Lithium batteries or AGM batteries? While there is no ‘one-size-fits-all’ answer to this, choosing a solar battery bank for your camper can be a daunting task. We’ve just switched over from AGM to Lithium (LiFePO4) Batteries for our battery bank. Here’s why we made our choice.
Quick note before we get started. This is just one part of an overarching “How to Install a DIY Camper Van Electrical System” series. If you’ve just stumbled on this article directly without seeing that, there are likely some things we’ve already covered. If you want to check out that step by step guide, you can do that here: https://www.explorist.life/diy-campervan-solar
Also, we have interactive solar wiring diagrams that are a complete, A to Z solution for teaching you exactly what parts go where, what size wires to use, fuse size recommendations, wire lug sizes, and all kind of other stuff to help save you time and frustration. You can check that out here: https://www.explorist.life/solarwiringdiagrams/
Switching from AGM to Lithium Batteries
The two most popular types of solar battery banks are AGM and Lithium. While flooded lead acid batteries are also an option, we aren’t going to talk about them today because of their many flaws (need to be vented, keeping up with chemistry, water levels, etc.).
When we originally installed our solar setup in our campervan, we put in Trojan AGM batteries. While we did want Lithium back then, there just wasn’t an easy, readily available drop-in battery for lithium (that we knew of). Now, however, the lithium battery industry has made huge strides and has produced a wide array of options that are easy replacements for AGM batteries. Alas, we have chosen to upgrade our battery bank from 700 amp hours of AGM to 600 amp hours of Lithium.
Battery Capacity AGM vs Lithium
Now wait a minute, how are we upgrading if we are going from 700AH to 600AH?
AGM batteries don’t like to be drained past 50% of their capacity, otherwise it will significantly decrease the lifespan of the battery. In essence, our 700AH of AGM was effectively 350AH. Lithium, on the other hand, can be discharged 100% and not affect the lifespan of the battery, making it a true 600AH of usable battery capacity.
For the sake of easy math in this post, we’re going to compare 200AH of usable battery capacity. That is, 2 x 100AH Battle Born LiFePO4 batteries versus 4 x 100AH Trojan AGM batteries. And while there are many, many brands out there of each type of battery, we’ve chosen these two brands because they are a) top of the line in their respective categories and b) the ones we have had personal experience with.
A Case for Lithium Batteries: Weight Savings
Battle Born LiFePO4 batteries are a direct drop-in replacement for AGM batteries, so they are very easy to install and get going. Let’s talk about some of the major pros of Lithium over AGM.
The first and most heavily weighing (pun intended) on everyone’s mind when building a camper van is weight. A 100AH Battle Born lithium battery weighs in at 29 pounds, for a total of 58 pounds for a 200AH lithium
The Cost of AGM vs Lithium Battery Bank
The biggest drawback of a lithium battery bank for your solar setup is the upfront cost. 200AH of Battle Born LiFePO4 batteries will set you back $1,900. The Trojan AGM batteries with a bank of 4 batteries for a usable bank of 200AH costs about $1,152. So choosing AGM over Lithium will save you $748. That’s a pretty big savings, right?
Well, not so fast…
Sure, the upfront cost of lithium batteries is a major investment. But let’s talk about long-term costs and replacement costs.
Lifespan of Lithium Batteries
Battle Born lithium batteries are designed to last 3,000 to 5,000 cycles. For this example, we are going to use the worst case scenario of 3,000 cycles. A ‘cycle’ is when a battery is drained, then recharged. Again, for the sake of the example, we will say a cycle is one day (use your batteries all night, then let them charge up during the day when the sun comes up). Denver gets an average of 300 days of sunshine per year, so in Denver, we would expect this battery bank to last 10 years at full capacity.
After that initial 10 years (3,000 cycles), the battery is still expected to hold 75% of its capacity, meaning that you would still have 150AH usable battery bank.
Lifespan of AGM Batteries
Trojan AGM batteries are designed to last 1,000 cycles. But, according to Trojan’s website, they consider their battery to be bad once it reaches 50% of it’s capacity. Comparing that to Battle Born’s 75% capacity isn’t exactly comparing apples to apples. Instead, we will take this graph (from Trojan) and adjust it based on how long the AGM batteries will last until they reach 75%, or 150AH usable battery capacity.
Based on this graph, that would mean that the AGM batteries will reach 75% capacity at around 525 cycles. Using our Denver example, that will last 1 year and 9 months. And that does coincide with the generally accepted lifespan of AGM batteries lasting around 3 years to 50% capacity.
Now that you know what type of batteries you are going to use in your DIY Camper van, now is a great time to head to the next lesson and learn how many solar panels you’ll need to recharge your batteries. Check that out here: https://www.explorist.life/how-many-solar-panels-are-needed-to-power-a-camper/
Everything that you are learning here is put to use in our FREE Interactive Solar Wiring Diagrams. If you haven’t yet, check them out as they are a complete solution for a camper van electrical system. Check them out here: https://www.explorist.life/solarwiringdiagrams/
Remember, this is just one part of a full camper van electrical educational series. To see all of the individual guides, click here: https://www.explorist.life/diy-campervan-solar
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22 Responses
In your diagram I can see that you have 6 lithium batteries in parallel with the positive lead at one end and the negative lead at the other. Is this how I should charge a larger lithium bank or would balance charging them be even better? Or would balance charging a lithium bank end up compromising the internal BMS of each individual cell?
The way I have shown in the diagram is indeed what I recommend even for larger lithium banks. If more than 6 batteries are needed, though… I’d recommend investigating larger batteries instead as paralleling more than 6 batteries gets cumbersome from a wiring standpoint.
This is super helpful. Thank you for putting it together and sharing. I’m trying to figure out my set up for my camper cargo trailer. I think I found the right solar kit but I was stumped when it came to batteries
Hi, you mentioned that the AGM battery’s life span shortens if regularly discharges bellow 50%. Is that not the case with Li batteries? Wouldn’t their lifespan also decrease if regularly discharged to 0% like you mentioned? I couldn’t find much info on that so I hope you can help clear that up. Thanks!
That is also true; but to a lesser degree. Now… how MUCH less of a degree I am struggling to find a source to back up a claim, so as far as that goes; “I’m not sure”.
My collaborator wants me to mount the batteries under the chassis to avoid dangerous fumes and danger of explosion. is this necessary with AGM or Lithium?
Neither AGM nor Lithium off-gas during usage, so no…
I very much do not recommend mounting batteries outside. Batteries like to be kept as close to 70 degrees as possible, so mounting them in side the climate controlled portion of your vehicle is ideal. If using lead-acid batteries, venting them outside is necessary, but not AGM or Lithium.
Wait so you said 200AH which is. 2 lithium batteries was 2000$? So you spent 6 grand on just batteries alone?? Jesus
I recommend performing a power audit to determine how many batteries YOU need for YOUR OWN project. Like you said, batteries are expensive and if you don’t need that much available battery capacity on a day-to-day basis, it’d be a waste of money. Here’s a tutorial for where to start with that: https://www.explorist.life/what-size-of-solar-system-is-needed-to-power-a-camper/
Here, you talked about which battery setup to use. Now how do we calculate, how much battery power you need?
This will help with that: https://www.explorist.life/what-size-of-solar-system-is-needed-to-power-a-camper/
Hi Nate.
I am currently battling this same question for my battery bank setup for my crusing yacht.
300 amp Lithium or 700 amp AGM.
Reading this post seems to make the choice clear but I am missing input on all the drawbacks that I am hearing in relation to the lithium option e.g.
– Risk of thermal runway
– Sensitivity to charging (cannot be charge directly from engine alternator)
– Generally more things to be aware of with DIY lithium as opposed to a more plug and play option of the “normal” AGMs
Can you maybe share your views on this?
Thanks in advance.
Hey Jakob!
With quality Lithium batteries like Battle Born or Victron, there is very little risk of thermal runaway. With less quality batteries with fewer quality control standards; that could be the case, but it’s still rare in the grand scheme of things.
Sensitivity to charging, Re: Can’t charge directly from the engine alternator. I don’t know where you heard that, but you absolutely can. All of the wiring diagrams on https://www.explorist.life/solarwiringdiagrams are set up to charge directly off of the alternator. They just need a special isolator that opens and closes at the higher voltages that the lithium batteries operate at.
LOVE this review! The only question I would have, is what would you recommend for folks living in a colder environment respectively year-round (Wisconsin, Michigan, etc.)? Do you think it would it make sense to go with AGM batteries per 3-4 months of the year being at or below 32F?
I recommend keeping your batteries, whatever type they are, inside the climate-controlled environment of the van/rv. Lithium batteries won’t charge if they are below freezing, but AGM batteries will have SEVERELY decreased capacity if they are that cold. Batteries like the stay warm.
@Nate Yarbrough, Further to this (going through Canadian winters): if Li won’t charge below freezing, then while the vehicle is at the ski hill the solar isn’t doing anything – correct? I get while the van is in motion or at least occupied, the batteries will stay warm when inside the cab, but once you are parked & shut off, you are not recharging.
If the batteries are below their charging temperature cutoff (about freezing) they will not charge, regardless of if you are driving or at the ski hill. If the batteries are above that temperature… they will charge regardless of where you are.
As a very good client to AGM batteries, I would choose lithium batteries in a blink. The pros are many but the main thing is AGM is not trustworthy due to it’s charge if its not fully charged (over almost 90%) and you can’t bring the sunrise earlier just because you are out of battery…
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Is there a kit I can buy to easily get enough battery life to run my portable AC all day and plug in at night. I can’t afford to also put the solar panels on right now. But I need to be able to stay cool now. I am no electrician so I need something I can shove under the bed, plug into shore power at night so I can plug in my AC, cell phone & computer during the day. I need to make it through 15 hours at least. Please email me: achaeos6@yahoo.com
Not really. You’ll be looking for a gas generator for that: https://amzn.to/2YXx5lY