Battery Engineering Hack Chat

The power in your pocket

Wednesday, December 14, 2022 12:00 pm PST Local time zone:
Hack Chat
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Dave Sopchak will host the last Hack Chat of the year on Wednesday, December 14 at noon Pacific.

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Of all the things driving technology forward, you'd have to say that the ability of chip makers to squeeze more complex circuits than ever onto silicon has to rank right up there. And while that's no doubt true, it only tells a part of the story. For our money, though, the advancements in battery technology over the last 30 years or so are the real champ, because without compact, cheap, energy-dense batteries, almost none of the cool stuff we see today, from smartphones to electric vehicles, would be practical.

Battery technology has come a long way from the days when carbon-zinc and nickel-cadmium cells were kings. New chemistries, better materials and methods, and engineering improvements have all contributed to incredibly powerful, incredibly compact batteries that make applications nobody could have thought of just a few decades ago possible.

Dave Sopchak has been in the thick of battery engineering since taking a doctorate in electrochemistry from Case Western Reserve. Since then he has worked at several fuel cell start-ups, and is now working on a lithium-air battery that sounds really interesting. We've asked him to help us wrap up the 2022 Hack Chat series with a discussion on battery engineering, with a focus on upcoming technologies and advancements that could really put some power in your pocket.

  • Hack Chat Transcript, Part 4

    Dan Maloney12/14/2022 at 21:57 0 comments


    Dave Sopchak1:05 PM
    OK. I'll send it after this

    Dave Sopchak1:05 PM
    what i'll give myself 15 more min before going back into my dank lab

    Thomas Shaddack1:05 PM
    the laboratory is a temple, because the chemist is a god.

    Dave Sopchak1:06 PM

    Dave Sopchak1:06 PM
    well it has its perks

    Dan Maloney1:06 PM
    And here I am just writing up the "time's up" thing...

    Thomas Shaddack1:06 PM
    magnetron sputtering!

    Dave Sopchak1:06 PM
    not all dank

    Dave Sopchak1:06 PM
    yes, that would be correct

    Thomas Shaddack1:06 PM
    should get into that. sadly, the only thing in my shop that does not suck is the vacuum pump.

    Dave Sopchak1:06 PM
    well @Dan Maloney is it ok if we go a little over if I promise to clean up?

    Dave Sopchak1:07 PM
    @Thomas Shaddack well, I know a guy...

    Dan Maloney1:07 PM
    Absolutely fine! But I'll just say the official "Thanks!" and let the conversation wind down naturally.

    Dave Sopchak1:07 PM

    kjansky11:07 PM
    Need to work on Mg Al batteries for lower cost and material availability.

    Dan Maloney1:07 PM
    Thanks to Dave for stopping by today and to everyone for a great discussion!

    Dave Sopchak1:08 PM
    it has been a pleasure. thanks for inviting me

    Tom Johnson1:08 PM
    As a comms-guy I feel like I should ask about any open-source BMS projects.

    Dusan Petrovic1:08 PM
    Thanks everyone!

    Tom Johnson1:09 PM time. Thank you.

    Dan Maloney1:09 PM
    You bet, I really enjoyed this one -- anytime I get to talk about plutonium is a happy time! Thanks for helping us wrap up the 2022 Hack Chat season with a bang!

    Thomas Shaddack1:09 PM
    Had a thought about the bidirectional buckboost. Change the architecture of e-vehicles. Have a small Li-titanate battery built in, as a low-temp tolerant high-current high-cycle tolerant primary source for the engines. Have a power bus from it to the bays with the buckboost nodes. Put anything into the bay - a conventional Li-ion battery, a hydrogen fuel cell, a turbine fed with dry-distilled waste plastic scavenged after the zombie apocalypse, a completely new emerging battery chemistry, or nothing if we conserve weight and do not need distance, and go.

    Dave Sopchak1:10 PM
    @Tom Johnson not my ball of wax but I'll keep my ear out for the BMS stuff. Grateful folks are working on other pieces of the puzzle. I only have two hands

    Dan Maloney1:11 PM
    FYI, I'll be posting a transcript once things wrap up a bit, in case anyone needs a link or whatever

    Dave Sopchak1:11 PM
    Mixing and matching power sources depending on the application is always a good thing to do. There are no one size fits all solutions

    kjansky11:12 PM
    I guess we just need to keep charging on!

    Thomas Shaddack1:12 PM
    Same for stationary power. Have matching circuitry that can feed a battery bank, a hydrogen electrolyzer, whatever we got. Without having to plan for things in detail during initial build.

    Dave Sopchak1:12 PM
    I haven't tried, but I would suspect some resistive heating of cold Li ion batteries might help them warm up faster. I'd be surprised if this wasn't used to some extent already, to the limits of what you could get away with without damaging things

    Dave Sopchak1:12 PM
    meaning, the battery is more resistive when it's cold, so its internal resistance should warm it up a bit...

    Thomas Shaddack1:12 PM
    Have a big power plant made from smaller modules. If needed, break off modules and move them where they are needed more. If something fails, we degrade performance by the percentage of disabled units and continue on.

    Thomas Shaddack1:13 PM
    I saw somewhere a battery with built-in resistive heaters.

    Dave Sopchak1:13 PM
    a nuclear reactor on every rooftop! What could possibly go wrong?

    Thomas Shaddack1:13 PM
    In every basement. Rooftops are for the backup generators in tsunami/flood areas.

    Dave Sopchak1:13 PM
    One time we started our fuel cells up from -30C. it took a while but it worked

    Thomas Shaddack1:13 PM
    well, the sun itself is a nuclear reactor fed with a fossil fuel.

    Dave Sopchak1:14 PM
    can't do that with nafion....

    Read more »

  • Hack Chat Transcript, Part 3

    Dan Maloney12/14/2022 at 21:56 0 comments

    kjansky112:36 PM
    C14 would be a great power source with its huge lifetime and low energy betas.

    Dave Sopchak12:36 PM
    yeah well be glad for Bosch-Haber Thomas!

    ILove Scotch12:36 PM
    @Dave Sopchak in the hackaday article it says "lithium-air battery" your working on. I didn't know you can reverse the process in the cell.. my only experience is with the open air ones.

    Thomas Shaddack12:36 PM
    Fritz Haber FTW, the man who feeds billions!

    Dave Sopchak12:36 PM
    when he wasn't killing thousands!

    kjansky112:37 PM
    Haber is very energy inefficient.

    Thomas Shaddack12:37 PM
    I saw some variants where microwaves were used instead of high pressure high temperature.

    Dave Sopchak12:37 PM
    maybe they should use a C14 betavoltaic to drive Bosch Haber

    Dan Maloney12:37 PM
    I'm working on an article about improved catalysts to increase the efficiency of Haber-Bosch, FYI

    kjansky112:38 PM
    That's one h--- of many C14 megacuries.

    Dave Sopchak12:38 PM
    @ILove Scotch yeah in a nonaqueous Li air battery, you make lithium peroxide on discharge. That's the easy part. Oxidizing the lithium peroxide back to oxygen without trashing the battery has eluded everybody...except me ;)

    Thomas Shaddack12:39 PM
    Better idea. Thorium reactor and microwave synth rig. Nitrogen from air, hydrogen from water, ambient pressure microwave-assisted reaction, scalable factory that can act as local power plant when the wind gets counterrevolutional ideas and stops blowing and birdwhackers stop providing.

    Dave Sopchak12:39 PM
    that nitrogen nitrogen triple bond is *not* easy to break, so it goes

    Thomas Shaddack12:40 PM
    microwave chemistry whacks the bonds directly without having to vibrate the whole atom including the nucleus that's there in only for a ride while taking the most mass.

    Dave Sopchak12:40 PM
    Born-Oppenheimer approximation?

    kjansky112:40 PM
    Catalytic nitrogen fixing bacteria with enhanced efficiency genetic would make Haber obsolete.

    Thomas Shaddack12:40 PM
    similar for photochemistry.

    kjansky112:41 PM
    Brute force Haber is inelegant!

    Dave Sopchak12:42 PM
    you know, if Bosch Haber didn't work, I'd say scrap it

    Thomas Shaddack12:42 PM
    Inelegant but nice to have. High volume density, and controllable.

    Dave Sopchak12:42 PM
    let's talk electrolytic steel refining

    kjansky112:42 PM
    It works just about as well as diesel engines work but for how long can be use it?

    Thomas Shaddack12:42 PM
    is it similar to copper refining, or to aluminium production? aqueous low-temp or hightemp molten salt?

    Dave Sopchak12:42 PM
    also @Thomas Shaddack cool with the kapton pyrolysis

    Dave Sopchak12:43 PM
    high temp, the trick is to use electrochem rather than coke to be the reductant.

    Tom Johnson12:43 PM
    Not sure if this is off-topic or not. Regarding storage ... on the control side, are things moving towards standardization? Meaning inverters becoming tightly integrated with BMS systems?

    Dave Sopchak12:43 PM

    Thomas Shaddack12:43 PM
    said kapton pyrolysis could be also useful for eg. making flexible capacitive touch sensors. alternative to conductive inks.

    Dave Sopchak12:43 PM
    even with aluminum, the carbon anodes get chewed up to CO2...

    Dave Sopchak12:44 PM
    @Tom Johnson not off topic but I have no idea. Anyone else?

    Thomas Shaddack12:44 PM
    ah, so no electrorefining, more like electrowinning. i understand refining as purifying a substance that's already produced in previous step.

    ILove Scotch12:44 PM
    @tom "Meaning inverters becoming tightly integrated with BMS systems?" Nope.

    Dave Sopchak12:45 PM
    @Thomas Shaddack Ah! I need to up my terminology game there ;)

    Dave Sopchak12:45 PM
    I say we turn this whole inverter issue on its head (ducks)

    Thomas Shaddack12:45 PM
    close enough to be understood with just a single question. :D

    Tom Johnson12:46 PM
    There are the Mesa standards modbus ... which seem to be supplanted by SunSpec. I was curious as to how fast integration was being taken up.

    kjansky112:46 PM
    Space vacuum mass spectroscopic refining is the way to go with unlimited solar...

    Read more »

  • Hack Chat Transcript, Part 2

    Dan Maloney12/14/2022 at 21:56 0 comments

    ILove Scotch12:02 PM
    Mods please delete my last link to licap, it's is incorrect and wrong page i linked. these are standard ultracaps.

    Dave Sopchak12:02 PM
    @ILove Scotch that lithium ion capacitor is not a battery, nor a hybrid. It's a capacitor. Look at that pathetic energy density. You're just shuttling ions, not doing reactions

    Dan Maloney12:02 PM
    So can you share a little more about how you got mixed up in electrochemistry? Sounds like it might be a cautionary tale...

    Dave Sopchak12:03 PM
    tbh, my first exposure to it was when I was a little kid and my dad showed me the penny/salt water on a bit of paper towel/nickel battery would make a voltage

    Dave Sopchak12:03 PM
    within a year I decided, hey how about a sheet of aluminum, a sheet of copper, and bleach? Got enough to run a model motor but fast!

    Mark J Hughes12:04 PM
    My understanding is that all batteries -- going back 200 years depend on electrochemistry. But if the pundits are to be believed, there's a movement towards quantum (solid-state) batteries that do not make use of ionic movement or chemical reactions. Do you know anything about these next-generation of energy storage devices?

    Dave Sopchak12:04 PM
    no I don't. You have linky?

    Mark J Hughes12:05 PM
    Also -- if someone wanted to study battery technology -- what should they start reading to better understand the lingo & problems battery engineers try to address?

    Dave Sopchak12:05 PM
    so, let's get a few things straight- a solid electrolyte does not a solid state battery make. There are volume changes on *all* battery electrodes depending on the state of charge

    anfractuosity12:06 PM
    not heard of that before sounds interesting, just looking at -

    Mark J Hughes12:06 PM
    Well -- one example:

    Dave Sopchak12:06 PM
    also, the definition of an anode, you know, the one Michael Faraday gave it, is an electrode that does an oxidation. An electrode that does a reduction is a cathode.

    Mark J Hughes12:06 PM
    (Sorry don't have anything immediately on hand that isn't marketing spiel from some place, so I went to academia)

    Peter Smith joined  the room.12:07 PM

    Dave Sopchak12:07 PM
    it doesn't matter what the voltage of the electrodes are, or if they're charging or discharging, all that matters is what they're doing- oxidation or reduction

    richt22 joined  the room.12:07 PM

    Dave Sopchak12:07 PM
    so despite the fact that the material scientists and others don't know their terminology...

    ILove Scotch12:08 PM
    Dave I meant this earlier "The negative electrode or anode of the LIC is the battery type or high energy density electrode. The anode can be charged to contain large amounts of energy by reversible intercalation of lithium ions. This process is an electrochemical reaction."

    alex.bailes joined  the room.12:08 PM

    Dave Sopchak12:08 PM
    this more informal and ever expanding definition of "battery" and other terms kind of muddles the water. I know I can count on you all to fight the good fight!

    Dave Sopchak12:10 PM
    hey @ILove Scotch OK, but still...they're stretching the definition there. Intercalation takes time. I'd like to see how fast they can charge or discharge it. If it's a battery, it's got a hard upper limit, otherwise you'll plate lithium out and screw up the cell

    Dave Sopchak12:10 PM
    double layer charging, even in solution, is much faster than a chemical reaction

    ILove Scotch12:11 PM
    it has properties of both, hence hybrid.

    Dave Sopchak12:11 PM
    I would hope it cycles faster and longer than a Li battery

    ILove Scotch12:11 PM

    jondaddio12:13 PM
    "New High-Performance Solid-State Battery Surprises the Engineers Who Created It" with link at

    Dave Sopchak12:13 PM
    I mean, at the moment Li ion...

    Read more »

  • Hack Chat Transcript, Part 1

    Dan Maloney12/14/2022 at 21:55 0 comments

    Dave Sopchak10:42 AM
    oh man I should put on a clean shirt

    Dan Maloney10:43 AM
    Hi Dave! We're strictly come-as-you-are around here. Thank God, because I'm rarely presentable

    Dave Sopchak10:44 AM
    I'm just happy to be here, hope I can help the ball club

    Dan Maloney10:47 AM
    Excellent almost "Bull Durham" reference ;-)

    Dave Sopchak11:03 AM
    we gotta build 'em one cell at a time

    Dave Sopchak11:12 AM
    So last week I was down in Pasadena, visiting my friend who runs SAFCell. They make cesium dihydrogen phosphate fuel cells that run at about 250C. It's a great temperature for doing internal reforming of methanol or ammonia. It's only waste heat if you don't use it!

    Dan Maloney11:16 AM
    That's interesting, we've been talking about fuel cells lately in our editorial meetings. Like from a "whatever happened to fuel cells?" perspective.

    Dan Maloney11:17 AM
    Weren't we supposed to have fuel cells generating electricity on a building-by-building basis by now?

    Tom Johnson joined  the room.11:22 AM

    Aidan Fraser joined  the room.11:23 AM

    Dave Sopchak11:25 AM
    fuel cells are still around!

    Dave Sopchak11:25 AM

    Dave Sopchak11:25 AM
    the ones running homes were using reformed natural gas

    Dave Sopchak11:25 AM
    and we doan wanna use no fossil fuels, even efficiently

    Dave Sopchak11:26 AM
    My neighborhood, I have a couple of neighbors with fuel cell cars- both the Toyota Mirai and one had a Honda Clarity

    Dave Sopchak11:27 AM
    they *loved* the cars, but even here in the commie SF bay, the hydrogen filling stations have had a spotty uptime

    Tom Johnson11:27 AM
    Hi Everyone. Self introduction. I'm an embedded developer working on renewable energy communications protocols, consulting with a DC-area EPC that has intentions of getting into the storage market. Happy to help with protocol questions ... except canbus since I don't have any experience in that one.

    Dave Sopchak11:27 AM
    one of my neighbors still loves his Mirai

    Dave Sopchak11:27 AM
    Hi Tom!

    Tom Johnson11:28 AM
    Hi Dave. Thanks for doing this. Looking forward to making small zaps in my backyard.

    Dan Maloney11:28 AM
    Seems like that's the essential problem -- can't have a hydrogen economy until you have hydrogen demand, and the demand won't be there until there's an infrastructure to support it.

    Dave Sopchak11:29 AM
    Fuel cells would still handily beat batteries for trucks- railroad too

    Dave Sopchak11:29 AM
    fast refuel, and if you want MOAR ENERGY just have more hydrogen tanks. The reactant is separate from the power generation

    Dave Sopchak11:29 AM
    just like with an IC engine (except so much better)

    Dave Sopchak11:30 AM
    whereas with batteries, for a truck, that's a lot more weight for more range

    Dave Sopchak11:30 AM
    even for a car, but 400 miles is pretty good for 99.9% of driving

    Tom Johnson11:30 AM
    Anyone working on battery trailers? That seems like a low-hanging fruit to get small EVs across the country nonstop.

    Dave Sopchak11:31 AM
    you think? hauling more weight?

    Tom Johnson11:32 AM
    Wepends on weight to energy.

    Dave Sopchak11:32 AM
    I've taken trips with friends here in California and from Connecticut to Ohio in the last year, and man Tesla has chargers all over the place for fast recharges

    Dan Maloney11:32 AM
    I've seen Teslas with generators stuffed in the trunk. That's kind of a solution /s

    Dave Sopchak11:32 AM
    oh man

    Dan Maloney11:32 AM
    Gotta grab some lunch, brb

    Dave Sopchak11:33 AM
    well, I suppose where things get sketch in the Great Basin maybe. Better to be safe

    Tom Johnson11:33 AM
    Gotta fill the interior with plants. Oh wait thats CO not CO2.

    Dave Sopchak11:33 AM
    well, just have a good catalytic converter on your generator and it'll be all CO2

    Dave Sopchak11:34 AM
    So Tom the closest I got to what you're doing was doing a USB device specification for portable fuel cells

    Dave Sopchak11:35 AM
    boy that'd be fun with USB type C now. Charge everything direct over USB

    Tom Johnson11:35 AM
    Something else to be stolen in bad neighborhoods.

    Dave Sopchak11:35 AM

    Read more »

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Dave Sopchak wrote 12/14/2022 at 02:31 point

Mike, check out

that's the Edison iron battery, or nickel/iron

  Are you sure? yes | no

malone.a.mike wrote 12/14/2022 at 10:49 point

Thanks for this, Dave.

I'm certainly no Chemist, and 'tis a long time since I was messing about in a school chemistry lab too.

That Nickel-Iron battery sounds interesting. Any idea why it is deemed expensive to manufacture?

As far as I remember, car brake lines are nickel placed steel, which could potentially provide a ready-made electrode.

The reasons the (Acquion style) salt water battery grabbed my attention are that it is a proven technology, can provide precisely what I need - 100W for hours at a time, thereby halving my grid electricity usage - is robust, safe (fire/explosion), non-toxic, long-life, seems to be relatively simple...

But perhaps real-life - as distinct from demonstration - DIY batteries are outside the capabilities of the ordinary guy.

  Are you sure? yes | no

Dave Sopchak wrote 12/14/2022 at 17:19 point

Aquion has that "DIY salt water battery" on one of the links, but you're not going to make a battery capable of delivering 100W out of copper wire and nails and keeping it in your garage. 

So from the way they describe that DIY rechargeable battery, it's a copper/zinc salt water battery. First thing I'd try with that after following their directions would be, what's the charge that such a battery could hold? If you use copper and zinc sheet and a thin separator, how much more charge could the battery hold and how many cycles could it do?

It's fun to try a DIY rechargeable battery, but nails and wire in a big jar of salt water does not lend itself to a lot of energy density for a battery.

Apologies I missed the link you provided to the aquion DIY instructions at first.

  Are you sure? yes | no

malone.a.mike wrote 12/14/2022 at 19:27 point

Hi Dave.

Can't seem to respond to your last message, so placing a response here.

I think that DIY battery is just the efforts of that particular web site team, and not the actual Acquion battery technology, which seems to use Manganese Oxide as the cathode and Carbon Titanium Phosphate as the anode.

Anyway, thanks for the time you have given me, and for the effort in trying to explain complex matters to an old guy like me.

Take care.

  Are you sure? yes | no

Dave Sopchak wrote 12/14/2022 at 02:22 point


Totally with you on giving a hearty f u to Russia. I have friends in Ukraine, but even if I didn't, my grandfather moved from there to the US in 1905.

Yeah looks like aquion has gone under.

When you think of rechargeable aqueous batteries, the oldest type of course is lead-acid. These days nickel metal hydride is another success story.

As far as a roll your own DIY rechargeable battery...I don't know of an easy one off the top of my head. I poked around on the internet this weekend because I should at least see what might be out there. I was thinking of the canonical Daniell cell, copper/zinc, from long ago. It's not rechargeable afaik, but with some playing around perhaps it's possible to get it to recharge a bit.

The thing that one wants to avoid when recharging a battery is breaking down the solvent, so in this case it's water. 

in the case of a Daniell Cell, when it's discharged, copper sulfate in solution plates out on the positive electrode (acting as the cathode now) and the zinc that the negative electrode is made of oxidizes to zinc ions in solution (negative electrode acting as an anode). To recharge it, you'd reverse the process, with the negative electrode becoming a cathode and hopefully plating zinc, while the now copper coated positive electrode becomes an anode and oxidizes the copper to copper ions back in solution.

We know that Daniell cells weren't used as rechargeable batteries, can plate zinc out in an aqueous solution. One of the big competing reactions there would be evolution of hydrogen/breakdown of water, and this would slowly but surely increase the pH of the electrolyte as hydroxide gets left behind when the hydrogen goes.

I worked on iron/chromium flow batteries, but I wouldn't recommend playing around with a lot of chromium chloride and hydrochloric acid, but they were rechargeable. 

There might be some iron chemistries out there that would work. Edison had an iron based battery...I think it was rechargeable.

If I was going to DIY a rechargeable battery, I'd start small and see how things go- I have a friend, ham radio operator, who asked me a similar question a few months ago.

As an example (although not rechargeable), I often do an aluminum-air battery as a demonstration. If I use a 10x10 piece of foil as my anode and some copper mesh/battery graphite for the air cathode, I can get enough potential and current to run a small hobby motor- about 0.5V at 100 mA, or 50 mW. Sounds nice, but...if I want to charge my phone, I'd need 5V and 1A, so I'd need an Al/air battery 100 times bigger, so a square meter of aluminum foil, and that's just to charge my phone. These demo batteries I make will last maybe half an hour to an hour.

  Are you sure? yes | no

Garth Wilson wrote 12/13/2022 at 20:21 point

malone.a.mike:  Ah yes, I was forgetting about the problem in Europe.  Our electricity here is $0.17 per kwh if we stay below 256kwh/month.  Most of the US is paying far less than that.  As for lead-acid batteries, it sounds like you're thinking of car batteries which are optimized for starting, rather than deep-cycle ones that are made to handle 1500 or more deep cycles and last 20 years or more if you take good care of them.  It only takes about five deep cycles to kill a car battery.  I have four 232AH 6V deep-cycle Interstate GC2 lead-acid batteries, meaning about 5kwh capacity (although I hope to never have to discharge more than 50%).  They're about seven years old.

Our refrigerator takes about 110W when the compressor is running, but several times that much when defrosting, which I think takes about 15 minutes four times per 24 hours, or something like that.  I had thought that if things get really bad, it'd be good to have one of those small office refrigerators that takes a lot less energy, and then just forego the luxuries like ice cream.  OTOH, if the food supply gets bad too, you'd want to be able to keep more on hand.

The problem I've had is that modified-sine-wave inverters are so easily destroyed, apparently by reflections off the ends of long connections, because of the fast edge rates of the waveform.  When you see people demonstrate them on YouTube, even with very heavy loads, they only have the 6-foot (2m) cord on the equipment, not 50 or 100 feet (15m or 30m) like it takes to get the power from our detached garage to the far end of the house.  We went through a lot of them; and although most were replaced under warranty, I say the best warranty is the one you don't have to use.  At the recommendation of another engineer friend, I finally spent the money on a Renogy pure-sine-wave inverter that's supposed to be able to do 2kw continuously and 4kw for a few seconds (not just a couple of cycles).  It's only been in service three months so far.  Hopefully it will last many years.

  Are you sure? yes | no

malone.a.mike wrote 12/14/2022 at 11:19 point

Hi Garth.

In my researches I had determined that a micro grid tie inverter - one little inverter per solar panel - would be the most suitable for my needs, and was in the process of designing one when I tripped across some already available via the usual Chinese outlets, and I bought a couple.

I already had a 100W polysilicon solar panel from a few years back that I got with the intention of sometime experimenting with it or putting in into service.

The Russians got my enthusiasm for that fired up and I hooked it up to one of the above little grid-tied inverters, while also acquiring a second 100W (monosilicon this time) solar panel.

I was surprised to discover that half of my average daily usage was that fridge-freezer. I *can* buy a newer model that would halve that, for maybe €800. I estimate it would take over 13 years to pay back that cost, even at the current - temporary? - elevated cost of electricity.

I think lead-acid might have a similar cost and payback time.

All to save in the region of 375Wh (0.375kWh, €0.16 ) per day.

Hence my interest in a potential DIY solution.

Although it might seem like madness to continue to pursue this when I have already cut back so much, nonetheless if I can halve my electricity usage yet again it is worth it psychologically to me. (And a few extra bob that I can send to Ukraine.)

  Are you sure? yes | no

Garth Wilson wrote 12/14/2022 at 21:03 point

Wow, I didn't know those micro grid-tie inverters existed.  That Trojan you linked to though is about twice what I paid for similar capacity in my Interstate batteries seven years ago, with no trade-in.  (It's cheaper if you trade in old ones.)  My main purpose in doing my solar was to have power if the grid goes down long-term because of social unrest, political unrest, EMP, whatever (as things weren't looking good at the time), but it would be nice if it paid for itself eventually too.  We have had some brief outages of a few hours since then, and it was nice to have.  I have wished the refrigerator had the intelligence to take an input from the solar to turn its thermostat a little colder when there's sun and a little warmer when there's not, and to bias the defrost-cycle timing to when there's sun.  As you may know, the fridge takes a lot more power in the first second of startup.  Ours takes over a thousand watts for that first second; so it takes a sizable inverter.

  Are you sure? yes | no

malone.a.mike wrote 12/15/2022 at 07:49 point

Hi Garth.

Replying here, as cannot reply to your most recent post.

Yes, if you need a standalone system then a sizeable inverter is required to accommodate motor startup currents, but for a grid-tie system then the grid provides for those momentary surges.

The system I have been putting in place has other driving factors, brought on by my desire not to give the Russians a penny, rather than being able to operate independently of the grid.

It would be really nice if I could have employed one of those Acquion type batteries as that would potentially have eliminated my fridge-freezer as a grid consumer, and halved my grid consumption at the same time.

(Maybe I'll come across on old forklift battery that I could use for the same purpose. That would probably even do my cooking too :)  ).

Hope you have a good Christmas.

Take care.



By the way, there are probably some things about those micro grid-tied inverters that you should know, just in case you are interested in them.

1) The enclosure is NOT waterproof, and there have been reports from some users that theirs have blown as a result of getting wet (inside). I have mine positioned on the underside of their respective panel and this seems to work OK, although I am only half way through the winter as yet.

2) They can get hot when operating near maximum power. Hotter than I would like. Heat is the enemy of electronics. Daily summer temperatures here rarely exceed 30 Celsius (86 F) so it you live in a warmer clime then that might be something to prepare against. (Maybe mount it on a metal plate, or stick the heat sink from the CPU of an old scrapped PC onto it.)

3) There are advantages to micro inverters, i.e. 1 inverter per solar panel.*

a) The power rating of the inverter can be better matched to the panel, possibly increasing efficiency

b) As each panel is operating at different solar and temperature conditions, the MPPT in the individual inverters will be better able to keep their panel at the maximum power point (e.g. if part of 1 panel becomes shaded that will not affect the operation of the other panels as 1 single large inverter would, and the inverter for that single panel will still maximise the power from that shaded panel)

c) The length of the low voltage heavy current cabling is reduced, reducing losses in turn

d) Easy to install - IMO - and easy to add extra panels to the system

* There does not HAVE to be 1 inverter per solar panel. Panels can be connected in series or parallel and share an inverter of the appropriate rating. E.g. 2 x 200W panels could be connected is series and make use of a single 500W inverter (I like to overrate a bit - I use 120W inverters for each of my 100W panels)

Indeed, the use of series-connected panels - which give a higher output voltage - could potentially increase low light (morning and evening) output, if the inverter can kick in at 'low' panel output voltages and the MPPT is reasonably well implemented.

There may be other things that I cannot think of right now.



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malone.a.mike wrote 12/07/2022 at 17:59 point

Re: Battery HackChat

Has there been any advances in simple to make DIY batteries that could be used to extend the usefulness of solar PV systems? Batteries such as the salt water type, for instance?

During the summer, my 100W fridge-freezer is my single greatest consumer of electricity on a daily basis. My small 200W - soon to be 480W - peak solar PV system would be able to be the source for most of this daily energy requirements IF there was a storage system that could source 100W for hours at a time, as salt-water batteries are claimed to be able to do.

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Dave Sopchak wrote 12/08/2022 at 19:08 point

Hi Mike, you have linky to the chemistry of the salt water batteries of which you speak? It would help to know what the typical energy you need for your fridge through the night- hook up a kill a watt and see how many kWh it uses over a 24 hour period, and when the sun ain't shining. 

Also, there's probably some non battery ways of getting your freezer to keep stuff cold longer...

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malone.a.mike wrote 12/13/2022 at 11:44 point

Hi Dave.

The Russians annoyed me. A lot. Near the beginning of this year I decided to cut down on my energy usage. I walk where I can. I cut down on heating. I cut back  non-essential electricity usage (water is just fine, even for this tea and coffee addict).

I began to monitor my electricity usage. To my surprise, my fridge-freezer consumed 0.75kWh/day on average during the summer. It is roughly 95W, and ran for maybe 1.5 hours out of every 4, or even longer on warmer days. (It starts off consuming about 110W, drops to about 100W after about 15 minutes. When running over an hour it had dropped to 90W or a bit less).

I live in Ireland.

By the end of the summer, I had got my electricity consumption down to 1.2kWh/day of which the fridge was still around 0.7kWh-0.75kWh.

I have 2 small (100W) solar panels than I got into service during the early summer for one and middle summer for the second. These were giving me about 18kWh per month by summer's end, with surplus going to the grid at no benefit to me.

If I had a battery that could supply around 100W for hours at a time then conceivably my solar panels could provide a lot of the energy required by my fridge. (And I could add another panel or two.)

I have tried lead-acid, and find them unsuitable for this. Lead-acid is very suitable for providing large currents for short durations - such as starting a car engine, where it might supply 300A or more for 5 seconds - but I find that even supplying 30W for more than 4 hours kills them (over a period of months).

And they are expensive.

LiIOn would certainly do the job, but would be gross overkill for my needs as well as expensive, and not at all environmentally friendly (as yet).

I came across this

Acquion manufactured a salt water battery that could supply the 100W for long durations and with a lifetime  in excess of a decade.

But they went bankrupt a few years back.

Water might be cheap and plentiful. But it is heavy and bulky, and therefore expensive to ship.

But this type of battery might be a candidate for the DIYer.

What would need to be known:

Salt type and concentration

Electrode material(s), shape, size and spacing

Any inter-electrode (gap) filler material

Suitable casing material

This type of battery could be located outside in locations where weather conditions permit, or could by built in a form factor that would suit European domestic appliance slot-in locations in a kitchen or utility room.

If able to benefit from time-of-day energy saving tariffs (e.g. night time low cost) then even a location with no renewable energy source could still charge the battery during off-peak and use during the day or other peak times. If with solar, then excess solar could be used to charge and the battery used to supply energy when insufficient solar available, with the possibility of using time-of-day charging as well for those times of the year when little or no solar energy is available.

It might not suit everyone, but it would suit me just fine.


Another link which might prove useful

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Garth Wilson wrote 12/13/2022 at 10:22 point

I had read of a promising salt battery almost 50 years ago that was supposed to do even better than today's lithium batteries for EVs.  I believe the claimed energy density was similar to that of gasoline.  Obviously it never materialized (like probably so many things in Popular Science magazine).

Whatever kind of batteries you make or buy, be sure to compare the cost of the battery wear to the cost of the utility.  Even here in California where we pay some of the highest prices of the nation for electricity, I find it still comes out cheaper to run things on the utility when the sun is down, rather than using the batteries; so I just have batteries for when the utility goes down, and otherwise try to mostly keep the load from exceeding the PV's output level.  Lead-acid's weight and size make it a lousy choice for EVs; but for the house where weight and size don't matter, their price is still good compared to lithium, and when they're shot, they can be reconditioned for a lot less than buying new, and when they can't be reconditioned anymore, they're still 100% recyclable, unlike lithium.

I don't use a cell phone, and the seldom times I use my laptop computer, it's almost always plugged into the wall, as its battery life is only a couple of hours max, even with a new lithium battery pack.  My 1980's HP hand-held computers OTOH go months or even years on a set of alkalines.  There's no watching videos there, but they still have their place.  What I get most benefit from modern batteries from is my bicycle headlight, due to the combination of better batteries and LED lights being several times as efficient as incandescent lights.  What we had in the 70's was terrible.

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malone.a.mike wrote 12/13/2022 at 12:06 point

Hi Garth.

(Also see my earlier response to Dave.)

My electricity costs at the moment are about €0.43 per kWh (about $0.45 at current exchange rates).

But the primary reason I am doing this is the Ukraine war. I am taking what the Russians are doing in trying to overthrow a nascent democracy and their war crimes personally).

I have a small 2 x 100W solar panel system which has 2 x micro grid-tie inverters. Having cut back severely, these can provide enough energy to power my daytime needs during the summer months, with any surplus going to the grid at no benefit to me.

I hope to add another couple of panels next year.

I have determined that my single greatest use of electricity on a daily basis is my fridge-freezer. This requires a nominal (as determined by me) 100W.

If I could come up with a battery system that could provide 100W nominal for hours at a time and last years then I could potentially eliminate my fridge as a grid consumer, at least during the summer months.

In my researches, I came across the salt-water battery concept, and a commercial manufacturer of these called Acquion Energy, now deceased. (They were reportedly bought out of bankruptcy by a Chinese outfit, and little to nothing has been heard of them since.)

Most of the information I have come across is of the publicity blurb type, and of no real use.

But the concept intrigues me, particularly the possibilities for the DIYer.


Another link which might prove useful

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