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Charging Trailer Battery

merf23

By merf23
in Ask A GM Technician

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merf23 Enthusiast

merf23

Posted
Posted

I have a 2008 silverado 1500 4wd, single battery, no brake controller

I tow a small trailer with a winch, but no electric brakes. I have a deep cycle group 24 battery on the trailer which i would like to charge while driving, but not when the engine is off. I understand that i need to hook the wire under the hood to STUD 1 and install a 40 amp fuse, however, from my forum searching it appears that this wire is HOT all the time, including when the ignition is off.

 

Is STUD 2 (the larger one) switched by the ignition? If so can i install a 40 amp fuse? If not, I am confident that 30 amps would be adequate for my purposes, because the winch is only used briefly between long drives.

If neither is switched, do i need to install a relay or is there a switched power i can use.

 

If my trailer battery is run down, will it try to draw more than 40 amps and blow the fuses or will it just max out at 40amps. I am planning on putting a 40 amp fuse on the trailer side of things too (i dont like fires!)

 

TIA

Sean

builderpaul Enthusiast

builderpaul

Posted
Posted
I have a 2008 silverado 1500 4wd, single battery, no brake controller

I tow a small trailer with a winch, but no electric brakes. I have a deep cycle group 24 battery on the trailer which i would like to charge while driving, but not when the engine is off. I understand that i need to hook the wire under the hood to STUD 1 and install a 40 amp fuse, however, from my forum searching it appears that this wire is HOT all the time, including when the ignition is off.

 

Is STUD 2 (the larger one) switched by the ignition? If so can i install a 40 amp fuse? If not, I am confident that 30 amps would be adequate for my purposes, because the winch is only used briefly between long drives.

If neither is switched, do i need to install a relay or is there a switched power i can use.

 

If my trailer battery is run down, will it try to draw more than 40 amps and blow the fuses or will it just max out at 40amps. I am planning on putting a 40 amp fuse on the trailer side of things too (i dont like fires!)

 

TIA

Sean

 

If the trailer battery is charged than it will not be drawing anything anyway. Just unplug the trailer when engine is not running, if you are concerned about it.

You should unplug before using your winch. That will blow the fuse. I have had that happen with a long pull.

merf23 Enthusiast

merf23

Posted
  • Author
Posted

I can unplug it, however, if i forget, i could run my battery down or if i dont plug it in again i could get a ticket!

If there is not a practical solution, i will just put a toggle switch on the battery to disconnect the trailer charging wire. if there is a STUD that will fit my needs that would be my first choice (that sounds BAD)

bill190 Enthusiast

bill190

Posted
Posted

It can be a bit complicated to install relays and such. I would suggest you install the wiring as suggested by the factory as this will be the easiest.

 

Then use the trailer as normal. Unplug the trailer wire as suggested above. Then you will only be using the trailer battery for the winch and will not be draining your truck battery. Then start your vehicle and connect the trailer wire, then it will charge.

 

(Or install the switch at the trailer to switch off the +12 volts from the vehicle.)

 

Then see if you have any problems with fuses blowing. I don't think you will have any problems.

builderpaul Enthusiast

builderpaul

Posted
Posted
I can unplug it, however, if i forget, i could run my battery down

 

I don't understand how you will run your battery down. Once the trailer battery is charged it will not draw any more.

mfennema Enthusiast

mfennema

Posted
Posted

Could you possibly wire it up so that your battery charges through the tail light wire? If your truck always has the DRLs on then wouldn't it only charge while the truck is on? Just a thought, you'd have to check amperage draw to make sure the wire could handle it.

merf23 Enthusiast

merf23

Posted
  • Author
Posted

I was thinking about the tail light option. I am going to put a relay on the trailer that will activate the charging circuit when the lights are on. Should be simple and effective.

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