7-Way Lead Gets Hot When Running Battery Charger Line Through Trailer Connector

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Question:

I installed a DC-DC charger in my trailer, not yours but equivalent to your Redarc BCDC1212 item RED96FR. While charging at full rate it could probably pull up to 400 watts of power. Power is transferred through the 7 pin connector to the trailer. When charging depleted batteries the 7 pin connector gets very hot to the point of softening the plastic around the positive pin on the plug. I do have a bit of voltage from battery to 7 pin 2020 Chev Colorado long bed crew cab so there may be 30-35 amps flowing through the 7 pin. Can the 7 pin safely pass 35 amps? it seems not owing to the heating The power pin is quite small while the ground pin is much larger. The vehicle socket is a pollak that looks like your item #PK11893. Is there an option that will safely pass more current? will replace both plug and socket Do I need to rig up a separate higherinch amperage connector to bypass the 7 pin? Seems to me like many trailers/5th wheels will have this issue especially if installing a charger like the Redarc BCDC1240 charger. Thanks for any advice/suggestions/recommendations you might share.

asked by: Joseph O

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Expert Reply:

The amperage rating of the battery charge line circuit which is run through the trailer connector will be based on the vehicle as not all are the same. That said, most trucks can handle up to 40 amps. If you see yourself exceeding this rating or your vehicle is rated lower you will need to separate the circuit from the trailer connector, we generally use winch wiring like the Bulldog Winch Booster Cable Set part # BDW20197 for this.

Please note, you will want to pay careful attention to the size of wire used with transferring high amps across distance so I do recommend you review the wiring portion of the install, the gauge of wire in particular.

expert reply by: Conner L

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Joseph O.

11/3/2021

Thanks for responding but you didn't answer my question. Yes, the wiring from truck battery to 7 pin should be upgraded. But the wiring in my truck doesn't get warm. The 7-pin, on the other hand, gets hot enough to soften the plastic indicating a high resistance connection. The wiring in my truck may be perfectly adequate with the voltage drop experienced at my DC-DC charger attributed to significant resistance in the 7-pin connector. Can the 7-pin connector safely pass 350 watts of power? (that's about 26 to 32 amps depending on voltage at the connector). The contacts in the 7-pin are pretty small. Contacts in 30 amp trolling motor plug designed to conduct 30 amps are substantially larger than the 7-pin contacts (c.f. Marinco 12VBRS2). You suggest upgrading the wiring in the truck but do not address how to transfer that power to the trailer. Use the 7-pin connector? Wire in a separate connector designed for higher amperage? Something else?

Reply

Victoria B.

11/8/2021

@JosephO The Pollak # PK11893 connector is rated for 30 amps and 12 volts. This comes out to 360 watts, but it does seem like one of these ratings is being exceeded if the connector is getting so hot that the plastic softens. Connor mentioned the Bulldog Winch Booster Cable Set # BDW20197. This set has connectors for the battery that may not work for your setup, so some modification to the wire ends is likely. This set is mentioned because it is much more highly rated than the 7-Way, and would mean the wiring and connector is not the limiting factor in your wiring setup. The Bulldog set comes with 2-gauge wires - rather than the 12 gauge wiring on your 7-way power connection - and is overall rated for 600amps. This would require you to make new connections at your vehicle battery and run the wiring to the back of your truck. The quick connector would be a second connection at the rear of your truck, with the other harness being installed on the trailer to the DC charger. This type of setup would require a second connection be made with these connectors when you hook your trailer up, but would allow you a much higher clearance for charging the system. You would want to check with the DC charger's instructions to see if in-line fuses are needed or any other special wiring instructions for your unit.

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7-Way Lead Gets Hot When Running Battery Charger Line Through Trailer Connector

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