Battery charging from the tow vehicle.

[stratus225]

Hi folks. I'm new here and will be here for a long time to come. It has been a weakth of information so far. But i do have one question (out of many to come I'm sure), that I cant seem to locate the correct answer for.
My trailer is a brand new 2007 prowler 32 foot with bunks and a slider and all the other toys. I amd new to the whole trailer thing and I cant get a straight answer from any of my techniciams at work on wether my trailer battery will charge from my tow vehicle. My shop foreman says I need to hook up an isolator and should be able to go straight into the 7 pin on the truck side to charge the battery while i'm driving or running the vehicle. What do I need to do to make this feasable as there alot of campgrounds around with no services? Is the trailer equipped from factory to do this or do I need to set up something on the trailer as well? Sorry for being as green as I am, but I guess we all had to start somewhere. Thanx for the help folks.

 

[Carl L]

Given that is is a 2007 Prowler it should have the trailer side wiring all in place.  The truck side wiring may be an issue.  If the harness is factory installed by the truck's mfr in a 'towing package' , it should have an isolator and heavy gauge wire (aleast #8)  back to the trailer connector.  If the harness was installed aftermarket you are goinig to have to check the work done.  Check out the truck.

Also check out the topic HERE.

 

[stratus225]

Its definately Ford factory trailer tow group. So what your saying Carl is that I shouldnt need to do anything and the tow vehicle should keep a constant charge to the battery when the trailer is plugged in to it? If thats the case, I am a happy man! I worry about getting stuck in the middle of nowhere with a dead battery and my slideout stuck out, etc etc. (like I said, I'm very new to all of this).
Thank-you for the quick reply Carl.

 

[Carl L]

Its definately Ford factory trailer tow group. So what your saying Carl is that I shouldnt need to do anything and the tow vehicle should keep a constant charge to the battery when the trailer is plugged in to it? If thats the case, I am a happy man! I worry about getting stuck in the middle of nowhere with a dead battery and my slideout stuck out, etc etc. (like I said, I'm very new to all of this).
Thank-you for the quick reply Carl.

If it is Ford, that only works if the ignition key is on and the engine is running to charge your battery. 

You have ONE battery?  My experience with a 23' TT is that you want at least two deep cycle group 24's to get you thru the night.  And your charging sufficiency will depend on your alternator's output and the gauge of the wire in the charging circuit.  If I were you, I would experiment with the idea of camping disconnected from the grid at a campground with electrical hookups at the site  -- that way you learn the capacity of your battery setup in the light of your usage at place where if you find out that you're running the battery down below 50%, you can plug in and finish off  on the grid.

 

[stratus225]

So, let me see if I understand this. My TV will charge the battery on the trailer, but over time of doing this may cause altenator failure such as continualy running the TV's battery will do to the altenator. (I guess thats just common sense) I would hope that Ford would have a beefier altenator with the TT prep group? (like I said, green like a martian here Carl, lol)
And two batteries is almost a definate need, not just a luxury.....Parallel or series?
And to put it into even simpler terms, A two hour drive to my destination will or wont charge my trailer battery to full capacity from a near flat state?

 

[Lou Schneider]

The factory charging wire will charge your battery at a 10-20 amp rate, about the same as a regular battery charger.  This is about the same amount of power as running your headlights (or windshield wipers or heater blower on "high", etc.) .  So it's unlikely it will harm or shorten the life of your alternator.

Driving for two hours will put no more than 40 amp-hours into the trailer battery (20 amps * 2 hours = 40 amp-hours).  A single battery has a capacity of about 80-90 amp-hours, so you'll replace no more than half of it's capacity in two hours of driving.  If you have two batteries you have twice as much storage capacity, 160-200 amp-hours.  In this case you'll replace about a quarter of the battery's capacity in a two hour drive.

So no, it won't charge the batteries to full capacity in that time.  But it will add to the amount of charge if the batteries are only partially discharged.

If you're connecting two 12 volt batteries, they're connected in parallel (+ to + , - to - ).  The voltage stays the same and the number of amp-hours add.

If you're connecting two 6 volt golf cart batteries, you connect them in series (battery 1 + to the trailer, battery 1 - to battery 2 +, battery 2 - to trailer).  The voltages add and the amp-hours stay the same.

 

[Gary RV_Wizard]

My TV will charge the battery on the trailer, but over time of doing this may cause altenator failure such as continualy running the TV's battery will do to the altenator. (I guess thats just common sense) I would hope that Ford would have a beefier altenator with the TT prep group? (like I said, green like a martian here Carl, lol)

No, that is NOT right. Charging your trailer battery while driving will not have an deleterious effect on the alternator. However if the alternator cpacity is relatively small, it may not charge the battery very much either. Remember, your truck is consuming electrical power too, so not all the alternator output is available for charging. And there may well be a limiting circuit breaker on the charge circuit as well.

Driving two hours probably will NOT re-charge a flat battery. It depends, of course, on how "flat" it is, size of the alternator, etc., but in any case two hours is unlikely to get you to 100% charge.  The rate at which a battery will accept charging decreases as the total charge increases, so the last 10-15% of charge takes many hours. We generally figure 24-48 hours to fully charge a dead battery.

Why isn't your battery fully charged when you leave home? Can you plug in the trailer and let its onboard charger bring the battery(s) up to 100%? Plug it in the day before you plan to leave.

 

[stratus225]

I wish it were that easy. Trailer is in storage and there is no where around my house in Calgary to park the house let alone the fact that leaving the trailer on the street the day before would result in a 200.00 fine. (stupid by-laws. lol) So we will be picking up straight from storage and off to the campsite on the designated night, usually two to three days before a weekend just to ensure a spot at any campgrounds within a 200 mile range. Quite the hassel, but still getting out of the city for a weekend is well worth the hassel.
I think I get it though, keep the battery (batteries soon) at home on a trickle charger may be the key here, and not forgetting to unplug the television when putting the trailer back into the storage lot may help me out quite a bit. Who knew a television drew so much power when turned off? (learned that from reading within RV forums, thanx guys. ;D )

 

[Carl L]

So, let me see if I understand this. My TV will charge the battery on the trailer, but over time of doing this may cause altenator failure such as continualy running the TV's battery will do to the altenator. (I guess thats just common sense) I would hope that Ford would have a beefier altenator with the TT prep group? (like I said, green like a martian here Carl, lol)

Did I say that?  I hope not.  An alternator with a low output will simply take a long time to charge a battery.  Everything is measure in amp-hours.  If you use 50 amp-hours over night, you will need to put 50amp-hours back.    Marine alternators which have the same problems as RVs, charging starter AND house batteries.  They can run up to 100 amp outputs -- after a $900 input from your Visa card that is.  ;D

And two batteries is almost a definate need, not just a luxury.....Parallel or series?

  Parallel if you use 12V units, series if you use 2 6V units.  The two batteries should be bought as a pair and should be RV deep cycle batteries -- not marine which are dual purpose starter and deep cycle and good at neither.

>>And to put it into even simpler terms, A two hour drive to my destination will or wont charge my trailer battery to full capacity from a near flat state?<<

Maybe a motorcycle battery but not yours.  More like 6-8 hours and if you have really flat lined the battery -- maybe never.  Going below a 50% discharge will harm the battery's capacity.  That is why two batteries.




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[stratus225]

Ok, so with all this being said, does the battery charge any quicker if the trailer is plugged in, or is it about the same as charging from the TV because of the limitations of the trailer wiring from the charging system itself?

 

[Carl L]

Ok, so with all this being said, does the battery charge any quicker if the trailer is plugged in, or is it about the same as charging from the TV because of the limitations of the trailer wiring from the charging system itself?

More like the battery does not discharge because converter/charger of the trailer takes over the DC load which would also include recharging the battery if it is down.

 

[MarkInNC]

I just went thru hooking up my trailer connections.  I am also new to RVs.  I have a lot of experience with boat trailering but not RVs.  I had not originally hooked up the wire from the cars 12V system and the trailer battery was not charging.  Since then I did hook it up and it is now charging.  As with any time you do this the plus side is obvious but the negative side is that you have the trailer battery hooked up in paralelle with the car when doing this.  If the RV battery is low/dead/or bad it is going to drain the car battery and visa versa.  I hooked up a battery on/off switch in the RV, (I think most RVs come with one but mine did not).  Also, I needed a light converter and chose a converter/isolator to drive my trailer lamps.  So, my trailer lamps are isolated from my car system.  There is no isolation for the brake circuti nor the charging circuit.

Mark

 

[Newt & Jan]

I'm not sure what would help during really cold weather but for milder times, have you considered solar panels to charge the batteries so that when you head out, your TV only has to top them off, if that?

For really brutal weather, taking the battery home with you and charging it in a warmer area is probably the way to go.