How Can I Keep My Flat Towed Vehicles Battery Charged while Flat Towing Behind Sprinter 3500?
Updated 06/24/2026 | Published 06/19/2026
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Question:
Will the curt 57003 work on a 2024 sprinter 3500 on the 12v pin in the trailer receptical. The vehicle I plan on towing does not have led lights but I need to charge the battery when towing
asked by: David F
Expert Reply:
Hello David,
Thanks for writing in!
The Curt 7-Way Trailer Adapter for Towing Trailers with LED Lights # C57003 is designed to address issues that can occur when towing trailers equipped with LED lights. Since your goal is to keep the battery charged on the vehicle you're towing, this will not do the trick.
If your 2024 Mercedes-Benz Sprinter 3500 is equipped with an active 7-way connector, it should already have a 12-volt power circuit available at the trailer connector. The better approach is typically to carry that charging power from the Sprinter to the battery in the towed vehicle.
For that, I recommend the Roadmaster Battery Charge Line Kit for Towed Vehicles # RM-156-25. This kit is designed specifically to transfer a maintenance charge from the motorhome or tow vehicle to the battery in the vehicle being towed. It installs between the towing vehicle's 7-way and the 6-way connector commonly mounted on the front of the towed vehicle, allowing the battery to receive a charge while you're traveling down the road.
Have you been able to test to see if you are getting power through the 7 way? I attached an image where I highlighted the black 12v hot lead.
What kind of car are you flat towing? Are you new to flat towing, or just getting a different car set-up?
(click to enlarge)
Product Page this Question was Asked From
7-Way Trailer Adapter for Towing Trailers with LED Lights
- Custom Fit Vehicle Wiring
- Trailer Hitch Wiring
- Vehicle End Connector
- No Converter
- No Tow Package
- 7 Blade
- Plug and Lead
- Plug-In
- CURT
more information >
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on Custom Fit Vehicle Wiring
Dennis S.
6/24/2026
The adaptor works great I use mine all the time with several different trailers.