Ken Zemach

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since Dec 24, 2017
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Recent posts by Ken Zemach

Ryan Hobbs wrote:  need to know what it is I have to have....

1. An old pair of running shoes. (~$5)
2. A rock (free) or an old knife ($1)

I would argue that’s the permaculture approach...
1 year ago
As an ultrarunner I find that the weight kinda falls off if one can run for about 8+ hours/week.  Plus it’s great for the mind.  As the saying goes, if you haven’t figured out the answer to your problems after a 5 hour run, you probably never will.  

All that said, while it’s supposed to be a bit tongue in cheek, the truth in the following rings true, and it’s how I approach exercise.
1 year ago
Another vote for Sandor Katz’ book.  He is the widely recognized modern western godfather of fermentation.  

We always have a container or two bubbling away on the counter.  Kimchee, asparagus, cauliflower+beets, broccoli and cauliflower stalks, Brussels sprout stalks, hot sauce... the list goes on.  Then, when we’ve finished the veggies inside, dilute the residual fermented brine with water and it makes an awesome pho noodle soup base. Waste not, want not.
1 year ago

Pearl Sutton wrote:What WOULD be safe then? I can't afford (and don't want) a premade powerwall, I will need something of this ilk at some point, what IS safe? I read your post and all the unsafe things, what is left? What is a good answer? You have a LOT more experience than me, what do I need to look at?

So perhaps I'm a bit more safety oriented, but I work in the field (obviously), so I'm going to lean on only releasing things which are safe.  There are generally three types of controls one considers when putting a complex LiIon system together:

1. Ensure the incoming cells are "as safe as can be reasonably assured."   This is done by a) only purchasing from a reputable manufacturer and b) assessing the health of each and every cell, even though they're brand new, before they go in a product.  There are a couple of ways this can be done, such as AC impedance checks, self-discharge rate, etc., but all require you to know what the results for that cell are supposed to be.  

2. Ensuring your assembly is well protected, monitored, and features various safety checks and disconnects.  Things like low voltage cut off (that's more to protect the cells; not so much a safety thing), temperature monitoring (and possibly control; note that Tesla and Chevy and basically almost every EV manufacturer out there save Nissan has liquid cooled/heated battery packs), current interrupters (usually an integral part of the cell design), PTC (again, usually designed into the cell already), brick level voltage monitoring (meaning monitoring the voltage and as well as charge and self-discharge rate of each parallel string of cells), and I'm probably forgetting a few, other than having your charge and discharge controller (part of your BMS) take all this into account.

3. A system design that accounts for what will happen WHEN a cell goes into thermal runaway.  Because it happens, even if you do everything right, there is a very very small, but not zero chance that any given cell may have an internal defect that was not caught in cell formation, incoming checks, and even the first few years of life.  So if that cell DOES go into thermal runaway, what is your propagation protection to keep it from setting off its neighbor, and then that one setting off its neighbor, and getting a chain reaction.   Sometimes it happens, but you'd be surprised at how a well-designed module or pack can have multiple cells be thermally initiated and NOT translate into the entire battery catching fire.    Think of this as planning for the worst case scenario.  Go search the internet for a video of a teardown to the cell level of a Tesla Powerwall, or Model 3. [Edit:  forget the powerwall videos, all the ones I just checked are from older Gen1; just go straight to the Munro work on the Model 3.] Then ask yourself "what the heck is all that stuff in between all the cells?"  Answer:  protection.

Honestly, what _I_ would do if I were going to do a home build is either salvage an entire pack from some EV that has hit end of life, or use deep cycle lead acid.   Seriously.  I would build a small module (say, maybe 9 cells in a 3x3 config max), but after that, you would not catch me trying to assemble a larger home build out of Li-Ion cells.   Ask yourself why the TSA won't let you check batteries.  Terrorists?  Riiiight.   If the general public knew the number of Li-Ion fires that occur on planes each year, they wouldn't complain about the packing rules so much.  Yeah, it's usually less than 10, but it's always more than 1. [Edit:  it's worse than I recall...  "According to FAA records, there were 46 incidents with lithium-ion batteries on aircraft in 2017 -- up from 31 in 2016."  Remember these are commercial batteries made by real companies.]

If after all that you still REALLY want to do it, and you don't want to buy something already assembled at the base level from a place like (which is still very ghetto, but better than a home-build), then just understand the level of risk.   I'm not saying don't do it, but if you're going to do it, figure out what your #3 is.  If/when something goes wrong, ensure it won't harm a person, or cause significant financial harm.   Then have at it.
1 year ago

Caleb Mayfield wrote: ...and only Primary (non-rechargeable) cells based on the Li-(CF)x chemistry can produce Hydrofluoric Acid as that is the only current Lithium based chemistry with Fluorine atoms.

Everyone:  I get that everyone is trying to help, and making suggestions, and you think that reading stuff on the internet that hackers and DIYers have done somehow makes it true, but the amount of incorrect, missing, and generally misguided statements which are unsafe in this thread is concerning.  

First off, CFx is absolutely not the only type of Li-based battery that forms HF in during combustion or venting.  All of the standard Li-Ion cylindrical cells you are proposing have a liquid electrolyte which is an extremely complex mix of usually more than 15 different chemicals and additives; things like EMC, DMC, and, of course, LiPF6 (lithium hexafluorophosphate).   The "F" in LiPF6 readily forms HF when exposed to water, including moisture in the atmosphere.  I am betting you don't have a calgonate kit on hand in case you get some electrolyte on your skin.  I'm betting you don't know how HF goes into your skin, and then effectively continuously leaches calcium out of your bones which if it happens to a large enough extent is painful, debilitating, and completely untreatable once it happens (unless you treat with calgonate quickly).   Which is why no one in our cell chemistry lab is allowed to work with or open cells until they've taken HF training along with specific cell safety training.

Other things of note: someone mentioned that if you charge cells below freezing it can kill the battery.  True.  But it's not that simple; you need to understand WHY that happens, because there is a direct safety implication there too.  When you charge a cell either too quickly, or below a certain temperature, you can't intercalate Li ions into the anode at the same rate you're pushing them across the separator boundary, and you end up plating out metallic lithium (which is then irreversible by the way).  That plated lithium forms dendrites which then eventually grow to puncture the separator, and short the cell internally.  If it's a small dendrite, it can form a "soft short" which keeps discharging your battery.  But if that grows, or forms a larger short as it tends to over time by melting back the separator in the surrounding area, and if you have no dV/dt monitoring to catch it and stop using that battery, there is a reasonable probability that you WILL start a fire.   So what's the magic temperature?  There is none, because it's a relationship between temperature and charge speed that is specific not only to a particular capacity or chemistry of a cell, but how cell is rolled, the porosity of the separator and any protective coatings on it, the electrolyte used, the level the anode was calendared (compressed), the ratio of natural to synthetic graphite used in the anode, blah blah blah.

I applaud anyone's efforts to do home-builds as I love the can-do attitude, but from what I'm reading here, just don't think for a second that your build is going to be 'safe.'  I'm not saying that it's not going to work and possibly work well for years, but that doesn't mean it's inherently safe.
1 year ago
Another vote for Chard. Plus it looks really nice. I love Kale but don’t grow it because it gets seriously infested with aphids.  Some sacrificial Kale here and there as aphid traps and to lure ladybugs to the area, yes, but it’s too frustrating to grow to eat for me.
I think it depends on what you’re going to plant in the resulting soil.  I’d say no root veggies obviously, and probably shy away from annual edibles.   In fact, if you have a choice I’d only go with drywall scraps for non-people edible areas.  It’s PROBABLY safe for something like fruit trees, but that’s not good enough.  

I’ve used it quite a lot for high-clay soils (I soak it in a trash can of water for a day or two to soften it up before mashing and mixing). If it’s from old drywall removal, then I still soak and make sure to peel off the top painted layer which actually comes off pretty easily.  Landfill the painted layer; use the rest.
2 years ago
So far I’m a big fan. I have two varieties, still both small, but growing quickly once they hit their second year.  Yield in our harsh dry conditions here (Reno NV) has been pretty good.  Wife thinks they taste too mealy, but I like the variety.

Didn’t realize they would easily hardwood root; I guess it’s time to start massive propagation projects!
2 years ago
Cool!  I’m at 215 bags this year.  Trash morning curb action.
2 years ago
I think there are two answers to this.

The first is how much biomass is actually contained in leaves/clippings.  Answer:  Not. Very. Much.  A giant bag of crass clippings might give once decomposed, dried out, and with some loss to wind/digestion/etc, I dunno, maybe a single handful of organic matter if you're lucky? Try throwing a cup of coffee grounds on the ground and see how much higher it is... not at all.

The second answer though is that said handful of organic matter should ideally get mixed into the top of your 'regular' soil by worms, blending the line between the two, and dual a bit of dual duty in total "good soil" creation.  

I find the best answer is to collect metric crap-tons of leaves during the fall, and inter-layer those with a bit of manure (I have to get mine bagged as I have no free source, and composted bagged manure from Home Depot is less expensive and easier to move around than bulk deliveries (which is strange, but true).  The manure (maybe use 1ft3 per every 4-5 full bags) results in a) weighing the leaves down a bit for the winter and b) much, much faster decomposition and saves me having to chop them, turn them, etc.  They don't break down all the way in a year, but good enough to plant through.
2 years ago