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Four Wheel Drive Dual Battery Setups

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(M4x4A - Divide Ride 7/26/2003 near Boulder, Montana)

With a four wheel drive vehicle, it is very easy to get yourself deep into remote places.   This is the last place you want to be when you have your only battery quit on you.    There are many reasons that a battery can can run flat.   But few devices will provide starting and operating security for all typical causes.   Most will provide this security only under certain failure conditions, but not others.   

When you venture out into remote places, you should prepare with a backup battery.   You wouldn't travel without a spare tire.    Some travel with spare gas cans.   So why not assure yourself of starting power with a spare battery.    Many 4 x 4 vehicles have dual battery setups for that one sad time when their main battery just will not perform.    Other 4 X 4 owners use the dual battery system to provide extra power during winching, or to ensure starting power after winching.    In the past, these setups have been far from ideal.    

Some people have used simple diode isolators.   But, for those who recognize the detrimental effects that diode isolators have on their battery's performance and life expectancy, they have opted for solenoid or relay type systems.   Neither system offers the ideal automatic operation with protection even from alternator failure, yet still provide full cranking performance all in one package.   Either system has their own sacrifices.  So the debate has continued and some have chosen diode isolators, while others have have chosen relay systems, and still others have chosen heavy duty switches along with diode isolators. Many Battery separator designs are just mechanical solenoid based.

The Hellroaring Backup Battery Setup

Now there is a better system!   The Hellroaring Battery Isolator/Combiner.    The Hellroaring Battery Isolator/Combiner model BIC-95300B is essentially dedicated to a dual battery Backup battery setup.   As a four wheel drive vehicle backup battery system, it installs very easily.   It will provide high charge rate capability to both batteries.   When the main battery becomes discharged, just flip a micro-switch to energize the backup battery and you can start and operate your gasoline engine.   If your alternator had failed,  and you started your vehicle with jumper cables, your engine would quit very soon after removing the jumper cables!.   Not so with the Hellroaring system.   You should typically have at least 2 hours of operating time with a 50 AH backup battery if you keep unnecessary accessories off. 

For vehicles with a Diesel engine that requires two start batteries, then two BIC-95300B units must be connected in parallel along with two Backup batteries to achieve full backup starting. Typically Vehicles with Diesel engines are more likely used for Truck Camper or trailer camper type loads and therefore, one BIC-95150B is excellent choice for an Auxiliary battery setup (not backup starting).

Excellent Choice for Electric Winches

BIC-95300B installMany four wheel drive vehicles have an electric winch as an accessory.  In some situations, such as winching from water, you must winch without the engine running.   A backup battery can serve either of two purposes.   One is to ensure that you have starting capability in the event you use all the energy from the main battery during winching.   The other is to provide extra power during winching and minimize the drain on a single battery.   In either of these cases, a backup battery and a Hellroaring Battery Isolator/Combiner model BIC-95300B is an excellent choice.   It performs all these functions in a single compact package.  


For this backup battery setup, we recommend that you connect all normal operating loads and the winch to the main battery system.   Then connect the backup battery all by itself just for backup.   Connect the Hellroaring Battery Isolator/Combiner to the backup battery and your starter as shown in Figure 1.   And to simplify installation of the Remote functions, we have available a Remote Module kit as an accessory.

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Figure 1

With this setup, you will have the security of a backup battery fully capable of cranking your gasoline engine even with a completely discharged main battery.  

To learn about how you can extend the life of your batteries, click on this link:

Extend the life expectancy of your batteries


Yes, I want to order one or more!!!!  Click on the Sales link at the bottom of this page.

If you have any questions regarding your particular application, feel free to send an e-mail question to the contact link below.


Contact Information

For General Information, Sales, Technical or Customer Support:

Telephone: 406-883-3801
Postal address: P.O. Box 1521, Polson, MT 59860
Electronic mail: sales23@hellroaring.com
Sales/Pricing info: Sales page

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Last modified: 10-31-2023