Is lithium really safe ?

[john61ct]

LFP is not **at all** physically dangerous by discharging all the way down. Barring a dead short or other super high current event, talking controlled load conditions.

But a dead flat event does instantly turn the bank into scrap, not worth anything for energy storage anymore. So much for that 15-year ROI compared to quality AGM.

That is why last-ditch LVD is the most important BMS functionality.

Multiple levels of LVDs should be isolating loads from the bank long before it ever gets near the BMS setpoint.

[OceanSeaSpray]

Over-discharge of the LiFePO4 chemistry, i.e. below 2.0V/cell, causes corrosion and dissolution of the copper current collectors and the formation of copper dendrites upon recharging.
These are a significant fire risk as they can puncture the separators between anode and cathode inside the cell and cause it to short internally at any time afterwards.

It has been studied and documented in detail, like here:

"Failure Investigation of LiFePO4 Cells in Over-Discharge Conditions". He, Liu, et Al., Journal of The Electrochemical Society, 160 (6) A793-A804 (2013)

Once they have been over-discharged, they are only good for the rubbish dump. The fact that they "can still be recharged" is completely irrelevant.

[LongRange]

I don't think that anyone is claiming that overdischarging is good practice, or that it should be attempted seven times for luck, or anything like that. By definition, OVERdischarging has taken the cell outside of its normal operational paramaters, and thus damage can be expected, especially to one's wallet.

The point is that a LFP cell, or a battery of LFP cells, in an overdischarged state will not start a fire. In an absolute sense, overdischarged is the safest state for any lithium-based pack.

The potential to burn and sustain a flame is proportional to the SOC. An overcharged pack is just asking for trouble. A 100% full pack is safe, and as long as currents are within design limits everything will stay safe. Below say 3.0V/cell all lithium chemistry batteries are essentially empty. Below 2.0V/cell you can drive a nail into it (not recommended) and nothing happens - in that state it is a plastic bag with some grit in it.

Regular overdischarging of LFP is going to reduce the effective capacity to the point where the pack is useless long before the little dendrites have a chance to bridge the anode to the cathode. Ask me how I know

[LongRange]

Somewhere out there, and perhaps reading this thread, is a guy or girl outfitting their boat with several grand worth of LiPo packs, swayed by the non-boat prices online.

Although thrifty and undoubtedly enthusiastic, he or she has little experience and even less understanding of the principles of balancing, balance taps, parallel charging, CA/CV charge phases...

Their boat will be the one that started that fire which burned through half the marina. The press coverage will focus on the fact that lithium batteries were involved, but in reality it's similar to an accountant deciding they can handle their own mains wiring for their new house.

[hellosailor]

Jon-
I may have been misinformed, but I thought that a potential problem with reverse-harging (i.e. one cell that goes bad first) in a battery array is that it encourages dendrite formation or other physical failure that can eventually lead to overheating and fire. Like the Walking Dead, lithium (and other rechargeable cells) never like to just die peacefully.

[OceanSeaSpray]

Originally Posted by hellosailor

Jon-
I may have been misinformed, but I thought that a potential problem with reverse-harging (i.e. one cell that goes bad first) in a battery array is that it encourages dendrite formation or other physical failure that can eventually lead to overheating and fire. Like the Walking Dead, lithium (and other rechargeable cells) never like to just die peacefully.

The situation you are referring to is when one cell goes flat and you keep drawing current from the other ones. The current gets forced through the dead cell. This causes more rapid destruction than just over-discharge of course, but it is not required to destroy the cell. EV people did that quite regularly in the early days while running long strings of cells they couldn't monitor individually.
Below about 2.0V, the LFP cell chemistry is no longer stable. It starts falling apart and the longer it stays in this condition, the more damage takes place inside the cell. Once it has gone below 2.0V, all bets are off. It is no longer a safe cell to use.

Nearly all the systems I have been involved with have at times been discharged to LV trip by their owners, lowest cell at 2.8V. It is never a question of "if", but just "when" it is going to happen. Some were unattended and they recovered automatically. If the system is well engineered, over-discharge should basically be impossible.

Li-ion cells do die peacefully when they haven't been abused... they just develop higher and higher internal resistance until they won't take any current and you get no capacity out of them any more and that's it. I haven't yet seen or heard of a pack of prismatic cells getting there in a house bank application, but they clearly pick up internal resistance with age.

[ctsbillc]

Even Phosphate type batteries are subject to catastrophic failure, and if they do fail, you will loose your boat and likely your life. Look at the many Tesla burning videos for an example of what happens when they fail. My next set after my AGM's die will be Thin Plate Pure Lead. Twice as expensive as normal AGM, you can discharge them a lot further, so you're getting a lot more capacity for your money. They also hold their change a lot better, and far improved charge acceptance rate means they recharge a lot quicker.


It's worth noting that nobody is suggesting Lithium for submarines, except Japan. Japan Goes Back To The Future With Lithium-Ion Battery Powered Submarines - The Drive

[curtis742]

Originally Posted by SV THIRD DAY

I don't want to turn this thread into a "hate insurance companies thread" but yes. I had to change companies to get "electrical fire protection" because the company I had was too ignorant to understand. The crazy thing is they knew I had LiFePO4 batteries because they were listed on the Survey for 2 prior years (policy renewals) but then all of a sudden.....wham-O.

So I'm not saying LiFePO4 batteries are not safe....I'm just saying make SURE your insurance company will cover them.

the main reason is the recent problems related to the Tesla cars bursting into flames and melting the vehicles.

True lead acid batteries can explode but it is a rare occurrence and generally just spray acid everywhere which can be flushed away with water and neutralized with baking soda. Lithium batteries burn with a great deal of intensity and cannot be easily extinguished. Personally I would not want them below deck.

[BenFranklyn]

I wish to add an additional fly into the ointment and that is the numerous companies that are out promoting their various systems. A couple of years ago during a refit in the Netherlands I installed a complete Victron system into my sailboat which had 2 of the 24volt 180 Amp hour battery packs and all of the Victron systems to support it. The installer was a recommended Victron installer and I was assured by the factory, the system was completely developed and ready to go. Long story short, it was complete crap. The factory had programmers on the boat for weeks trying to solve basic charging problems and failures which showed the factory had jumped in and sold a system and used me as the a trial that they should have done before going to market. Two years later and several parts replacements and more software upgrades than I can count the system kind of works but will still fault out for no apparent reason and need to be reset.

Moral of this story, they don't call it the bleeding edge for nothing. If I could go back in time I would have purchased the best AGM's I could find and waited it out. I can't even calculate the time and money wasted on that project and during the first year of operation I lost just about an entire season of sailing. Once you commit to a system Victron you are at there mercy and they have proven to be completely untrustworthy. Won't even talk with me about the system. In addition, when you are out cruising good luck finding anyone who will work on them anywhere but the biggest ports. These are absolutely NOT for world travelers.

[DLT]

Originally Posted by a64pilot

Airlines don’t let you turn on your cell phone either, although I’d bet that there’s not one single accident you can attribute to the interference of one being on.

As I understand it, that's an FCC thing, not an FAA issue.

[DLT]

Originally Posted by gmakhs

They are new .

Link?

[Lamb Chops]

Hi! I found the attached article extremely helpful. I've decided to go with lifePO4

https://marinehowto.com/lifepo4-batteries-on-boats/

[gatorman49]

Ask Air Bus, Boeing, UPS and FedEx

[Colin A]

Originally Posted by ctsbillc

Even Phosphate type batteries are subject to catastrophic failure, and if they do fail, you will loose your boat and likely your life. Look at the many Tesla burning videos for an example of what happens when they fail. My next set after my AGM's die will be Thin Plate Pure Lead. Twice as expensive as normal AGM, you can discharge them a lot further, so you're getting a lot more capacity for your money. They also hold their change a lot better, and far improved charge acceptance rate means they recharge a lot quicker.


It's worth noting that nobody is suggesting Lithium for submarines, except Japan. Japan Goes Back To The Future With Lithium-Ion Battery Powered Submarines - The Drive

I'm pretty sure Australia France and South Korea are all planning on Lithium for their next subs. The US still uses Lead Acid made by Exide.

[Theros]

I have just installed an 80 volt lithium battery bank to run my electric engine on a Gibsea 42. Lithium can be very safe but safe charging means using a BMS or battery monitoring system and a proper charger for lithium batteries. I built my battery pack from Nissan Leaf modules and it works great. My charger and BMS are from Thunderstruck EV and I am very confident that they are safe.