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Old 07-21-2020, 07:05 PM   #1
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Join Date: Jul 2020
Posts: 28
Battery and fridge questions (and more)-building new 388rk


About to order a new 388RK (formerly 38DBRK). Dealer is offering 4-6v batts in lieu of 2-12v, for $600 upgrade. Is it worth it? Not sure if wet or gel or AGM on upgrades.

Also, with the residential fridge, can I set up 6-6v in parallel (series?) to handle more load?

Will my dual 440 amp alternators on my Ram 2500 charge RV batts while under tow?

1-190 Watt Go Power Solar Panel included. should I buy a 2nd?

Is Truma instant hot water worth it?

Should I upgrade to THIRD 15,000 BTU AC?

All info is appreciated.
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Old 07-21-2020, 07:55 PM   #2
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Join Date: Nov 2017
Location: Dayton Ohio
Posts: 2,151
More batteries are better. About 430 Amps for the six volts. 2 12ís are about half that. Weigh half as much.

The six volt batteries likely installed are gc2 from interstate/Costco. Cost $90 each. Typically a trailer comes with a cheap marine battery. Wet cell batteries require vented cabinet space. Not just anywhere. Six weigh a bunch. #400.

RVís with residental fridges can consume batteries quickly depending on you, the weather, etc. not a good plan for boondocking. Likely 4 sixes will not make two days. One day or less with the furnace on.

A 100-200 watt solar panel is good for keeping the batteries partially charged during the winter. At most, on the best day ever you might get 25 amps per 100 watt panel. The other 95% of the time you will get less.

Technically your alternators can recharge batteries. Actually, from the factory no. Nada. The issue is the #14 wire from the truck to the rv batteries. The line loss is substantial. You have to change wire size or something else.

We have the standard ac/gas fridge. The Truma is considered best. Gas only. The others are problematic. Our 12 gallon unit when plugged in and the gas is on reheats quick. Never an issue. Works for free at the trailer park.

A third ac is a good idea if you expect temps over 95 degrees. Two units were barely enough for our 37í fiver in Houston in the summer. If your fiver is longer with two units you will never get under 80 degrees in Houston in the summer days. Night will be ok.

800 watts of solar and 4 Battleborn batteries would help. Likely without ac you will consume more than 100 amps of electricity a day. More than the two panels would produce.

Batteries are the weak link.
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Old 07-22-2020, 10:18 AM   #3
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Join Date: Feb 2015
Location: Oswego il
Posts: 2,226
My question to you, are you going to Boon Dock or not?

If you are not than I would stick with just one good 12V battery, less weight is better when cargo capacity is concerned for storage. I use a 12V NAPA battery made by East Penn MFG CO. I have had my residential fridge since 2015 and I have never have had spoiled food do to towing our trailer. The battery will provide enough electrical power through the inverter to operate the fridge for one day if fully charged. We also do not Boon Dock choosing instead to stay at 50AMP full service campsite when traveling. The battery will be fully charged by the next day by the converter when we set out to travel for the next day.

I see no need for Solar Panels if you are not planning on Boon Docking. Extra expense and weight plus an obtrusion into the sealed roof were a leak can occur.

Your dual 440 AMP alternator will maintain the battery in the trailer, but not charge it! Why, the wire in the harness for the 7-pin connector is not large (diameter) enough to carry the charge load required to charge a battery.

I personally prefer the 12 gal stored hot water tank that is gas/electric instead of the on demand units! We will use the gas to initially heat the water for the first time and than switch over to the electrical heating element to maintain the water temps.

Regardless where you camp the third A/C is a great option to have. There has been times we could have used a third A/C unit in our Cedar Creek.

I would also look at if still available as an option an awing on the dining room slide room. This will help in keeping the unit cool and provide more shade to sit under when the sun is on the curb side.

If the TrailAir King pin box is still an option I would order that too. This will improve your towing experience as there will be less up and down motion that is felt in the tow vehicle!
Jim W.
2016 34RL CC; 2008 Ram Mega Cab 2500HD, 6.7L, 68RFE 6 speed, 4X4, Smarty S67, TDR 135K+miles
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Old 07-22-2020, 10:44 AM   #4
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Posts: 388
Is a 2500 truck big enough ? Big rig for " total newbie ".
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Old 07-22-2020, 11:11 AM   #5
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Location: Dayton Ohio
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How big is big?

A 3/4 ton truck is much the same as a 1 ton. Designed to beat the dmv rules to lower license cost. They have payloads from #1600 to over #3000.

A 1 ton truck has payloads up to double that.

for the most part you need a 1 ton for a big fifth wheel. Maybe a dually.
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Old 07-25-2020, 11:42 AM   #6
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Join Date: May 2018
Location: Texas
Posts: 1,151

Look at the Payload sticker on your driver's door. The pin weight of that trailer may exceed your number prior to any additional gear. Like hitch, people, dog, propane, batteries, food, beer etc. Many of us have paid for our mistake w/ the expense of a new truck purchase. Also consider trailer manufacturing is conservative on the weight of their trailers. Many times it is several hundred lbs. heavier than specs.
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battery, fridge

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