12V supply to trailer batteries?

[doublereefed]

I[font='Helvetica Neue', Helvetica, Arial, sans-serif] have a 30' enclosed cargo trailer with electric brakes and air suspension. When I install charged batteries everything works great, but the batteries deplete through use. I need to get the 12V supply back to the batteries (there are 2). Before I trace the wires back... I'm wondering if I'm actually on the right path with regards to just connecting up the 12V supply from the truck to these two batteries in parallel. Is that how it works, i.e. the truck 12V system keeps my 2 trailer batteries charging during use?[/font]

[font='Helvetica Neue', Helvetica, Arial, sans-serif]Thanks in advance,[/font]

[font='Helvetica Neue', Helvetica, Arial, sans-serif]-Richard[/font]

 

[John61CT]

No, you need to verify the volts and amps input at the target battery for proper charging, likely need a very thick couple wires right back to the alternator/starter battery to safely carry high charging amps.

Also a direct parallel connection will cause your "house loads" to drain your starter battery.

Google combiner, ACR and VSR.

Also DC-DC charger, and battery-to-battery. That will help reduce voltage drop if you want to avoid a **very* * thick wire.

Then comes the fact that your alt won't full recharge yourbattery unless you drive 6-8 hours a day.

You'll want at least enough solar to supplement if you do drive say two hours a day, ideally in the morning.

Or get a little gennie, then just one panel may be enough.

 

[highdesertranger]

you should have a 7 pin trailer connector.  if it was factory installed one of those pins is for battery charging of the trailer batteries.  is your connector factory?  if not factory you will need to see if whoever installed it put in the charge circuit.   here's a pic of the wire schematic for the plug,



see if you have 12v at terminal 4.  you should only have power when the key is in the run position.  you will not get a big charge off this wire because of the length to the alternator and the size of the wire.  even if you could up the charge,  charging off the alternator is not ideal like John said you would have to drive many, many hours to recharge your batteries.  this is an important charge source but only one you need others.  you can never just idle your vehicle to charge the trailer batteries it would take days,  it's not very reasonable.  highdesertranger

 

[John61CT]

you can never just idle your vehicle to charge the trailer batteries it would take days,  it's not very reasonable.

True for any dino juice source.
Shore power or solar are the only way to treat the bank right.

 

[John61CT]

I should say for above "can use dino juice for the first hour(s) then solar to get to 100% over the next 3-5"

 

[highdesertranger]

that's true what John said. also I am not saying don't use a generator or your vehicle, what I am saying don't rely on the as your only charge source. highdesertranger