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Old 01-01-2022, 11:14 AM   #1
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Power output from the 7-pin trailer connector

I have been curious as to how much power is supplied through the trailer connector. A few weeks ago I installed a Victron SmartShunt battery monitor, so I conducted a test.

2021 Surveyor, 100Ahr AGM battery, 2020 Ram 1500 TV.

In my driveway, I turned off the solar panels and unplugged from shore power. I turned on the refrigerator and let it run several hours until the battery was at about 75% state of charge.

I turned off the fridge and plugged the trailer into my Ram. The battery monitor showed a current flow into the battery of about 12A.

I unplugged the trailer plug and plugged into shore power. The current flow into the battery from the WF-8735 power center is about 11A.
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Old 01-01-2022, 12:38 PM   #2
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Power available for charging from 7-wire cable will vary widely by vehicle.

Biggest variables will be wire size manufacturer used and how far from alternator to 7-pin connector.

Some report as low as 2-3 amps. More than 10 amps on a stock system is at the high range.
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Old 01-01-2022, 12:40 PM   #3
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I assumed that was the case. that's why I noted what my tow vehicle is.
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Old 01-03-2022, 01:51 PM   #4
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I assumed that was the case. that's why I noted what my tow vehicle is.
Alternator output varies with RPM. Given that you are getting a generous 12 amps, that's probably with engine RPM above 1500 RPM. So I'm guessing that in your test you did "idle up" the engine to the RPM it would normally be at when traveling? If you didn't, the truck's computer might have idled up for you. In any event, I'm envious of your 12 amps.
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Old 01-03-2022, 01:58 PM   #5
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Originally Posted by faithie999 View Post
I have been curious as to how much power is supplied through the trailer connector. A few weeks ago I installed a Victron SmartShunt battery monitor, so I conducted a test.

2021 Surveyor, 100Ahr AGM battery, 2020 Ram 1500 TV.

In my driveway, I turned off the solar panels and unplugged from shore power. I turned on the refrigerator and let it run several hours until the battery was at about 75% state of charge.

I turned off the fridge and plugged the trailer into my Ram. The battery monitor showed a current flow into the battery of about 12A.

I unplugged the trailer plug and plugged into shore power. The current flow into the battery from the WF-8735 power center is about 11A.
Thanks for doing that test. I was going to try that with a VOM but never got around to it. I am assuming that is the hemi TV? We have the 2019 Ram hemi with a 2020 Surveyor.

Have fun!
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Old 01-03-2022, 02:06 PM   #6
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Appreciate the test.
I've advocated here that many get more charging from the 7 pin than others want you to believe.
I've gotten a similar result from several of my tow vehicles.
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Old 01-03-2022, 07:46 PM   #7
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Thanks for doing that test. I was going to try that with a VOM but never got around to it. I am assuming that is the hemi TV? We have the 2019 Ram hemi with a 2020 Surveyor.

Have fun!
yes, a 2020 hemi and a 2021 Surveyor. the ram was at idle and I wouldn't swear to it but I don't think the computer idled it up. when I get back home in a few weeks I'll re-run the test and make note of the engine RPM.
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Old 01-04-2022, 12:36 AM   #8
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yes, a 2020 hemi and a 2021 Surveyor. the ram was at idle and I wouldn't swear to it but I don't think the computer idled it up. when I get back home in a few weeks I'll re-run the test and make note of the engine RPM.
Thanks, appreciate it.
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Old 01-04-2022, 11:01 AM   #9
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I did this test with my 2015 Chevy 2500HD. I got 4 amps at idle and 9 amps at higher RPM. The truck has 10ga wire and a 30A fuse for the charge line so I installed a Victron DC to DC smart charger rated 18A. Now I always get 14.2V @ 18A going to the 5er batteries. I was thinking about a 30A, but the voltage at the DC-DC input was only 13.7V so I needed some amp headroom to get that up to my desired voltage of 14.2 going out of the smart charger.
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