Battery Disconnect Switches & Parts

Types Of Car Battery Disconnect Switches

Match the battery kill switch style to battery location, electrical load and how you want to cut power, whether by hand, by remote or automatically:

• Terminal disconnect knobs install on the negative post and are rated for 500A surge and 125A continuous on 12V, 16V or 24V systems.
• Knife-blade switches mount on top of the battery and step up to 750A surge and 250A continuous for heavier loads.
• Rotary master disconnect switches come in 2-post versions for battery power only and 4-post versions that add an alternator circuit.
• Remote battery disconnect kits from Painless Performance Products pair a solenoid with a toggle switch, so you can cut power from inside the car without opening the hood.
• Push/pull E-stop switches give you a simple pull-to-kill control by hand, with options rated at 10A.
• Automatic switches, such as the Flaming River FR1052 Electro-Wizard, are built for 12V systems.

How To Choose The Right Amp Rating

Pick a switch whose continuous rating covers your normal electrical load. Its surge or peak rating should cover the current your starter pulls.

Continuous amps are what the switch can carry all the time. Surge or peak amps are the short spikes it can handle without damage.

Here's how the ratings step up. Longacre Racing offers the 441-45748 at 125A continuous and 500A peak for lighter loads.

Its 441-45760 2-terminal switch moves up to 175A continuous and 1,000A peak, and the heavy-duty 441-45782 4-terminal switch is rated at 175A continuous. For bigger loads, the JEGS 555-103050 4-post master switch carries 300A continuous.

Voltage matters too. Many master switches cover 6-36V, while terminal disconnects list 12V, 16V and 24V support. Match the switch to your system voltage, then run battery cables sized for the same current so the wiring doesn't become the weak link.

Battery Kill Switch Requirements For Racing

If you race, you'll likely need a battery kill switch, since NHRA and SCCA require one for many classes. NHRA also requires a remote battery disconnect for trunk-mounted batteries. Check your class rulebook before you buy, and plan the switch location when you install one of our battery relocation kits.

Alternators add a catch. If your engine keeps running after you flip a 2-post switch, the alternator is backfeeding power. To stop it, route the alternator output through a 4-post switch or add a secondary ignition cut-off.

Several switches in this category handle that alternator circuit.

The Moroso 74101 is a twist-style, heavy-duty switch for street and race cars with alternators, rated at 175A at 6-36V DC. The Ron Francis Wiring MS-56 master switch includes an alternator circuit. Flaming River adds the FR1013 combination battery and alternator kill switch, plus the FR1010 Big Switch for magneto and battery setups.

Battery Cut-Off Switches For Storage, Security And Service

A battery cut-off switch gives you a fast way to shut off power while a vehicle sits or while you work on it. You don't need to pull cables every time. Just turn the knob, flip the lever or remove the key.

For seasonal storage, a terminal disconnect is a simple fit because it installs right on the negative post. For shop and service work, a master switch lets you kill power before you touch wiring. Options include a 100A, 24V 2-post cut-off with a mounting bracket and the Flaming River FR1003-2 Big Switch with a lever kit.

Keyed switches add a layer of security, since the car's electrical system stays off until the key goes back in. If you lose your key, Flaming River offers the FR1009K replacement key. When the stored car also needs a fresh battery or new hardware, browse our full selection of batteries, terminals and wire.

Installation And Wiring Tips

Plan the switch location, cable routing and circuit before you drill a single hole. Start by disconnecting the battery, then mount the switch where you can reach it quickly and where cables can run without sharp bends.

Clean and tighten your battery terminals so the new switch gets a solid connection. On a 4-post switch, one pair of posts carries battery power and the other carries the alternator circuit. Label each wire before you connect it.

Remote kits add a toggle and solenoid, which means extra wiring runs to plan. Route those wires away from heat and moving parts, and secure them so vibration can't wear through the insulation.

If you want a step-by-step walkthrough, see our guide on how to wire a battery disconnect switch. It also helps to know how to read automotive wiring diagrams before you tap into the alternator or ignition circuits.