Posted 2006-07-02 2:07 PM (#43889 - in reply to #43888) Subject: RE: Batt. charging circuit.
Regular
Posts: 70 Location: Spanaway,Wa
Sorry, I screwed that up.
Ok, I just installed a 4D batt. under the goosneck so when the truck isn't hooked up we have lights, etc. My question is I want to use a small gauge power tap from the truck to trickle charge the battery while we're driving. How would I keep the trailer from pulling too much amperage though the charging wire? I don't really want a manual switch that you could forget to switch. I assume a resistor inline between the trailer batt. and truck plug would do it. Am I correct and what resistance? I just don't want to use the inverter in the trailer and end up burning up the charge wire or blow the fuse.
Posted 2006-07-02 2:46 PM (#43891 - in reply to #43889) Subject: RE: Batt. charging circuit.
Extreme Veteran
Posts: 524 Location: Lone Oak, Tx
paintthatain't
What brand truck do yo have. I know on the Fords, they have a relay that prevents any discharge or use of the tow vehicles battery when the vehicle is turned off. I'm not sure about the Chevy's or Dodge's. I just ran a wire from my trailers distribution box to the battery. I used a 14awg wire for that connection.
Posted 2006-07-02 2:58 PM (#43893 - in reply to #43888) Subject: RE: Batt. charging circuit.
Regular
Posts: 70 Location: Spanaway,Wa
I have a 03' Chev. The power from the truck to the trailer is always live. The only protection is the fuse. I don't really want the trailer drawing alot of current from the truck hence the need for a resistor. Just not sure if my thinking is correct. Or if someone has a better idea....
Posted 2006-07-02 10:20 PM (#43905 - in reply to #43893) Subject: RE: Batt. charging circuit.
Expert
Posts: 2689
The GM/CHev truck +12 is always there.
You don't want a manual switch.
Any resistor (or diode) will cause a voltage drop and therefore incomplete charging.
ONE form of manual switch would be to unplug the trailer.
You could do something tricky with a relay... hmmmm
Since that truck turns it's lights on when you start it up, how about a relay that is called by the truck's running lights ? Switch whatever you want with it.
Posted 2006-07-03 7:24 PM (#43950 - in reply to #43888) Subject: RE: Batt. charging circuit.
Regular
Posts: 70 Location: Spanaway,Wa
Reg, Thanks for the post but that isn't true with a constant 12v. increased resistance would cause a current drop not a voltage drop correct? And a diode is just a check valve for current so there is no standard v. drop acrossed. I know this has been done. Was just hoping to find someone that has done it.
Posted 2006-07-03 8:14 PM (#43956 - in reply to #43950) Subject: RE: Batt. charging circuit.
Extreme Veteran
Posts: 379 Location: Columbia, TN
My 99 f350 came with the constant hot and my 05 now has it but when I got it you had to have the key on. Just put a breaker in the line so if you bump something it doesn't blow the fuse it just trips the breaker and it automaticlly resets.
Posted 2006-07-03 8:16 PM (#43957 - in reply to #43950) Subject: RE: Batt. charging circuit.
Expert
Posts: 2689
Originally written by paintthatain't on 2006-07-03 7:24 PM
Reg, Thanks for the post but that isn't true with a constant 12v. increased resistance would cause a current drop not a voltage drop correct? And a diode is just a check valve for current so there is no standard v. drop acrossed. I know this has been done. Was just hoping to find someone that has done it.
Thanks, PTA
Picky, but you're still wrong (-:
For what you seem to want to do, it doesn't matter.
WhatEVER you put between the truck and the trailer's battery will cause some voltage drop, so you won't get complete charging.
You seem to want something that you have made rules against.
If you want a utility high current resistor use a headlight bulb, just cobble up a socket and use the HL beam that isn't burned out. If you want to shunt across it to provide max charging when driving home, a relay could do that for you.
Posted 2006-07-04 11:15 PM (#44023 - in reply to #43888) Subject: RE: Batt. charging circuit.
Regular
Posts: 70 Location: Spanaway,Wa
Ok Reg, I thought about the relay idea and I think I'll put one in the +12 Batt. circuit and use the taillight circuit to latch it. I don't want to "cobble" anything. I'll have to check my electrical theory but I still think I could have limited the current draw with a resistor. I guess it doesn't matter I think the relay will work fine.
Posted 2006-07-05 3:00 AM (#44030 - in reply to #43888) Subject: RE: Batt. charging circuit.
Regular
Posts: 83 Location: Cheshire England
Hi im sure you can get a relay kit that hooks up to the alternator so when your truck is running it puts out a feed to your rv batery thru a separate line hope this helps...
Posted 2006-07-05 8:54 AM (#44042 - in reply to #44023) Subject: RE: Batt. charging circuit.
Expert
Posts: 2689
Originally written by paintthatain't on 2006-07-04 11:15 PM
Ok Reg, I thought about the relay idea and I think I'll put one in the +12 Batt. circuit and use the taillight circuit to latch it. I don't want to "cobble" anything. I'll have to check my electrical theory but I still think I could have limited the current draw with a resistor. I guess it doesn't matter I think the relay will work fine.
Thanks, PTA
You can.
You could do both.
I was just pointing out that a headlight bulb might be a suitable current limiting resistor. The "worst case" would be that of a dead short in the trailer, as a load on the truck that would appear as one headlight (say 5 amps max).
You could ALSO put the relay across that current limiting resistor (short it out) so that you get max charging amps to the trailer's battery when actually driving the truck.
Posted 2006-07-08 11:14 AM (#44263 - in reply to #43888) Subject: RE: Batt. charging circuit.
Regular
Posts: 70 Location: Spanaway,Wa
I have access to Relays, diodes, and resistors so I can pretty much get what I need very easy. I plan on installing the wiring today. I'll let you know how it works out. I plan on hooking up my ammeter at first just for saftey sake.
Batt. charging circuit.
