---
product_id: 5407144
title: "Battery Doctor 20128 Battery Disconnect Knife Switch for Side Terminal – 12v Battery Kill Switch for Negative Post – Perfect for Saving Car Battery and GM-Type Batteries - Made in USA"
brand: "wirthco"
price: "€ 49.90"
currency: EUR
in_stock: true
reviews_count: 8
url: https://www.desertcart.nl/products/5407144-battery-doctor-20128-battery-disconnect-knife-switch-for-side-terminal
store_origin: NL
region: Netherlands
---

# 250A continuous, 750A surge power 3/8-18 bolt for easy cable connection Stops parasitic drain & theft Battery Doctor 20128 Battery Disconnect Knife Switch for Side Terminal – 12v Battery Kill Switch for Negative Post – Perfect for Saving Car Battery and GM-Type Batteries - Made in USA

**Brand:** wirthco
**Price:** € 49.90
**Availability:** ✅ In Stock

## Summary

> 🔋 Power down, level up your battery game!

## Quick Answers

- **What is this?** Battery Doctor 20128 Battery Disconnect Knife Switch for Side Terminal – 12v Battery Kill Switch for Negative Post – Perfect for Saving Car Battery and GM-Type Batteries - Made in USA by wirthco
- **How much does it cost?** € 49.90 with free shipping
- **Is it available?** Yes, in stock and ready to ship
- **Where can I buy it?** [www.desertcart.nl](https://www.desertcart.nl/products/5407144-battery-doctor-20128-battery-disconnect-knife-switch-for-side-terminal)

## Best For

- wirthco enthusiasts

## Why This Product

- Trusted wirthco brand quality
- Free international shipping included
- Worldwide delivery with tracking
- 15-day hassle-free returns

## Key Features

- • **Safety First, Always:** Instantly disconnect power to prevent theft, electrical fires, and ensure safe maintenance.
- • **Universal Compatibility:** Seamlessly fits GM-type batteries and works across cars, RVs, ATVs, trucks, boats, and campers.
- • **Quick & Intuitive Operation:** Knife switch design with easy bolt connection means no-fuss installation and instant power control.
- • **Made in the USA, Built to Last:** Precision-machined for durability withstanding 250 amps continuous and 750 amps surge at 12V.
- • **Extend Battery Life Effortlessly:** Cut parasitic drain and save on costly replacements with a simple switch.

## Overview

The Battery Doctor 20128 is a rugged, USA-made 12V battery disconnect knife switch designed to prevent parasitic drain and enhance vehicle safety. Rated for 250 amps continuous and 750 amps surge, it fits GM-type batteries and a wide range of vehicles, offering an easy, reliable way to extend battery life and protect your investment.

## Description

Stop unwanted parasitic power draw with our patented Battery Disconnect Knife Switches. It is perfect for mounting on a negative battery side post to disconnect the ground and battery. Easy to install and use. A fast and effective way to extend the life of your batteries. Great for cars, RV, ATV, UTV, trucks, boats, campers, and other power disconnect purposes.

## Features

- PROLONG BATTERY LIFE: Stop parasitic drain to save money on battery replacement; Ideal for GM-type batteries.
- INCREASED SAFETY: Prevent vehicle theft; Shut down power during maintenance and avoid electrical fires
- EASY TO USE: Open the knife and cut-off power; Has 3/8-18 bolt for receiving eyelet cable connector
- COMPATIBLE: Use on cars, RV, ATV, UTV, trucks, boats, campers, and other power disconnect purposes
- TOP QUALITY: Made in the USA; 250 amps continuous and 750 amps surge at 12 volts. 3-1/4"W x 3-3/4"L x 1-1/2"H

## Technical Specifications

| Specification | Value |
|---------------|-------|
| Manufacturer | WirthCo |
| Brand | WirthCo |
| Model | 20128 |
| Item Weight | 0.8 ounces |
| Product Dimensions | 5.9 x 4.2 x 1.5 inches |
| Item model number | 20128 |
| Is Discontinued By Manufacturer | No |
| Exterior | Machined |
| Manufacturer Part Number | 20128 |
| OEM Part Number | 20128 |
| Lift Type | OFF-NONE-ON |

## Images

![Battery Doctor 20128 Battery Disconnect Knife Switch for Side Terminal – 12v Battery Kill Switch for Negative Post – Perfect for Saving Car Battery and GM-Type Batteries - Made in USA - Image 1](https://m.media-amazon.com/images/I/81bRUFkY9SL.jpg)
![Battery Doctor 20128 Battery Disconnect Knife Switch for Side Terminal – 12v Battery Kill Switch for Negative Post – Perfect for Saving Car Battery and GM-Type Batteries - Made in USA - Image 2](https://m.media-amazon.com/images/I/81XpqTvFLQL.jpg)
![Battery Doctor 20128 Battery Disconnect Knife Switch for Side Terminal – 12v Battery Kill Switch for Negative Post – Perfect for Saving Car Battery and GM-Type Batteries - Made in USA - Image 3](https://m.media-amazon.com/images/I/81lAkC9-S1L.jpg)
![Battery Doctor 20128 Battery Disconnect Knife Switch for Side Terminal – 12v Battery Kill Switch for Negative Post – Perfect for Saving Car Battery and GM-Type Batteries - Made in USA - Image 4](https://m.media-amazon.com/images/I/81MsQh40tML.jpg)
![Battery Doctor 20128 Battery Disconnect Knife Switch for Side Terminal – 12v Battery Kill Switch for Negative Post – Perfect for Saving Car Battery and GM-Type Batteries - Made in USA - Image 5](https://m.media-amazon.com/images/I/81OHwN1mrJL.jpg)

## Customer Reviews

### ⭐⭐⭐⭐⭐ Works great, so far….’06 Silverado
*by S***S on October 24, 2021*

Just installed on my 2006 Silverado hunting truck. So far so good…seems to be working great. Some reviews say the bolt that comes with it isn’t long enough to fit in the battery terminal….without the thick washer, it fits in my DieHard battery just fine.I rarely use this truck in the spring and summer, so it’ll be nice not to have to jump it every time I do need it.I’ll be sure to edit this review, if I have any problems, but as for now, I am pleased.

### ⭐⭐⭐⭐⭐ Works Great
*by D***N on December 10, 2011*

This Wirthco Knife switch was just what I was looking for. I have a 95 Chevy Tahoe that sometimes doesn't get driven frequently enough to keep the battery up (I believe it also has a small draw that I can't find). I mounted this on the battery (GM style) and now when I am done driving it for a while, all I have to do is pop the hood, flip the knife switch, and the battery will still be charged up when I go to drive it a month later. Seems to be high quality and built to last. Good product.

### ⭐⭐⭐⭐ Will work under moderate loads, once you find proper replacement bolts.
*by B***3 on March 1, 2018*

Takes an hour to install, not including trip to store for different bolts, as others have said. Need a 3/4" long half inch bolt to screw into battery, not the 5/8" long one that they send. How much would it really cost for manufacturer to send the right length bolt? Then, on my Silverado, the bolt that came with the battery cable was not threaded to bottom. So I had to buy a new battery bolt to attach the cable to the new switch, as would not tighten fully otherwise. On the upside, the tension on the pop rivet was perfect, not too tight as others found, so the switch moves with the perfect amount of force. But, be careful not to break the black plastic backbone of switch when tightening cable. Brass in terminals is nice and heavy. Rest of current carrying parts appear to be real copper and brass. I don't have this truck in a real cold climate. Otherwise, I would be worried if switch blade is heavy enough to carry full cold cranking amps. Otherwise, this is most convenient solution for putting a switch on a side-post battery.

## Frequently Bought Together

- Battery Doctor 20128 Battery Disconnect Knife Switch for Side Terminal – 12v Battery Kill Switch for Negative Post – Perfect for Saving Car Battery and GM-Type Batteries - Made in USA
- WirthCo Battery Doctor 20108 Battery Disconnect Knife Switch for Top Post Terminal – 12v Battery Kill Switch for Negative Post – Perfect for Saving Car Battery - Made In USA

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*Product available on Desertcart Netherlands*
*Store origin: NL*
*Last updated: 2026-01-26*