New owner, 2006 2720SL

[B_and_D]

I outfitted our TM by going to the Goodwill or Salvation Army stores. They have most anything you need for your kitchen needs.

[Bill]

Good point. In one of our earlier TMs, I ran new, uninterrupted lengths of #10 wire from the alternator to the truck's 7-pin Bargman connector, and then from the TM half of the Bargman directly to the TM battery post. As I recall, #8 wire would not fit into the truck's Bargman connector, but #10 could be squeezed in. It helped quite a bit, though it was not a perfect solution.

I'm not sure when the truck's alternator would be putting out 14.8 VDC for any length of time. The alternator output voltage will be determined by the voltage of the truck battery. When you start the engine, the alternator may go to some high voltage for a few seconds to replace the charge used by engine starting, but then will settle back to the truck's proper float voltage, which will be around 13.8 VDC

This lower voltage makes your big-wire solution even more important, or course.

Bill

[Wavery]

Originally Posted by Bill

Good point. In one of our earlier TMs, I ran new, uninterrupted lengths of #10 wire from the alternator to the truck's 7-pin Bargman connector, and then from the TM half of the Bargman directly to the TM battery post. As I recall, #8 wire would not fit into the truck's Bargman connector, but #10 could be squeezed in. It helped quite a bit, though it was not a perfect solution.

I'm not sure when the truck's alternator would be putting out 14.8 VDC for any length of time. The alternator output voltage will be determined by the voltage of the truck battery. When you start the engine, the alternator may go to some high voltage for a few seconds to replace the charge used by engine starting, but then will settle back to the truck's proper float voltage, which will be around 13.8 VDC

This lower voltage makes your big-wire solution even more important, or course.

Bill

Correct on all points and more to the point...... yes, when the alternator is putting out 13.8V the voltage drop is 1.2V (I measured it before and after my mod). After I installed the larger wire the voltage drop was less than 0.2V

If one was to use the larger wire size, the alternator/regulator would pick up the 'Line voltage". It doesn't know where that voltage is coming from. If the TM batteries are in a constant discharge mode from the 12V fridge circuit, that would reduce the line voltage and increase the charge rate from the alternator enough to keep both batteries fully charged.

I know this because I've done it (before I added solar) and it was quite successful on a 10-hour drive from Los Angeles to San Francisco area. I arrived with a cold fridge and fully charged TM batteries.

[ShrimpBurrito]

Yet another option, which is what I did in addition to running the larger gauge wire between the battery and fridge, is install a DC-DC battery charger in the TM near the battery. This device draws more current from the TV, and then bumps up the voltage to be delivered to the TM battery. They come with various capacities, and since you don't want to draw too much current over than long run and max out that circuit, you need to select one of appropriate size. What I did was look at what the fuse rating of that circuit is under the hood of the TM, and then select the charger such that the input current would not exceed that rating. If I recall, that current rating was 20A.

I bought one by the Australian manufacturer Redarc, because that was the only one I could find at the time. I think it was this one:
https://redarcelectronics.com/produc...attery-charger

But Renogy has since gotten into the market, and they sell what appears to do the same thing (though I have not explored it in detail) for a fraction of the price, probably a benefit of being made in China. See:
https://www.amazon.com/Renogy-Batter.../dp/B07Q5VYPCF

At least in my case, this delivers adequate current to the TM batteries while running the fridge on DC, and also delivers a small charge on top of that. If the fridge were off, it would deliver a significant charge.

Dave

[Kmikesell]

Great Idea!