Charging Trailer Brake Battery

   #1  

covefarm

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I have a 5 ton GVW flat bed trailer with dual axles and electric brakes. I rarely use the trailer. The brake battery does not get charged as a result. I thought it charges whenever the trailer electric is plugged into my truck and the truck is running but now I'm not sure it does charge. It's a 12 volt battery approximately 6" tall by 4" wide with flat blade terminals. Should it charge when my truck is running? Can I use a regular 12 volt battery charger to charge it? Appreciate the advice.
 
   #2  

Dmacleo

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is the 12v constant on the tow vehicle actually hooked up and working?
easy to blow a fuse (eg the 2011 silverado 2500hd uses a 40A j case fuse) and if so battery won't charge.running dump trailer with bad battery can pop this fuse a lot....ask me how I know LOL
hard to say w/o knowing vehicle/pin specifics.
 
   #3  

slckeys

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Those batteries aren't exactly known for lasting long as well.

But first I would check to see if there is voltage going to the battery with your truck hooked up and running. Fuse is a simple place to start as mentioned. If not getting voltage, start working backwards towards your tow vehicle to see where it stops.
 
   #4  

Roadworthy

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Generally these are a small motorcycle or lawn tractor type battery. Three years would probably be considered a good life span. I do not recommend a regular charger. It can source too much current and boil the battery dry.
 
   #5  

Doughknob

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I have charged those small types on the 2amp trickle setting on my charger. An auto-shutoff charger is also a good thing.
 
   #6  

oldballs

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I remove the battery from my now seldom used trailer....and....put it on the Maintainer now and then as it (battery) sits in the garage.

Cheers,
Mike
 
   #8  

MillWeld

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It is my understanding that the little trailer battery operates the brakes if the trailer breaks loose from the truck severing the electrical connection between the truck battery and trailer brakes. As long as the trailer is properly connected what else does the trailer battery do? Is there a way to test if it can deliver enough current to operate the brakes without jacking up the wheels and unplugging the trailer brake connection from the truck and trying to spin the wheels? My trailer/brake system is about 10 years old so (based on this thread) I bet my trailer battery is toast. With the trailer disconnected I will measure the voltage and put a trickle charger on it if necessary. Need yout comments.
 
   #9  

deezler

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^ Yeah that is my assumption too. I think it should be lightly "charging" whenever plugged into the tow vehicle, no? It's a small battery after all. Since you only need it to work for 30 seconds in case of a towing catastrophe, does even a mostly dead battery provide adequate performance?
 

bdhsfz6

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I also have a trailer that is infrequently used. After replacing that 12V battery 3 times, I bought one of these battery adapters:

61TEbQYffvL._AC_SL1500_.jpg


I just plug in one of my 18V Dewalt power tool batteries whenever I use the trailer. The higher voltage doesn't seem to affect the braking and I've never had one fully discharge even on a long trip.
 
  
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#11  
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covefarm

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is the 12v constant on the tow vehicle actually hooked up and working?
easy to blow a fuse (eg the 2011 silverado 2500hd uses a 40A j case fuse) and if so battery won't charge.running dump trailer with bad battery can pop this fuse a lot....ask me how I know LOL
hard to say w/o knowing vehicle/pin specifics.
Dmaacleo - Yes it is working. The light on the battery box comes on when I plug the trailer in and the truck is running. Thanks.
 
  
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#12  
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covefarm

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I have charged those small types on the 2amp trickle setting on my charger. An auto-shutoff charger is also a good thing.
Doughknob, I have a 2 amp setting on my regular charger. I'll give it a go. Thanks.
 
  
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#13  
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covefarm

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It is my understanding that the little trailer battery operates the brakes if the trailer breaks loose from the truck severing the electrical connection between the truck battery and trailer brakes. As long as the trailer is properly connected what else does the trailer battery do? Is there a way to test if it can deliver enough current to operate the brakes without jacking up the wheels and unplugging the trailer brake connection from the truck and trying to spin the wheels? My trailer/brake system is about 10 years old so (based on this thread) I bet my trailer battery is toast. With the trailer disconnected I will measure the voltage and put a trickle charger on it if necessary. Need yout comments.
MillWeld, That is my understanding as well. Thanks
 

Dmacleo

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from the sounds of everything it seems there is no issue.
you can see if battery works by disconnecting from truck, yank out the pin from break away switch and try towing. if brakes on trailer locked up all is working as it should.
 

mojoinco

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Fwiw, your battery is toast if it's 10 years old.

You checked, you have a 12v available lamp lit.

To check the brake you have to pull out the lanyard (well, the pin) on the switch mounted to the tongue. It's a good thing to test in any case.

It may break. They can be bought at a lot of places. Iirc, there may be more than one type. Fairly easy to replace the switch if you have to.

Then (working battery, pin removed and switch closed) pull the truck forward. The brakes should come on.

They will be at 100%. Do this on softer ground and have a helper note which wheels lock up (or, don't lock up).
 

timbatrader

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What I have is a small solar panel battery charger hooked up on an Anderson plug it sits on the trailer deck when the trailer is not in use it keeps the battery topped up makes the battery last much longer
 

MillWeld

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Yesterday I had about 2500 lbs of lumber on my trailer to be delivered so I decided to check its battery voltage before pulling because it had been about 1 or 2 months since the trailer was towed. I measured 12 VDC. Good, I thought - now can it deliver the current to lock the wheels? I said in an earlier post that the battery is about 10 years old - I really don't know when I bought it but it was certainly between 5 and 10 years ago. I disconnected the plug to the truck battery and pulled the lanyard to disconnect the trailer battery and started to pull it and all 4 trailer wheels locked. Wow - pretty good for and old battery. I bought it from eTrailer - see pic below.
 

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   #18  

Fallon

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I've got a power tilt deckover & the battery for the hydraulic pump is also the emergency battery. Makes it handy to monitor the battery condition. If it tilts to load/unload the emergency brakes will still work. Have a 20 watt solar panel & charge controller to keep things working. Never use the 120v on board charger as the solar keeps it topped up.

The +12v line on the trailer plug should charge the trailer battery(s). In RV power draw & battery charging situations the power loss due to small wires between the alternator & trailer batteries often prevents good battery charging. That shouldn't be a problem for a small emergency battery though.

Many trucks lack a fuse or relay to energize the +12v line on a trailer plug. My 2009 Tacoma was that way. Easy fix just checking the plug with a multimeter, then adding the fuse or relay. The truck usually needs to be running or at least on. A relay usually cuts out to prevent a trailer from killing the battery on the truck while off.
 
 
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