recharging battery in closed TM

???
Awhile back there was a thread which also discussed recharging a TM's battery while the trailer was closed. Since I couldn't locate that thread, I decided to start another one about that subject.

Recently I had to install a new connector socket on the rear of my truck. The previous one was sheared off and smashed when it struck a steep graded driveway (I wasn't towing anything). That started me thinking about the feasibility of recharging my TM's battery by connecting it to a battery charger through a connector socket dedicated just to recharging. That is, this loose socket would have just 2 wires connected to it: a black  one attached to its battery charge terminal and a white one attached to its ground terminal. To recharge the TM's battery the trailer's Bargman plug would be inserted into the socket and the 2 wires connected to the positive and negative leads of a battery charger.

To those of you who are EE's and others who are knowledgeable about DC trailer circuits and automobile charging circuits, would this simple system work? Like many other TM owners I would like to find an easy way to bring my trailer's battery up to full charge without having to unfold it each time.

By the way, when I told my local RV repair shop that my connector socket sheared off, I was told that it happens all the time to tow vehicles. Since that shop had installed my previous socket (with two 8-32 sheet metal screws into the underside of my truck's rear bumper), I decided that I myself could do a more permanent installation of the new socket. It is now encased in a framework of 3/8" steel plate which is bolted to the hitch with grade 8 bolts. It's now more likely to plow a furrow into a concrete driveway rather than break off (not that it is my intention to test it out on concrete driveways!).

I would have to say yes, it is that simple. Provided the two leads in the connector are the right ones. Case in point, my TM's in the shop right now. Just two hours ago, I stopped in to have the guy show me some stuff with the wiring he's fixed. (Yeah, I do trust them on something like that....read the thread under general maintenance for a detailed discussion about this shop under front clam shell problems....lol) Anyway, one thing I observed, as my battery wasn't charged enough to push the lights and all. He simply plugged two leads into the connector cord to the TM from a "test battery" he had sitting on the ground in front of the TM. Stands to reason your TM battery gets the juice from the vehicle's charging system the same way, that should work. Another even better option is to spend 25-30 bucks on one of those solar "battery" maintainers, and mount it in the tm to where it can get light through the skylight, yet be protected from the rain and other weather. (Velcro works fine, and can be taken down easily for asthetic purposes). This will also save you some money on your electric bill from pushing the charger year round. One more option is what I have hooked to my boat. It's an automatic trickle charger that you can leave plugged in year round that maintains both of my trolling motor batteries, as well as my starter battery. When at full charge, it stops charging automatically. You would have to simply run an extention cord through the front of the closed shell. I have no clue how much one would cost as it came with my boat that I bought used, but it's self contained, and doesn't get hot or anything. That is it's EXACT purpose. (Unlike you're standard car battery charger which buzzs, has vents on it, runs warm, and generally would make me nervous about leaving in an unattended closed up TM.) :-/ It's MADE to be run in enclosed spaces where there may or may not be gas vapors. Unfortunately my boat's in the shop getting a few repairs of it's own so I don't have the name of it, or a model number or anything, but mine maintains 3 deep cycle batteries at one time, if you have an extra battery you'd like to keep charged up as well.

Bill -n- Karen

Yes, I've done this with a 10amp+ charger if I'm running the refer over the night before we leave and must keep the unit close.

Simply push a battery charger through the two proper terminal on your trailers 7 way Pollock connector.  Specifically, Pin 1 [white wire] is common ground.  Pin 4 [black] is your battery charge.

If you jury rig the setup just be careful you don't accidentally short the leads -- the best scenario is you'll blow a fuse in-line with the battery; OR if you don't have a fuse, you'll have some fireworks.

As far as keeping the battery topped off (we store the TM in our garage) I use a small 12v DC wall transformer which plugs into a special jack in the side of the battery box.  The wall transformer delivers approximately 200mA to trickle charge the battery.  

Update on the battery charger. It's a Guest Charge Pro Model 2613. It has a 10/2amp automatic charging circuit. I.e.....it charges at 10amp till the battery's fully charged, then charges at 2amps to maintain the battery.

Happytrails

I solved the problem of checking battery charge and recharging the battery with the top closed with a BatteryMinder recharger I got from Camping World.  This is a computer controlled charger that automatically shut's down when the battery is fully charged.  It has a long charging cord with an inline connector and two separate ends; one with alligator clips and one with eye terminals.  I permenantly connected the end with eye terminals to the battery and extended it out the bottom of the battery box where the inline connector just barely sticks out the bottom of the camper.  Now whem I want to check out the battery or recharge, I plug the BatteryMinder into the connector.  This unit also has a "desuphation" circuit that is supposed to remove sulphation from the plates of bad batteries.  I haven't had a chance to try that out yet.

Maybe my trailer was set up differently, I could access my battery while the trailer was closed, since it sat right there in the open on the tongue.

The Guest chargers are quite good.  I bought a 2612 (if memory serves me) from West Marine.   About $100 bucks.    If you want, you can find Guest chargers that can be permanently installed.

Don't try pushing more than a 10amp charger, the wiring harness might not like much more current than that.

Two more things to consider.  First, the battery really should be ventilated when charging.  The vapors are nasty and potentially explosive.  Second, if the wire from the connector to the battery is long and a light weight guage, you might never really get a full charge on your battery as there could be a voltage drop over the wiring harness.

Your plastic battery box is well ventilated as it sits.  

Actually line resistance in charging a battery is harmless and sometimes intentional.  Line resistance may limit rate of charge but intended max charge will be reached.

The charger connector through the battery box is good.  A mating 7way Pollak connector would also serve the same purpose.

How does the battery vent when the TM is closed?

Wade

Wade,
After my previous battery expired, I installed an AGM, or absorbed glass mat, battery. This kind of battery does not require any ventilation as the gases are reabsorbed by the battery.

AGM batteries have other unique features. Since the sulfuric acid in these batteries are absorbed in glass mat, they do not contain any liquid. They therefore are spill-proof, may be mounted in any position and do not require electrolyte level checks. I like this latter feature a lot as the battery box in my 3124KS is located in a well at the bottom of a cabinet, and, it is an arduous tasks to get the battery out for an electrolyte check. The primary disadvantage of AGM batteries is that they cost twice as much as conventional lead acid batteries. They may last 1-1/2 to 2 times as long as the latter type, however, so that AGM batteries may be a good value after all. :

Larry, thanks for the tip on the battery. Sometimes things slip by me a bit and missed some posts, but I went back and checked. I'm glad I did.....I'll be replacing my battery soon. Would one of those "Optima" marine deep cycle batteries be one of these types, (AGM)? I'm sorry, I know very little about "types" of batteries.

Happytrails........