Cole Hersee 48122 4-Stud 140 Amp 12-36V DC Battery Isolator

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LittelfuseSKU: LIT-48122

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12-36V DC Negative Ground Electrical Systems


For vehicles equipped with two batteries, the Cole Hersee 48122 isolator serves to electrically isolate the batteries, preventing the battery with a higher charge from draining into the one with a lower charge. This ensures each battery maintains its charge independently, optimizing their performance and longevity. Additionally, the isolator allows both batteries to be charged simultaneously from a single source, with its amp rating matching the maximum alternator rating.

On vehicles with newer alternators featuring integral electronic voltage regulators, such as Delco's 'Delcotron-type alternators,' the 4-stud battery isolator is recommended. The additional stud facilitates connection to a circuit switched by the ignition switch, ensuring compatibility with the newer alternator design. While a 4-stud battery isolator can also be used with older pattern alternators, the 4th stud may remain unconnected. Conversely, a 3-stud battery isolator is not compatible with Delcotron-type alternators, making the 4-stud variant necessary for optimal performance.


  • General purpose Battery Isolators for 12-36V DC negative ground systems.
  • Prevents the charge from flowing from one battery to another, and can be charged from one source.
  • Electronic components are embedded to give excellent protection from adverse conditions, such as contamination and vibration.
  • Integral heat sink provides efficient heat dissipation.
  • 90 day limited manufacturer's warranty.

Battery isolators are typically rated per leg, indicating the maximum current each leg can deliver to either battery. Littelfuse Cole Hersee brand battery isolators adhere to this standard, with the per leg rating being equal to half the alternator rating. For instance, the 48051 model, rated at 75A, features a per leg rating of 37.5A per leg. This ensures efficient and balanced power distribution between the batteries, maximizing their performance and longevity while maintaining compatibility with the vehicle's electrical system.


Alternator Rating 140A Max
amps 140 Amps
Dimensions 6 x 4 13/16 x 3 11/32"H
Mounting Four 9/32" ( 7.14mm) Diameter Holes
Number Of Terminals 3
output voltage 12-36 Volts
Stud Terminals Three 1/4"
studs 4 Stud
Terminal Diameter 5/16"
Terminal Diameter (AWG) #10

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