Trailer Battery.

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Just a general tip as it may be useful to some of you out there. If you are doing some extensive dry camping where you have no hook up you can reduce the drain on your trailer battery by hooking up your tow vehicle plug. This way your tow vehicle battery will share some of the drain or load. This can greatly extend your trailer battery charge & prevent over discharging & damaging your battery.
Not to worry, your tow vehicle battery will not go dead unless the battery is old & on its way out. When you use your tow vehicle the battery will charge back up again.
This is especially helpful now that the weather is cool & you'll be running your furnice etc.
There is a big voltage drop between your tow vehicle battery & trailer battery due to long wiring & the various connections involved. But enought voltage will get through to help save your trailer battery
& keep your lighting bright & furnice running strong. MANZI

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Joe is right, in fact I seldom bother to disconnect my umbilical cable unless I am also unhitching, but you have to be careful that you have enuf energy left in the truck battery to get the engine started again.

However, if you have installed any kind of isolation (diode or relay or manual switch) to keep the "house" (trailer, camper, motor home) requirements from depleting the engine battery, this won't work unless you turn off the isolation.

Also, if the truck battery has been discharged enuf that it tries to get help from the house battery to start the engine, it might blow the usual 30Amp fuse at the house battery in the process (Voice of FirstHand Experience speaking here). If you don't replace the fuse, the truck alternator will not be able to recharge the house battery while you are driving down the road to the next campsite.

Keep in mind that the truck battery is usually a starting battery designed for the immediate discharge/recharge requirements of engine starting and will be damaged if it is drawn way down and not recharged within just a few hours. OTOH, the house battery is usually a deep-cycle battery designed to withstand many long, slow discharge-recharge cycles.

Pete and Rats

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Hi Pete, Naah, I'm not talking about killing the truck battery. Leaving it hooked up for a night to assist the trailer battery is not going to kill it . It would take a lot to draw it way down. When you run the truck the next day it will charge right back up again.
Its just to assist your trailer battery in a pinch. Always exceptions to this but for most its a neat trick to know. MANZI

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It is a good way to go, but consider this, scenarios I just thought of, admittedly not likely, but far from the impossible:

A. For some reason, the 30Amp fuse at my house battery is blown (and the battery is already dead; maybe the fuse blew during a failed recharge by alternator) or the cheesy little inline fuse holder has become so resistive that the batt is not charged. I pull into CG, and just hop out and disconnect nothing, as is a common practice for me. When I turn on the lites, they work because the truck battery is still connected, so I have no clue that the fuse is blown (if I disconnected, the lites wouldn't work, forcing me to discover the fuse). Because it's a cold nite, I turn on my RV furnace and hit the hay after supper (at this point you can tell it's a scenario, because I have a ventfree heater, not an RV furnace with a blower). At Oh-Dark Thirty, with a false dawn shining off the snow outside, I wake shivering to a cold trailer, because the blower (and the typical wiring losses between front of truck and blower) have depleted my truck battery. I stumble out in the dark, try to start the truck and hear the Dreaded Clicking Noise that signals insufficient voltage in battery to do anything more than trip the starter solenoid.

B. Alternative scenario would be both batts working but dumb camper (that would be me) leaves refrigerator in 12VDC position and then runs furnace and blower (and reefer and furnace are working against each other), perhaps after watching color TV for a while; same ending at Oh-Dark Thirty...

Either of the above is a good reason to have a JumpIt or some sort of isolation device.

Fortunately for me, I don't have a reefer or a blower furnace, and I carry a good sleeping bag, warm hats and LongJohns (I could be fairly comfortable outside in a snow bank if need be).

Pete and Rats

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Well guys, glad it worked for you, but IMHO, leaving your trailer plugged in, as you describe is,

.........bad advice.:o

Leaving the trailer hooked up overnite CAN kill the tow vehicle battery. Lots of variables.

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Hi All,
I use a 50 amp Battery Combiner (www.yandina.com) to isolate the house and truck batteries. What I like is how it will only "combine" both when one or the other is fully charged and above a certain voltage. The way I have my camper set up, when on shore power, the house battery is out of the circuit and being charged by a Surepower battery maintainer. Then it will top off the truck battery when the house battery is charged. When under way the truck system charges the house battery as needed.

I wanted to use, and even purchased, one of the 90 amp battery isolators at Autozone but I just did not like the way it hooked up. The Combiner installation is much cleaner for what I wanted plus it is mounted on the camper. I have a 50 amp battery plug and 30 amp circuit breaker in the truck (under the hood) to connect house power. I use a dedicated 10 gauge SJO cord to connect power to the camper. On my truck, the 7 pin trailer plug only has a 12 ga wire for the (+) power circuit. After much research I decided it was not adequate to run the refer on 12v while traveling.

I can't imagine much worse that being stuck in the middle of nowhere with all batteries dead. That'll surely ruin a nice weekend.:o

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Are any of you battery geniuses going to any of the trailer get togethers? I need to see the real battery system or pictures, or directions in very laymen terms. This is all just whorling around in my head.:spin :hap2 I like the sound of SteveB's set-up.

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I have an old Layton trailer stored in Florida. Its hooked up to 110 most of the time. But when I do take it somewhere & camp I just leave it plugged into my truck battery as my trailer doesn't have a battery in it.
To run some lights, a fan, radio, water pump etc doesn't even put a dent in my truck battery. Just don't leave that refridge on 12 volt. That will kill everything for sure - its a huge drain - worse than 10 cigarette lighters pushed in at once.
Then my old girlfriend who had a 30 year old Scotty Sportsman just used a motorcycle battery to power her trailer. It had state of the art connections which was a few jumper wires with alligator clips. And it worked just fine. Even powered some lights outside etc.
And her state of the art water supply system was an old army surplus 10 gallon water tank & had state of the art pump called graviety feed. I was amazed how well it all worked. Well, maybe she knows something we don't? MANZI. PS: The water tank was on the bed of the pickup, lashed down with some old clothes line! We kept a jug of water inside the trailer too.

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Hi All
All this battery stuff is hard to follow. I think we all have a tenicy to put more into it than whats needed.Its not my intention to affend anyone, so please don't take it that way. I just carry a spare battery which is not hooked up to anything. I allways got power even if everything is dead.
Just a thought.:crazy-ii

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Ches, I just now focused on your avatar. Wiley Coyote. so cool.

I'm in the can't deside mode and there are so many choices.
How and when do you charge the battreys?

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Thomas/Janifer
Hi. With spare battery which is not in use, I keep it charged at home with a cheap battery charger, when were not camping. When we are dry camping i just put it back of truck.I only use it when needed, if needed. I would not want to use my vehical battery as a backup. My spare can be used either in vehical or TT. The isolater people are talking about is to prevent power drainage from vehical battery.Ps my spare is only a cheap car battery just for emergencys
:reyes

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My trailer doesn't hook up to the tow vehicle. so I guess I'll skip the isolator. had one on the MH, but never knew if I had it turned off or on. Had two batteries in the MH and the furnace could run them both down over night. so no furnace in the TT. yep one or two batrys extra and maybe a solar thing, and I'll be all set in the power area. I mostly camp plugged in to 110 anyway.

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As soon as I stop I leap out of the vehicle and unplug 'cos I was told to. I love the idea that i could use the vehicle battery to back up the T.T. battery .My plug has 8 slots in it but what does an isolator look like , where do I look?
Jana, why don't you have a wiring harness are you going too ?or will you always hook up to 110v/

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Hi pippa
The last isolator i had was mounted in vehical engine compartment. I also had 2 batteries in engine compartment and the one on TT. The isolator would let you charge all batteries when vehical running but would isolate your starter battery so that you could allways start tow vehical. The size of isolater was about the size of a can of small beans.
:inbox

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Ches, I think mine is the size of a small can of beans:laugh
I will look tomorrow. Will it have a switch on it?I remember when we had the m.home ,it seemed I was always hearing "Oh your isolators' shot ,you need a new one!

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Pippa
No their was no switch on mine, Which I think is good so that you can't leave it on by axccident. I will be doing the same set up again this spring. At present time I have 2 batteries on my 17ft boler and i will put in my spare as a third power source, but it will be in truck.I know some tecnical guy will jump into this conversation (ha):wave and will give us all the does and don'ts of this setup. Its worked for years for me and I don't have any regreats.Oh before I forget I did upgrade my Alternater/Generator so I would have greater output. I found it not expensive(car wreaker place 2nd hand).
Take care:)

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"why don't you have a wiring harness are you going too ?or will you always hook up to 110v/ "
Well maybe I said it wrong Pippa. I have running lights that I plug in, you know brakes and such. I don't have a battery connection for charging. It might have had one as there are wires bent back and taped down, but I thought those were for the brakes. Guess they could be for charging, I don't know yet.
I like using 110. most of the time that's what I have, but there are a few times here and there where I'm on my own. usually in the fall so it would be chilly at night. I like Charles idea of changing batteries with a plug up unit, if I can figure it out.
Is that what you ment?

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Yes Jana that is what I meant, Maybe you are all hooked up for battery charge, mind you all the battery does for us is give us lights,which are better to read by and a cube heater in Sept./Oct.. Our fridge runs either on propane or 110v we never run it on 12v. we don't hook up often as our Prov.Parks have such huge sites with lots of privacy(no hookups) it spoils us for the private campsites .When we do the 110v is a treat .I think one of the slots in our harness socket is for electric brakes which we do not have connected.