Is lithium really safe ?

[gmakhs]

I am not looking to benefit from saving fuel is mostly an experiment.
Total costs are low 1000 for 4 X 160 ah lithium 12 v batteries plus 500 for the motor and controllers this is 1000 litres of diesel and around 2000 engine hours for me ..... So really it's not for the cost .

The current engine is 8 hp Volvo penta pushes the boat at 3 knots with 25knots of wind (speed may be variable depends on the current and the waves )
Usually i don't use the engine in most conditions , since the boat can sail with really light winds and if there is wind there is no point to use the engine (is slower than the sails )
Why do you believe the electric motor won't be able to achieve this speed ?
I would have made the setup permanent but since my next trip includes rivers I don't trust the electric.

Ps : even if I try to charge with solar the boat has not enough space to charge the batteries quick, so electric motor would be at best 1 hour a day .

[hellosailor]

As John said, LFP (LIFePo4) batteries are in a class of their own. Yes, they can get agitated but they are also the only "lithium" battery chemistry that does not use a flammable petroleum-based electrolyte, so they are in a class of their own when it comes to safety. Any other type of lithium battery needs a special extinguisher if it catches fire.

Then there's the minor problem that depending on which manufacturer you listen to, all lithium batteries require a special battery management system (BMS) to get anything like the proper performance from them. They can be easily abused and killed if they are not treated right. And that becomes a very expensive mistake.

[john61ct]

Originally Posted by gmakhs

1000 for 4 X 160 ah lithium 12 v batteries

Link to the model please?

I assume second-hand?

[44'cruisingcat]

Originally Posted by hellosailor

They can be easily abused and killed if they are not treated right. And that becomes a very expensive mistake.

Actually they are tougher than the publicity would have you think.

Two people I know have seriously over discharged their LiFePO4 batteries. Down to less than 2volts per cell. (Less than 8v in a 12v system.) One system at least was left like this for months.

They contracted their suppliers and following their advice recharged the batteries.

Both battery banks are now working fine, one guy (the one who's batteries were flat for months) estimates less than 5% capacity loss.

I'm not sure lead acid batteries would be any more robust.

[john61ct]

Loss of lifetime cycles, if the bank cost thousands, most of it down the drain.

BMS won't allow such deep discharge.

[44'cruisingcat]

Originally Posted by john61ct

Loss of lifetime cycles, if the bank cost thousands, most of it down the drain.

BMS won't allow such deep discharge.

In at least one case the BMS CAUSED the deep discharge.

There was a load on which dropped the batteries to BMS disconnect. Unfortunately this not only disconnected the load but also the solar. Then the BMS itself continued consuming power resulting in the severe discharge.

Anyway this was years ago and the batteries are still performing well.

[gmakhs]

Originally Posted by john61ct

Link to the model please?

I assume second-hand?

They are new .

[Kiwi Dave]

Exploding batteries?
I am an Eye Surgeon and have seen a lot of patients who have been injured from lead acid batteries (usually flooded), and some who have lost eyes as a result. As mentioned lead acid batteries produce hydrogen.

Lithium Iron Phosphate (LiFePo4) do not explode, catch fire. All batteries can cause a fire by a short circuit. There are may examples on YouTube of prismatic LiFePO4 cells having nails driven into them, shot at, over charged, direcly short circuited etc.
Other lithium chemistry (such as lithium ion polymer) certainly can catch fire/thermal runaway (The Boeing 787 aircraft example (see quote below), Cell phones, electric hover boards).

I have gone the LiFePO4 way when it came time to replace 6 x 220 Amp Hour flooded Lead acid batteries. I am happy with the decision, but it is certainly not for everyone.

"The FAA also conducted an extensive review of the 787's critical systems. The focus of the review was on the safety of the lithium-ion batteries[363] made of lithium cobalt oxide (LiCoO2). The 787 battery contract was signed in 2005,[206] when this was the only type of lithium aerospace battery available, but since then newer and safer[369] types (such as LiFePO), which provide less reaction energy during thermal runaway, have become available"
http://https://en.wikipedia.org/wiki/Boeing_787_Dreamliner#Lithium-ion_battery_problems

https://www.youtube.com/watch?v=WEs-...mDscLj&index=5

[LongRange]

LiFePO4: Safe, but like all lithium chemistries requires a (LiFePO4-specific) charging and discharging control regimen, almost always implemented as a BMS. Not as energy-dense as the other two types, but still far superior to lead-acid chemstries.

Li-Ion: Higher energy densities than LiFePO4, but not as safe. Common in laptops and phones, where the BMS is top-notch.

LiPo: Beelzebub's own battery chemistry. Seductively energy-dense, and in some cases capable of sustaining 30C+ discharge rates (not useful on boats, but very useful in other contexts), but dangerous to the point of being irresponsible to use of specific scenarios.

My "other hobby" is radio controlled helicopters and planes. Lipos are the chemistry of choice, but they require significant knowledge, constant watchfulness, and (preferably) a large concrete slab where the charger and the lipos can be left in the middle with nothing flammable anywhere near. Some RC aficionados carry their lipos around in perforated ammo boxes (without vent holes, that box becomes a bomb).

Despite years of experience with lipos and very complex BMS, or perhaps because of that experience, I would NEVER use lipos on a boat. Big Li-Ion banks also make me nervous. LiFePO4 is fine, but the prices charged for boat-sized BMS are outrageous.

[LongRange]

LiFePO4: Safe, but like all lithium chemistries requires a (LiFePO4-specific) charging and discharging control regimen, almost always implemented as a BMS. Not as energy-dense as the other two types, but still far superior to lead-acid chemstries.

Li-Ion: Higher energy densities than LiFePO4, but not as safe. Common in laptops and phones, where the BMS is top-notch.

LiPo: Beelzebub's own battery chemistry. Seductively energy-dense, and in some cases capable of sustaining 30C+ discharge rates (not useful on boats, but very useful in other contexts), but dangerous to the point of being irresponsible to use outside of specific scenarios.

My "other hobby" is radio controlled helicopters and planes. Lipos are the chemistry of choice, but they require significant knowledge, constant watchfulness, and (preferably) a large concrete slab where the charger and the lipos can be left in the middle with nothing flammable anywhere near. Some RC aficionados carry their lipos around in perforated ammo boxes (without vent holes, that box becomes a bomb).

Despite years of experience with lipos and very complex BMS, or perhaps because of that experience, I would NEVER use lipos on a boat. Big Li-Ion banks also make me nervous. LiFePO4 is safe enough, but the prices charged for boat-sized BMS are outrageous.

[SV THIRD DAY]

Originally Posted by 44'cruisingcat

In at least one case the BMS CAUSED the deep discharge.

There was a load on which dropped the batteries to BMS disconnect. Unfortunately this not only disconnected the load but also the solar. Then the BMS itself continued consuming power resulting in the severe discharge.

Anyway this was years ago and the batteries are still performing well.

Ah...but there's the BS Rub.
There is this head in the sand feeling that if only you spend the money on the "right BMS" then you have nothing to monitor or worry about...let the BMS Controller take care of everything...kinda like a Tesla Autopilot. No one wants to talk about what happens when the Circuitry in a BMS Fails because we all know...Circuitry and Cruising boats never has failures....

[Kiwi Dave]

However the question was "Is Lithium really safe". I submit that LiFePO4 is a safe chemistry.

I agree any battery will be damaged if not maintained correctly, be it the required BMS (battery management system) for LiFePo4, or the simpler charger or regulator for lead acid.

One makes a decision based on personal knowledge/situation/desire/money etc & has to be prepared to cope with the consequences.

[OceanSeaSpray]

Yes, it is safe as long as it is installed properly and nothing stupid has happened, like discharging it flat and recharging it.

Should you do it? Mainly if you live aboard, i.e. your battery is basically never full. The key advantage is that it gets rid once and for good of sulfation and the recurring half-dead no-capacity-won't-hold-charge battery problem.
If you only use the boat occasionally... a lot of complications for what? What you need is a solar panel and a float charger.

Hybrid, electric propulsion? Haha. Just calculate the weight of the battery you need to hold the energy of 1L of fuel at the propeller shaft:

Burning diesel in an engine: ~230 grams for 1kWh
100Ah LFP cell: 3.15kg for 320Wh

So... that's 43kg of lithium cells to store the equivalent of 1kg of diesel: the Great Hybrid ********.

[LongRange]

To clear up something, over-discharging any of the lithium chemistry batteries is perfectly safe, in the sense that there is no risk of fire or explosion. In fact, that is how they're meant to be discarded oce their useful lifespan is over - by overdischarging as close as possible to zero, to make it safe to dispose of the pack.

In normal operation, overdischarging is deleterious to the longevity of the cell/battery, and hence to the owner's wallet, but overdischarging will not cause the boat to burn to the waterline.

Overcharging LiPos results in that "charred smokey mess" effect.

[hellosailor]

On the contrary, I've been told overdischarging any lithium cells is dangerous.

Take any one cell of them (let's say four in series in a nominal 12-volt bank) down to under about two volts, for any length of time, and it may physically be damaged internally. The entire battery set may need to be replaced.

Take a battery bank down to maybe 8 volts...and you're risking one cell being flat and the others applying reverse polarity to it, bigger risk as the battery voltage goes lower of course. Applying reverse polarity can cause internal damage, which can lead to a risk of fire. Again...not so good, even if it is not a dramatic fire.

Lithium cells, like all rechargeables, can and do take damage if discharged below a certain voltage. It just becomes much more expensive damage because of the replacement costs.