Words by Perry Mack
Your first question may be, ‘do I need a dual battery set-up?’ This is the right question. The main purpose of a dual battery system is to isolate your main battery from all of the electrical devices that are running, which could draw it down to the point where you can’t start your vehicle. As you can imagine, this is bad. If you’re in a group you could always ask someone for a jump, but every time you drain your battery you could be damaging it as it continually carries less of a charge.
The electrical system in your vehicle is designed to handle everything that comes with it in stock form, while your engine is running. However, weekends on the trail and overlanding have a camping component, which means you may be running fridges, lights, a coffee maker, stereo, GPS, fans to cool your tent at night, and even charging accessories like power tools, cell phones, laptops, and tablets.
As mundane as it may sound, the place to start in choosing a dual battery set-up is determining the electrical draw you plan to use. It’s the same as knowing how much fuel you need to get you home and back again (or point A to B) without being able to buy more or how big of a tank you will need.
If you’ve decided you need a dual battery system, here are some options that we have tested and still use.
Perry Mack
Many options are available for your specific applications and budget.
Solution #1: Weego 66 or similar
For minimal use like running some LED lights around camp and charging your laptop and cell phone, you can get away with your vehicles existing battery and charging system. Our safety suggestion is to purchase a battery back-up like the Weego 44 or 66. This is a case of more is better and we carry the Weego 66. These are jump starting power backs that can be charged from your wall outlet at home and recharged from your auxiliary outlet while you’re on- or off-road.
The 66 has a smart USB port that automatically detects and applies your devices fastest charge rate, and can recharge your phone up to seven times before it needs to be recharged itself. Aside from juicing up your cell, tablet, laptop, and other USB devices like a GPS or a Zoleo Satellite communicator, it has a 12V port to run small camp accessories and portable compressors. There is also a built-in 600 lumen flashlight, which does the typical steady beam, and also has a strobe effect (campfire dance night?), and will auto flash Morse code for SOS.
In addition, it has a 600 CA jump starter in case your battery gets below the starting threshold. The Weego won’t start your vehicle on its own, but it will assist a somewhat rundown battery to get your engine going. Cables for everything except USB are included along with a handy carrying bag to keep everything together.
The key feature here is portability. Weighing in at 1.13 kg (2.5 lb) and dimensions of 23.5 x 8.3 x 3.8 cm (9.25 x 3.25 x 1.5 in) you can move it from vehicle to campfire to backpack to motorcycle if the need arises.
While not a ‘full on’ dual battery system it does offer a layer of powered convenience and safety that will separate your power consumption from your main battery. Weego says it will last through 1,000 full charge cycles, but we’re still testing this claim. We’ve had it for a few years now – only about 850 charge cycles to go.
The MSRP is $149.99 USD but it is often on sale for $105. Smaller models like the 44 and 22 start at $49 USD.
Read the full review here: https://suncruisermedia.com/4WDrive/accessories/orange-is-self-reliance/
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Perry Mack
The Weego 66 with accessories.
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The ports of the Weego 66.
Solution #2: Dometic PLB 40 (or similar)
A step up is the Portable Lithium Battery (PLB) from Dometic, which is designed to run a portable fridge/freezer like Dometic’s CFX40 for 40 hours. In addition to running the fridge, it has a couple of USB ports, and a standard 12V, 15A auxiliary port (aka the cigarette lighter of pre-historic days). Slip a small 150W inverter into this port and you can power small electronics with an AC plug.
It can be charged at home through your vehicles 12V auxiliary port, and has a built-in charge controller so a solar panel with an Anderson SB50 connector will add juice to the PLB40. Its design allows it charge in your vehicle while it powers your fridge/freezer. The food and bevvies stay cold and you arrive on site with a fully-charged battery
Like the Weego it’s very portable at 7.3 kg (16.1 lb) and 20 x 25 x 20 cm (7.76 x 10 x 7.76 in). It comes with a solid, comfortable, retractable carrying handle so transferring it from vehicle to vehicle to RV to boat is a simple process. While we wouldn’t be backpacking or riding with this battery, we certainly would move the cooler and battery closer to the campfire to enjoy a cold beverage and food without having to get up!
Power comes from the special Lithium Iron Phosphate battery cells delivering an energy supply of 40aH/512 Wh. The 2,000 charge-cycle lifespan (before dipping below 80 percent capacity) is roughly four times other lithium power packs currently on the market.
There are two downsides to the PLB40. First, it can’t jump start your vehicle or even assist. The second is the price of admission as the MSRP is $990 CAD or $880 USD.
Oher options include the Goal Zero Yeti 400 or 1400 and the Inergy Apex (Kodiak)
Read the full review here: https://suncruisermedia.com/4WDrive/accessories/dometic-plb40/
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Perry Mack
Dometic’s PLB40 with the CFX40.
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The series of ports on the PLB40.
Solution #3: The ArkPak
We’ve been toting the Arkpak around for almost seven years of trail, camping and overland adventures. It uses a car battery as a power source and has built-in ports and inverters to charge and power your electric devices. In addition to charging your mobile devices through its USB ports, the built-in 150W inverter (ArkPak 715) will provide up to three days of 110V power, allowing you to charge cordless power tools a dozen times or power a small television for 72 hours.
It will hold any Group 31 or smaller 12V battery. Drop in a 130 amp hour deep cycle battery and you have loads of power for fridges, LED lights and more for days. You can recharge it through your wall outlet at home, the 12V auxiliary port in your vehicle, or connect it to a solar panel via the built-in 50-amp Anderson plug.
Plus, it’s still portable, comes with handles, and can be moved to various locations in the same way as Dometic’s PLB 40, but you’ll need to eat your spinach and Wheaties first as your average 130 aH battery and ArkPak weighs in around 36 kg (80 lb) – 4.5 times the PLB40. For maximum safety and portability, use the Absorbent Glass Mat (AGM) or Gel batteries, which are sealed and won’t leak if tipped.
Since it is powered by an automotive battery, you can use the ArkPak’s battery to jump start your vehicle, but only after you remove it from the ArkPak, which is as simple as disconnecting the leads and pulling it out of the ArkPak.
Lifespan of your AGM battery depends on the quality of the battery you purchase, but it could be as high as 1000 cycles @ 50 percent depth of discharge (DOD). In other words, you can run it to 50 percent remaining power and recharge it 1000 times. The good news is the ArkPak has a 7-stage smart charger built in, which is the key to extending the life of any deep-cycle battery.
You have to factor in the cost of a battery when calculating the affordability of the ArkPak. A Group 31, 105 aH battery from Canadian Tire can run $330 to $480 CAD.
The ArkPak 715 (150W inverter) has an MSRP of $449 CAD ($329 USD) and the 730 (300W inverter) is $595 CAD ($449 USD) and you can bundle it with a 30W solar panel for an extra $270 CAD ($200 USD).
Read the full review here: https://suncruisermedia.com/4WDrive/accessories/arkpak-%E2%80%93-the-alternative-to-a-dual-battery-system/
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Perry Mack
Powerful and portable – the ArkPak Smart Charge Display and 12V Ports.
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The ArkPak with the handy Anderson, USB and AC outputs.
Solution #4: The ‘traditional’ built-in dual battery system
Some vehicles come from the factory with a secondary tray in the engine bay. Unfortunately, this isn’t the case in most vehicles. Since we have a 2015 Jeep Wrangler JKU, we sourced the Rugged Ridge Universal Dual Battery Tray to accompany the Rugged Ridge Battery Relay.
Compared to the previous solutions, this system loses any element of portability and relies on the ports in your vehicle to charge your devices. It will also require some install time (about three to five hours) or cost some money if you have it professionally installed. Many overlanders add a power inverter to the vehicle as well so they have 110V AC power, plus extra 12V ports for all their devices.
What you gain is no-brainer use. Just start your vehicle and go camping. The dual battery is already in the car and charged (or will be when you arrive at your destination). Being tucked in the engine bay, it doesn’t use any interior space so there’s more room for you, your companions and your gear. In the event that your main battery dies, you can use the second battery to start your vehicle. Inside your vehicle you’ll mount a three position switch that allows you to decide how you want your auxiliary battery to be engaged – only use and charge your main battery, only use your main battery but charge both, or use and charge both batteries.
The quality and lifespan of this system is similar to the ArkPak, where a better quality battery will last longer and provide more consistent power. If the battery wears out, put a new one in. You don’t discard the portable device and buy a new one.
You have to factor in the cost of a battery when calculating the affordability of this dual battery solution. For our Jeep it’s a 48/H6, which from Canadian Tire is an AGM battery and can run $241 to $390 CAD.
Rugged Ridge Universal Dual Battery Tray – SKU 11214.54 MSRP $150 CAD, $110 USD
Rugged Ridge Dual Battery Relay – SKU 17265.01 MSRP $ 293 CAD, $220 USD
As you can see there is a solution to suit everyone, and while we’ve used our favourites in the examples, there are plenty of options from different manufacturers that may work just as well, and if you’re lucky, at a lower price.
Perry Mack
The Rugged Ridge Battery Tray and Isolator Relay ready for install.
Do You need a dual battery system?
Dual battery setups are great for those looking to put additional loads on a battery while the vehicle is not running. A dual battery setup for devices like winches and a lot of lighting while the battery is being charged by the alternator, is not warranted
List the devices you plan to take with you. A watt meter can measure the power usage/draw that each device needs. Alternately, most devices have a power supply label on them that will allow you to calculate the watts, or the internet can be a fast way to find the numbers. The formula looks like this;
Think of it like your house meter; you get charged by the watt-hour as a watt is a certain amount of energy (a joule) that passes a point in one second.
We’ll do the math for roughly a 24 hour trip just for simplicity sake;
Watts-hours you need = hours you use the device x amps x volts
As an example, our Dometic CFX 40 runs 24 hours in a day x 0.87 amps x 12 volts = 250 watt-hours.
Your phone may run for 24 hrs on a single charge and charges in an hour. If the battery holds 1800 mAh your formula looks like - 1 hr x 1.8 amp x 5v = 9 watts-hours
Our total is 259 watt hours. After you’ve totaled up your usage there is a general rule of thumb applied to battery discharge. Don’t continually draw it below 50% capacity or you will reduce its ability to retain a charge. If your battery has an amp hour capacity of 72 Ah (usually rated for a 20 hour period), it will deliver 3.6 amps per hour for 20 hours. But since your threshold is 50% then you don’t want to draw more than 36 Ah (half of 72) or 1.8 amps per hour for 20 hours to remain above the 50% threshold.
Now we convert the watt hours to Ah using the formula Ah = watts-hours / (hours * volts). For us this is
Ah = 259/(24*12) = .90 amp hours – only half our limit of 1.8 amps per hour for the rated 20 hours of the battery.
So far so good. BUT, let’s say it requires 500 cranking amps (CA) to start your engine. You can convert CA to Ah by dividing by a 7.25 constant. In this example, we need 69 amp hours to start our engine, BUT we only have 54 Ah left;
We started with 72 Ah in our charged battery, but used 0.9 Ah over 20 hours (18 Ah). We may not be able to start our vehicle without a boost. We will need a dual battery system, or we’ll have to charge our battery sometime throughout the day.