The Stovebolt Site Forums The Shop Area Engine Shop Battery disconnect switch?

Any of you use a battery disconnect switch?

I would suppose this is easier than removing the terminal from the batt post each time I need to disconnect power.

Any particular brand or style to look for or to avoid?

Do you use it on the POS or NEG side?

Thanks!

Dave

I got a great one at a car swap meet. It goes on the neg terminal of your battery and then the cable attaches to it. You disconnect the battery by just turning the round green knob to the left. Cost about $5

I don't have a disconnect switch, but that is not a bad idea.

On large equipment, and this should pertain to trucks, too, the switch is located in the hot lead, not the ground, between the battery and the first place the hot battery cable is connected.

Negative ground systems have the switch on the positive cable. Locate the switch where it is convenient, but away from anywhere you could accidentally ground the hot connection on the switch.

Even if you have a disconnect switch in the line, it is still a better idea to remove the positive (hot) cable connection at the battery to work on the electrical system.

The biggest drawback to "disconnect" or "kill switches" is that they introduce a very small resistance and voltage drop in the circuit.

Not usually a problem, but once, we were trying to start a BIG piece of equipment that didn't want to start, and things started getting warm. The disconnect switch was a lot hotter than the cables, and I could feel the heat int he cable through a pair of leather work gloves.

I used one before that had a knob you turn to break the connection. They are really great if trying to keep the battery from draining. The other way I've been keeping my cars charged is by getting a "battery tender" charger. This is different than a trickle charger. It charges only when needed. It's great but more expensive than a switch.

When you disconnect with a switch (for a few months), do you polarize your voltage regulator when you reconnect?

Thanks,
Tim

Generally, anytime you break the connection to the battery - you need to polarize the generator again.

What do you mean by polarize the generator? I have this type of switch on a later model Corvette, not my truck so I'm not sure what you mean.

I have one mounted to the firewall on mine, you can see it on my recent post re: 235 aftermarket air breathers, it is mounted on the firewall passenger side, the off/on handle is mounted thru the carpet on the inside,, this part is hidden but I can reach it from the drivers seat,,I got mine from the local auto parts, paid about $20 but it is a nice heavy duty one,,I did have to buy one extra long cable because of where I have it mounted,,,regards,,Fred

Michael,

http://www.chevytrucks.org/tech/generator.htm

http://www.autosite.com/garage/subsys/bachar01.asp

If you have an alternator, apparently it is not necessary to worry about polarization.

Tim

The generator will retain its polarity indefinitely, power on or not, unless it's handled roughly. Take it off the truck, drop it on the floor a few times, and you'll need to re-polarize. Otherwise, don't sweat it! Polarizing the generator creates "residual magnetism" in the armature that will produce about 2 volts DC at the armature terminal, when the generator spins up, even with no wires attached. This starts current flowing through the regulator, and back to the field coils to start the charging process. That's why a generator-equipped vehicle can be push-started, even without a battery installed. Don't try that with an alternator, it can't produce voltage without at least a little juice from the battery.
Jerry

I would like to add that every time you turn the truck off, the generator is disconnected and you don't have to polarize it every time you start the truck.

We used a Cat master switch off a piece of heavy equipment. Not the cheapest switch around, but it's got a removeable key and threaded on the neck like a ignition switch. Can't rememeber the part number (think it's 7N0719), but just go the your local Caterpillar Equipment dealer and ask them for a Master Switch.

You should be able to find a good quality battery switch at a marine supply store, or maybe even Walmart. It's a common item on boats and wireing is very simple, hot lead in, feed line out. It can be mounted almost anywhere.

The switch is required equipment on the roundtrack cars we race, accessible to the driver and the emergency crew in case of a crash. It's usually mounted on the roll cage near the driver's right hand, and an easy reach from the passenger's side window for a fire crewman. Try the JEGS catalog, roundtrack section, for a good, heavy-duty switch.
Jerry

So, to polorize a generator, all you do is get a piece of wire, and connect the two leads for just an instant? Maybe I should try that on my 55, since it isnt charging and it has been sitting for a long time without a battery.

- Shane

The safest way to polarize a generator is to disconnect the Armature lead from the regulator connection, and flash it to the Battery terminal for a moment. Some people just short a screwdriver blade between the two terminals, but I've seen regulators damaged that way. It's safer to disconnect the "A" lead. Just a quick flash is all that's necessary, less than a second of contact. A properly polarized generator should develop about 2 volts at the Armature terminal with the engine running, and the armature and field leads disconnected.
Jerry