TV drawing power from trailer

[SilverWind]

Originally Posted by ROBERT CROSS

I just un-plug the 7pin when not moving....That lesson learned years ago when both the TV & Safari were dead as a doornail
POI We do have lithiums, and no DC-DC. SFSG.

Bob
🇺🇸

Ditto. Night drain shouldn't happen but can depending on vehicles. So very easy to disconnect the 7 pin.

[rickcaz]

Originally Posted by KK4YZ

A) yes. The dc/dc converter will act as the “isolator” I referred to in my original reply. It will prevent discharge of the trailer batteries into the TV batteries

B) Given that your existing setup provides little or no charge current to the trailer batteries from the TV, that answer would be “yes” as well. How much charging current will be provided depends on your selection of dc/dc converter, how you configure the dc/dc converter and the wire gages involved.

Your trailer has the incessant side exhaust refrigerator fan that will draw just roughly one amp, most of the time, even during winter. If the Television amplifier or subwoofer is "on" you might accidentally draw more current. I unplug my subwoofer.

Over-charging your tow vehicle batteries from your Lithium batteries or solar charge controller is not a good idea, even if Airstream battery drain isn't catastrophic.

The (almost perfect) 9 amp Victron isolating DC-DC convertor allows you to arrive with batteries topped off. Higher power DC-DC convertors might overload your existing vehicle tow-package wiring and fuses. The voltage drop to the trailer would limit your charge while towing to a trickle even with lower voltage (LA or AGM) batteries. 9A will be a nice improvement.

I recommend mounting the DC-DC in your tow vehicle (rather than inside the trailer) and using the remote enable provided. We use our Airstream 7-pin connector for connection to our portable solar panel. That won't work properly through an isolating convertor.

[suncoasteng]

Originally Posted by dznf0g

Diodes would cure the backfeed situation, but does nothing to help the tv to charge the AGMs which require a higher voltage.
I just want though 2 days of very heavy overcast, drizzle and thick fog. Solar didn't do much.

You are right, the diodes will not allow your TV to charge your TT batteries when they are at full power,,,,,but then that is not when they need to be charged. When you are running down the Interstate at 65 mph, the alternator in the TV will usually be able to charge the AGM's in the TT as they start to loose power. So first, check your alternator output, just get a multi-meter and put in on the TV battery, then run the engine up to 2,500rpm and see what voltage your read on the TV terminals. And when the AGM's need charging, they wont need 40A, just a simple 1A or 2A trickle charge while you drive. Anyone know what rabbit hole Bob just went down with that 40A charging issue?