Trailer battery charging--How to

[Sregorb]

Ok, I have a 6X6X12 Haulmark cargo trailer with a breakaway electric brake. The battery appears to be weak (pin pulled only produces quick flash of the green LED then out). According to the stamped instructions it's time to charge up the battery... ...



What's the easiest way to do this???



I thought this would charge the battery in the trailer hooked up to the truck but that doesn't appear to be the case. Is this something that can be "jumpered" off the truck or how are other RV/trailer people charging isolated batteries?



Brian

 

[Alan Reagan]

I can't remember which pin it is but there is a 12 pin (the center one I believe) that I believe is hot all the time. So you have to be careful or you'll kill the truck batteries. A switch would eliminate that problem. Just look inside the connector cover on the truck. It gives the pinouts to you.

 

[wcjp]

The original battery that came with my car hauler was not recharged from the tow vehicle. It required a recharge every 6months. That is if I remembered. It wasn't long until I had it swapped out for a better design. The current battery setup recharges when I have the tow vehicle's lights on. Which means the battery is always full. This makes me feel a little safer instead of finding out at the wrong time I failed to manually recharge the trailer battery.

 

[klenger]

Here's some information on the trailer connector pinout



http://www.klenger.net/dodge/trailer-connector-wiring.pdf

 

[paccool]

Brian,



A word of caution here. I'm assuming the green light you are talking about is on the brake controller in the truck. I just put a new Prodigy controller on and the instructions said that when ever testing the breakaway system, be sure to unplug the plug from the trailer or damage to the controller can occur. Not sure if this is a big problem or if the controller people are just covering their butts but I will take their advice and unplug first.



Stan

 

[Sregorb]

paccool- Agreed and noted. No the LED I'm speaking of is on the breakaway switch on the trailer (not connected to truck at all).



Here's the theory as I surmise it. Trailer plug installed, tow chains connected, and breakaway line connected to truck and we're cruising down the highway. Whatever reason the hitch snaps off, then the chains tighten and both break, followed by the 7 pin plug yanking out. Next as the truck and driver (completely oblivious to anything so far) keeps on pulling away from the trailer, now coming to an abrupt halt by gouging into pavement, gets far enough away to pull the breakaway pin out of the switch. The battery (of course MANUALLY fully charged) now activates the trailer's electric breaks without the standard brake signal coming thru the plug line and brings the trailer to a smooth, controlled stop.



I'm just after 1. some way to manually charge this battery easily and 2. wire in a "when connected to the truck-charging" without interrupting the intended purpose. If #2 is easy enough to do I'll ignore solutions to #1. If #2 is too involved then I'll do #1 whenever the battery is low.



The #2 I'm after sounds exactly the way wcjp described. wcjp-Can you share the details of how you set it up please?



Brian

 

[klenger]

I thought I heard one time that they hook up the battery charge line (through a diode I assume) to the brake lights on the trailer. That way it gets a small charge everytime you put the brakes on, but is never on enough to cook the battery. If your's is hooked up this way, maybe the isolation circuit (diode) is open, and not allowing any charge voltage to the battery.

 

[Sregorb]

Is this something I can run jumper cables from the under hood batteries to the trailer battery while running the motor? Similar to jumping... .

A battery is a battery with a 12V ratings whether 100 amps discharge capability or 1200 amps, right?



Brian

 

[CFAR]

I've got an 8'x16' haulmark myself, when leaving it I always put the Gorilla gaurd on and pull the break away cable out of the switch, I figured the battery will discharge, but if someone tried to steal trailer it would not be towable, now reading this post, I assume that my battery is discharged and the break away will not work. Hmmm. Time to test.

 

[MLee]

breakaway

if you want to discharge your battery," pull the breakaway cable" there is a charge line wired in to the trailer package. use a test light to find it, then rewire the other plug to match it. i have 95 and rewired to 7 pin tractor/ trailer plug so mine is not the same as stock but like it a lot better, more positive. as stated you will never fully charge the battery while driving, just maintains it. it's a good idea to check it periodically, for breakaway, but don't leave it out. if you get a chance, go to battery seminar, you will be enlightened, as i was.

just my penny's worth.

Marv.

 

[Sregorb]

No, no I'm not after how to discharge, I'm trying to charge it-manually if necessary... .



Brian

 

[y-knot]

Look, go to a motorcycle shop, or just get on the web, rocky mountain atv is a good store, and ask for a battery tender. They come with a quick connect plug, that once attach to the battery, charging is simple. plug the tender into an outlet (120V), and snap the quick connect cable together, and forget it. They are fully automatic, and made for small batteries. The cost will only set you back about 35-40 bucks, and your battery will always be ready when you are. Good luck.