Choosing a Battery for your Overland Rig

Back in March of 2014, I spent too much time (is that possible?) researching batteries before finally selecting a DieHard Platinum as the new juice box of my newly winch-equipped overland rig. Once it was installed — I’ve moved on and forgot about all the time I had spent reading forums and running equations about batteries. And instead turned my attention to suspension.

Then earlier this year a friend bought a fridge and came asking me about batteries. So I went to dig up what I could on the topic to point him in the right direction (and find out to my horror that the DieHard Platinum was discontinued). Then just a few days ago another friend came asking the same question.

That’s when it hit me. I’ve spent hours and hours and hours researching various aspects of overlanding equipment and gear. Why not summarize what I find? So here we go (the first of many)!

Battery Types

Deep Cycle Batteries

These are best thought of as “marathoner”. They have decent output over a long period and like to be run from a full charge into the ground dead and back again. The latter is the real beauty of a deep cycle battery. These are often found in RVs, boats or as a “house” battery in a dual battery setup.

Starting Batteries

If deep cycle batteries are “marathoner” — then starting batteries are “sprinters”. They have great output for a short burst, then tail-off. They also hate being discharged and instead prefer a constant charge. This is what just about every car in the world comes from the factory with.

Battery Builds

Flooded Lead Acid

These are the oldest types of rechargeable batteries. Most cars come with this type from the factory because they’re cheap. But their construction makes them prone to failure when exposed to hard hits and vibrations found overlanding. Most are not sealed and produce some off-gassing (not safe for interior use).

AGM (Absorbed Glass Mat)

This is actually a lead acid battery too — but uses a different construction including fiberglass (glass mats) that create a completely sealed battery with a higher energy to weight ratio than your standard lead acid batteries. This is definitely the preferred construction type for overlanding since they can be mounted in many positions (including inside), produce a lot more energy,  and are far, far more rugged.

These don’t need anything special for use and can be dropped in to replace your factory battery now. How they differ from flooded batteries:

  • If completely discharged, they can be tough to revive
  • They hate being overcharged (you can kill them this way, which is tough to do with a flooded battery)
  • Their resting voltage is 12.8-12.9V rather than 12.7V

Spiral Wound Cells

This is simply a construction type of AGM batteries. Best known as Optima batteries.

Battery Brands and manufacturers

Like most things these days, there are only a handful of batter manufacturers anymore. Below is a great reference on who makes what.

Brand Manufacturer
Sears/DieHard Lead Acid Johnson Controls
Sears/DieHard Platinum AGM Enersys
Sears/DieHard Gold AGM Eastern Penn
Interstate Johnson Controls
AutoZone Duralast Lead Acid Johnson Controls
AutoZone Duralast AGM Eastern Penn
Wal-Mart Everstart Johnson Controls
PepBoys (Bosch) Exide
Napa Lead Acid Johnson Controls
Napa AGM Eastern Penn
Optima Johnson Controls
Varta AGM Johnson Controls
Costco Johnson Controls
Northstar (X2Power) Northstar
Duracell Eastern Penn
Rayovac (Batteries Plus) Lead Acid Johnson Controls
Rayovac (Batteries Plus) AGM Eastern Penn
Deka Eastern Penn
Exide Exide
Odyssey Enersys


Johnson Controls makes most of their batteries in Mexico (including the Optima line) and from what I’ve gathered from the forums and experience — is definitely a “value player” (concentrating on cost and not quality). I’d personally steer clear of any Johnson products.

Eastern Penn is a step up from Johnson and along with Exide; make up the bulk of the market. Eastern Penn and Exide seem to have a better reputation, but Exide can’t seem to keep from claiming bankruptcy every few years or keeping their plants operating in an environmentally safe way. Both make all their batteries in the US. Between the two, I’d look for Eastern Penn/Deka.

Northstar is a new player to the game and much smaller — but easily the second best when it comes to product quality. The best of course is the only company approved by NASA and the US Military for use, Enersys (Odyssey).

Understanding Battery Specifications

Ok, so we now know we want an AGM battery (in most cases) and who makes what brands (and which are best). Now it’s time to figure out what the heck you’re looking at when you start comparing batteries.


This is exactly what you think it is. There’s a general rule of thumb that you should replace your battery (regardless its condition) after its fourth winter. Seems like decent advice depending on where you live and what “winter” means (remember that heat kills batteries, not cold). Things I’d consider about a warranty:

  • Get as long of one as you can. If you’re torn between two batteries that are close in price, get the one with a better warranty
  • Warranties are only as good as being able to warranty them. If you’re globe trotter, make sure you can get the battery warrantied where you’ll be traveling to and through. If you can’t, then this is a moot point.

CCA (Cold Cranking Amps)

Cold Cranking Amps tell you the current a battery will put out for 30 seconds at zero degrees Fahrenheit  without dropping below 7.2 volts. This number, while usually pointed to as important, really doesn’t mean that much. Get something with at least as many CCAs as your factory battery. More is better, but not necessary/required.

Reserve Capacity

This is what really matters. Reserve capacity tells you the number of minutes at 80 degrees Fahrenheit a battery can put out 25 amps before it is drawn down to 10.5 volts (most vehicles need ~7.2V or greater to start). In other words, the bigger the number the better.

If you’re running a fridge, lights, etc. while at camp and the truck isn’t running, you’ll want something with a lot more reserve than what came from the factory. Even more important to consider if you’re parked for multiple days and don’t have a solar panel or another way to keep the truck charged. All that said, your specific needs will vary. Do the math.

But which one do I get?

More or less I think batteries fall into four categories.

#1) stock replacement with few-to-none

Maybe you have some off-road lights or a CB or nothing not factory. Then you need something that meets your factory CCA and reserve capacity. That’s it. Piece of mind will come with an AGM, but it’s definitely not required. I’d personally get a lead acid from Eastern Penn with the best warranty I could meeting my factory specs and battery size.

#2) stock replacement with fridge, lights, OBA, etc.

You have goodies that draw when the truck is off. Nothing that draws a lot of power, but you want piece of mind when running your fridge for two days at camp. Believe it or not, most factory batteries could handle this just fine. That said, piece of mind and reliability come with a good AGM battery. Especially when supplemented with solar charging or an emergency jump pack.  For me, I’d look at Eastern Penn (preferred) or  Exide for an AGM battery with as much reserve capacity I could find that had at least the same CCA in my factory battery size.

And a small side note on the topic. Some vehicles come with battery protection from the factory. Things like “battery separators” which are solenoids that disconnect the battery from a circuit when the battery’s voltage drops to a predetermined level. Fridges and other accessories also sometimes offer similar protections. I mention that because your worry here is likely less so that you’ll end up with a dead battery and more so that you’ll have melted ice cream in your fridge.

#3) Stock Replacement with (electric) winch

If you have a winch, it’s likely you have other things too. You’re a #2 plus winch. And that’s what separates you. Winching draw huge amounts of power. It’s actually possible with your truck running to draw so much power out of your battery that if you were to shut the truck down after a long pull, it wouldn’t start. Most winches pull more amps out of your battery than your alternator (especially at idle) can put back in. Because of the extended high output needs of electric winches, look only to your best AGMs. Your winch manufacturer will likely have some CCA and/or reserve capacity recommendations — follow those and beat them if possible. I’d personally look to AGMs from Enersys (Odyssey, preferred) or Northstar and get as many CCAs and reserve capacity I could from a factory battery size.

#4) Not stock

You’ve elected to go dual battery or move away from your factory battery size. This article is likely elementary to you… so let me touch on what might be helpful to those looking at this as an option (haven’t yet taken the plunge).

Dual batteries are great and work just like they do in boats. You end up with a house battery that runs your lights, fridge and other goodies when the truck is off (ideally, a deep cycle battery… but can be done in any combination, including two starting AGMs). And a starting battery reserved for just starting the truck (other setups exist, but this is most common). Too boot — you also get some redundancy. If your starting battery were to completely fail for some reason, you could swap in your house battery to limp home.

While ideal, the complications/availability/cost of these systems change how realistic a setup like this is. Certain makes and models have far more in the way of options (and hood space) than others. Xterras for example, leave you to a home-brew solution (no kits or standards).

My two-cents on this front is that the complications/availability/cost associated with this upgrade leaves it as an option to very few. I think most are better served with a premium AGM battery combined with a jump pack and/or a solar charging setup. But that still won’t work if you’re:

  • Spending days or weeks parked without starts, with accessories running, and there’s little to no sun
  • You have too many doodads running at camp (fridges, lights, TV, margarita machine, karaoke machine, etc.) for a single battery (is that even camping?)