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PriorityStart! 12v ProMax HD Low Voltage Disconnect Switch - PSI-12V-PROMAXHD

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Product InformationStore Part Number: PSI-12V-PROMAXHD


Installation PhotoPriorityStart! is the only automatic computerized on/off protection system for your battery, alternator, and electrical system in the market today. If battery voltage drains below 11.7 volts when engine is off, it automatically DISCONNECTS the load, leaving starting power. The 12v PROMAX HD is recommended for Law Enforcement, Work trucks, Heavy Duty vehicles, and any vehicles with increased electrical/load demands.

To RECONNECT and START: simply step on the brake pedal, activateheadlights, or operate any other accessory, and starting power is RECONNECTED! No buttons to push, no switches to flip, and there is no hardwiring. It's positive to positive, with a ground wire, and you're done.

Universal design fits top and side post batteries. No hardwiring or modifications required. Transferable. Manufactured to ISO, USCG, and SAE standards.

Extra Benefits over the Standard 12v ProMax Unit:

  • Heavier Load Capacity: Up to 1600 starting amps/400 continuous amps
    • 60% increase to contact disc
    • 60% increase to spine gear & holding nut
    • 40% increase to jack screw
    • 40% increase to busses
  • Heavier ground wire connector thicker/stronger for heavier duty vehicles
  • Top post contact material raised/increased to improve GM connections
  • Gear cover for added strength & durability
  • Motor cover for added strength & durability
  • Higher intensity LED on top, improved visibility
  • Redesigned circuit board


  • Automatic battery reconnect: Convenient, safe
  • Easy to attach: 3 connections
  • Maximizes battery life: Maintenance free
  • Handles 1,600 starting amps/400 continuous amps
  • Designed for under-hood temperature extremes
  • Engine run protection
  • Transferable from Vehicle to Vehicle
  • Universal design fits both top & side-post batteries
  • Ability to use accessories when engine is off
  • Engine Run & Hazard Light Protection
  • Universal Design Fits Both Top-Post or Side-Post Batteries


*Flat Rate shipping is for the lower 48 states only.

Tech Specs

  • Dimensions (LxW): 5 x 3 in
  • Depth: 1.25
  • Weight: 1.5 lb
  • Model: PSI-12V-PROMAXHD
  • Manufacturer: BLI/Priority Start
  • Shipping Weight (lb.): 3
  • Regulatory Approval: Certified to SAE J1171, ISO 8846, CE, USCG Certified
  • Manufacturer Part #: PSI-12V-PROMAXHD
  • Made In: USA

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Do you own the PSI-12V-PROMAXHD? Please, tell us what you think about it. It helps us provide you with better products. Please note that it may take up to 72 hours for your review to appear.

I have a Challenger RT and it has a push start button so I can't turn the ignition to run position, so this product in my case was not use full at all to me.
***Note from***
In order to re-engage the battery all you have to do is simply depress the brake pedal or turn your lights on. Once the unit senses the large amp draw it will re-engage the battery allowing your to start the vehicle the normal way.
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Written by on May 29, 2019. Verified Purchase — (3 of 3 customers found this review helpful

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Dual Battery Setup

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