LiFePo4 batteries – how low can they go?
Not sure if anyone has checked recently, but LiFePo4 batteries suitable for home energy use have been dropping in price precipitously.
Well reviewed 12.8v 100ah (1280 wh) batteries have dropped to about $330 each with free shipping.
Does anyone have any idea how low in price they could go? With prices like this is it worth revisiting old assumptions about home battery use? Has anyone tried them?
Based on price history data, they have gone from about $600 -> $330 this year alone.
A few examples (no idea the difference between them):
https://www.amazon.com/LiFePO4-Battery-Perfect-Applications-Warranty/dp/B084DB36KW/
https://www.amazon.com/LiFePO4-Battery-2000-5000-battery-Off-Grid/dp/B08FMTRYPT/
https://www.amazon.com/Zooms-LiFePO4-Battery-Rechargeable-Phosphate/dp/B094NN5KWY/
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Well, other than the fact that , "Random no-name manufacturer that has some good amazon reviews" is a pretty low bar to set for quality -- these are also just a step above bare battery cells. They have a pretty basic management system that's meant to make them a drop-in replacement for a single 12V lead-acid battery; I wouldn't necessarily trust them to build a larger battery bank for substantial energy storage. Yes, prices for bare battery cells, recycled / secondhand batteries, and questionable off-brand stuff seem low -- but to use them in a practical home energy storage situation, you need a fair bit of supporting equipment, some electronics skills and knowledge, and be willing to accept the liability of something that doesn't have a slew of compliance & safety approvals. In short, for the DIY crowd, it's great that prices are coming down, but for mainstream use the availability of these products means nothing, except that hopefully the prices of commercially available energy storage systems will continue to decrease.
As an aside, if you're in the DIY crowd, I'd recommend looking at used EV battery packs rather than these -- there's a handful of recycling companies that sell these, and there seems to be a community of people who have built their own energy storage systems using these batteries. Probably cheaper than what you're linking, maybe better quality, and dealing with individual cells provides the opportunity for a better battery management system.
Other than not being able to operate as well in lower temps, there are several advantages to LFP batteries over the NMC ones used in cars. About 3x the lifetime charge cycles, much safer (no runaway fires), etc. The main reason they're not used in cars is their lower power density- something which doesn't make a lick of difference in a house.
Plus, at scale, these batteries don't have cobalt, which is the least "green" component of NMC battery tech. BattleBorn batteries haven't dropped as much as other brands in price, but they do sell whole house systems of LFP batteries. https://battlebornbatteries.com/product-category/battle-born-bundles/off-grid/
Agree with you about the unknown quality. And the lack of any proper certification makes the idea of using them in a home questionable.
Their sales materials indicate they can be used up to 4 series, 4 parallel which is getting to be a decent sized bank. Not sure how this works if there is no way for the battery management systems to communicate, I don’t see any connections on the batteries besides the main positive and negative terminals.
We love our reputable brand LifePo4 bank as it replaced a hideously large 8 x 6V LA bank that drank too much water. I wouldn't touch all those cheap single batteries out there. With these types it's all about the balance of the system and you want to make sure it's well tested. That means spending over $6500K for one that should last 30 years.
What brand of LiFePo4 did you go with? I'm ready to replace my 8 Trojan 6v battery bank and trying to make the final decision on brand.
Thanks, Daniel
I've had a lot of issues with random lithium batteries from on-line retailers (replacement batteries for E-bikes, power tools, phones and laptops). Almost none of them ever had the nameplate capacity and most had questionable construction and wiring/fusing/electronics details.
It is very easy to build a lithium ion pack but very hard to build one that is robust, tested and durable. I wouldn't touch any of these with a 10' pole for use in your home.
Overall, lithium ion has gotten surprisingly cheap over the years. Significantly better cycle life than lead acid, more power and much higher round trip efficiency. A good LiFePo4 pack is worth it.
I would never use random batteries of this chemistry in a continually operating, unattended system. I'd really rather not use any "random" batteries at all. If you have a failure, all that stored energy will get out and cause a lot of damage. I like to say that stored energy is like an angry genie, and that angry genie doesn't care who or what he hurts on his way out of the bottle. This isn't a good place to try to pinch pennies. Even with quality equipment, I still recommend building fire rated battery rooms. At work I build 1 hour rooms, but they're monitored (with hydrogen sensors interlocked with exhaust fans, and a sprinkler system). For a home, a 2 hour room might be a good idea (that's four layes of 5/8" drywall, two on either side of a studwall, AND the ceiling if you have attic space above). That fire rating buys time for you to get out of the house if the batteries light off.
All that excitement aside, a 1,280 watt hour battery pack is storing a little over 13 cents worth of electricity at the US average per-kwh electric rate. Put another way, that battery pack is storing about an hour's worth of electricity for a typical home. If you're not going off grid where you really have no choice, I would not recommend home battery storage. Just run a grid tied solar system -- use net metering if it's available in your area, otherwise go with a peak shave system. Batteries are a lot of extra cost and risk for very little real benefit.
Bill
As with a lot of things on Amazon, it feels like the marketing has outpaced the quality. I, too, would be weary of these fly by night brands. Going back literally 20 years, I've bought PowerSonic batteries from Mouser, as PowerSonic was well respected at the time. PowerSonic (unsurprisingly) is now in the lithium business as well. Their 1,280 Wh LiFePo4 variants seem to be in the $1,000 range, though.
But, like I said, I bought batteries from PowerSonic 20 years ago and they're still here. Something tells me "Zooms Younger Bolder Stronger" (https://www.amazon.com/Zooms-LiFePO4-Battery-Rechargeable-Phosphate/dp/B094NN5KWY/) was not around 20 years ago...
Check out Will Prowse’s YouTube channel. He has a lot of useful information and is very honest. He buys all the equipment he puts on the test bench and accepts no freebies. lifepo batteries (in general) are safer than other lithium batteries and will endure thousands more charge/discharge cycles than other lithium battery chemistries. They have less energy than the other chemistries per weigh but are still excellent and are the lithium battery of choice for stationary application like home uses. Check out this video of his where he tests his new benchmark for Lifepo batteries.
https://www.youtube.com/watch?v=wMJbbXPD0JA
Very interesting. Thanks for sharing.
I have been waiting for this thread! I bought an ampere time 200 ah battery and paired with a pure sign wave inverter, charger and some 200 watt panels and a mppt controller. It all works great - not grid tied but with the grid as a backup. I did this about 6 months ago and its just gotten cheaper and easier since.
Lithium ion batteries are very challenging, lot of details have to be done properly from the start of cell manufacturing to building a pack.
You can see that even the big guys (ie Bolt recall) can be caught by a very small defect creating huge issues. The problem is most packs have hundreds of cells in them, so even if you have defect in a very small percentage of cells, it could effect all the packs.
When things go sideways even the electrical energy stored in pack is an issue. A 10kWh pack has the equivalent energy to a liter of gasoline, which has to go somewhere.
Chemistry and cell safety has come a long way since the days of exploding laptop batteries. Since most cells still use a flammable liquid electrolyte, there is always a risk. LFP is overall less energetic, but not zero risk.
Cold weather charging is an issue for any Lithium chemistry that has a carbon anode. Charging at higher rates in cold can cause lithium to plate on the anode, LFP and NMC have the same issues. Since LTO has a different anode so it doesn't have the same issues but they are much less energy dense. If you want your batteries to last, best to charge them inside.
NMC cycle life has come a long way, in a well designed system with quality cells, thousands of cycles is not an issue. I think the reason you don't see so much of it is there are fewer companies making it and generally won't sell cells to random battery manufacturers. There was a big push for LFP a while back in China which meant everybody was making cells which is why there is more packs out there. I remember going to cell manufacturers that felt like nothing more than a warehouse where someone picked up some roll to roll machinery and a bunch of workers to stuff jelly rolls into cells.
Pack design itself is also not as simple as welding up a bunch of cells and shrink wrapping it. For example, a cell by itself could be fairly benign, even if you put a nail through it (test to simulate an internal hard short). Now you wire say two dozen of them in parallel for a pack. Unless specifically designed, when a cell shorts out, all those other cells will dump energy into it making a big mess. Even simple things like how far cells are space and what is used as separation between them makes a big difference.
There is also a lot that detail that needs to go into the electronics design. This means all packs should monitor each series element, pack temperature and current. Since cell voltage is a critical item, you want redundancy on sensing and diagnostics (broken wire detection, balancer operation check, reference voltage check). There should always be at least two layers of overcurrent protection, a physical fuse plus an electronic fuse. The pack also needs to have provisions for overcharge and over discharge protection.
Overcharge is obviously bad for any lithium cell. Over discharge is one that is rarely handled well in packs I've seen. Once a cell is over discharged, especially if allowed to sit like that, you get copper dissolution. Besides effecting capacity, when recharged the copper will plate out and grow dendrites which can short out the cell. Once a pack is over discharge and allowed to sit, it is pretty much garbage. This can be an issue for something that has sat on a shelf for a long time.
So always charge your tool batteries at the end of the day, don't run them flat and they'll last much longer. If they'll be stored for a while, make sure they are charged.
Someone above stated LFP isn’t used in vehicles, which is definitely dated info. Tesla is shifting to LFP even though it has lower density. They will only do NMC for the biggest capacity packs.
Signature Solar gets a good pack with a BMS built in 24v or 48v, 5kwh packs for $1500-1800 depending on the model. This is in the $300/kwh range.
I looked at all the comments and couldn't find one that said LFP batteries weren't used in automobiles. Perhaps I missed it. Whatever the case I think LFP batteries are here and have more than sufficient energy density to be used in automobiles as well as in home storage. They are heavier than NMC batteries per rated energy so in the highest performance EVs or ones with high power demands, such as EVs Semis, then NMCs are favored.
However, the elements LFP batteries are constructed from are far cheaper than NMC and don't require cobalt, which is a major and good change. I think you may have read more into the reason for using LFP for stationary battery applications than was actually written.
Edit: I just found the erroneous comment that LifePo batteries aren't used in automobiles. You were right, I was wrong. Good catch.
It is interesting that the materials for LFP are cheaper than NMC but retail cost of LFP is more. I suspect this is just an economies of scale issue that will not be the case much longer as more LFP manufacturing comes online (was reading an article that factories for LFP are even being built in the US).
Hey Daniel!
I went with Eclipse 48V 200AH with Backwoods solar as they've been around as long as I have and I really trust their choices.
https://backwoodssolar.com/product/eclipse-48v-200ah-ver-2-lifepo4-battery/