How to Choose The Best Dual Battery Setup

inergy kodiak dual battery setup for power supply while off grid overland truck camping

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When we decided to turn the truck into a truck shell camping adventure vehicle, one of the most challenging elements we had to consider was a reliable way to meet our electrical needs on the go. Especially with our plans of working remotely while off grid.

In this post we’re going to walk you through our decision making process, the power supply options available, and why we chose the Inergy Kodiak solar generator as our dual battery setup for our pickup truck camping build.

***DISCLAIMER: We are NOT professional electricians. The information provided in this post is bore solely from our personal experience and opinion. A professional should always be consulted when dealing with any electrical system****

Assess Your Needs For a Dual Battery Setup

First start by narrowing down all the electrical devices you feel will be needed to enjoy your camping experience or travels while maintaining an acceptable comfort level.

For us that list looked fairly simple at first glance:

However, then you have to consider what exact equipment you want/need and the power consumption (watt usage) of all those devices from a day-to-day perspective - especially if you’re planning to travel for any length of time.

Then, you can begin to make choices on a power supply based on that information.

A watt meter* - which is a device that measures power usage/draw - is very handy for determining the power consumption of your devices for planning purposes, or you can look at the device’s power supply label and use the below formulas to get a good idea:

Watt Need = hrs of usage x amps per hr drawn by the device x volts

As a specific example, ours looked something like this:

  • A Refrigerator

    • Through a bit of forum scrubbing I was able to determine that our 60L ARB Elements Weatherproof Fridge draws 0.89 amps/hr on average and it runs 24 hrs a day when in use

    • So a day's usage is 24 hrs x 0.89 amps x 12 volts = 256.32 watts

  • Charging Mobile Devices (2 Cell phones, a laptop/or tablet)

    • Our cell phones draw about 5 amps when fast charging and take about 1 hour to fully charge and a charge is good for 24 hrs

    • So a day's usage is 1 hr x 5 amps x 12 volts = 60 watts

      • (x2 phones) = 120 watts

    • Our laptop draws about 15 amps when fast charging and takes about 1 hour to fully charge and a charge is good for 48hrs

    • So a day's usage is 0.5 hrs x 15 amps x 12 volts = 90 watts

  • A Vent fan

    • The MaxxFan Deluxe we chose uses about 4.5 amps when running full blast, but we normally run it at 70% speed at most, which draws 2 amps and we only use it when we’re sleeping in the heat (about 8 hrs)

    • So a day's usage is 8 hrs x 2 amps x 12 volts = 192 watts

  • Lighting

    • All of our truck bed camper interior lighting is LED and is used so minimally that it would hardly register - less than 5 watts

So if we were to use everything on the same day and need to charge our cell phones and laptop from completely dead we would use around 663 watts or 55 amp hours.

Note that real consumption is typically far less than this, but this gives a good baseline to make decisions off of.

Some of your lists may look simpler than ours, while some may be more complex, but keep in mind: the longer your list the more your budget becomes a factor.

Consider Your Dual Battery Setup Budget

Cost is an important factor in all our decisions.

If we didn't need a fridge and a vent fan we could have gotten by using the truck’s existing 12v electrical system, and forgon a dual battery setup altogether.

Or we could have ran a traditional dual battery setup like we had in our previous RVs.

But because we were downsizing from the fifth wheel and wanted to ensure we’d never have to worry about power while off grid we splurged by using an Inergy Kodiak solar generator as our dual battery setup.

Let’s walk through these options in order of expense, so you can see which best fits your journey and budget.

Choose a Dual Battery Setup That Works For You  

OPTION 1 - Single Battery Setup

Your vehicle’s electrical system consists of an alternator that charges a battery that supplies power to start and run your vehicle as well as the 12v accessories.

  • If your needs are no greater than running a few LED lights, charging your phone(s), and the occasional laptop, this may be sufficient and you may not need a full dual battery setup

  • By using your vehicle’s existing electrical system and a cheap inverter* that you can pick up from pretty much any big-box retailer or automotive store, you can simply plug the inverter into your vehicle’s 12v outlet and then plug your devices into the inverter and you’re ready to roll for a total of about $40.

  • ***TIP: Try to find and use devices and lighting that already operate or can be charged on 12v (car chargers) - all modern phones, and even most laptops can be. But there are also some great 12v slow-cookers, ovens, and refrigerators out there.

  • Remember to assess your wattage needs: Most standard starting batteries are limited to 35-75 amp hours (only 50% of which is usable).

    And if you’re not running your vehicle regularly or traveling daily, devices like 12v slow cookers, ovens, and refrigerators will potentially draw more power than your vehicle’s single battery can supply while maintaining enough charge to start your vehicle when needed (leaving you stranded).

    So you may need to consider the next option.

OPTION 2 -  Traditional Dual Battery Setup

In a traditional dual battery setup there is a battery isolator that enables your vehicle’s alternator to charge both the starting battery and a second “house” battery independently of one another.

  • This setup is a very flexible option, and can still be done with a modest budget if needed.

  • By adding additional batteries (commonly lead-acid deep-cycle, AGM, or Gel type) for your devices’ power needs,  you keep your starting battery “isolated” so that it is never at risk of being run completely dead and leaving you stranded.

  • This also enables you to add enough capacity/amp-hours/batteries to supply power to things like a crock-pot, a fridge, or even a microwave when combined with a properly rated Power Inverter.

Considerations When Planning a Traditional Dual Battery Setup

  • Weight - Lead-acid, AGM, and Gel type batteries are bulky, and often weigh a substantial amount.

    A 105 amp hour AGM battery, for instance, weighs almost 70 lbs!

  • Usable Capacity - Typically it is not recommended to discharge these types of batteries lower than 50% of their rated capacity to avoid damage or shortening their life-span.

    So a battery rated at 75 amp hours only has 37.5 usable amp hours (or 450 watt hours)

  • Size - Though some trucks have a factory location for a second battery in the engine bay, finding a place for a big 105 amp-hour lead-acid deep-cycle battery can be difficult (but not impossible).

    So determine your need (in amp-hours), pick a battery that meets that need, then make sure the dimensions of that battery (or batteries) can be fit into your planned build/application/space.

  • Cost - To effectively use a dual battery system you need more than batteries.

    At minimum you need an inverter, a separate 12v fuse panel for your “house” wiring, a battery isolator, heavy gauge DC wiring (0, 2, 4, 6 ga - depending on the length and power draw) for supplying power to and from the battery isolator to your additional battery, and if you want solar - a solar charge controller for charging your house battery, a solar panel(s), and wiring to connect it all.

    All these things can add up to a substantial amount, and may even outpace the cost of an all-in-one solar generator dual battery setup.

    But it doesn’t have to cost a fortune:

    • In our old Toyota Sunrader RV we installed:

      • A battery Isolator ($80)

      • 105 amp hour lead-acid deep-cycle battery ($130)

      • 1000 watt pure sine wave inverter ($300)

      • About 25 ft of 2 to 4 gauge DC wiring ($100)

      • We chose not to implement solar, due to cost at the time. Plus we were driving daily for hours which enabled us to always maintain a charge from the alternator.

        But now you can get a solar charge controller, and a 100 watt panel for under $250.

    • So for about $600 (or well under $1000 if we had added solar) we had an off grid power system that could run all our lights, a vent fan, a fridge, a 2-quart slow-cooker, and even a microwave (for a very limited amount of time - reheating food or warming a drink here and there).

  • Complexity - There are a lot of components that go into a traditional dual battery setup. A lot of wiring, and a lot of space is needed for all those components.

    If any of these aspects of a dual battery setup give you pause, a solar generator solution like the one we chose for our DIY truck bed camper build may be worth considering.

OPTION 3 - Solar Generator as a Dual Battery Setup - 

A solar generator is intended to provide an all-in-one off grid power solution. It consists of a battery, charge controller, as well as an inverter.

They come in a variety of shapes and sizes to suit your needs, and also offer lithium-Ion battery options which decreases weight and size substantially while increasing usable capacity to 80% (versus the 50% usable capacity of the other battery types).

However with so many solar generator options out there, and new models becoming available all the time, it’s hard to tell what to look for. And it’s even harder to choose what model would be best for a dual battery setup.

Considerations When Planning a Solar Generator Dual Battery Setup

  • Usable Capacity - Typically it is not recommended to discharge lithium batteries more than 80% of their rated capacity to avoid damage or shortening their life-span.

    So a solar generator rated at 90 amp hours (1080 watts) has 72 usable amp hours (864 watts).

  • DC Charge Rate - This is very important when it comes to using a solar generator in a dual battery setup while vehicle camping.

    If it cannot charge at a fast enough rate, or worse, if it has no way to charge from a 12v DC outlet (car charger) at all - then it likely won’t be practical as a dual battery setup while vehicle or truck bed camping.

  • Size - Again determine your need (in amp-hours or watts), pick a solar generator that meets that need, then make sure the dimensions can be fit into your planned build, application, or space.

  • Cost - This is the biggest caveat to using a solar generator in a dual battery setup.

    We’ve found that above a certain price point it may become more practical to go with a traditional dual battery setup.

    This is largely dependent on your personal needs and budget, but during our search, anything above a 1400-watt capacity began to lose justification from a cost-benefit perspective.

  • Power Output (110v AC & 12v DC) - The power inverter converts the DC power stored in the solar generator to AC power for devices that don’t operate on 12v DC power.

    Consider the devices you want/need to power, and make sure the inverter in your solar generator can accommodate the device’s power draw (e.g., if you want to use a 1000w microwave, the solar generator’s inverter needs to be rated for more than this amount).

    You also want to make sure the DC output of the solar generator offers a high enough amperage for your 12v devices.

  • Feature Set - Does it offer enough 110v and 12v ports? USB ports? Is it’s capacity expandable? Does the built-in LCD display monitor provide the information you need, and is it accurate? Is the battery user replaceable?

    Review all the solar generator’s features and make sure you’re happy with them.

When considering which solar generator model would best fit our personal dual battery setup in our truck bed camper, we were able to eliminate most by taking the above considerations into account and ultimately narrowed our choices down to 3 units that could work.

Let’s walk through our final 3 selections, in order of cost, to show how we ultimately chose the best dual battery setup for our DIY truck bed camper build.

  1. Goal Zero Yeti 400 Lithium

  • Usable Capacity: 428 watt hours or 39.6 amp hours (10.8V) = appx 342 usable watts or 31.7 amp hours

  • DC Charge Rate: 120 watts at 12V with factory car charger ( appx. 3 hours to fully recharge from dead)

  • Size: 11.25” Wide x 7.5” Tall x 7” Deep

  • Power Output: 300 watt continuous (1200 watt surge) Inverter putting out 2.5 Amps at 120VAC. Can output 10 Amps at 12VDC.

  • Feature Set:

    • Output Ports: 3 - USB, 2 - 120VAC, 1 - 10 amp 12VDC car port, 1 - 10amp 6mm 12VDC port

    • User Replaceable Battery


2. Inergy Kodiak (now Inergy Apex)

  • NOTE**: Since our write up Inergy has come out with a newer version - The Inergy Apex Solar Generator* - with faster solar charging and Lithium Expansion ability at the same capacity and dimensions!

  • Usable Capacity: 1100 watt hours or 90 amp hours (12.6V) = appx 864 usable watts or 72 usable amp hours

  • DC Charge Rate: 240 watts at 12V with factory car charger (appx 4 hours 30 min to fully charge from dead)

  • Size: 14” Wide x 7” Tall x 8” Deep

  • Power Output: 1000 watt continuous (3000 watt surge) Inverter capable of putting out up to 30 Amps at 110VAC. Can output 15 Amps at 12VDC.

  • Feature Set:

    • Output Ports: 6 - 10 amp 110VAC outlets, 1- 30 amp 110VAC outlet (like you plug an RV into!), and 2 - 15 amp 12VDC car ports (plus 2 - 10 amp DC 5.5x2.5mm jacks), 4 - USB outputs

    • Expandable - there are hook-ups to tie-in additional lead-acid/AGM/Gel batteries to double (or triple, etc.) the capacity if needed, provided the additional batteries are of a similar 90 amp hour size

    • Battery is NOT user replaceable

3. Goal Zero Yeti 1400

  • Usable Capacity: 1425 watt hours or 132 amp hours (10.8V) = appx 1140 usable watts or 105.6 usable amp hours

  • DC Charge Rate: 120 watts at 12V with factory car charger (appx 9 hours 30 minutes to fully charge from dead)

  • Size: 15.3” Wide x 10.1” Tall x 10.4” Deep

  • Power Output: 1500 watt continuous (3000 watt surge) Inverter putting out 10 amp at 120VAC. Can output 10 Amp at 12VDC

  • Feature Set:

    • Output Ports: 4 - USB, 2 - 120VAC, 1 - 10 amp 12VDC car port, 1 - 10 amp 12v 6mm port, 1 - 10 amp 12v power pole port

    • User Replaceable Battery


Once we looked at these aspects, in terms of how they would both meet our power needs as well as fit into our budget and intended application (DIY truck bed camper build), we were able to make an informed decision on our dual battery setup.

And after careful deliberation, we selected the Inergy Kodiak.

Why was the Inergy Kodiak solar generator the perfect off grid dual battery setup for our truck camping build?

  • It provided more than enough capacity for our worst-case scenario 663 watt need

  • The inverter was capable of meeting any AC power needs we may have

    • It could run a microwave, blender, a number of power tools, etc.

  • The huge selection of output options - namely having two 15 amp capable 12v ports enables us to run our fridge from one, and the rest of our truck bed camper’s 12v needs from the other.

  • It is the PERFECT size for the space in our truck bed sleeping platform design.

    With a 7” height this was the shortest option we found available, allowing us to store it completely underneath our sleeping platform while maximizing headroom.

  • It’s expandable - the ability to tie-in additional lead-acid/AGM/Gel batteries to double (or triple) our capacity meant we wouldn’t be limited if our power needs changed

  • MOST IMPORTANT OF ALL, the factory supplied DC charge cable charges at a rate of 240 watts (we’ve actually tracked 280 in our configuration) which will fully charge the Kodiak in 3-4 hours.

    This ability to quickly charge on the road is essential.

We currently have our Inergy Kodiak hard-wired from our truck’s starting battery using the Inergy Kodiak DC car charging cable, a 20 amp fuse, 10 gauge pos./neg. wires, and a relay switch that “opens” the DC charge to the unit when the truck is running.

The diagram below shows roughly how this was done.

But you could simply plug the Inergy Kodiak DC car charging cable into your 12v outlet on your vehicle and have an instant dual battery setup!

We also use a 100 watt solar panel to keep things topped off when stationary - this can usually offset the power consumption of our fridge while off grid, allowing us to stay out longer without the need to idle the truck to recharge the Kodiak.

So far this has been a great off grid dual battery setup for our truck shell camping adventures, and we’ve found that the Inergy Kodiak solar generator will easily supply enough power for a long weekend of using our camping fridge, gadgets, vent fan, and lights without needing any charge at all!

And often by the time we get home it’s already fully recharged from the truck’s 12v DC and ready for the next adventure.

Having a reliable dual battery setup while off grid is incredibly valuable and can really improve your comfort level while truck bed camping or traveling.

For more on our truck camper setup or adventures as a truck camping family of three, click SUBSCRIBE!

As always, thanks for reading!

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