen is maxed.
You don't need a full charge. You only need enough to get you back home or to the nearest L2 or DCFC.

I plan on purchasing a 'stretchy tow rope' and keeping it in my 'survival bag' along with a 12' 12ga. extension cord and outlet tester.
I should get out the towing eye bolt and pop out the cover just to make sure I'm ready.

I have AAA, but why ride the "Flat Bed of Shame" when you can call a Bud to give you a short tow, (to anywhere, it doesn't matter, "just pull me Bro" ).
I'll save the AAA rides for my gasser and real emergencies.
 
Great points Norton. My only concern is the motor (generator in this case) getting overheated. Do you happen to know the kw needed go up a steep hill at speed? The motor's high kw rating is far above what a "continuous" rating would be. I'd like to be sure I don't exceed it's continuous rating, if there is one. Knowing how much power is drawn on the steep hill - especially with 3 adult passengers - would be the highest regen rate I'd want to go.

David
 
dangerHV said:
Great points Norton. My only concern is the motor (generator in this case) getting overheated. Do you happen to know the kw needed go up a steep hill at speed? The motor's high kw rating is far above what a "continuous" rating would be. I'd like to be sure I don't exceed it's continuous rating, if there is one. Knowing how much power is drawn on the steep hill - especially with 3 adult passengers - would be the highest regen rate I'd want to go.

David

There's a display setting that shows you how much kw is being used/generated. I think the peak I've seen used is 80 or 90 kw-- not sure what a high "continuous" level would be, or what the highest regen rate I've seen is either (but offhand I would say it's closer to 30 kw or so).
 
I drive mine in L on city streets and when braking from highway speeds, I've seen it exceed 40kW regenerating. If you're tow-charging, I would just set it in L then don't touch the pedals (and don't exceed a safe speed, probably 35MPH.) That should be good for ~30kW or so steady-state. Remember both the motor and batteries are liquid-cooled so the car will compensate.
 
The motor is in an oil bath of ATF that circulates through a cooler as needed. The inverter has a coolant system. The battery has a coolant system.
The max power of the motor is way more than the max regen for a reason.
You are not going to be doing this 'Recharge' for a long time. Just long enough to get enough range to get your sorry azz home.

As said above, a fully load car climbing up a steep mountain is way more work and I'm sure well within the design capabilities of this EV hot rod.
There is some thinking that this is the Drive Unit that will end up in the Bolt and it is SW limited in the Spark EV.

Using L would put a continuous big load on your tow buddy's vehicle. Using the brake pedal allows you to blend in regen at the best times.
If you are being towed by a smaller car or pickup you might not want to load it up with 43 kW immediately using L.
 
Hi Pegasus, The term "tow charging" fits perfectly. I haven't heard that before. I'll check Wiki.
35-40 mph sounds safe but I won't know til I try it. I also want to add a quick release cord in case the tow driver decides to get crazy. I don't like the idea of being at the mercy of a stranger in a potentially dangerous situation like this.
I will be experimenting with low and drive modes. I don't like cruise control- it's too easy to drift off (mentally) and forget that lifting my foot up will not slow the car down. (I use my left foot for braking, this may be what messes me up)
Hey Norton, I think the regen would have a limit on it determined by the max battery input more than any thermal issues. As far as the tow vehicle, I wouldn't consider anything that wasn't designed for towing. (I use the estimate of 1Kw = 1Hp, 75% efficiency for rough calculations. These days that's quite conservative) So the tow vehicle should have a "spare" 40 Hp or so. Imagine how much strain would be put on a small car?

David
 
FYI AAA in Portland has special ev trucks that can give you about 10 mi of range from a generator. Wish there were more of those!
 
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