Recommended Charger For Keeping Winch Battery Charged w/a Tow Vehicle
Updated 07/26/2026 | Published 07/20/2026
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Question:
I am going to be using a large winch on my trailer that draws high watts. I want to run the wire from the trailer junction box to the on board trailer battery to charge it when connected to the running tow vehicle. My question is will there also be a large draw on the wire from the trailer junction box to the battery? And will that draw go all the way back to the alternator of the tow vehicle? Thanks
asked by: joe a
Expert Reply:
No, it will not Joe. The large draw is going to be on the batteries you connect to. The accessory circuit on your tow vehicle's 7-way connector isn't going to provide enough power. It is designed to recharge your trailer's battery but it only provides 12v. That's not going to put stress on your alternator but the 7-way won't power the winch if you kill the battery or batteries and it won't recharge them either. At best the 7-way way maintains an already charged battery. You're going to need a big battery, 70 - 100 amp hours on your trailer to run a winch. High-power winches draw hundreds of amps under load.
To charge the battery being used for the winch, I recommend the Redarc In-Vehicle BCDC Trailer Battery Charger item # RED36TR. This will tie into your vehicle's alternator and allow it to charge the winch battery even if it was dead as it's able to send much more power through the dedicated wiring.
You will also need the fuse item # RED86FR and battery wire item # RED66FR.
The Bulldog Winch Rear Wiring Kit item # BDW20207 is also an option to power large winches on trailers. It connects directly to your vehicle's battery.
How many amp hours is your trailer's battery and what are you going to be using the winch for?
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Product Page this Question was Asked From
Redarc In-Vehicle BCDC Trailer Battery Charger - Dual Input - DC to DC - 12V - 12 Amp / Solar 40 Amp
- Battery Charger
- Battery Charger
- RV/Camper
- Trailer
- 12V
- 24V
- Charges and Maintains
- AGM
- Calcium
- Gel
- Lead Acid
- Lithium
- Solar Panels to Auxiliary Battery
- Vehicle Battery to Auxiliary Battery
- Smart Charge
- Trickle Charge
- Redarc
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Norman G.
7/26/2026
I wanted to wait until we had some trips under our belt with the device to confirm it was working as I wanted it to. PROBLEM: (As mentioned in other comments) our 2019 F150 was not charging the trailer battery while underway effectively. I now understand that the F150 alternator is designed to drop the voltage back once the truck battery is charged to a level too low to charge the trailer battery. The device takes that lower voltage and then adjusts it upward for 3 stage charging (we have lead acid deep cycle batteries - other programing options are available) of the trailer battery..... I did not pay much attention to the solar option when I ordered the device but learned that when I took my traditional solar charger out of the circuit (ran directly from the PV panels to the RED36TR) it did a much better job of using the solar panels effectively..... It also functions as an energy choice device in that if there is enough power coming from the solar array to charge the battery without using power from the truck it will use the free solar power in preference to the power generated by the ICE engine. Overall this device exceeded my expectations.