Dual Battery Setup For Off-Road Vehicles – Tips and Suggestions

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The first rule of thumb when it comes to batteries for your Jeep or other 4X4: Get the the most powerful battery you can fit into the battery tray. You should get the highest quality, most powerful battery that you can afford. Batteries aren’t something you should scrimp on if you’re gonna be off-road on a regular basis. Eventually things can and will happen, and you may find yourself depending on the battery to get you home.

Dual batteries

Dual batteries setups - like these dual spill-proof Optima Red Top Batteries (click for more info) - are a smart way to give your off-road rig more capability

If your alternator goes out and you have a very powerful battery, it can possibly get you back to civilization before dying (not true of an inexpensive, low power battery). And if you use a winch or other big electrical device (like that phat surround sound with double 15’s under the seats), you’ll need more than just the average “starting” battery. Using a winch even a few times can negatively affect the life of your battery.

Often times off-road enthusiasts consider a dual battery setup (a.k.a. adding a second battery to your rig). If you’re into going deep into the wilderness, and you don’t want to give up things like the killer sound system, rack lights, charging your phone and laptop and camera…you may be a great candidate for a second battery.

And if you’re going to be winching, you really shouldn’t do that on a regular “starting” battery (or with the vehicle off for that matter). It would be much better to have a double battery setup with isolators. That way if one of your batteries runs down while you’re winching, you’ve got a backup. Isolators are nice because they’ll make sure both batteries don’t run down at the same time.

Warn 28022 Dual Battery Isolator 120 Amp

Warn 28022 Dual Battery Isolator, rated at 120 Amps. Click image for more info.

A dual battery setup shouldn’t be a substitute for an overloaded charging system (a.k.a alternator). If your idea is to be able to play your high amp stereo system without the engine running, you can still overload the charging system and run down batteries. What you need to do in that case is also upgrade your alternator.

If you decide you want to upgrade your charging system to allow two or more batteries, you’ll want to decide between using a battery isolator or simply wiring the two batteries in parallel. If you plan to use two different types of batteries (or two different sizes), you’ll need to use an isolator. Different batteries discharge differently, and an un-matched pair wired in parallel will cause havoc with your charging system (not to mention erratic performance when it counts the most). You should also use an isolator if you plan to dedicate one battery to the vehicle and one to the accessories.

One more note about wiring batteries in parallel – if you decide to go this route, in addition to matching battery size and type, you should also buy the same brand (different brands use different rating procedures and invariably have different actual capacities) and each battery should be the same age. That’s right – if you go the parallel route you’re going to need to buy TWO new batteries.

Now you know why isolators are so popular.

Painless Wiring 40103 Battery Isolators Easy Installation

A Painless Wiring 40103 40103 250-Amp Weather Resistant Dual Battery Current Control System - from $200. Click image for more info.

There is one additional option for running a dual battery setup without using an isolator – you can purchase a special high-output alternator with dual outputs. Less common, but still feasible, is to use two alternators, one for each battery. In either case, you can skip the isolator.

Well…there you have it. Now you just need to recharge your own batteries and get started on your battery decisions. With this information you’re bound to make the best possible choice for your vehicle.


  1. Lateisha says:

    I’m so glad that the innertet allows free info like this!

  2. Now that’s subtle! Great to hear from you.

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