Why Does The Negative Battery Cable Need To Be Removed To Flat Tow A 2021 Chevy Spark Manual

Updated 04/05/2025 | Published 10/16/2021

Products Featured in This Question

Roadmaster Direct-Connect Base Plate Kit - Removable Arms

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$575.00

Brake Buddy Select 3 Portable Flat Tow Brake System - Proportional

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$1460.95

RoadMaster 68" Single Hook, Coiled Safety Cables - 6,000 lbs

(654)

$71.02

Roadmaster Battery Disconnect for Towed Vehicle w/ Flat Tow Brake System - Gas Only

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$227.78

Roadmaster Smart Diode Kit for Variable Voltage Incandescent Tail Lights - 7-to-6-Way Adapter Cord

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Question:

If I am running a charge line from my motor home to my toad chevy spark, why do I need to disconnect the neg on the battery? If the battery is getting charged, why not just let the lights and radio stay on while I tow it since they are getting power? Thanks.

asked by: Kirk

Expert Reply:

The reasoning behind removing the negative cable from your 2021 Chevy Spark's battery isn't a charging/maintaining battery level issue. Chevy has you do this to disable certain functions of your vehicle to allow it to be safely flat towed. As time goes on cars are getting progressively more and more computerized and by not following the manufacturer's required steps, such as removing the negative battery cable, could potentially harm these components. To make disconnecting the battery as simple as flipping a switch you can install the Roadmaster Automatic Battery Disconnect with Switch for Towed Vehicle w/ Supplemental Braking System # RM-766.

If you haven't already purchased your entire flat towing setup I have the following recommendations for you below:

Tow Bar: Roadmaster Falcon All Terrain, Non-Binding Tow Bar # RM-522. This tow bar features a non-binding design and large hookup radius to make connecting and disconnecting on any terrain a breeze.

Base Plate: Roadmaster Direct-Connect Base Plate Kit # RM-523202-5. This direct-connect style base plate makes connecting/disconnecting easy and the removable arms will provide a clean look when not in use. This base plate fits LS and LT models excluding the ACTIV edition.

Tow Bar Wiring Kit: Roadmaster Smart Diode 7-Wire to 6-Wire Wiring Kit for Variable Voltage Incandescent Tail Lights # RM26FR. This complete kit includes everything you need to connect your RV's tail, brake, and turn signal lights to your Chevrolet Spark with variable voltage lights while flat towing. The included 7-Wire to 6-wire Flexo-Coil adapter cord lets you easily run power from your motorhome to your towed vehicle.

Braking System: Brake Buddy Select 3 Portable Supplemental Braking System # HM39524. This breaking system offers intense, emergency braking or steady, smooth braking in a single portable system. Easily switch between proportional or full braking using the included remote from the convenience of your RV. This system also comes with a charge line kit included to keep your battery charged while towing.

Safety Cables: RoadMaster 68" Single Hook, Coiled Safety Cables - 6,000lbs # RM-643. The coiled design of these cables will help prevent them from dragging on the ground and being damaged.

You may also need to use a high/low adapter to keep your tow bar level while towing your Chevy Spark. This requires a little bit of measuring so I've attached our help guide article to assist you in this process.

I've also attached some videos that will review these products and show you installation as well.

expert reply by: Kevin C

Tim

4/5/2025

On my 2024 chey equinox i have to remove the negtive term on the battery to flat tow. I installed a sw. to do this instead of removing the wire and there is no wires attached to it before the sw.. when i wire it ( Brake Buddy Select 3 Portable Flat Tow Brake System - Proportional). How does the system stay running when there is no negitive. does the brake buddy get the negtive somehow from my motor home thru the 6 pin connector.

Jerred H.

4/5/2025

@Tim To power the Brake Buddy Classic 3 Portable Flat Tow Brake System item # HM39494 you'll need to install the 12 Volt Outlet Kit, 20 amps item # RM-9332 and wire it directly to the battery. The charge line included with the Brake Buddy will keep your battery topped off.

Tim

4/5/2025

@JerredH I have the HM39524 select 3 as stated in the email would it be the same rm- 9332