LiFeP04 Batteries for Solar & BMS

[PNjunction]

Thank you Sunking for bringing us back to reality.

It's enough to make one want to crumple their tinfoil conspiracy-hat in disgust. I know I did, and am still fine tuning the new one.

The litmus-test for me always has been availability to the common man, under NORMAL means of business without having to hack anything. There are hacking forums for the hacking crowd. Not all of them are safety-unaware, but because kids don't see lifepo4 at their local auto store, they may assume that getting damaged goods is how it is done.

Ok, my tinfoil hat is adjusted and properly blocking the gamma rays now. Time for me to cool off I guess.

[Sunking]

Interesting. So, the heavy metals are worth recovering. Well, at least the stream is getting processed.

My comment is in respect to the after market of used or salvaged EV batteries.

There is a market for salvaged batteries. In fact a huge demand and every Auto Salvage Yard operation knows it. They have waiting list and prices are fixed high for what you get which equates to a huge gamble. When you look at the end result, the economics are not there even if the gamble pays off unless it is a niche application like a Go-Kart, Golf Cart, E-Bike, Electric Buggie etc. gain a considerable loss of weight and higher energy density boost. In a solar application role there is little to no benefit lithium energy density brings with it unless it might be a boat or RV where space and weight come at a premium. But it would be insane to install salvaged batteries into an RV, Boat, or a home taking the chance to burn it down. No professional would even dare suggest or recommend such a thing.

As for Nissan, Tesla, Toyota, Chevy or whatever manufacture you want to name reclaiming used batteries and reselling them is complete nonsense for the same reason no professional would do that. Liability risk is huge. The batteries are worth more sold as SCRAP to a recycling center. Only time a manufacture is going to take possession of a used battery is a Warranty Claim replacement or Maintenance replacement. Otherwise all others go to Salvage dealers who sale it as Junk.

Salvage Yards are the only ones who can get away with selling wrecked or used batteries. The fact that you are buying them knowing they are salvaged and no warranty or liability is assumed by the seller. You bought junk knowingly.

Putting salvaged batteries in something like a Go Kart or Golf Cart is one thing where there are no codes or ethics. Putting them in a home, RV, or Boat is just plain dangerous and careless. It does not conform to any known or defensible codes or practices. Something a Hack or DIY does either out of ignorance or stupidity if they know better.

Manufactures do not sell used underwear.

[nativewolf]

It is easy to recycle lithium batteries. Issue is there is no money or demand for lithium recycling. The cost of obtaining lithium from recycling batteries is 5 times higher than buying it from a refined source from South America. No company would chose to use recycled lithium.

Don't think just because lithium is not recycled there are tons of batteries just lying around because that is not the case. Recycle operators run them through the hammer mills to recover Cobalt, Nickel, Copper, Aluminum, and Manganese. The lithium recovered, what little there is, (3% by battery weight) is thrown in the trash pile because there is no market for it.

Interesting. So, the heavy metals are worth recovering. Well, at least the stream is getting processed.

[Sunking]

Question: How do you recycle 200k LI battery packs? FAL is messy but understood now (caused a lot of issues figuring it out though). How is society going to recycle all those battery packs?

It is easy to recycle lithium batteries. Issue is there is no money or demand for lithium recycling. The cost of obtaining lithium from recycling batteries is 5 times higher than buying it from a refined source from South America. No company would chose to use recycled lithium.

Don't think just because lithium is not recycled there are tons of batteries just lying around because that is not the case. Recycle operators run them through the hammer mills to recover Cobalt, Nickel, Copper, Aluminum, and Manganese. The lithium recovered, what little there is, (3% by battery weight) is thrown in the trash pile because there is no market for it.

[SunEagle]

I know nothing about the 123 issues but I guess folks were hawking rejects from that process. I suspect that LG, NEC, and Tesla/Panasonic will all be hawking battery packs. The Tesla packs are interesting right now and like all Musk things...well he is going to sell. I've got no crystal ball but having met Musk I can assure everyone that he will sell. I also don't understand some of the comments about making a buck off of Musk. The only person that is going to make a buck off of Musk will be SolarCity and Tesla shareholders. Having seen some pictures of the "home made projects" some of these projects seem too "hacked" to be safe. Some seem to be very well engineered compared to professional jobs, to compare I guess I need to tour some off grid homes. Is there such a tour in the mid-atlantic? I guess I'd need an engineer to tour with.

Are some folks here saying that the Tesla power packs are not safe? If so why? Has any commercial EV ever caught fire sitting in a garage? By commercial I mean Tesla, Leaf, Volt too I guess.

I didn't mean to contribute to a hornets nest either. It just seems like a logical fate for 200k (and growing) EV battery packs. I don't see them getting destroyed anymore than a used anything with value getting destroyed and if bouncing around in a hot vehicle did not cause the battery packs to destroy themselves than I don't see how sitting still in a controlled space will make them more dangerous. I'm just trying to figure out alternatives to a $60-120k utility connection fee. I'm a year away from building in any case so I suspect I will see lots of news on the PowerPacks etc in the meantime. It does not seem out of the realm of good engineering to be able to repurpose battery packs assuming safety is taken into account. But if this is not kosher let me know, I actually would rather discuss panels sizing/wattage/ground mount suggestions.

Question: How do you recycle 200k LI battery packs? FAL is messy but understood now (caused a lot of issues figuring it out though). How is society going to recycle all those battery packs? What an interesting thought. I mean we are quickly getting to the point where 50k a year will be coming out of service (say in 2020?).

My mistake was in trusting that the EV sellers (like Nissan and Tesla) to have a plan in place to properly dispose or retire used battery banks because as you noted there are going to be a lot of them in a few years. If they have not done their due diligence of creating a disposal plan then they have contributed to a very big issue by adding to our toxic waste problems.

I am not complaining about batteries used in commercially built EV's. They continue to get safer and better and I will probably purchase one in the future.

I am concerned about the DIY're reusing EV Lithium battery packs for home energy storage systems. While some of the home built systems look "engineered" they are not. Add the complexity of a volatile battery chemistry with a very unique charging system and cooling requirements just increases the chance of someone making a mistake and causing a fire. Even the experts make mistakes.

I just want to caution others who think they can save money reusing old batteries that sometimes saving a few bucks results in pain and sorrow if safety isn't kept at the top of the list.

[Living Large]

I'm just trying to figure out alternatives to a $60-120k utility connection fee.

You and me both. I am right in the same ballpark at $60K and $133K, depending on which route is approved by my HOA.

It does not seem out of the realm of good engineering to be able to repurpose battery packs assuming safety is taken into account. But if this is not kosher let me know, I actually would rather discuss panels sizing/wattage/ground mount suggestions.

Question: How do you recycle 200k LI battery packs? How is society going to recycle all those battery packs? What an interesting thought. I mean we are quickly getting to the point where 50k a year will be coming out of service (say in 2020?).

You could start a thread on recycling L-I batteries, if that is an interest - where it would be more "kosher". As far as repurposing EV batteries in solar applications, my read is that discussion has already taken place here, assuming it isn't deleted by attempting to continue.

[nativewolf]

Unfortunately, mostly in the hands of hacks and kids that don't know any better until it sets their home on fire. One only has to look at A123 counterfeits and used rejects ending up in the wrong hands, when they should have been destroyed.

Oh well, just because you can doesn't always make it right - suppose I can't do anything about that. Maybe Nissan SHOULD!



Hah, FLA salesman said that 5 years ago already and probably will 5 from now. Gotta love battery guys with crystal balls. ALWAYS wrong, but it does sway the gullible.

Good luck with your project. I'd be more interested if it wasn't 99% about pricing issues and salesmanship, even if you aren't one.

Tip: as much as I LOVE my lifepo4 batteries, peppering the threads with an anti-FLA crusade really destroys your street-cred. I don't use FLA either. But, it shows that you are out of touch with reality, and are not really matching the battery to the application at hand. For now, and for MANY years to come, FLA is the proper battery to use for many applications, NOT lithium. Lithium, even my beloved lifepo4, is not a one-size-fits-all solution, and NEVER will be.

I know nothing about the 123 issues but I guess folks were hawking rejects from that process. I suspect that LG, NEC, and Tesla/Panasonic will all be hawking battery packs. The Tesla packs are interesting right now and like all Musk things...well he is going to sell. I've got no crystal ball but having met Musk I can assure everyone that he will sell. I also don't understand some of the comments about making a buck off of Musk. The only person that is going to make a buck off of Musk will be SolarCity and Tesla shareholders. Having seen some pictures of the "home made projects" some of these projects seem too "hacked" to be safe. Some seem to be very well engineered compared to professional jobs, to compare I guess I need to tour some off grid homes. Is there such a tour in the mid-atlantic? I guess I'd need an engineer to tour with.

Are some folks here saying that the Tesla power packs are not safe? If so why? Has any commercial EV ever caught fire sitting in a garage? By commercial I mean Tesla, Leaf, Volt too I guess.

I didn't mean to contribute to a hornets nest either. It just seems like a logical fate for 200k (and growing) EV battery packs. I don't see them getting destroyed anymore than a used anything with value getting destroyed and if bouncing around in a hot vehicle did not cause the battery packs to destroy themselves than I don't see how sitting still in a controlled space will make them more dangerous. I'm just trying to figure out alternatives to a $60-120k utility connection fee. I'm a year away from building in any case so I suspect I will see lots of news on the PowerPacks etc in the meantime. It does not seem out of the realm of good engineering to be able to repurpose battery packs assuming safety is taken into account. But if this is not kosher let me know, I actually would rather discuss panels sizing/wattage/ground mount suggestions.

Question: How do you recycle 200k LI battery packs? FAL is messy but understood now (caused a lot of issues figuring it out though). How is society going to recycle all those battery packs? What an interesting thought. I mean we are quickly getting to the point where 50k a year will be coming out of service (say in 2020?).

[SunEagle]

5 years ago EVs were a novelty, now the volume is probably >100x higher with lots of models from different manufacturers. Battery production capacity is climbing extremely rapidly, Teslas new factory alone will output as much as all of todays battery factories together. Production price for lithium batteries for EV use is expected to decline to around $100/kWh in a short time. Thus the announcement of the PowerWall. So we will see in 5 years time, I would however expect much more to happen in the next 5 years than in the previous 5.

There is no question that the battery chemistry used for EV's will continue to improve and go down in price. The problem is using this type of battery technology for "non EV" systems that are not properly built, tested and safety approved before they are sold to the public.

Using EV batteries (especially used ones from "retired" EV's) is not safe or smart. Most DIYer's that believe they have the knowledge to build a home energy storage system using junk parts are in way over their head and more than likely will get themselves or others hurt.

Now since this thread involves LiFePO4 batteries and not EV rejects please get back to the Topic or I will close the thread and purge all postings involving junkyard batteries.

[jkirkebo]

Hah, FLA salesman said that 5 years ago already and probably will 5 from now. Gotta love battery guys with crystal balls. ALWAYS wrong, but it does sway the gullible.

5 years ago EVs were a novelty, now the volume is probably >100x higher with lots of models from different manufacturers. Battery production capacity is climbing extremely rapidly, Teslas new factory alone will output as much as all of todays battery factories together. Production price for lithium batteries for EV use is expected to decline to around $100/kWh in a short time. Thus the announcement of the PowerWall. So we will see in 5 years time, I would however expect much more to happen in the next 5 years than in the previous 5.

[PNjunction]

Whether you like it or not, uset EV batteries will be used for stationary storage. Do you think Nissan will recycle all the swapped Leaf-batteries?No, they will all have a second life as stationary storage before recycling. An EV battery with 70% capacity left still has a huge value.

Unfortunately, mostly in the hands of hacks and kids that don't know any better until it sets their home on fire. One only has to look at A123 counterfeits and used rejects ending up in the wrong hands, when they should have been destroyed.

Oh well, just because you can doesn't always make it right - suppose I can't do anything about that. Maybe Nissan SHOULD!

Large LiFePO4 cells will be a dead market in 5 years if the prices aren't slashed at least in half, probably a price of 1/3 of todays is needed to still be able to compete.

Hah, FLA salesman said that 5 years ago already and probably will 5 from now. Gotta love battery guys with crystal balls. ALWAYS wrong, but it does sway the gullible.

Good luck with your project. I'd be more interested if it wasn't 99% about pricing issues and salesmanship, even if you aren't one.

Tip: as much as I LOVE my lifepo4 batteries, peppering the threads with an anti-FLA crusade really destroys your street-cred. I don't use FLA either. But, it shows that you are out of touch with reality, and are not really matching the battery to the application at hand. For now, and for MANY years to come, FLA is the proper battery to use for many applications, NOT lithium. Lithium, even my beloved lifepo4, is not a one-size-fits-all solution, and NEVER will be.

[jkirkebo]

You just don't get it and keep on slyly hawking used batteries, regardless of whether or not you get them to "work".

That is entirely irresponsible here. Sure, in some of the experts hands over at DIYELECTRICCAR that can be done safely and properly. Take your wares over there, where that crowd can deal with them responsibly. Or take it to Endless-Sphere, where some are responsible, there is a whole crowd who think nothing of using duct-tape and junk cells. I frequent both, but I always keep in mind the engineering needs here are different. And oh yeah, it is also different from hacking laptop cells to power your flashlights over at Candlepowerforums.

The engineering for a solar housebank is DIFFERENT from that of an EV, regardless of whether you can hack those cells to work.

I can see the keyboard fingers flying. Hmmmm how can I make a buck on the Musk market - I know! Tell amateur hacks they can duplicate it with crash-victim Nissan cells of their own.

No matter your self-justification, replete with salesman-like figures, it is just WRONG and can be in many cases illegal. Some might actually want to know who your source is, so we can start to examine the hazmat shipping records for compliance all along the chain, where these cells, regardless of whether they work or not, are intended for TRUE recycling, and not slipped out the back door for resellers. I think Nissan might want to keep track too.

Did your wrecking-yard provide you with a warantee? - I think not. You are a GAMBLER, and here we don't like to gamble with safety.

A123 pouch cells suffered the same fate from amateur hacks like yourself promoting used and unsafe batteries under the umbrella-term of "recycled". So it is no surprise to see that done here.

What you are promoting is admittedly finely crafted prose in order to not set off any immediate red-flags, but I read right through it and cannot willingly help to create any sort of black-market buzz.

Note that I'm not new to this game either - when years ago reject / recalled Optima agm's were slipped out the back door by non-authorized dealers instead of being sent back, recycled or destroyed - looking to make a quick buck on the cheapskates and unknowing.

Instead of promoting responsible use of lithium, you are helping to destroy the industry - if you can look that far.

Whether you like it or not, uset EV batteries will be used for stationary storage. Do you think Nissan will recycle all the swapped Leaf-batteries? No, they will all have a second life as stationary storage before recycling. An EV battery with 70% capacity left still has a huge value. Nissan probably won't sell to the solar off-grid marked, but rather to markets like cell-tower backup, data-center or hospital backup etc. No-one will scrap cells and modules with many years of life left.

Probably more vendors specializing in off-grid applications will appear, buying up modules and building finished battery banks with several years of warranty and all safety equipment built in, for a price a lot lower than new LiFePO4.

Heck, Tesla is already taking orders for the PowerWall, a finished product which they are selling cheaper than bare LiFePO4 cells. The PowerWall is complete with BMS and all necessary safety equipment, which makes it a much safer option than builing your own LiFePO4-pack.

Large LiFePO4 cells will be a dead market in 5 years if the prices aren't slashed at least in half, probably a price of 1/3 of todays is needed to still be able to compete.

BTW, I don't sell any battery products and I don't make any money from it. I work as a train driver. And I get my battery modules locally, as shipping lithium is an expensive hassle.

My next project is building a portable battery for my Waeco cooling box, from 4 Leaf modules and a DC-DC. I am tired of lugging around 200Ah of FLA.

[Sunking]

Time for the Devil to speak and advocate. Buying salvaged batteries from wrecked EV is a great idea, and can be an economical good choice if the application is worth the risk, and you are willing to gamble the batteries are still good working condition.

If you think this idea is unique or new please think again as it is anything but new. Every salvage yard in the country has a waiting list for EV battery packs and they go to the highest bidder in most cases. Going price for a Nissan Leaf battery is $2200 to $2750 depending on model year. Is that a good price for a 24 Kwh battery. Not really once you consider you likely have a 2 to at most a 5 year battery. You can buy top of the line 7 year FLA for $200/Kwh so price wise it is more than top of the line FLA and is a complete gamble buying a salvaged battery. A new Rolls or Trojan Industrial cost less, will likely last longer, and comes with a factory warranty and support.

As for the size and capability question. 24 Kwh is not that large for a home sized Off-Grid System. In a LFP about a 6 to 8 Kwh per day battery requiring a 2 to 4 Kw panel system to generate that much energy. So from a charging point of view, much higher charge rates on solar than a Level 1 EV home charger at 1500 watts. So charge and discharge capabilities are a moot point and do not really enter the conversation. Does not matter what flavor of lithium you like, any flavor will exceed all but extreme solar applications. There are only 2 real meaningful things using a lithium battery in a home system can do for your.

1. Is use a little less panel wattage because charge efficiency is higher. However will not offset the higher cost of the batteries.
2. Will allow you to use a smaller capacity battery on a large Inverted. FLA batteries you want to limit to no greater than C/6 and C/8 is the recommended max discharge rate on FLA. With any FLA battery out there you can run 1C discharge rate and still have less than 2% voltage sag.

Back to the issue of where to use salvaged lithium batteries. If you are thinking of using them in your home or an RV that you sleep in and have limited exit points. No way would any professional would recommend such such primitive risky behavior. If any professional even attempted such silliness deserves to loose their license and sued out of biz so they never darken any ones door again. That is what hacks do.

However you wanna build a golf cart, buggie, or some outdoor gizmo, then you have a candidate application of salvaged lithium battery. But be warned from a financial POV is still most likely a looser, and high risk of catastrophic failure which may result in a fire.

[solar pete]

GREAT question actually and I'm glad you brought it up because this isn't a new phenomenon, and especially important for a newbie.

For now, forget the chemistry - it doesn't matter whether you use lead-acid or lithium. What happens is that the newbie is struggling to just get the basics down - that is, power consumption over time, proper charging parameters, solar insolation hours etc, and STILL the system is failing despite to be seemingly following all the rules. With used batteries, you don't know WHERE you are going wrong. Is it faulty power measurements, my wiring, my panels, my batteries? Or is it a combination of all these things?

In other words, you may be chasing your tail endlessly without actually knowing how bad your batteries are.

By starting from fresh, the mistakes you make with the battery will be all your own, and aids you in figuring out problem faster. Not only that, but it is cheaper if you totally blow your first battery from mistakes - in fact you can actually learn a LOT from that! But you don't want to do that to a very expensive bank at the outset. We commonly call these "learner batteries".

Take a look at the cost of some high-end floodeds like Rolls-Surrette. If you came to me asking about them, and me knowing that you don't even know what a hydrometer is, and how to use it, your very expensive bank could end up being very heavy trash very fast. That would be irresponsible of me to foist that on you, unless I was trying to SELL you something and slink away. Instead, I would recommend something cheaper that would provide you the education you need, and if a major mistake happens, you haven't totally blown your budget and are now out of the game completely.

This is not something we invented here - ALL major forums that deal with batteries, especially with newcomers are pretty rigid about safety. This one is no stranger to battery safety either, and does not promote used batteries for the beginner:

http://forum.solar-electric.com/forum

Thing is, "hacks" are popular, and there are many outlets for that there to attract your click-throughs and whatnot. Essentially, most of them are unsafe, or at the best, badly engineered. Ever see a 5-year "followup" video on their junk? They don't want you to become educated - they just want you to pay up sucker.

RE - EV vs solar housebank cells. I kind of covered it here:

http://www.solarpaneltalk.com/showthread.php?22145-Basic-LiFePo4-purchasing-primer

Essentially, small cylindricals, unless they are A123, are in the first place not LiFePo4, but a different lithium chemistry that is engineered to provide HUGE amount of current in a very tiny space to fit inside vehicles. They are higher in energy density than lifepo4, have much tighter charge control routines, and have a very TINY margin for abuse. In other words, instead of just venting or bulging with abuse, those EV non-lifepo4 small cylindricals tend to vent with flame. I know which chemistry I would use in my garage.

Consider that the major motorcycle powersports battery makers that use lithium that you SIT ON TOP OF, that is Shorai, Antigravity, and many others all use LiFePo4, NOT the chemistry used in EV type cells. Of course those cells are too small in capacity for our use.

Forget about abuse - when you are dealing with a common solar housebank, you are sizing the capacity to give you what - 8 hours to days of operation? That means that your power draw will be very slight, and even the large prismatics may tend to think of our dinky loads as a mere irritant. BUT, if you try to build it lunchbox size, then the engineering is different (requires laptop like cells whose chemistry is not as safe as lifepo4), and multitudes of additional complexities arise.

Lastly, by paying for small cylindricals whose current handling capabilities are waaay beyond your solar needs, you are wasting money on a feature you'll neve take advantage of. Yes, they work of course, but are not ideally matched to the application at hand.

We call this "shoehorning" when we mis-apply things to the application. Usually this appeals to the cheapskate in all of us, and there are many out there with wringing-hands just waiting for your wallet to open.

In these forum threads, the point here is to enjoy solar and battery operation safely and efficiently with each other, although it does sometimes degrade to "bench racing" specifications. When it just comes down to "how to save money!!! (read salesman emulating a user), and doesn't care if you blind yourself, blow off a finger, endanger others, or somehow avoid the advice from those who know how to play it safe - beware.

So really it is not an attack at all - but an education from those who have been down this road many chemstries ago.

+1 ,Nice Post, well said sir.

[SunEagle]

We're not talking about cars that are junked because of age or flooding here, or cars that have been in major accidents where the battery too has suffered structural damange. We are talking about new to 3-4 year old cars that have been in accidents serious enough to not make it economical to repair, but which have also left most of the cars parts in good shape. Typically except fenders, hood, trunk lid and so forth. Car repairs have been getting more expensive the last years, EVs even more so, so it doesn't take all that serious a collision to send an EV to the wrecking yards. The battery modules from those are generally of exceptional quality, closely matched together and needing minimal balancing.

Heck, you could even buy a used 2012 Leaf just out of lease, dismantle the battery and end up with a cheaper 24kWh battery bank than you can get from new large prismatic LiFePO4. For example, to get ~24kWh from these: http://www.ev-power.eu/Winston-40Ah-...-2V-400Ah.html you'll need 19 of them for a total cost of over $10k + shipping. You can get a nice Leaf for $10k with minimal battery degradation, and you'll still have a whole car to sell parts from after dismantling the battery. A nice pack would be 6P8S from the modules (which are 2P2S internally) for a 12P16S battery (60V nominal).

And the EV batteries keep falling in price fast, while large prismatics really haven't moved much lately. Nissan already sells a new 24kWh pack for $5000, though you need to return the old one. Tesla sells the 10kWh PowerWall for $3500 which is $8400 for 24kWh. Still 16% cheaper than LiFePO4 cells. The LiFePO4 manufacturers really need to get the prices down or be left in the dust. Their problem is that the volume is so small compared to EV battery volume.

It doesn't matter to me if the EV is old or new. If it has been taken out of service then the lithium batteries need to be properly disposed of and not used for a barnyard designed home energy storage system.

Saving money is not a justification to use a potentially dangerous device and I would be surprised if your local authorities would feel it is safe to use in your home.

My guess is you have broken a number of codes and rules building your system. So my advice is to make it safe and don't get anyone hurt.

[PNjunction]

Huh from a newbie perspective with no, and I mean no clue on building a solar system (other than a few weeks reading of forums- this being like my 3-4th post) you seem to be awfully keen on attacking this idea. I just thought it was clever. but then I'm a forester and farmer and consultant, so I like clever solutions to expensive troubles. So, educate me. Why are the EV lithium cells different? Why would the Tesla power pack work?

GREAT question actually and I'm glad you brought it up because this isn't a new phenomenon, and especially important for a newbie.

For now, forget the chemistry - it doesn't matter whether you use lead-acid or lithium. What happens is that the newbie is struggling to just get the basics down - that is, power consumption over time, proper charging parameters, solar insolation hours etc, and STILL the system is failing despite to be seemingly following all the rules. With used batteries, you don't know WHERE you are going wrong. Is it faulty power measurements, my wiring, my panels, my batteries? Or is it a combination of all these things?

In other words, you may be chasing your tail endlessly without actually knowing how bad your batteries are.

By starting from fresh, the mistakes you make with the battery will be all your own, and aids you in figuring out problem faster. Not only that, but it is cheaper if you totally blow your first battery from mistakes - in fact you can actually learn a LOT from that! But you don't want to do that to a very expensive bank at the outset. We commonly call these "learner batteries".

Take a look at the cost of some high-end floodeds like Rolls-Surrette. If you came to me asking about them, and me knowing that you don't even know what a hydrometer is, and how to use it, your very expensive bank could end up being very heavy trash very fast. That would be irresponsible of me to foist those on you, unless I was trying to SELL you something and slink away. Instead, I would recommend something cheaper that would provide you the education you need, and if a major mistake happens, you haven't totally blown your budget and are now out of the game completely.

This is not something we invented here - ALL major forums that deal with batteries, especially with newcomers are pretty rigid about safety. This one is no stranger to battery safety either, and does not promote used batteries for the beginner:

http://forum.solar-electric.com/forum

Thing is, "hacks" are popular, and there are many outlets for that there to attract your click-throughs and whatnot. Essentially, most of them are unsafe, or at the best, badly engineered. Ever see a 5-year "followup" video on their junk? They don't want you to become educated - they just want you to pay up sucker.

RE - EV vs solar housebank cells. I kind of covered it here:

http://www.solarpaneltalk.com/showthread.php?22145-Basic-LiFePo4-purchasing-primer

Essentially, small cylindricals, unless they are A123, are in the first place not LiFePo4, but a different lithium chemistry that is engineered to provide HUGE amount of current in a very tiny space to fit inside vehicles. They are higher in energy density than lifepo4, have much tighter charge control routines, and have a very TINY margin for abuse. In other words, instead of just venting or bulging with abuse, those EV non-lifepo4 small cylindricals tend to vent with flame. I know which chemistry I would use in my garage.

Consider that the major motorcycle powersports battery makers that use lithium that you SIT ON TOP OF, that is Shorai, Antigravity, and many others all use LiFePo4, NOT the chemistry used in EV type cells. Of course those cells are too small in capacity for our use.

Ironically, these lifepo4 large-format prismatic cells are mainly targeted to industrial, amateur or retrofit EV users, who need to keep things simple with a low cell count, and have properly done a power budget for the car's current capabilities, which in many cases is not needed with the advanced small cylindricals that commercial outfits need to use. In other words, prismatic's lesser capabilities as compared to small cylindricals is just fine for us. Not to mention using the safest version of lithium chemistry out there as well.

Forget about abuse - when you are dealing with a common solar housebank, you are sizing the capacity to give you what - 8 hours to days of operation? That means that your power draw will be very slight, and even the large prismatics may tend to think of our dinky loads as a mere irritant. BUT, if you try to build it lunchbox size, then the engineering is different (requires laptop like cells whose chemistry is not as safe as lifepo4), and multitudes of additional complexities arise.

Lastly, by paying for small cylindricals whose current handling capabilities are waaay beyond your solar needs, you are wasting money on a feature you'll neve take advantage of. Yes, they work of course, but are not ideally matched to the application at hand.

We call this "shoehorning" when we mis-apply things to the application. Usually this appeals to the cheapskate in all of us, and there are many out there with wringing-hands just waiting for your wallet to open.

In these forum threads, the point here is to enjoy solar and battery operation safely and efficiently with each other, although it does sometimes degrade to "bench racing" specifications. When it just comes down to "how to save money!!! (read salesman emulating a user), and doesn't care if you blind yourself, blow off a finger, endanger others, or somehow avoid the advice from those who know how to play it safe - beware.

So really it is not an attack at all - but an education from those who have been down this road many chemstries ago.