In the first post of this series:
I explained the chief downsides of Lead Acid batteries, the tried and true battery technology that powers essentially every RV electrical system made.
And in part two, I explained about the advantages Lithium Ion batteries, the latest and greatest battery technology to come along.
In particular, I raved about the new hotness on the battery chemistry block – the fabulous and happily non-explosive Lithium Iron Phosphate (aka LiFePO4 or LFP). On paper at least, LFP batteries seem to be ideal for RV house battery use.
Other than the expected “pioneers get arrows in their back” downsides of exploring any emerging new technology, the one chief downside of lithium I pointed out was the cost.
There is just no ignoring that a battery bank made up of quality AGM-style lead acid batteries will cost a lot less upfront than a similarly sized lithium battery bank.
But if you consider the lifetime cost, and the fact that lithium batteries should (theoretically) far outlast even the best high-end AGM’s, the math starts to look compelling.
So lets look at the numbers….
Lead Acid Costs
Lead acid batteries can be had at almost any price – ranging from generic no-name flooded cells on up through list price name brand AGM batteries.
And because lead acid batteries are so common – it is actually possible to find decent-enough (hopefully!) batteries for sale used. We know of people who have gotten essentially unused AGM batteries that were being scrapped from other projects for pennies on the dollar.
But for the sake of comparison, lets take a look at the prices you might find on new 8D-sized AGM batteries, the type that would be considered the prime choice for building a large RV battery bank in a pre-lithium world.
- One of the most respected AGM battery makers is Lifeline. The Lifeline 8D AGM battery has a total capacity of 255 amp hours, and weighs 158 lbs. Googling around, I’ve found this battery available ranging from around $660/ea on up to a staggering $966/ea!
- A similarly specced off-brand 8D AGM costs around $550/ea.
- If you’re really persistent you might be able to find a wholesaler willing to sell direct, and you can end up with name brand 8D AGM batteries for less. Our friends Sean & Louise of Our Odyssey just bought a new battery bank of eight Trojan AGMs and they managed to only pay just $488 per 230 amp hour battery, each weighing in at 167 lbs. (Their post is very worth checking out, as it goes over the math they used to analyze the lifetime costs of their bank.)
If you are certain that you will be able to keep on top of the maintenance required (and are willing to put up with the other drawbacks), you can save some money by going with quality flooded cells (often referred to as ‘golf cart batteries’), such as 2x Trojan T-145’s which will give you 260 amp hours for around $408 total cost (and 144lbs total weight).
To keep things simple for comparison purposes – we’re going to use a reasonable “good” average price of $2.30 per amp hour (or $460 for 200 amp hours) as our baseline for comparing the cost of lithium vs AGM lead acid batteries.
And keep in mind, when talking about any lead acid battery, you should only consider 50% of the bank to be “usable” power.
Lithium Battery Costs
One of the hardest things about buying lithium batteries for RV use is finding someone actually willing to sell them. A few years ago when I designed the electrical system for our Oliver trailer, I actually fantasized about going lithium, but I couldn’t find a practical supplier at any cost.
You need to keep in mind that with lithium, it is about more than just finding a battery – you also need to design your entire DC electrical system to be lithium compatible. You need to make sure in particular that it is impossible to over charge or overly drain the lithium batteries, which can easily permanently damage them.
To do this, most lithium systems incorporate some sort of EMS (Energy Management System) that can cut off current to/from the batteries when necessary. Some battery suppliers integrate this functionality right into the battery, others sell it as part of a complete system package, and if you are building a system from scratch you will need to procure all the necessary components yourself.
These are a few of the lithium battery providers I tracked down in the course of my research:
Marine & High End Suppliers
There are now a few big name manufacturers bringing lithium battery systems to market primarily targeting the high-end marine market (where cost is no object).
- Valence: Valence sells very advanced lithium iron magnesium phosphate (LiFeMgPO4) battery systems, generally custom built with custom pricing. If you have to ask, you probably can’t afford it. But if you don’t have to ask, this is a good place to start planning the system for your next mega-yacht.
- Victron Energy: We were very impressed by the specs of the Victron inverter / chargers (and ended up buying one – we’ll detail why in a later post), so it was really exciting to learn that Victron is bringing a line of LiFePO4 batteries to market. But to date, Victron appears to be only in trials, with no pricing available yet. When the batteries are ready, Victron will be updating their inverter / chargers to communicate directly with the battery EMS system – a very nice feature that sadly does not seem possible as a retrofit.
- GenaSun: GenaSun sells complete lithium systems including battery management circuitry. A 200 amp hour setup (designed with redundancy for the cruising market in mind) currently sells for $5500, and weighs 70lbs. A 360Ah setup sells for $7,700. And keep in mind – “An on-site system inspection by a Genasun technician or representative is required to activate the warranty on batteries and battery management systems.” This isn’t a system for the do-it-yourself type.
- Mastervolt: MasterVolt has been selling lithium battery systems to the marine market for a few years now, and the 12 volt ML 12/320 is appropriate for RV use – delivering a sizable 320 amp hours in a 120lb package that will set you back between $6,600 and $8,360 (the range I found on Google today).
Pre-Built RV Targeted Packages
There are some new companies emerging targeting the RV market with slightly more practical pricing on pre-packaged systems.
- Lithionics: Lithionics offers several lithium batteries specifically targeting the RV market, but they do not currently list any prices. Lithionics was also under evaluation for potential resale by AM Solar, but the Lithionics battery failed under their typical RV use, and AM Solar ended up reporting that: “We have severed ties with Lithionics for several reasons that are very important to us and our business ethics and will not be following up with a second round of tests on the Lithionics batteries.” AM Solar has a well respected reputation in the RV world. Based on their public statement, I was hesitant to pursue a Lithionics system until all the issues have been demonstrably resolved… and I will keep an eye on their progress for our future projects. (Though the Lithionics three year warranty is somewhat reassuring.)
- Smart Battery: Smart Battery used to be a distributor for Lithionics, but now they are going it alone designing their own pre-packaged battery systems. I’ve noticed their design go through several iterations over the past few months, but the current pricing listed has a 200 amp hour system for $2,299, and a 400 amp hour system for $3,399. I’ve been in regular contact with Smart Battery, and they seem to understand what it takes to build a reliable battery system. But until they have demonstrated a track record, we consider them unproven but promising. There has been some mention that they might like to send us a sample system to test – and if they do I will certainly share our results.
- AM Solar: As I mentioned above, AM Solar had been evaluating Lithionics but is now pursuing having its own custom made LiFePO4 battery systems made to resell. They have had great success with this model building custom RV-targeted solar systems, so I intend to keep a close eye on their progress. The folks at AM Solar are fully RV focused, and they have a great reputation.
Not everyone is willing or able to build a system from scratch, and thus we think that these pre-packaged battery systems will be the way most RVs will eventually integrate in lithium battery banks.
We are watching this evolving industry closely.
(BTW: One thing about at least two of these battery companies I have noticed that I find tacky is the claim “Made In USA” tacked on to the batteries they are selling. But in truth, the batteries are only assembled in the USA, and as far as I am aware all LiFePO4 battery cells are currently made in China.)
Do It Yourself Wholesale Suppliers
If buying one of the pre-packaged solutions linked above isn’t in your budget or isn’t your cup of tea, there is an opportunity for hands on folks to custom build their own solutions. There are several companies catering to the electric vehicle hobbyist market that wholesale LiFePO4 cells imported from China, and they are willing to sell to anyone who clicks the ‘Buy’ button.
If you go this route beware that you will be treading into rather uncharted waters potentially without a lot of support.
Of course, that is what we chose to do….
Elite Power Solutions: After getting a lot of our more technical questions answered competently by the helpful techs at Elite Power Solutions, we decided to make a go of building a system around five of Elite’s GBS-LFMP100AH 100 amp hour battery packs. Elite’s price for these packs was $620, making the list price of our battery bank $3100.
But to create the 500 amp hour battery bank that we desired, we actually had to disassemble five 100 amp hour 12-volt batteries of four cells each, which we then re-assembled (using a hydraulic press) into 4x 500 amp hour 3.2 volt batteries (with 5 cells each). We then bolted these batteries together in series to make a single 500 amp hour 12.8 volt block… weighing in at just 140 lbs.
As I said, a process not for the faint of heart, and it took us nearly 8 hours of unscrewing, screwing and pressing. But it was also a heck of a lot of fun to build our own battery bank.
Elite isn’t the only provider of LiFePO4 cells – if you search the electrical vehicle market you will find many other companies selling LiFePO4 cells. We know of one other RV’er planning an even more affordable system using HiPower cells – purchasing 600 amp hours for $2,880 (plus shipping from China).
We honestly didn’t evaluate a ton of the alternative in this space – we went with Elite because they were nearby to where we were at the time (in Phoenix), knowledgeable, had stock on hand, and they were excited to work with us. They even invited us to their facility to use their equipment and coached us on building our bank. This was invaluable to us.
And so far we have been very pleased with the followup support we have gotten.
But… To be clear, if you are not electrically knowledgeable and ready to assemble the components of an EMS (energy management system) from scratch – building your own battery bank from components is probably NOT a good path to pursue!
You might be better off pursuing a more integrated system where the EMS that protects the cells is hidden and integrated inside the battery, or sold as a complete system.
Or… Wait a few more years till all this stuff is cheaper, and mainstream.
The Lifetime Cost Math
Our goal in building our battery system was a system with at least 400+ usable amp hours, which could run one of our roof air conditioning units full blast for around 2-3 hours before resorting to the generator – perfect for keeping our cat Kiki cool while we leave her behind in the bus to run errands.
(When it comes down to it, everything in the end is really all about the cat…)
To get that capacity we needed roughly 800 amp hours of AGM (at 50% usable), or 500 amp hours of lithium (at 80% usable). If we take the numbers above for simplicity sake (it’s difficult to directly compare them, as the packaged batteries come in different sizes), the upfront costs we were comparing were:
- 800 amp hours of 8D AGM – $1840
- 500 amp hours of lithium – $3100
Things look bad for lithium based on upfront costs.
For those of us full timing and/or anticipating a lot of unplugged time in our RV – this is where the lifetime costs start to look promising.
Laboratory results indicate that we should expect to see 2,000 to 5,000 cycles out of a well cared for LiFePO4 battery bank. In contrast, even the best deep cycle lead acid batteries are typically only good for 500-1000 “deep” cycles.
Cherie and I crafted up a quick spreadsheet that tries to make the comparison as simple as possible, summarized:
No matter how we played with the numbers, formulas, and assumptions – over time lithium worked out to be at worst break even compared to AGM, and under most scenarios showed the potential to come out way ahead by not needing to replace our batteries every couple of years.
When you then consider the weight savings, and all the other advantages Lithium Ion batteries, suddenly investing more up front in a lithium system seems very worthwhile indeed!
For anyone planning on heavily utilizing their battery banks, or trying to maximize a solar installation, lithium makes particular sense. For those that mostly move from plug to plug, with just a night or two off grid while in transition – the costs probably won’t make sense for a long while.
The rest of the system…
Of course, it takes more than just batteries to build a proper lithium battery system.
Here are all the components of our system, and their cost:
|Elite Power Solution GBS 100Ah Cells||$3100|
|Elite Power Solutions EMS CPU||$240|
|Elite Power Solutions EMS-4SB Sense / Balance Boards||$66|
|Victron MultiPlus 3000VA Inverter / Charger*||$1890|
|Victron Blue Power Panel & Battery Monitor||$427|
|Misc EMS Components (fuses, contactors, etc.)||$500+|
* Victron gear is fabulous, but relatively hard to find in the US market. The best prices (listed above) and availability I found was via Ward’s Marine, but I always encourage shopping around.
It all adds up fast. We have over $6000 invested in our battery & electrical system … so far. Of course, things like the inverter/charger and battery monitor we would have needed even with a traditional AGM system.
But – off-grid power is not necessarily cheap!!
I’ll go into more details on the features and reasons we selected our inverter, and the details of the battery EMS system we built, in a future post.
The Next Chapter
So now I’ve explained the system we built, and how we justified investing in it.
But how has it been working out so far? In what ways has theory failed to match reality?
Overall we are still just getting started exploring what is possible with our electrical system, and mostly we are loving our lithium battery bank. But even so, there have already been a few hiccups along the road.
But I’ll save those stories for the next chapter…
By the way, we should note – we are not trying to motivate anyone to follow us on this path. We are not selling these batteries, we are not affiliates with any battery dealer, we paid for all our components, and we do not have any financial stake in the technology beyond our own systems. We are simply full time RVing technomads who are designing our own cutting edge home & office on wheels, and are sharing our research & project. Of course we’d love to have more folks out there pioneering and helping us take the arrows in our backs. Right now, we do not consider this technology ready for most, and those contemplating this technology need to be a bit savvy with electrical and battery technology before jumping in.