Simple on/off 12V disconnect switch

trail-explorer wrote:

Kidoo wrote:
Wires are connected to camper using lift type connectors.

What is a "lift type" connector?

Lift Gate Connector

This connector is about the same size as the standard 7-pole round RV connector, but can handle 4 or 6 gauge wire at 200 amps. I would recommend using at least 6 gauge wire if you expect to get a decent rate of charge to the camper battery. You will probably be surprised how long the wires will be once you start running them if you take them all the way from the alternator to the camper.

:):)

As I had posted many times before, I make my own battery isolators with complete control from in the cab or under the hood. My isolators consist of one 80 amp starter 4 connection solenoid about $20. Two (one for each end on the + in the truck) HD marine screw clamp fuse holders (80 amps is a lot of current therefore I use the screw clamp type to assure full blade contact) from West Marine with 80 amp slow blow fuses. Prices vary and the last I bought were $20 each. The copper welder cable isn't cheap but it's a must.

I ordered our D/A with dual alternators for real fast recharging capability and it sure does. However, the size (gauge) of the wire (both + and -) going back to the batteries in the RV determines how many amps can actually be delivered to the RV batties. I use #2 fine strand welder cable because at times I have up to 7 (depending on which RV we use) group 31 deep cycle batteries with a 215-225 mnute reserve at a 23 amp draw each. Lots of battery bank for even our 2500 watt inverter system. but depending on your wants and needs, #4 same wire may be ok. Why fine strand welder cable? It can flex and bend without fatigue or breaking! To enable or disable the 4 connection 80 amp solenoid, I use a 65 amp or 80 amp HD slide switch under the hood as a master shut off control.

I also have an illuminated control switch mounted in the cab at the bottom of the IP that cut current from the ignition if or when wanted. When the cab switch is on, the key in and turned on, the the truck's ignition current auto activates the solenoid. Then there's my double alligator end jumper cable I keep under the hood or the hard wired switch from the nearest truck battery to activate the solenoid and send the RV battery bank to the truck to start it if the truck batteries were dead as a backup. Similar to the backup start system that's in many class A's and C's.

What's a 4 connection solenoid if you aren't familiar with solenoids?

A starter etc solenoid for auotmotive use is an electromagnetic action very HD switch that takes low amps of 12V DC to activate the contacts plunger which connects the HD circuit and allows the very high amps of 12V DC to pass thru. They have a spring return that disconnects the HD current when power is cut to the electromagnet. Very simple and dependable. The 4 outside wiring studs are 2 large dia for the HD current (amps) in and out. One small stud is for the electromagnet + wire and the other is for the - wire. Using the 4 connection solenoid assures true 12V DC current always to the electromagnet and is not dependent upon how clean the solenoid housing contact with the truck's ground chassis is like a 4 connection solenoid relies on. Rust, oil,
dirt, paint, corrosion, etc compromise electrical continuity and can be a PIA to find.

BTW, I also have 2 of the same batteries always mounted in the truck's bed on the driver's side ahead of the rear wheel inside fender and an HD junction block with Stainless Steel wingnuts on 3/8 dia solid brass studs. Can use up to a 1500 watt inverter anywhere anytime with or without an RV with us. Handy as heck and never draws from the truck's engine batteries! Run 117V AC power tools, entertainment systems, TV's, grill food turning motors, you name it and no generator needed! The batteries clear the Lance TC lower sides by approx 1-1/2" and I have #4 short jumper cables dropping down from under the TC's battery compartment that connect to the junction block with the wingnuts so we have 3 of the big group 31 batteries for the 1500 watt inverter inside and also the for the TC's 12V needs without ever drawing down to 50% charge. 20 miles down the road and all are back to full charge. Slick as snot and been using this system on our RV and cabined boats for 26 years now and there's NO down side or noise with an inverter. Never had a failure yet but did blow one fuse when I dropped one cable and it's end hit the other's bare end. Replace the fuse and all it well!

So simple to move from truck to truck when you get a different truck. 2 hours max.

I like interchangeability and things done right and not on the ragged edge of failure. Buy the components once, do it right, and never have to buy stuff again except for a fuse if you blow it! So cheap in the long run and NO surprises!

Kidoo wrote:
Wires are connected to camper using lift type connectors.

What is a "lift type" connector?

kohldad wrote:
Not all trucks disconnect the 12V from the plug when turned off.

Correct.

GM trucks are wired so they are hot all the time. I don't know if that has changed with the new body 2015 HD trucks.

The ratings are for switching a load at the rated level.
You should be fine with what you have.

Install the surepower and forget about it. They also have perfect product support, btw.

bwc wrote:
One question in closing...my truck's alternator is rated at 120 amps and the Blue Sea is also rated at 120 amps. Is the Blue Sea enough?

Yes. I have 0AWG from truck to house batteries and have never seen more than 65 amps of charge current (3 batteries), so 120 for contact rating is more than adequate in your setup. Your charge current will be much lower: 2 batteries + 8AWG.

Thanks to everyone who gave suggestions to my relay question and to the ones that answered me via PM. I may go with a Blue Sea 7610 ACR for the simplicity and their great warranty. One question in closing...my truck's alternator is rated at 120 amps and the Blue Sea is also rated at 120 amps. Is the Blue Sea enough? Is 8 gauge wire adequate for my application. I have two Grp 27 batteries. The camper does not have an inverter etc and the 12V draw is very low with all LED's. I also have a Honda 2000 gen set. Thanks.

I installed a constant duty 80 amps Solenoid with a switch that has a light in the toggle so I do not forget it. One advantage on this is I can charge the truck batteries with shore power or with the generator while charging the camper's batteries.

Also, using no.4 gauge wires, it charges quickly. Wires are connected to camper using lift type connectors.

I installed the Sure Power. Attached it to the plastic fuse box cover under the hood. Works great. Its been in over 3 years and no problems.

bwc wrote:
Is there such a thing as a manual 12VDC battery disconnect switch that will separate the truck from the camper when parked but will allow 12V for the camper. Most if not all that I see do not allow any 12V to camper when turned off. If not would the Sure Power 1314 be another choice? I am happy with current charge rate, just want to keep truck and camper separated when parked. Also, would the Sure Power be installed in line of the camper's positive battery wires, 12V in and then 12V out along with a ground or does it need to be installed on the charge wire in the camper? Thanks.

You can use a simple switch to turn the charge line on/off as long as the switch is rated for the max. current of the charge line . It also helps if the switch is lighted as a reminder that is on or off .

I use a combination of a continuous duty solenoid and a lighted switch to energize the solenoid . The switch is located in the truck dash , it seems more convenient than in the camper .