Battery envy.
I recently received a very nice email from Mike in Missouri where he described converting his home off grid system to lithium batteries, at a cost of over $7000.00 USD! My own home system is still on old school flooded batteries because I have not recached a point of financial bounty where I can afford to cross over to lithiums. I’m truly envious of Mike and folks like him who have the means to pull it off. Lithium vs flooded
It did get me thinking, though: What is the true cost of lithium vs. other types of batteries? What are lithium users really getting for their money, and is it “worth it”?
It’s not as straightforward as I thought it would be.
As it goes, making an objective “apples to apples” comparison was not as easy as I thought. Manufacturers give themselves generous wiggle room when publishing specifications about their products, and real world data is hard to come by. Furthermore, our goal here is not to consider only battery performance. If that were all that mattered, there would be nothing to talk about. Lithiums would easily win, and it wouldn’t even be close.
What I’m doing instead is evaluating batteries on a “bang for the buck” basis. Although my analysis is not as scientific as I’d like it to be, I think I got close enough to give off grid radio amateurs a good frame of reference to make confidant battery decisions.
Accounting for variables.
It is very difficult to calculate meaningful numbers when there are so many variables. For example, in the “dollars per charge cycle” category, I provided a range based on the highest and lowest values for each type. But what about everything in between? This illustrates the futility of trying to pin down exact values for every possible scenario. If it could be done at all, it would fill hundreds or even thousands of lines on the spreadsheet. Lithium vs flooded
The ground rules. Lithium vs flooded
The analysis was based on a 100 amp hour battery of the type that would be used in a permanent home installation. I also assumed that the system was built and maintained by the average hobbyist paying retail prices. So, we are not looking at high end batteries made specifically for solar power. Most radio amateurs buy their batteries from a big box or on line retailer, so I approached it with that viewpoint.
Also, I did not include small batteries used for portable or QRP operations. Absorbed glass mat (AGM) and lithiums are affordable in lower capacities. Since hardly anyone uses flooded batteries in these applications there no benefit to analyzing them. If there is reader interest, I’ll do a separate article comparing AGM to lithium for portable & QRP.
I included median costs in some of the categories. This is probably the best way to even out the inconsistencies and offer a firm number for each type of battery. 
The results were…interesting. Lithium vs flooded
Placing the numbers side by side provided some surprising insights. I thought for sure the lithium batteries would sweep every category. If all we cared about was battery performance, they would. Yet, let’s not go into this looking for a predetermined outcome. The dollars per amp hour purchase cost is the true price you will pay up-front for the battery. The dollars per charge cycle is the price of the battery amortized over its entire service life. Or, put another way, what it will cost every time you charge the battery. Lithium vs flooded
As expected, the old school flooded batteries have the lowest initial purchase cost. But does that low price tag pay off over the long run? Well, actually, they cost more, but not a lot more, than lithium battery technologies in terms of the lifetime ownership amortization. The AGM batteries are the most expensive to own over time. “But,” some hams will say, “flooded and AGM batteries will need to be replaced more often than lithium.” That is true. Does it matter? Lithium vs flooded
So the question now is, do how many flooded batteries can one buy for equal to or less than the cost of one lithium or AGM battery? Litvs flooded
Some basic math. Lithium vs flooded
Let’s run some examples using our median numbers. The median price of a 100 amp hour lithium battery is $600. Therefore:
$600 ÷ $131.00 (median flooded battery price) = 4.60
$600 ÷ $275.00 (the medianAGM battery price))= 2.20
What this means is for the purpose of replacement, 4.6 flooded batteries or 2.20 AGM batteries equals one lithium. Here’s what you get for your money in terms of long term use:
Lithium: 1.00 batteries x 2500 to 3500 charge cycles per battery= 2500-3500 charge cycles.
Flooded: 4.60 batteries x 300 to 1000 charge cycles per battery= 1380-4600 charge cycles.
AGM: 2.20 batteries x 500 to 1200 charge cycles per battery= 1100-2640 charge cycles.
What this tells us is that when evaluated for total charge cycles as a function of cost, flooded and AGM batteries compare very favorably to lithiums, and depending on the situation, can even exceed lithiums. Wait, rewind this article a few paragraphs. Didn’t I just say that flooded and AGM batteries actually cost more? Yeah, I did. This illustrates the frustration of making this analysis. What is “better” and “cheaper” depends on what data one uses to formulate a decision.
A huge hole in all of this.
Before all you accountants & statisticians out there pepper me with critical comments and emails picking apart my numbers, let’s preemptively get a few things out of the way.
These calculations are based on medians, averages, and manufacturer provided data that we all well know is padded. As they say, “your milage may vary.” How batteries are used, stored, and maintained can profoundly effect performance and service life. There is also an issue of build quality. Are $300.00 off brand lithium batteries as good as the $900.00+ popular name brands? Will you get the same performance? I don’t know, but my gut says probably not. If you are a survivalist/prepper or EMCOMM person, do not let your mission-critical communications depend on the cheapest battery you can find.
If any reader out there is qualified in statistics and would like to address this issue in more/better detail, please reach out to me and we’ll do a follow up.
Other things to think about.
Many charge controllers cannot be used on lithium batteries. If you are switching to lithium from another type and you have an incompatible controller, that expense will have to be added to the total cost of the upgrade.
Also, you can use lithium batteries at almost any temperature but they cannot be charged when they are below 32F/0C. This refers to the internal temperature of the battery, not the ambient air. Charging at sub-freezing temperatures will permanently damage Lithium batteries. But don’t worry, they have internal circuitry that does not allow charging if they are too cold. Flooded and AGM batteries can be used or charged at any temperature a ham may experience, but the performance degrades at the high and low extremes.
So what battery should you get?
What battery is “best” for you cannot be determined by an internet blogger. The purpose of this article is to give off grid amateurs a perspective other than electrical characteristics and performance. As you can see, the ownership cost of any type of battery depends on personal priorities.
I’m not trying to promote or disparage any particular battery technology. As for what I would personally pick, if I had the money I’d dump my flooded batteries immediately and go with lithiums. As economies of scale bring the cost down, lithiums will become more attainable. At some point the numbers will tighten and flooded/AGM batteries will no longer be price competitive. As the data shows, the true cost of ownership is more complicated than just the initial purchase price.
Good post,Chris have taken into account that a 100amp hour flooded or agm battery should only be discharged about 50% or it could shorten its life.while a lithium can be discharged to about 90%.
Keep up the great work
Ve7gde
You are right Jack, and I regret leaving that important detail out of this article. Flooded batteries can not (or should not) be discharged below 50%, so in effect you have half a battery. It’s like having a 100 gallon gas tank on your car but can never use more than 50 gallons.
Thanks for your input!
A quality real deep cycle battery like Crown or Trojan make can be taken down to 20%. It will shorten the life if you do it regularly, like not having enough amps to do what you need. It will not damage it or shorten life if only done on a bad week of no Sun. It will fully recover. The important thing with a flooded battery is proper maintenance and equalizing them once in awhile, they will last. I really like your news letters, I know they are lots of work ,Thanks !
Thanks for your support! It’s true that better quality batteries on the whole will last longer than the basic stuff available at Wal Mart. I work professionally as an electronics tech in a communications facility; we have flooded batteries that are 20+ years old and still going strong.
Good article when comparing Lithium-ion to Flooded or AGM. Not so good when comparing Flooded or AGM to LiFePO4. We mustn’t lump all lithium technologies into one basket. For lithium-ion, 300-500 cycles are quite normal without any special care given to charging. For LiFePO4 2500-3000 cycles is normal without any special care given. Lumping these two together creates an erroneous outcome in the numbers. Next, we will also never get a thousand charge cycles out of AGM or flooded technologies, without experiencing diminishing capacity along the way. It is also important to point out the AGM or flooded battery is only half of is listed capacity. This is why we need to double up on AGM or flooded to meet our capacity requirements. With lithium-ion or LiFePO4 what you get is actually what you get. A 100ah AGM or flooded battery only truly nets 50/60% of its stated capacity. Discharging it any lower will reduce the cyclic life of the pack, forcing us to replace it much sooner than lithium-ion or LiFePO4. With lithium-ion or LiFePO4 we get an honest 90-95% of the stated capacity without long term damage to the packs.
There is another aspect of AGM and flooded not found with lithium-ion of LiFePO4. Peukerts law accounts for the diminishing capacity under repeated heavy loads. To make up for this effect, we again stack more packs in parallel to minimise the loss of capacity. This doesn’t happen with lithium or LiFePO4 batteries, so there is no need to double up on parallel sets as with AGM or flooded.
Finally, the cheap battery issue is a real one. If we focus on quality cells from manufacturers like Sony, Panasonic, Headway, A123, … we never see the quality and capacity issues mentioned in your article. This is strictly a problem buying repackaged used cells from auction sites where cells have been repackaged t represent something they are not. For this, we need a reputable seller or critical.
Anyway not blasting your article! AGM and flooded do appear cheaper to buy at the cash register but not always the best long term investment.
73
Julian oh8stn
Hi Julian, lately you seem to have a fixation on me. Are you OK? I’m not sure how respond to a guy who leaves a long reply detailing everything wrong with my article, ends it by saying he’s not “blasting” me, and then proceeds to post an even lengthier article on his own blog further picking apart what I’ve said…and doing all this in less than 24 hours. Maybe I missed the sarcasm. Maybe over in Northern Europe “blasting” means something different than in the USA.
Not all my articles are home runs and I will concede that I should have taken more care to inject additional factual clarity into this article. Still, what is there is useful and the reader will leave better than they came, as they do with all my articles. This website does not have sponsors. I do not get cool free stuff to try out in exchange for favorable articles, nor am I wealthy enough to constantly buy new equipment for the purpose of blogging about it. I work a full time job; I do not have time to play radio and blog and post on social media all day. In other words, I do the best I can with the time and resources I have.
Anyway, I still respect you even if you don’t respect me. Your reaction is disappointing but I nonetheless wish you the best.
Julian,
On your blog (https://oh8stn.org/blog/2022/02/16/lead-acid-vs-lithium-or-are-bloggers-lying/) you say that the off grid ham is now on your “hit list” because you perceive a bias (whatever that may be?). I think that your corporate-sponsored roleplay is more biased than the off grid ham’s blog. How many times can you say “powerfilm” in one video before dropping a bunch of affiliate links? You raise some good points about the analysis in this post, but I think that your two-faced reaction to this post is uncalled for and disappointing! Also I find that both of you are making a huge error by considering exclusively amp-hours, when you should be considering watt-hours. A typical lead-acid battery will be 12 volts, but a lithium cell is approximately 4 volts. For any comparison to be accurate, you need to compare the available energy over the full discharge curve of the battery, down to the minimum voltage that is decided per the application (depth of discharge). You will find that your lithium batteries will also wear out disproportionately faster the lower that you discharge them.
Thanks for your support Aaron. I agree that Julian having sponsors throwing free stuff at him makes him a less-than-perfect messenger to be telling me I’m biased, or as he put it, “subjective”. Still, that does not necessarily take away from the value of his work any more than technical omissions or oversights takes away from the value of my work. We all have something to contribute; there is no need to get in a pissing match over who is more pure.
I do take a lot of offense to the implication that I am “lying” (in the title of his post).
Once again, thanks for your support!
Great article, Chris! I’ve often wondered about what the price differences would be between the different battery types but never got around to doing the math myself. Getting some ballpark figures about the actual costs, recharge cycles, etc. is very helpful. You’ve proved what I already suspected, that it’s damned hard to get reliable numbers from the information provided by a lot of manufacturers. It gives us enough info to work with to at least get a general idea of costs.
Hey Randall, yes these are ballpark figures but should get you pretty close. I never totally relay on manufacturer data but we can only work with what we have.
I’m right in the middle of my Solar project. 4 lifePo4 100 AmpHr batteries in parallel and series for a 24 volt system. New combo charge controller/inverter and 4 210 watt panels. All is working well on grid power. All is well on PV. Utter failure on battery. Why? Cables. I scrimped on the battery cables trying to use #4 AC line. I was getting 7amps out instead of the needed 30. So, don’t scrimp on quality cables.
Thanks for the battery battery info.
Hi Max, by saying “#4” I assume you mean 4 gauge wire? That should be plenty big enough for most installations unless there is some unusual situation, like a long cable run. Some hams cut the clamps off automotive jumper cables and use them to connect their batteries. I’ve done this myself and it works pretty good.
Another few points to add to the above: Efficiency. The 4 lifePo4 batteries I installed over a year ago charge noticeably faster than the flooded batteries they replaced. On the discharge side the increase in efficiency is almost lost in the fact that they have so much usable power left at 60% state of charge compared to flooded batteries. Flooded batteries were approximately 90-92% efficient whereas lifePo4 are 98% efficient. The lithiums produce heat that is almost not noticeable in use.
Another advantage for me is much less generator run time. Living off grid in the PNW there are 3 months of each year that I run the generator regularly and a month of that daily. The greater efficiency shows up there too. Add to that the fact that lithiums do not need an absorb charge. I can not set Absorb = 0 on my system but Absorb = .1 (hour) is fine. So the generator runs at the full charging capability of my system right up to that short absorb, which serves kind of like a cool down) and is done. No more do I have to run the generator for hours after the bulk cycle and only drawing 500-600 watts to complete the absorb *required* for flooded batteries. There is much lower use of fuel now, including not having to make the 3 hour round trip to get fuel at 13 mpg ;-(
Hi there JR, you are right batteries in general are very inefficient, meaning, you have to put a lot more energy into them than you get out. Lithiums close that deficiency quite a bit. In your case the the cost of you lithium batteries is partially offset by lower fuel costs to charge them.
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Have you seen these? https://www.18650batterystore.com/collections/lifepo4-prismatic-cells/products/eve-lf280k
$900 normal price, plus a $200 BMS, and yeah, you have to do some of the assembly yourself. But a (claimed!) 6k cycle life? Using a price of $1200:
$/cycle: .20
Ah/$: 4.28
And they’re quite a bit lighter than the lead batteries, too. I’m not saying they’re for everyone, but they’re pretty dang impressive.
Hi Derek, yes they are impressive! I use lithium batteries in my portable station and the performance is amazing. I’m waiting for the price to come down so I can convert my home system
Nice article, I am looking at this investment but with a clearer vison
Than before. de wb5eat
Hello Bob, thanks for your comment. The whole purpose of this blog is to give amateurs useful, practical information they can use in the real world.
This is a well-written article and very informative! Like most ‘real world’ people, my disposable income is limited and, as has been stated, pretty much everything in HAM radio is a compromise.
I enjoy lithium batteries for their lower weight and flatter discharge curve, and can squeeze a surprising amount out of them when running QRP and slightly above. Digital modes, for example, including Winlink, don’t need a lot of power to be heard over a long distance. But, in my job I also have access to a ready supply of lead-acid batteries from uninterruptible power supplies which are past their service life. They’re heavy and don’t have much capacity left but in my experience have been more than adequate for portable operating, giving me reliable power for a few hours especially when paired with a boost-type voltage converter / regulator, even when running SSB phone. Anyway, vert nice article and website, and count me as a subscriber!
Hello Greg, welcome to Off Grid Ham! I’m really glad to have you along.
As you indicate, even a nearly-spent battery is good for a little more juice. I use lithiums for my portable rig. Repurposing UPS batteries is fine as long as you are ok with lugging them around.
Thanks again, and I hope you’ll come back soon.
Hi Chris, really appreciate your efforts with the blog here. Regarding your comment under the ground rules, I would be very interested in a follow-up covering portable ops. I seem to spend a lot of time pulling my hair out trying to figure out the best bang for buck on everything and frequently get to the point of analysis paralysis. Any help is always welcome. Keep up the good work
I’ll keep your request on file, JR. Thanks for your input!