AGM vs. LiFePO4 – Choosing the Best Type of Battery for Van Life
What's the best type of battery for van life? Well... it really depends. Each battery type has a unique set of pros and cons when it comes to van life setups.
We are going to look at the two most common types of batteries used in vehicle electrical systems — AGM and LiFePO4 — and compare all the important factors. There are other types out there, but these are the most common.
If you were like me when I first got into van life, you probably haven’t even heard these names before — and that’s ok! The basics are quite simple, and we don’t need to get technical to help you pick what’s best for you.
AGM Battery
AGM stands for “Absorbed Glass Mat” and is a type of Lead-acid battery. There are other types of Lead-acid batteries, such as “Flooded Lead-acid” and “Gel”, but they are less common in DIY camper van conversions. With an AGM battery, the acid of the battery is stored in a fine fiberglass mat which prevents spilling and limits off-gassing. Both of which are important when you’ll be sleeping within feet of your batteries.
First a little history
The Lead-acid battery was invented way back in 1859 by a Frenchman named Gaston Planté. It was the first type of rechargeable battery ever created and is still one of the most prolific batteries out there.
But, a technology that’s this old can’t be the best option, right? I mean, did they even brush their teeth back then? The answers are, it very well could be and no they didn’t.
There’s a reason Lead-acid batteries have been around for 160 years. They are reliable and very cost-effective. In fact, every car relies on a Lead-acid battery to start.
They are cheap and reliable, but what else makes them good for van life? — A: They are the cheapest option for cold weather usage.
Even after all this time they are still the cheapest option for cold weather usage. An AGM battery can be charged at temps as low as -4°F (-20°C) without being damaged. Lithium types can be used in the cold, too, but only if they are heated and this feature is a bit more costly. And while most of us don’t go looking for cold weather, it’s bound to happen. So, for all you full timers out there, either an AGM or heated Lithium will be your best option.
The two main downfalls for AGM are lifespan and weight
Lifespan can vary widely depending on how well you take care of it. Proper charging voltages, limiting the discharge, and proper storage all play a role (which is why you might want to consider a packaged product.
Most manufactures say to expect 300 to 400 cycles out of an AGM. But this is really just before a decrease in capacity is noticed. You can still expect around 80% capacity after this many cycles. If the battery is properly charged and taken care of, you can expect to get about 3 years of van life out of them.
They are heavy, at about 55 pounds for the typical size. You don't want to be moving them around; It’s made of lead. But the truth is, this isn’t much of a downfall for van life. Most batteries are installed and never moved. You may think it will have an effect on gas mileage, but it’s pretty negligible. The engineer in me got curious and did some research. Turns out an extra 100 pounds in your vehicle decreases gas mileage by about 1%. This ends up being about $10 more in gas per 1000 miles of driving if you have AGM batteries.
LiFePO4 Battery
LiFePO4 batteries are becoming the go-to option for vehicle and RV electrical systems. It’s a type of Lithium-ion and stands for “lithium iron phosphate”, or LiFePO4. As you can imagine, this is one of the primary materials used in the battery.
Ready to learn more useless but interesting facts?
Why are "LiFePO4" batteries used instead of other Lithium-ion chemistries you may ask? The main reason is this: LiFePO4 and Lead-acid batteries are both about 12 volts. This is because — and I'm simplifying a tad here — each battery chemistry has an innate voltage they produce, and for LiFePO4 and Lead-acid this just so happens to be 12 volts.
Since Lead-acid batteries have been used in vehicles for so long, a 12 volt standard was developed. Because of this, most accessories and components use 12V as their standard, or a multiple of it. This is why you most commonly see 12V, 24V, or 48V components. Solar panels, fridges, and alternators are all designed based on the 12V standard. Other types of Lithium-ion chemistries like LiCoO2 (used in many electronics) cannot be formulated to produce a nominal 12V, which makes them incompatible with vehicle electrical systems and useless for van life.
Developed in the late 90s, LiFePO4 is the most promising newcomer to the industry. Huge strides have been made in recent years that are rapidly decreasing production costs, and they are now becoming economically competitive with AGM.
The main advantage of LiFePO4 batteries is their massive lifespan and high capacity to space ratio
Most manufactures say that you can expect 3000 to 5000 cycles and 10 to 12 years out of them. This, of course, depends on proper charging voltages and yatta, yatta… But wow, that’s about 4-5 times the lifespan of AGM.
Another check on the pro list for LiFePO4 is their high capacity to space ratio. This means that you can store much more energy in the same amount of space when compared to AGM. So if space is a major constraint for you, you may want to consider LiFePO4. Basically, you need two AGM batteries for every LiFePO4 battery.
They are also about 1/3rd the weight. Lithium is much lighter than lead, after all. This makes installation of LiFePO4 batteries a much easier process and saves a bit on gas over time.
But, they need to be "heated" to work well in the cold
A standard LiFePO4 can only be charged down to 32°F (0°C). Some manufactures offer a self-heating function. Charging below freezing will cause damage if the LiFePO4 battery lacks this feature.
That's why your phone dies in the cold but your car still starts.
A quick note about understanding Amp-hours (Ah)
If you’re shopping for a battery, you have probably noticed that their “capacity” is typically listed in “Ah” or Amp-hours. An Amp-hour is actually not a unit of capacity, it's a unit of power. What it means is relatively simple; a 100 Ah battery should be able to discharge 1 amp for 100 hours when fully charged.
To determine a battery’s capacity, you must account for voltage. The unit for capacity is Watt-hours (Wh) and the formula for Watt-hours is the Amp-hour rating times the nominal voltage. So, a 100 Ah 12V battery has 1200 Wh of energy (100 * 12 = 1200). Make sense?
To make things a little more confusing, you can’t use 100% of your battery’s capacity without causing damage over time. This is referred to as it’s “usable capacity”. The usable capacity of battery depends on the type. For example, you can discharge a much higher percentage of LifePO4 batteries without causing damage.
Here’s a chart to help you compare.
Battery Type | Ah Rating | Nominal Voltage | Usable Percentage | Total Wh | Usable Wh |
AGM | 100 Ah | 12V | 50% | 1200 Wh | 600 Wh |
LiFePO4 | 100 Ah | 12.8V | 90% | 1280 Wh | 1152 Wh |
Conclusion
For most of you it will come down to the money. Are you on a shoestring budget? Then AGM is probably your answer. Are you already spending 8 grand on the rest of your build? Might as well go for LiFePO4. Otherwise, you may want to consider all the factors like how much you expect to be in cold weather or your space constraints. In the end, it’s up to your situation.
Mohamed Bellamine
I'm the blogger behind Goo SolarPower. As a solar engineer, and a strong supporter of renewable energy. I've always been interested in Solar devices. I loves to write articles, guides, and tutorials about solar PV technology. Through goosolarpower.com I want to help people build and understand how solar power systems work.