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  • Justin B.
    started a topic Tesla battery pack?

    Tesla battery pack?

    I was poking around looking at different used/surplus batteries and came across listings for Tesla Model S battery modules, 24V, 250Ah. Since Li can be discharged a lot further than SLA/AGM would something like this be a good replacement for a 600 Ah AGM bank or could they be ran in parallel? Pricing was in the $1300 - $1400 neighborhood.

  • HollySprings
    replied
    Bravo!

    This thread was an interesting read. Pulled from the bash-em-all-to-hell toilet, at the brink of being closed, only to end up being constructive and informational.

    All I have to add is that the UL, in UL 1974 entitled "Standard for Safety for Repurposing Electric Vehicle Batteries" says "UL wants to help manufacturers make sure the batteries that power these vehicles are used to their full potential. Today, rather than simply disposing of the batteries when they no longer provide the power needed by EVs, they can be repurposed. However, for this to be possible, the batteries must first be safe, meaning every pack must be evaluated according to established standards to determine its condition, safety and energy capacity."
    https://standards.globalspec.com/std/13082523/ul-1974

    I am not currently in this business (repurposing batteries) so haven't bought and read the 41 page UL document, but it's out there. Perhaps in the near future, we'll see UL rated Repurposed EV Batteries on Ebay. Time will tell, but there sure will be a ton of batteries available over the next decade compared to the last. Companies are forming in this space to address the (mostly future) market.

    It goes without saying, but this business (ESS) is a new industry using new technologies, so in the big picture we should expect growing pains.

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  • PNjunction
    replied
    Actually it would be good for another topic thread.

    The way these cells are shoe-horned into solar bank use is if they are excessively large in capacity compared to the need (which usually *never* meet the typical solar 2-3 day minimum!), or are so cheap, because the cells are either old stock, surplus crash damage, counterfeit, and the like that this is the only way the project makes any financial sense.

    But back to life-cycle - the way we get any cycle life beyond about 360 (maybe a year's worth of cycling) cycles, is to purposely engineer the use-case to only use a small amount of cycle capacity.

    Which brings us back to LFP vs other chemistries:

    Salesman-type data: (only used for comparison since we murder our batts in the real world)

    LifePo4 - 2000 cycles or more to 100% DOD
    NON-LFP - typically about 360 cycles to 100% DOD

    So right off the bat, there's no comparison. When one takes the vehicular use-case data away, and put into our application, things don't look so bright for non-lfp, unless on is doing a "one-off" diy project that nobody else is going to duplicate - at least not over the counter.

    And that's kind of the point - NOBODY would "diy" a non-lfp bank, if they had to pay FULL PRICE for quality Tesla cells, bought directly from Tesla as if they would! It's one reason why A123 stopped selling to diy'ers long ago, and the gray market, rejects, and counterfeits showed up. Heh, we've been through this all before.


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  • nebster
    replied
    Originally posted by PNjunction View Post
    Well, yeah - most people don't realize that like all cobalt-based li-ions (or anything non-lifepo4), the cycle-life is ridiculous in our application.
    I'd like to discuss this further, perhaps in another thread. The data I've had a chance to look at (mostly self-reported large sets, but also a few papers) suggests that some of the cobalt chemistries are performing much better than perhaps had been expected or extrapolated in earlier years. In fact, given the substantially lower cost of these cells, it looks close enough to possibly meet or beat LFP for total lifecycle cost. Which is interesting. I'd be interested to learn if your understanding is otherwise and to see your evidence, if so.

    Also, I agree with the rest of your post.

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  • PNjunction
    replied
    Well, yeah - most people don't realize that like all cobalt-based li-ions (or anything non-lifepo4), the cycle-life is ridiculous in our application.

    Basically the wrong battery for the wrong application. Yes, we can shoehorn these cells into our application if one know what they are doing and willing to accept the cost/benefit.

    Unfortunately, what we see mostly happening is diy'ers trying to turn lithium trash into gold on the cheap, without investing any knowledge, and crying when we won't tell them how to wire up their trash. Just like we don't go deep into depth on the guy wanting to build a bank out of 100 little 5ah agm's found at the dump.

    I think the differentiation is this: does the forum serve to discuss "over the counter" projects from reliable distributors, or just support the diy'er trying to cobble stuff together without regard to his/her own safety on the cheap.?

    Not everyone here fits that description obviously. That's usually seen when they take safety seriously - regardless of battery chemistry. When they get offended, that's when I become suspicious of a marketing agenda for crash-victim battery projects.

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  • nebster
    replied
    Originally posted by PNjunction View Post
    Funny thing is we get sucked into long discussions about a battery chemistry (NON-lifepo4) that is not ideal for adequate solar storage, and thus getting off on the wrong foot from the get-go.
    I think one of the issues is that some users are specifically looking for a mobile storage solution, and in that scenario the risk/benefit equation is surely different. We do now see name-brand, production manufacturers shipping cobalt chemistry packs for use on boats and RVs. Not on my boat or RV, mind you... but nevertheless, it is gradually becoming something people think about and sometimes even do.

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  • PNjunction
    replied
    Funny thing is we get sucked into long discussions about a battery chemistry (NON-lifepo4) that is not ideal for adequate solar storage, and thus getting off on the wrong foot from the get-go.

    Much like discussing how to make a solar storage bank out of vehicular starter batteries. Not only that, but the Tesla batteries aren't purchased from Tesla or a direct authorized distributor directly - they are from vehicular crash dumps.

    Hi, I want to build a 48v solar storage bank out of batteries that I got from the wrecking yard - and you guys are too uncool to tell me how to do it!

    Whether li-ion, or even lead acid, such foolish threads don't even need to get started. Safety, even if you know li-ion like the back of your hand, doesn't START with cells of unknown pedigree. Game over.

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  • Mike90250
    replied
    Originally posted by Ampster View Post
    ...... In the case of a Tesla battery being used in a stationary application as was the point of this thread it is unlikely that the battery would be stressed like in a car provided the user uses common sense.
    And sadly, the "common sense" regarding Li batteries has not had time to develop. Like stressed cells gassing. Some of that gas is Hydrofluoric Acid which is never good with life.
    But "Who Knew" ? Or that deeply discharging a bank and then rechargeing it, sets it up for dendrite shorts in a month. Nobody ever connected last months deep discharge, with the fire.

    and the different flavors of Li batteries, all have subtle charge/discharge differences. I got this pack from a dead XYZ, and stripped off all this extra stuff and use 3, 48V golf cart chargers to charge it. Why is it smoking all the time ?

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  • jflorey2
    replied
    Originally posted by SunEagle View Post
    If you go back to the original post it has to do with used Tesla batteries wired for a home energy project. Not Tesla EV's, Powerwalls or other manufactured home storage systems. All of those have been engineered with charging and cooling systems that will help reduce the potential for a fire or worse.
    That is a very important point.

    An EV (or an indoor battery storage system) is designed from the ground up around a battery. There are BMS systems, cooling/heating systems, different charge and charge protection systems and limited draws. There are protection devices, often several. There are contactors to isolate the battery when the car is off. There's a smart controller limiting charge and discharge. And the manufacturer has a very detailed tracking system that tracks the cell from receiving all the way to the finished product rolling out the door.

    In other words, they are pretty safe.

    A second life EV battery has none of that. Generally it does not have a BMS. It doesn't have the contactors and protection devices. It doesn't have that cooling/heating system. It doesn't have a very smart controller deciding whether to continue charging. It may have been in a wreck. It may have been partially submerged in water. It may have been abused by an idiot with a homemade charger or homemade battery tester. It may have endured a guy with the wrong size impact wrench trying to remove it from the car.

    In other words, they are less safe.

    UL has begun to address this, and now has testing and handling standards for second life EV batteries. It is safe to say that most people working with them do not bother with such testing.

    That's not to say they are deathtraps. I have two 3kWhr Tesla batteries that I am experimenting with; they are connected to a charger, inverter and charge controller set up to reduce my house load to zero during "reduce your use" days (which the utility then pays you for.) But they are also in a steel box outside my house, set up with a bib that lets me flood the box if they go up in a fire. There's no way I would keep them inside my house - and anyone who does so is literally playing with fire.

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  • solar pete
    replied
    Hi All,

    Just thought I would chime in here, as someone stated the mods and admins dont and cant be expected to know everything about all subjects all the mods are unpaid volunteers who spend some time here to keep the wheels turning for all members and lurkers benefit. Some days the mods or admins have a bit of time to deal with matters that arise other days they have the delete or ban buttons, the mods are all knowledgeable good people and I support their decisions 100%. This is not a democracy, posts will be deleted and people banned as we see fit, cheers

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  • sdold
    replied
    Originally posted by Ampster View Post
    Details could be important depending on what was said. Any more relevant examples? Perhaps the law has evolved since the BBS days. Don't get me wrong, anybody can be sued. The real issue is has there been any judgements of significance?
    There was no judgement, but there didn't need to be to cause real damage. It cost me over $8000 to hire a lawyer and defend in a case that was eventually dropped because (according to my lawyer) it was a weak case that should never have existed. He told me that by moderating the forum and not editing or deleting certain posts I was implying that they were true and that was why I was named in the suit. The first amendment doesn't protect you from the consequences of saying things, it just means the government won't stop you from saying them. I don't speak for the forum owners or other moderators, but liability is something I consider when I see what I think is dangerous advice that's unchecked. Sometimes I might err on the conservative side, but I'd rather occasionally throw the baby out with the bathwater than have the forum owners involved in the kind of thing that I went through, or worse, hear that someone's home has been destroyed or someone is dead.

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  • Ampster
    replied
    Originally posted by sdold View Post
    A long time ago I ran a forum (actually a BBS) and ended up as a defendant in a suit because of something that happened on the forum. A lot of details have faded from memory but one that stands out was my attorney telling me that I was liable for things said on the forum unless I did no editing or moderating, Since the owner isn't going to let this turn into a free-for all, we'll be moderating as best we can with safety in mind, but also to keep things civil.
    Details could be important depending on what was said. Any more relevant examples? Perhaps the law has evolved since the BBS days. Don't get me wrong, anybody can be sued. The real issue is has there been any judgements of significance?
    Not applicable to private forums. Besides, if someone suggests something that we think is dangerous, free speech notwithstanding, we'll remove it.
    I was referring to First Amendment protecting forum owners from liability under the theory that posters were protected from liability by the First Amendment. I am am curious to hear from the forum owner since It seems like in this short part of this thread there is already inconsistency among moderators. Does the forum owner have a policy? Is that available in some form as a guideline to us posters.

    For example, I was timed out six months ago and I don't know if it was because I disagreed with a moderator or he did not understand what I was suggesting. As Aaron has said, it would have been a better educational experience for the lurkers and participants to understand what the moderator thought was dangerous and what was not. Since then I have posted virtually the same comment that in California there is no legislation that says I have to ask permission of the POCO to install a UL certified Hybrid inverter if it is behind the meter and not connected to the grid. Same as a generator. Of course in the case of a hybrid inverter one has to obtain a building permit and I assume the same for a transfer switch for a generator. I went so far as to ask a building inspector in Sonoma County and he agreed. I also asked a lineman from PG&E and he could not refer me to anything or anybody that said anything different.

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  • sdold
    replied
    Originally posted by Ampster View Post
    Are there any real world examples of Forum owners being sued.
    A long time ago I ran a forum (actually a BBS) and ended up as a defendant in a suit because of something that happened on the forum. A lot of details have faded from memory but one that stands out was my attorney telling me that I was liable for things said on the forum unless I did no editing or moderating, Since the owner isn't going to let this turn into a free-for all, we'll be moderating as best we can with safety in mind, but also to keep things civil.

    Originally posted by Ampster View Post
    I thought there were First Amendment protections for free speech?
    Not applicable to private forums. Besides, if someone suggests something that we think is dangerous, free speech notwithstanding, we'll remove it.
    Last edited by sdold; 04-29-2019, 03:48 PM.

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  • AaronTSchultz
    replied
    Originally posted by nebster View Post

    The real issue with the moderating on this site is that it puts the mods in a position of needing to be subject matter experts as well as behavioral moderators. Yet, you guys cannot nor will ever be true experts on all the possible things people will want to discuss here.

    When those two things get conflated, the forum loses value and membership -- relative to other places where open discourse is permitted. Already this subforum has been essentially reduced to a quiet wasteland.

    To your point you made a few posts ago, you all made a conscious choice to have it this way. And that is fine! But, I'm not convinced that your measures have to be so draconian. It may well be possible to permit open discourse, to minimize liability, and still to be able to sleep at night after you've read what others have posted. Goodness knows, a bunch of other forums have managed to figure it out.
    Thank you for stating this in a much more effective, eloquent manner than my abilities permit.

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  • Ampster
    replied
    Originally posted by SunEagle View Post
    ................

    So if you feel my posts are not reaching the bottom 99%, then think again. I have to make sure anyone that comes to this forum gets answers to their questions and are given safe instructions to use the Solar pv technology. If I have to be a little stern or abrupt in my posts then suck it up because you are not responsible for the people that come here. I have been tasked with helping and keeping them safe. You have not.
    I have heard several moderators say that they are responsible for keeping owners of the forum from being sued. Are there any real world examples of Forum owners being sued. I thought there were First Amendment protections for free speech?
    There is also risk telling people what a safe process is unless you cover every aspect of the procedure. As noted above I think the First Amendment covers that also. I think a disclaimer at the beginning of this forum or something that people acknowledge when they sign up would be more effective but that is the owner's call not mine.

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