house bank using Tesla battery modul 24V, 235AH and 5.2kWh

[CaptainRivet]

Hi all,


is anyone using the Tesla moduls for the P85 as housebank batteries?
With 24V, 235AH and 5.2kWh for around 1000-1300$ on ebay quite often thats actually a steal. Also well known reliability and high current supply above all you ever need on a boat.

2 of this moduls is 10,4kwh. 1000W solar and 2 wind gen plus solar charge controler and BMS you have all you need. With a 24V to 12V converter I run my 400W of 12V gear you normally have (bilge pumps, radio...), there are bigger converters too in case you have more and all are cheap.
Most higher power is 220V via inverter anyhow which is better with a 24V housebank. I will mostly electrify my galley with it too and get a 24V water maker that should run of it.
self sufficent setup with sun and wind, 2x120A alternators as 3rd charging backup.


It's not a topic/theme here to run 24V instead of 12V or a mixed system. This just as background info so you know what I want to use it for.
Interested in people who have used the Tesla modules, wanna do it or can tell why its maybe a bad or great idea to use them.
thanks.

[john61ct]

LFP and maybe LTO are IMO the only LI chemistries safe enough for that use case.

Risk of thermal runaway, i.e. fire, boom bad, is just too high for use in a small mobile living space.

[barnakiel]

Check first if it is fine for the conditions you want to use it (heat, humidity, vibrations, Gs, etc.). Your insurer may or may not like it.


b.

[CaptainRivet]

its for mobile use and all that requirements for a boat a Tesla car has as well plus a dozen others like really dangerous high voltage fast charging. no boat application will suck 1000A out but a e-motor of a tesla does. All is certified and prooven to be secure.

these are full battery packs with all the security electronic with it, which fullfills even the crash norms and all other tests regarding thermal runaway, fire...
https://www.ebay.de/itm/Tesla-batter...YAAOSwETJbs0Em

non of the chinese Lifepo batteries, renamed, rebaged and branded for all the supplier out there, sold and put on boats of a lot of owners here wasn't even put through 10% of that extensiv testing and aren't certified at all.
I don't know any insurance that denies insuring a tesla.

[john61ct]

The point is, the car surrounds the packs with sophisticated monitoring, control and protection systems that are no longer present once the cells are removed.

In particular temperature control systems, millions invested in engineering those.

These have not been reverse-engineered yet, and personally if someone claimed to sell such I'd be **very** skeptical.

There is an ABYC committee working on guidelines for non-lead power systems. When these are released, then perhaps some surveyors will be recommending compliant DIY setups for insurance coverage, but such changes do take time.

In the meantime, strongly suggest sticking with LFP.

[CaptainRivet]

thanks john.
You are right. Only LFP.

Talked to a master mechanic of Tesla...they regularly evacuate the whole workshop when a failure of the battery appears till he removes the cell and puts on a special cooling/discharge bench to secure it from therminal runaway.
"On a boat, if you discover that therminal runaway due to a failure of a cell early enough, only chance would be to throw it overboard. if too late discovered, its so hot you cannot touch it anymore...what will 25kg of TNT do to your boat?" he said.

So Tesla battery modules noGo for a boat!!!

[bolbliksem]

Originally Posted by CaptainRivet

thanks john.
You are right. Only LFP.

Talked to a master mechanic of Tesla...they regularly evacuate the whole workshop when a failure of the battery appears till he removes the cell and puts on a special cooling/discharge bench to secure it from therminal runaway.
"On a boat, if you discover that therminal runaway due to a failure of a cell early enough, only chance would be to throw it overboard. if too late discovered, its so hot you cannot touch it anymore...what will 25kg of TNT do to your boat?" he said.

So Tesla battery modules noGo for a boat!!!

I stil think it is an interesting idea, sure the safety electronics shoud be included , but if its safe in a car its safe on board

[john61ct]

No, the "safety electronics" are not inside the packs, they are part of the car's systems.

And the thermal management systems / TMS are even more critical, circulating fluid to keep the packs in the right Goldilocks range.

One day maybe open-source engineers will reverse-engineer standalone infrastructure to make these packs safe enough to use inside our dwellings, but for now statements like this are the height of irresponsibility

Originally Posted by bolbliksem

if its safe in a car its safe on board

[alansmith]

Would it also be true...that Tesla packs being sold on fleabay come from Tesla cars that were demolished in wrecks and considered to be “totaled?”

That is another factor to be considered if you put any faith in prudence.

[StuM]

Originally Posted by alansmith

Would it also be true...that Tesla packs being sold on fleabay come from Tesla cars that were demolished in wrecks and considered to be “totaled?”

That is another factor to be considered if you put any faith in prudence.

So at the very least they have been subjected to strong "shock loading" of their components.

[CaptainRivet]

Originally Posted by alansmith

Would it also be true...that Tesla packs being sold on fleabay come from Tesla cars that were demolished in wrecks and considered to be “totaled?”

That is another factor to be considered if you put any faith in prudence.

They are safe if car is totalled. Its totalled 99.9% time because of the aluminum structure that is super expensive to repair, a light bump is already enough if on the right spot. And battery bank is low down in the middle on the P85, so even a crash with multiple roll overs won't damage the the packs. Saftey/health of the bat pack can be checked by any Tesla workshop.


That's not the problem:
As John wrote:

"No, the "safety electronics" are not inside the packs, they are part of the car's systems.
And the thermal management systems / TMS are even more critical, circulating fluid to keep the packs in the right Goldilocks range."
They are partly in the pack and can be used but its unclear how it effectly reacts because some are missing. Thats what john meant with carefully reverse engineered. But even if that is solved there are 2 other facts:
1) Have a look at the battery pack in the ebay add...Its not 100% sealed means the electronics and connector of the cells oxidate in the salty air at sea. In the Tesla they are in a case incorporated into the chassis. That could be maybe made too but if you add that costs its not such a good deal anymore...
2) the killer is that LioIon used by Tesla have the tendency of thermal runaway and the tech I talked to said they evacute the workshop in average one time a month even with all the certified controls placed everywhere in the car (which you don't have). Well thats definitly not safe for me. One car of maybe 200 that has a problem.
...that thermal runaway start small in one of the cells and takes a while till data gets out of spec. Only then control sensors discover that, exclude that cell to slow down the process and send you immediatly to the workshop. If discovered soon enough that can only be stopped with the special Tesla battery workshop bench, which you don't have. A 25kg Tesla bat pack equals to 25kg TNT i was told by the tech. Thats why they evacute the workshop while the bench does the magic stop it. So if you get a thermal runaway best case is you discover it right away, rip it out the pack and throw overboard. More likley the pack will melt his way through the GFK hull and cause a fire too.Worst and most likly case due to the tech is you experience what the equivalent of 25kg TNT does to your boat incl. everything and everybody thats on it


LIF or LifePo4 have non of that risks and are safe for boat use. Best is

a) no DIY: you buy the Liefpo4 with garanty as long as possible which has BMS included and this will be good as long as the garanty of the battery is. Because its sealed you can not see what BMS and balancer is inside and thats the critical part that mostly breaks, not your cells...(info from a guy who maintaince solar systems). The cells itself will come out of one of the 4 big chinese production facilities anyhow and are quite identical, doesn't matter where you buy it. Then these cells togehter with BMS/balancer will be put in a sealed case by the "manufacturer" and sold to you as eg a Relion, Mastercraft or any of the other brands..... Because its sealed you cannot repair the broken balancer/cell BMS inside and have to throw away the whole battery.

or

b)what I prefer and got recommended when DIY: you take prismatic LifePo4 cells and add your own high quality BMS and balancer. Like this you know what BMS and balancer you have and can easyly repair /exchange them or add cells or replace a cell that is broken or switch the first cell of the bank (who gets the most wear) to the last cell and enlarge life time of the total bank. You can also combine new cells and used ones with the same specs, you just have to balance them properly before putting them together as a bank. Your balancer and BMS cares about the rest. Like this you can end up at the same price (if taken used cells) then with the used Tesla pack and be safe. The used prismatic cells come mostly of medical or emergency gear where the certification is only valid for 5 or 2+2 years, after that they have to exchange the battery doesn't matter how good it still is. These are mostly 40AH, 90AH or 100AH cells with 3.2V. I was adviced you should put max 4 cells parallel (more work too but reduced the lifespan of the whole bank quite significantly) which gives you a 400AH bank in 12V, 24V or 48V depending on how many you put in serie. So 16 cells (4 in serie is one 100AH 12V battery and then this 4 in parallel) with 3.2V is a powerful 400AH/12V bank. And they have mostly more AH then on spec sheet as for medical (so even the worst unit coming out of production fullfills the spec) so I was told is in practise it's a 500AH-600AH bank. If you want more AH just make 2 separate banks. Will go this way.

[a64pilot]

Originally Posted by alansmith

Would it also be true...that Tesla packs being sold on fleabay come from Tesla cars that were demolished in wrecks and considered to be “totaled?”

That is another factor to be considered if you put any faith in prudence.

Certainly, almost always from totaled cars.
Just like Prius packs, but I assume just like a Prius pack, they are pretty much centered in the car and extraordinarily protected because of the fear of a high voltage battery pack, first responders were initially told to approach hybrids like snakes, every high voltage cable on a Prius is covered in high vis orange covering for first responders to be aware of. Is this sort of ridiculous? Yes I think so because have you ever heard of a fireman being electrocuted using the jaws of life?
That was the initial fear at least for hybrids.

The gas tank on a regular car of course is way, way more dangerous, but it’s mainstream, been around for a Century and people are no longer afraid.

Although I have never taken a Tesla pack apart or even seen one in truth, it’s nothing but a metric arse load of Panasonic 18650 cells. Ought not be too difficult to inspect.

Would I have one on my boat? Not on a bet, especially if I slept on the boat.
I’d be dreaming of that dive boat in California, even if it had nothing to do at all with a battery fire.

[CaptainRivet]

Originally Posted by a64pilot

The gas tank on a regular car of course is way, way more dangerous, but it’s mainstream, been around for a Century and people are no longer afraid.

A gas tank will never explodes, that just a myth from all the action movies.
Thats why diesel or e-motor with LifePo4 is better and the max. 2x20l jerry cans for dingy gas is quite a small amount. Sure also they have some risks but they can be quite well prevented and easly discovered.

A tesla battery pack can explode.
They refurbished 2 years ago the workshop where the Tesla tech I talked to works. It was "just" roughly half a pack of a P85 that exploded but enough that the whole workshop inside, windows and roof was completely gone...and that battery bench is standing in a separate room with thick concrete walls. Just waiting till that happens somewhere public on the street and Musk cannot cover it up any more...**** will hit the fan.

Not bashing the Tesla, great cars and force the slow and sleeping competiton to finally innovate. But Tesla is just a small car builder so far and start to experience the hell of automotive series production now with model 3....

[barnakiel]

In a car, the alarm sounds, stop the car, evacuate the crew, watch the fireworks.


In a boat underway, what do you want to do? Jump overboard?


If a battery is not rated for this kind of service, it should not be used onboard.


There have been plane accidents with craft downed. Craft that transported palettes of PERFECTLY SECURE lithium batteries. Google your friend.



b.

[john61ct]

Can buy packs brand new, but doesn't make using them any safer.

Tesla will come out with "powerwall" type banks designed for mobile use one day I bet, likely to comply with ABYC by then too.

But an inherently safe chemistry internally will to me always be worth sacrificing even half the energy density.