Installing DC to DC Charger for Trailer House Battery - Do I Need to upgrade Alternator?

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blacktail

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I have a 2006 Eddie Bauer Expy with the tow package and a small travel trailer.

I plan on installing a 20 amp DC to DC charger to recharge a 100 ah lithium battery in my travel trailer while driving between campsites. This charger connects directly between the car's battery and the house battery on the trailer.

The vehicle does not have a navigation system, so I am assuming it has the 110 amp alternator. There is a sticker on the alternator that says "A1358F", which I have not been able to cross reference anywhere.

The charger will only be used when towing the trailer. This means that the front and rear AC will also likely be going, the headlights will be on, the dvd player/stereo and phones plugged into cigarette lighters charging via USB adaptors.

While driving, the engine is usually at around 2,500 rpm and will rarely see 3,000 on the occasional hill. It's a very light trailer.

I feel like I should upgrade to a larger amperage alternator, but I understand that using the 130 amp one can cause issues.

Maybe I am mistaken and the total load will be acceptable with the factory 110 alternator.

Any advice would be appreciated.
 
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JasonH

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Are you using campsites with hookups? If so, your battery should be charged most of the time and the trailer connector output won't really be a factor.
 
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blacktail

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We do occasionally, but prefer boondocking.

The trailer is the same age as the expy, so even when plugged into AC on shore power, the charge converter will only get the lithium battery to about 80%. I can top it off using a portable solar array, but it takes time.

I like the idea of the DC to DC charger so that on long trips, we can draw down the battery in the evening before driving to a new boondocking location and be recharged.
 

JasonH

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The numbers I've seen for the trailer output suggest 10 amp, but you can also check the fuse or put a load on it and measure it with an ammeter.

If you're boondocking, it might make sense to have a small portable generator that can top off the battery. This way you wouldn't have to change anything mechanically on the Expedition to ensure you can keep the battery charged. You could also add a small, roof-mounted solar panel system.
 
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blacktail

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I was going to incorporate some kind of 200w suitcase solar system. That way, we can place it in the sunlight when parked in the shade, and/or adjust its position throughout the day.

Do you have a good reference for the 10 amps? I could probably live with that. Was under the impression that the house battery was receiving less than 5 amps.
 

JasonH

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I saw the number on an F150 site, but there are so many model years and configurations it's dificult to say for sure. I was actually going to measure today because we're prepping for a trip. But I forgot the multimeter since I have like 20 things I need to do ahead of the trip.
 
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blacktail

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Following up on this, I ultimately passed on installing a direct DC to DC connection. Because, I discovered that the previous owner had purchased, but not installed, the dealer trailer brake connectors. SK-4L1T-15A416-AA

In the package was a 30 amp fuse and a relay - for charging the trailer house battery!

I installed these both according to the instructions and initially seemed to be getting ~8amps sent to trailer via 7 pin. My TT battery has a shunt installed and a charge monitor so I can view exactly what’s happening.

However, towing all day yesterday, little more than ~0.5 amp was being sent.

I know sometimes Ford requires you to do a special procedure to “recognize” that a trailer is being towed. Perhaps I did this without realizing it at first but did not do it yesterday.

Any thoughts on what the special trailer hook up dance is to send power?

06 Eddie Bauer.
 

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rollinstone

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I'm thinking of adding a dc to dc charger to boost the amps going to my trailer house batteries while rollin' down the highway. I've noticed that the fridge running on the 12-volt system doesn't really stay that cold. And it's been said the a dc-dc charger will give the house batteries longer life. To do this it looks like i have to run 2 gauge wiring from the engine compartment/alternator to the dc-dc charger mounted in the trailer somewhere to the batteries. Seems like a real PITA. Is there an easier way to do this or is that what I'm faced with?
 

JasonH

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I'm thinking of adding a dc to dc charger to boost the amps going to my trailer house batteries while rollin' down the highway. I've noticed that the fridge running on the 12-volt system doesn't really stay that cold. And it's been said the a dc-dc charger will give the house batteries longer life. To do this it looks like i have to run 2 gauge wiring from the engine compartment/alternator to the dc-dc charger mounted in the trailer somewhere to the batteries. Seems like a real PITA. Is there an easier way to do this or is that what I'm faced with?

Get a good 100ah or 200ah LFP battery and fuggeda bout it. The 12V fridges will suck at cooling on electric. If it's dual fuel, use propane and stick some frozen jugs in there to provide an assist. The LFP batteries will provide thousands of cycles if you keep them between 20 and 90% capacity.
 

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