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Safest yes, but not by any amount that matters much to me. Implementing proper safety devices will in my opinion make LiMn at least 99% as safe as LiFePO4. A charger with a conservative voltage cut-off combined with a charging safety relay controlled by the BMS will more or less eliminate the possibility of overcharge. Two levels of protection and a lot of voltage headroom if one of them fails.
What's left are the possibility of a short making fireworks, especially during installation. That possibility is in my opinion worst with FLA as they can explode and spray you with acid. Also FLA needs a lot of maintenance while lithium can be left alone, which menas lower risk for shorts (like dropping a wrench on the battery poles).
Heat problems from charging should be non-existant in any off-grid applications as charging is VERY slow compared to for example EV applications. Usually no more than C/5 maximum, while EV charging can be 10x faster.Leave a comment:
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Wait, what? Other than different charging specs, are you saying that you are disputing the reason why lifepo4 is the SAFEST variant of lithium chemistry currently available? Please tell me I'm wrong.
Still, we're dealing with deflectionary tactics now to go back to pumping your Nissan cells.Leave a comment:
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I would not put any kind of batteries in large quantities inside my house. Especially not FLA which puts out hydrogen gas. If I were to have batteries at home they would be in a separate building like a concrete shed. If one follows that practice every battery is "safe" in the context of house fires etc.
I'd maybe make an exception for the PowerWall as it is a finished product and in the same category as an EV, battery wise. But I would certainly make no distinction between for example LiFePO4 and LiMn.Leave a comment:
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That is not locally at all, I could just as easily buy from China. Still import hassle, shipping hassle, VAT to pay and customs taxes which makes it a very expensive proposition. Buying 35kWh of LiFePO4 from EV-Power will cost me more than $20,000 delivered, while I paid $3750 for my Leaf modules. Well over 5x more expensive and thus not a viable option. If that was the only option I would still use my old inadequate FLA bank and running the generator _a lot_. A warranty is worth maybe 20% additonal cost for me, not 450%. And since shipping a single failed LiFePO4 cell back costs a fortune the warranty is'nt worth much if the seller is not local.Maybe you haven't tried hard enough. Here are just TWO places that you might be able to get them from in Norway easily, legally, and holy cow - with a warrantee:
and
Your argument held water about 8-10 years ago. Not today.
(Local defined as in the same country at least, preferably not further away than 100 miles)Leave a comment:
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Look before this thread gets out of hand I will openly say that using lithium batteries from wrecked or out of service EV's for your home energy storage system is just plain unsafe and I will not endorse it on this forum.
If you want to gamble with your life just to save a few dollars then go for it. But I will start posting against you and anyone else that states and encourages the use of what I feel is a very unsafe practice.Leave a comment:
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Maybe you haven't tried hard enough. Here are just TWO places that you might be able to get them from in Norway easily, legally, and holy cow - with a warrantee:
and
Your argument held water about 8-10 years ago. Not today.Leave a comment:
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That's probably one of the differences between Norway and the US. Larger sized lithium batteries is not available through normal outlets here, you have to import them yourself. And shipping lithium is sometimes quite the hassle and also expensive. While cells from wrecked hybrids and EVs are readily available many places.
There is two outlets for these; the guys that buy up batteries, dismantle them, test the modules and sell them in the quantity you want. This costs more of course. Then there is the wrecking yards which will happily sell you a complete battery pack for cheap but you'll only be able to do a quick visual check and measure the whole pack voltage. A bit more risk but with a high chance of paying off in reduced cost.Leave a comment:
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All good and sane paramaters for non-lifepo4 chemistry certainly.
Still, we are dealing with specialty cells with only two recognized sales outlets since Nissan does not sell to the public directly (unless you turn in your old existing leaf batts).
1) From the back of a guy's van down by the river at midnight who knows a guy who knows a guy...
2) Hoping that the salvage yard that turns them over to a reseller has a new influx of crash victims to replenish stock. Something sick about crossing one's fingers over that to build your system. But that's me.
Speaking of crashes, I don't know how well those leaf cells are designed to hold up to intense shock. Certainly they look well mounted, but high-g impact can't be good for them. Maybe they survive well. What we do know when you subject cells to extreme shock is that there is a possibility that the anode / cathode alignment is now askew leading to "overhang" problems. Early counterfeiters and cheapskate lifepo4 manufacturers in the early days didn't do overhang properly (made them the exact same dimension or misaligned them), which led to dendrite problems along the edges and so forth. Getting a crashed cell to me would be like buying new ones and throwing them on the floor before installation.
I guess I'm just trying to concentrate on easily available lithium batteries that are available to the common man through normal outlets. Ok, my rant is over.Leave a comment:
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That is true. There should be redundant safety systems when dealing with litium batteries of any kind. Also for protectiong one's investment. For my bank the first "line of defense" is the Outback FM80 which is set to charge the bank to 57V and then float. 57V/14S is 4.07V per cell. Way below critical voltage, and such banks should never be charged to 4.2V anyway because the liftetime will be dramatically lower.
The second line of defense is the BMS, which really should be present in ALL stationary storage lithium battery banks. Mine is set to allow a maximum charging voltage of 4.15V for any cell. If the FM80 breaks and continues to charge above that, the BMS will open the charger safety relay which then disconnects the PV array from the FM80.
The BMS also monitors battery temperature and will prohibit charging at high currents when it is too cold and also disconnects loads if a cell voltage dips too low (currently set at 3.4V)
That said, FLA can also have "events" if charged too high. Excessive gassing and a resulting explosion can happen. Car batteries exploding is not unheard of.So a FLA bank should have adequate ventilaton, which is not necessary with a lithium banks. Different safety measures for different types of batteries.Leave a comment:
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You guys are probably pretty sick of me by now....
That is true, but there is a safety factor in play when choosing energy density for your application and needs some reviewing - which is not fear mongering.
Out of all the lithium chemistries out there, lifepo4 is the least energy dense and from a safety standpoint, the safest. The key to this is the FePo4 or iron-phosphate, which is a greedy material which does not like to give up oxygen atoms even when abused. However, ALL other lithium chemistries achieve higher energy density without the greedy iron phosphate and you had better have your act together - which you guys seem to do. Naturally, lifepo4 being on the lowest end of the density scale is the largest physically - but still about 2/3 the size of lead.
The difference is venting vs. venting with flame.
No chemistry likes to be abused, but consider the lifepo4 cell with say an upper limit of 3.8v before damage starts to occur. Going higher than this will harm the cell, but it takes about 30v to go catastrophic. But yes, severe damage has happened.
ALL OTHER lithium chemistries have very slim margins for abuse. Take an LiNMC cell which charges to an upper limit of 4.2v. What happens when you charge to 4.5v accidentally ? Event.
Proper and precise battery management techniques mitigate this problem. But the diy guy may not get so precise. Lifepo4 gives them that headroom for error from catastrophic events, even though their entire battery investment may be gone when going beyond the norm.
So in a fixed installation where you can actually afford the space, why not choose the safest lithium option - lifepo4 the least energy dense material. (And no, Boeing did not use lifepo4).Leave a comment:
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Yeah - no criticism.
I'm just saying that unless you know *exactly* what you are getting into, recommending used batteries regardless of the chemistry, is starting out newcomers on the wrong foot since you don't really know what kind of life it has led before.
This is what we don't want from a safety standpoint - guys using can openers and machetes to extract used leaf cells:
Or this dude with cells scattered, duct-tape, and a bucket or two of chicken:
The other issue is that with lithium, capacity measurements are not an actual indicator of health. Far from it. "Sudden Death" syndrome is where one day you have full capacity, and the next day the cell is dead without any apparent discharge. This is mainly from oxidation holding the voltage too high, or even milder voltages too long, and of course high heat. The SEI layer finally just clogs not allowing any intercolation to happen, although just hours before everything was hunky dory. There is plenty of capacity left, but you just can reach it because the sei layer is now closed due to prior abuse. Unlike other battery chemistries, you usually don't get any real warning flagged by reduced performance.
It might be a discussion for another thread about top balancing and the problem of going bananas over matching cell voltages which take too long, and keep the cells at elevated voltages too long each cycle ... oxidation then sudden death sei closure.. which some EV'ers may not even be thinking about - oxidation time.
I just think a dedicated leaf battery thread would be more appropriate, and less hijacking - even from myself would keep it on track. Guys that know what they are doing with used cells and prepared to accept the consequences is one thing - but promoting used cells, regardless of chemistry sets off red flags from 3rd party resellers.Leave a comment:
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I wouldn't call what PNjunction posted as criticism. He is trying to let others, (that are non versed in battery technology) that any type of Lithium battery needs to be treated a little different then a standard FLA type which is what most people have hands on experience and are familiar with.
Getting good data on battery banks from those that understand it like you and a few others is very valuable info.
You just have to understand the number of DIY people that come in here can get themselves hurt because they; first believe everything they see on Youtube and second, think they can "safely" build their own system yet they have ZERO knowledge of electrical systems or batteries.
It is better to be a little cautious when providing details of a specialized system likes yours and let others know it could be more difficult then baking a pound cake.
I too feel that the future is a battery chemistry other than FLA. Yet I have not seen a cost effective manufactured system yet being offered. So until then FLA still falls as my first choice for both economics and IMO safety.Leave a comment:
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I can agree with that. The new 35kWh lithium pack cost the same as my old FLA pack consisting of 3 Rolls 4KS25PS. That is 12V 1900Ah, or around 10kW usable when only using it down to 50% SOC. The new pack has nearly half the weight of the old one and has 2,5x the usable energy for the same cost (well, nearly, I had to buy a $500 BMS too). Also 10 module stacks of Leaf cells weighs 35kg and is very easy to transport and move compared to a 152kg Rolls battery...Leave a comment:
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