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Discussion Starter #1
Poking around there is a lot of discussion, but I have not seen any official docs from Smart that list what year/model can be towed behind another vehicle and what is required to do so safely.

I have a 2012 Passion and have towed for several years and many miles.
Key on
Shift N
key off
bungee wheel
disconnect battery

This is my procedure as it was told to me by another Smart Car owner.

In question is the battery disconnect. Seems there were several major failures in the beginning of flat towing because of a fail safe system (so I am told) that applies the brakes if wheels are turning, and engine is not running! Also reports of XMSN damage with battery connected.

I have not had any problems, but this week met up with another Passion owner towing flat with a 2013, and he has never disconnected the battery. So was there a change and at what year model?

A list by year and model and what is required would be very helpful to someone looking to buy a Smart new or used and flat tow.

This is not a hard request. You can dispute any part of my procedure, but it works.

My main concern is do I really need to disconnect the battery? Doing so is a pain, but I do it with a battery solenoid and key fob remote. Easy... unless I for get to disconnect when parked and find a dead battery in the morning.

And is my friend in danger of major damage if he is not disconnecting?
 

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AFAIK, no one has taken the time to go back through all the years of owners manuals to compile what the flat-towing recommended procedures are and if there were any changes.
Therefore the best way to find out what the factory recommends is to check your specific manual.
The manuals are available online https://www.smartusa.com/vehicle-manuals
For my 2009 Passion, the procedure in the manual says to disconnect the battery, so that's what I do.


 

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Discussion Starter #3
So a quick comparison of 2009 thru 2015 looks like they all have the same manual requirements for Flat Towing as I have been doing, and they all say to disconnect the battery after the ignition is turned off. 2016 is a different animal all together.

2008 has the same procedure but no mention of disconnecting the battery. Is that how people found out? The hard way? If so it seems to me they would have revised the on line manuals to include the battery off step. So maybe it is OK to leave connected.

Thanks for the link to the manuals...
 

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.......So maybe it is OK to leave connected....
Could be a risky choice. If the car's computer somehow becomes active while the car is underway and decides to shift the trans or activate the ABS, there's going to be a lot of expensive damage. All it would take is for road vibration, pothole, or loose cargo to nudge the key.

The keyswitch detent is not very strong in the position where you have to leave the key turned to.
 

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I just finished setting my 2017 ICN/DCT to flat tow. The battery disconnect switch I used came with a fused jumper wire to bridge the disconnected battery so the onboard computer continues to get juice. I did not use the jumper wire as it seems to me that would defeat the whole purpose of disconnecting the battery. Am I missing something?
 

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Discussion Starter #6
My last message was that it was not advisable to leave the battery connected. All the manuals say to disconnect. My friend is in the process of installing a battery disconnect as well.
 

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With regard to disconnecting the battery, the instructions for flat towing a DCT C/A453 state:

"Failure to follow the battery disconnect t procedure in the proper sequence may result in data loss in the vehicle's control units."

"Not disconnecting the battery and leaving the key in starter switch position 1 (ignition on) my (sic) result in
> The ESP being activated. Active braking action through the ESP may seriously damage the brake system which is not covered by the smart Limited Warranty.
> In a discharged battery."

">Turn the battery off using the previously installed battery switch or disconnect battery."

I take the above to mean that the battery needs to be completely disconnected and that using the fused jumper wire provided would allow enough juice to flow through the system to power up the ESP.

My guess is that the manufacturer of the disconnect switch thinks the battery disconnect is being used to disable the starter by providing a small amount of amperage through the jumper the computers retain memory but if you tried to start the car the starter would pull enough juice to blow the fuse. However, there were no clear instructions provided with the switch. So far, the only thing I've noticed losing when I disconnect the battery is the clocks on the dash and in the radio along with the station pre-sets.
 

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Seems best and safest to do. I bought a surface mount battery cut-off switch and mounted it on the pass. side under the dash (switch came with mounting bracket). Ran two wires down center console & under carpet to battery. Using connectors, one wire to disconnected negative cable and one to battery neg. terminal. My procedure is start engine, shift to neutral, make sure N shows on gauge cluster, switch off to first stop. Important: wait for gauge cluster to go off indicating computer has shut off. Then turn cut-off switch off.

Restarting is mostly reversing steps. Turn key to on. Turn on cut-off switch and quickly shift to park. Wait for computer to cycle and indicate P on gauge. Turn off annoying radio that blasts automatically. Reset clock.
 

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Another note on my procedure above... Yes, a key is left in and the driver's door is unlocked (I lock all doors first). I do have a non-electronic key that I sometimes use, but have to hold a regular key just right close to dummy key to be able to switch ignition off or on. Kind of a hassle. So, a bit of a security concern. But with cut-off switch pretty much hidden from view, and needing to use the proper procedure to start the car, I'm not worried about someone driving the car off. And anything I have in the car is not of concern for loss either. We've never had a problem with casual daytime stops. If I am concerned, or park for extended times in tow mode, I will reset the car and lock up.
 

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I haven’t tried it yet but I have two key fobs. I thought that if I wanted to lock the car (2017 453) after the battery is disconnected that I could do so with the key that flips out of the key fob?
 

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On my 2009 I have a procedure which disconnects the battery and still allows all the doors to be locked while I'm towing.




.
 

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Discussion Starter #14
I do also Ron. Mine had a remote control solenoid that I installed that disconnects the battery after I close all the doors I hit a button on a keyfob and the solenoid releases disconnecting the battery. My only shortcoming to the system is if I don't release the solenoid, it stays connected and will over night run the battery down. So I have two buttons to push in locking and shutting down the car for the night, no big deal unless I forget one of them!
 
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