Battery On/Off Switch

[pbeverly]

I am going to install a battery on/off switch on a TT. Where would you put the actual switch? A lot of pictures I have seen they are on the plastic case the battery sits in.

[ajriding]

The answer is, anywhere you want it. Were is going to be convenient to have access to it? Close to the battery of course as you can.

Another option is to use a solenoid switch, the old mechanical kind, or a large relay to connect/disconnect. The only advantage of this method is you can put a small switch anywhere in the camper to operate the solenoid switch or relay. The switch will draw a small amount of power, so it will be a drain, but using a relay you can wire it that when you cut the battery OFF that the switch uses no power. This is called NO I think- Normally Open. The other setting on a relay is NC - Normally Closed. It would be the 87a terminal on a typical relay, where when no power goes to the relay the relay conducts the power, and when power is sent to the relay via the switch the relay cuts the battery power off. If you conect to the 87 terminal it is the opposite.
So, you can wire it that turning the switch off (using no power) also cuts the battery off. This means that when you have the battery power on the switch will use a tiny amount of power too.
You would have to wire the switch directly to the battery so that when the battery is cut off the switch is not dead also.
If interested we could walk you through this in more detail.

Also, a cheaper route is to use a circuit breaker instead of the big expensive on/off switch. Breakers for DC come in many amp ratings. I use a 100amp breaker for the battery cutoff.

[Bobbo]

fj12ryder wrote:

Bobbo wrote:
Either the hot wire or the ground wire will accomplish what you want. However, if you put it on the ground wire, you disable the breakaway brakes on the trailer, so you HAVE TO remember to turn it back on before towing. If you put it on the hot wire, that is not the case. The breakaway brakes (should) wire directly to the battery.

Okay, you lost me. I'm no electrical whiz, but how does disconnecting the negative terminal affect the breakaway switch, but not the positive? Or are you saying you disconnect all the power from the positive except the breakaway switch?

The hot wire you want the switch on is almost the diameter of your thumb, or at least your little finger. The breakaway brake hot wire is also connected directly to the battery, but is no larger than a lamp cord, if that large. You leave that little wire permanently connected to the battery.

The ground wire from the breakaway brakes connect to the chassis of the trailer. If you disconnect the ground wire at the battery, the chassis is disconnected from the battery, so the breakaway brake is disconnected from the battery.

[Lwiddis]

I completely agree...as close to the battery as you can.

[jdc1]

fj12ryder wrote:

Bobbo wrote:
Either the hot wire or the ground wire will accomplish what you want. However, if you put it on the ground wire, you disable the breakaway brakes on the trailer, so you HAVE TO remember to turn it back on before towing. If you put it on the hot wire, that is not the case. The breakaway brakes (should) wire directly to the battery.

Okay, you lost me. I'm no electrical whiz, but how does disconnecting the negative terminal affect the breakaway switch, but not the positive? Or are you saying you disconnect all the power from the positive except the breakaway switch?

Exactly.

[fj12ryder]

Bobbo wrote:
Either the hot wire or the ground wire will accomplish what you want. However, if you put it on the ground wire, you disable the breakaway brakes on the trailer, so you HAVE TO remember to turn it back on before towing. If you put it on the hot wire, that is not the case. The breakaway brakes (should) wire directly to the battery.

Okay, you lost me. I'm no electrical whiz, but how does disconnecting the negative terminal affect the breakaway switch, but not the positive? Or are you saying you disconnect all the power from the positive except the breakaway switch?

[Dave_H_M]

I googled it and up popped an (open roads forum) post with pics. 😉

[Bobbo]

Either the hot wire or the ground wire will accomplish what you want. However, if you put it on the ground wire, you disable the breakaway brakes on the trailer, so you HAVE TO remember to turn it back on before towing. If you put it on the hot wire, that is not the case. The breakaway brakes (should) wire directly to the battery.

[QCMan]

The closest you can get to the battery the better. No reason to have to make long runs of heavy gauge wire.