Modification: Battery Disconnect Switch Install

Corfu

This evening I mounted a Battery Disconnect to the top of the battery box cover on a 2014 T@B S Maxx.

Materials:

• 1X BWD Model S5404 Battery Disconnect Switch
• 4X #10-32 X 1/2 inch stainless steel round head machine screws
• 4X #10-32 stainless steel nylon lock nuts
• 1X Length of #10 multi-strand jacketed copper wire
• 2X Ring Connectors

1. Cut out a 1 3/4 inch X 2 1/8 inch hole in the battery cover in the desired location to accommodate flush mounting of the switch. I used a Dremel to cut the hole out carefully, as there is not much tolerance between the edge of the cut out and the holes for the screws to secure it.
   
2. Insert the switch into the cutout in the battery cover.
3. Using the 4 existing screw holes in the switch as a guide, drill through the battery cover at each of the 4 locations.
4. Secure the switch to the battery box cover.
5. Cut the desired length of wire to reach from the positive battery terminal to one of the switch terminals, strip the ends, and attach one ring connector to each end.
6. Remove AC power from the trailer.
7. Turn off all items in the trailer (lights, etc).
8. Put the battery disconnect in the Disconnected (OFF) position.
9. Disconnect the wires from the NEGATIVE side of the battery and set aside securely.
10. Disconnect the wires from the POSITIVE side of the battery, and connect them to one terminal of the battery disconnect switch.
11. Attach one end of the wire from Step 5 to one of the posts of the battery disconnect switch using the ring connector.
12. Attach the other end of the wire from Step 5 to the positive side of the battery using the ring connector.
13. Reconnect the wires from Step 9 to the negative side of the battery.
14. Test that there is not DC power in the T@B (try turning a light on or something).
15. Turn the battery disconnect switch to the Connected (ON) position.
16. Test that there is DC power in the T@B (try turning a light on or something).
17. If there is no catastrophe, do a happy dance.

Notes:

• I mounted the switch on the opposite corner of the cover from the negative battery terminal to minimize the chance of accidental contact between the negative battery terminal and the switch terminals.
  
• I painted the screw heads to indicate which position was connected (ON = Green) and disconnected (OFF = Red).
  
• DO NOT tow with the battery disconnected UNLESS you have wired the trailer breakaway system to function even if the switch is in the OFF position (recommended)
  
• There is much debate whether the disconnect should be on the positive or negative. I chose the positive.
• Be sure the length of wire you choose for Step 5 is adequate enough to easily remove the cover and set it aside if you ever want to top off the cells with water, or remove the battery entirely.
• I've never installed one of these before, so please let me know if I did anything wrong or stupid.

XPADREX

Neat install. Quick question... is there an advantage to such a switch vs pulling the fuse on the battery (other than convenience?)

[Deleted User]

The switch does the same thing as removing the fuse XPADREX.  I like the step by step explicit instructions. Many battery switches have the ON / OFF indicators displayed on the switch itself; I think I would have prefered one of those 

Corfu

Me too Neil, but I had that switch handy. You can;t remove the key unless it's in the OFF position, so that's something. I guess I just wanted to do some arts and crafts. :P

XPADREX, I've also heard that if there is load when you reinsert the fuse an arc/spike could blow the fuse. 

XPADREX

Interesting... ...and logical. Intriguing!

[Deleted User]

Replacing the fuse (with no load) needs to be a very deliberate action. If you are very casual about it and hover the fuse over the contacts you will definitely hear and see some minor arcing. A disconnect switch solves that problem but also introduces two more contact points to trouble shoot when things go wrong in the electrical system  @-)

jbug10

Plus getting the battery box cover off the battery is a nightmare and I would not want to have to do it everytime I camped.  Neil, I want one of those but I will have to find someone to do that for me.  Unless you want to swing by SW MO and do a quick install for me. 

[Deleted User]

The only time I take the fuse out is when Columbia is in storage. Orignally to keep the parasitic drain from affecting the battery and now since I've added a stand alone charger connected to the solar plug, I remove the fuse because I don't want to feed voltage back through the converter in the opposite direction it was intended to pass. I'm assuming the converter has diodes that only allow current to flow in one direction but I also know that diodes don't like to have a continous source of current working against them. This is my personal theory and not something I have data for. If the camper is going to sit for less than 2 weeks, I just leave the fuse in and keep the battery up with the shore power connection.

scuba

Is a dead battery still able to be charged?

XPADREX

In most cases, yes... unless the battery is too old, sulfated, or dry. Some modern glass mat batteries qill require a big shock charge before they will accept a trickle charge. Most of my battery experience is motorcycling... these deep cycle jobbies are new to me.