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Author Topic: Lithium cell balancing  (Read 657 times)

mobile_bob

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Re: Lithium cell balancing
« Reply #15 on: November 02, 2021, 08:06:30 PM »
this battery thing has been something that i too have given considerable thought to, a lot of research, and i too have concluded that the lithium batteries (and the variants) while showing promise look to be problematic for all the reasons previously discussed.

"if" one were to rethink his energy needs, i think an argument can be made for the simplicity and low cost of a system based on the lowly golf cart battery.

now if one wants all the modern creature comforts of modern living, then large traction batteries are likely something that is hard to beat, given a "complete" cost analysis (including risk factors).

"if" one gets really down in the weeds, and is willing to focus on an efficient system, with low cost per kw/hr, i can make a good argument for the automotive starting battery.  however not many folks want to get down into that level of use, or rather adapting to the system, rather than forcing a system to adapt to modern use.

we are probably still 10 years away from getting a quality lithium based battery, that is well protected and has a low risk of failure.  how low that risk factor gets is anyone's guess, and even if it does get to a low risk, that level of risk may well still be too high in the analysis.

in the end, it is hard to get a battery with the energy density of a gallon of fuel, as dependable, and at so low a price.  it appears to me that the lead acid battery still is a strong contender for stationary use.

bob g
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Fred8

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Re: Lithium cell balancing
« Reply #16 on: November 03, 2021, 02:46:20 AM »

Long story short, he'd had one cell die of sudden short every year for 3 years, and was so pissed at the unreliability of his  very expensive premium matched cells that he was considering changing his power system to locally available 48V fork lift batteries.  ​

I believe I know the gentleman you speak of.  I talk with him regularly.  IMHO the man is  an electronics genius and by nature a very through, rational, well educated and experienced in a wide range of industries and intelligent person as well as very helpful to others.  Far as I'm concerned, if he can't make these things work then they are garbage and unfit for purpose.  There is no way that he did anything but nurse the things with kid gloves and I know he was very disappointed  with them.  He is going to LA fork batteries and I doubt unless given to him he'd every consider  Lithium anything again.

Did he maybe just have bad luck? Maybe but aside from all the other failures people have had, he's had a failed system and been left very out of pocket through no fault of his own. Why would a sensible person do the same thing again and expect a different outcome?
Too big a risk for me because I know I'm never lucky.


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already some folks are very pleased with the reliability and lifespan of the very, very expensive BattleBorn 12V LFP batteries in marine applications (where size is a concern and cost is not so important.) 

I have also read glowing reports of the battlebornes and some not so good ones.  I think your statement of Cost not so Important is key here. The things are worth their weight in gold, or at least silver.  As you say, in marine applications, justifiable perhaps but for stationary storage, I do not see the point.  The cost of even 10 KWh of these things would probably by 30 or 50Kwh of LA.

I'm not even sure of the Benefits of Lipo in boats? Weight and size generally isn't an issue  In larger craft over 30 Ft and smaller don't carry many batteries anyway. Generally LA batteries are changed out annually because of the vibration boats experience. I really can't see the Lipos being more reliable and generally larger craft  have House and starting batteries that can be all paralleled for starting and  have reserve on the start batteries anyway.

Even if they took the replacement out to 2 or 3 years, I can't see the Lithiums being cheaper nor work out what the advantage is.
When these vessels carry couple of ton of Fuel, another ton or more of water and weigh 16T plus all up, can't even see what saving 2-300Kg of batteries is going to achieve. If they only have 1-2 Batteries, again, the weight saving would be lucky to be a 1% weight saving over all.

I know Lithiums are all the rage in the Caravanning/ RV game but weight savings there make sense.

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Lastly, I'll add that 3 or 5 W, 3.2V zeners do not provide a useful non-manual  balancing system- for many reasons, such as connecting and disconnecting them manually  is a farce,

Sounded like it to me as well simply because of the ability to forget the things while doing the balance and cook them this way. The rest sounded Hokum as well but I'm no electronics expert although it sounded suspect to me so I avoided going down that rabbit hole given the rest of the claims made I knew were complete and utter rubbish.


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  Likewise the absurd notion that only US made submarine lead acid batteries are good when I'm surrounded by off grid homes all reliably and affordably run on a variety of LA batteries.

I have no idea what a submarine battery is? I suspect it's nothing but a traction battery of a certain specification/ capacity.  I would bet they are used in other applications like telecoms backup etc rather than being made exclusively for subs. In any case, no matter how good they are, where do I and Joe public get them? Not a lot of Submarine  Supply stores round me as I think My Country only has half a dozen anyway so not going to be able to Nip down to  " Sub supplies are Us"  to grab a few.

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That is a well acknowledged fact, and it's why cell voltage monitoring is built into LFP packs; typically charging is disconnected when any cell goes to max voltage, and discharging is disconnected when any cell goes low.  This to required save the cell(s) from destruction. 

No smart or Conscientious DIY pack builder I have read of does without a BMS. Pretty much like running an alternator in your car without a voltage regulator somewhere in the system.
Contrary to the claims made, lithiums are a LOT more sensitive to voltage and charging than LA and to run a Lipo pack without a BMS is merely a ticking time Bomb.

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The LFP prismatic cells were then destroyed by excessive voltage.  The cell balancing hardware was also destroyed by too high voltage.  So a complete and total loss of well over $10K worth of new LFP batteries, all a cascade of destruction from a MPPT failure.

I have read of similar occurrences. poor quality BMS that crap out in short order and take everything else with it. Even the preferred brands are not fool proof.  Another common one is not having the setting incorrect for the particular Chemistry.  Some DO LA, lipo, Lif4 etc and all have different parameters. Incorrect setting May not kill them straight away but 6 Months can be enough to render valuable packs useless.


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I'm hoping that the quality demands of automotive manufacturers will force rapid improvement in LFP quality and reliability, and the price of bargain B grade cells today will purchase reliable cells in the future.

This will happen eventually but I can't see it for a long time. The relevant thing for me is your next comment.....

 
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I accept that I may still live out my life on lead acid batteries, and at what is now $17/month battery bank replacement cost, I won't lose sleep over that.  I won't switch until it becomes clear that it's cheaper for me to do so.

I -MIGHT- have 20 years left in me.  I'd like to think so but I also think I'm kidding myself a bit.  That means that an LA pack is well within capability of seeing me out.... if they don't come round trying to drag me out my house against my will to administer " Medications" to save my life before hand.  I don't see my electrical needs being much different in time to come and with days of reserve capacity anyhow and a well oversized solar system as well as WVO fuelled generators, what works for me now is still going to be workable in 10 to 20 (Ha!) years.

The only real requirement to me for longevity is  Return on investment.  As long as I get a decen't run out of something so it's amortised cost is reasonable, then what is the problem?  You mentioned $17 month for your batteries.   50 Cents a day is cheap power in anyone's language.  I have friends in the country that pay $1.56  SUPPLY charge then they pay for the power they use on top of that.

I don't need something to last 20 years or even 10. As long as the cost per day/ month works out as being reasonable, I'm not concerned if I have to spend a day every 3 years replacing something and getting new.
If one looks at something like those Tesla power walls, I have never seen a scenario in any country where the cost price can be recoupled in 10 years.  See a lot of convoluted slight of hand accounting to say they can which is largely BS. The maths is real Simple.

They hold 13 KWH of energy useable.  Multiply 13 by the cost of power per KWH in your area. Work out the value of that power over 10 years. This will assume you use that full 13 Kwh every day which will never happen but for arguments sake... Does the value of the power saved outweigh the cost of the battery?  NO! Not even close.  Won't work out over 15 years and then you have lost about 20% I think it is in battery degradation according to official ( and VERY optimistic IMO) figures which blows the ROI out further.

Compare that with an LA pack one may well get their ROI in 4 years and the numbers are very different and even if the things lasted 5 Years you are still ahead over lipo. 
For me, the cost of the power I use from the grid would be almost $5K year.  2 years and I have my entire LA system paid off. 

To me, THAT is a return on investment. 
Anything that take 10+ years  is a Justification for a toy or a hobby, not a financially sound or worthwhile decision.

LA is a financially sound decision for storage. Lithium is merely grandstanding or trying to show off at this point in time.

Fred8

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Re: Lithium cell balancing
« Reply #17 on: November 03, 2021, 03:37:15 AM »

"if" one were to rethink his energy needs, i think an argument can be made for the simplicity and low cost of a system based on the lowly golf cart battery.[/quote]

Where I am they are much more exy per KWH than fork packs.  I realise they are much cheaper elsewhere but one has to go with the best bang for the buck available to them.

If they were cheaper, it's only a matter of series/ paralleling them to get the required capacity.  as long as the DOD is not going to be too excessive, I see no problem with them.

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now if one wants all the modern creature comforts of modern living, then large traction batteries are likely something that is hard to beat, given a "complete" cost analysis (including risk factors).

This is what I have Found.  At my stage of life I want to enjoy the creature comforts. Not interested in living in a shoe box to save on bills, not interested in going round and unplugging wall packs to save 20W a day, I want to be comfortable and enjoy myself.  I have put up a very large for a domestic solar system and can generate more than I use so I use it within reason. Not stupidly, just so I don't have to concern myself with Running the AC or heating the whole house rather than walking from a warm room to a frigid one.

Fork pack allows these comfort with it's capacity and that of the solar I have and the backup gennys if I need them.

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"if" one gets really down in the weeds, and is willing to focus on an efficient system, with low cost per kw/hr, i can make a good argument for the automotive starting battery.

If the Number of batteries was sufficient so they operated within their design parameters of maybe an average discharge of only 10% DOD,  then again don't see why they wouldn't do.  Might only have a 3-4 yr life anyway but if the cost works out, nothing wrong with that.
A Large car battery is around 100 AH which you might have to rate as 10  useable so you would probably want a few but that's a storage not a technical issue.  Cost of leads and terminals between them all might be a significant cost though.

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we are probably still 10 years away from getting a quality lithium based battery, that is well protected and has a low risk of failure.

I believe quality Lipos are available now.  It's just the cost of them is excessive and people naturally gravitate to the cheapo 2nd grade cells  which are the good ones that failed in the manufacturing process to meet the required standard of the first quality cells.
If you want good lithiums, they are out there. If you want a good Car Rolls Royce is still available and similarly priced.
I'm happy with a Ford or Gm but some people now are buying those Chinese cars.  Good luck to them!

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in the end, it is hard to get a battery with the energy density of a gallon of fuel, as dependable, and at so low a price.

It is in fact IMPOSSIBLE by a very long measure to get a battery anywhere near the energy density of any liquid fuel.  I forget the number but 9x less energy on the best batteries to liquid fuel seems to stick in my mind.
Put it this way, a large car battery has roughly 1 Kwh of energy and that's Pulling it way down below where it's meant to go.  1 Litre of liquid fuel has 10 KWH of energy. Lithiums are better but still impractically short when compared to liquid fuels.

I saw a Doco on this a while back.  They compared some ultra High density battery to liquid fuels and got it to about a quarter I think it was of comparable density.  The battery had to be super cooled and was highly unstable.  They compared the energy density of other materials and said  a battery with the same energy density as liquid fuels is called a Bomb because of the energy that would have to be stored in it and the instability of such a chemical composition.

They also showed what it would take to make a long range airliner electric powered.  Not going to happen in my lifetime or anyone else's here I suspect. One thing they pointed out was the further a regular place goes the lighter it gets as fuel is burned off. With an electric, it's draging round the dead weight of the discharged battery cells the whole distance.  Makes a big difference to the energy required  for a long distance flight.

I have some battery chainsaws and they are great.  No lighter than a similar sized petrol  one but they have great torque and good endurance.  Matter of horses for courses.

Same with EV's. so much less range than an IC.  Say that and the tesla fans jump up saying the model whatever can go so far on a charge.
Not really.

I learned recently when talking to an owner the range is nothing like stated. Go over 80 KMH and the range plummets.  Highway speeds here is 100/110.  At that speed you loose 100km+ in range on these EV's,  Yes, if you want they can " Hyper Mile" along at 80 which is borderline if not flat out illegal on highways here causing an obstruction and adding hours to a journey one can do in an IC in one go, then yes it will go that far. Of course then a 4 hour trip turns into an over nighter by the time one allows for recharging.

I saw a new model release ( when it's available in 3 years or whatever)  where they said it would go this much further thanks to the battery break through. The only breakthrough was making the cell size larger and stuffing more of them in the vehicle. Wasn't a higher energy density, just different packaging.



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it appears to me that the lead acid battery still is a strong contender for stationary use.

It has few drawbacks in this application and a huge advantage in cost.

I spoke to someone about Buying some  UPS backup bank batteries that were being replaced earlier in the week.  A sizeable storage room full that are turned every 5 years.  They are being replaced with more LA because they are the most cost effective and reliable in the industry's view.

LA is a Long way from dead yet.
Not well suited to any portable use, the weight savings and power density of lipo  kill LA but for fixed uses, best bang for the buck by a long shot.


mobile_bob

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Re: Lithium cell balancing
« Reply #18 on: November 03, 2021, 01:15:13 PM »
my point with the automotive battery argument is as follows

prefaced by the tiny  home movement, wherein the owners are all about efficiency
and live in an area in northern climates where it is cold more months than not, poor wind resource, and less than optimum solar exposure.

lets add to that the owner being a 20-30 something that works away from home, leaves for work at around 7am and returns home at around 5pm,  about an hour to and from work, which is not too far fetched as tiny home folks generally like to be out of the city where they are less hampered by zoning and codes.

so he/she gets up at 6am to take a shower, make breakfast/coffee, and maybe start a load of clothes to be dried that evening.

the  house sits empty during the day,

basically with a little thought, one could get his heavy energy needs down to an hour in the morning and an hour in the evening.  during the rest of the day, the tstat is lowered and presumably heated with propane, the only power need would be the blower fan, and possibly the fridge topping off.

under such conditions, it would be a good use for a small cogen unit designed to fit the need.  provide the heavy load power in the morning, and evening (2hours per day) make the domestic hot water for washing, showering, cooking. and also used to top off a set of batteries that would be used to provide power during the day while the owner is gone and at night while he is asleep. all excess heat recovered could be used for domestic space heating, to lower the load on the furnace.

with such a system, a cogen might need no more than a 30 seconds to come on line and provide for those needs.  a bank of automotive batteries that are called upon to provide for that need twice a day should last at least 7years.   it would only need to cover the loads for the amount of time needed to get the engine driven cogen up and running, thereafter switchgear would switch the loads over to the cogen.

now 30 seconds is a long crank time for a car battery, however 2 such batteries would effectively be 15 seconds each, 4 such less than 8 seconds which is not a bad draw on a 4 battery bank that would presumably be in a more temperate environment, and with a much better controlled charging system than is typical of an automotive regulator.

the savings in avoided conversion steps, along with the batteries low cost due to economies of scale, all make for a relatively low cost of operation and certainly a lower first cost.

couple that with a small bank of golf cart batteries (again relatively cheap due to economies of scale), to provide power for the furnace blower, the fridge and maybe a few led lights used after the cogen shuts down in the evening to provide lighting and i think one could make a system that does about everything one would need to do given the constraints of location and size at a low cost and give a good life span.

mount a couple of those golf cart batteries in the commuter car, using a cord and anderson plug and you have a source of power that likely would reduce the fuel economy of the car below the margin of error.

add as much solar as one can afford, and the system gets much easier, even if the area is limited in that resource.

with a little more pencil work, i think the system could be scaled up so that a more comfortable space might work out just as well.

throw in a spouse and a pack of teenage kids, and all bets are off.  :)

bob g
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mikenash

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Re: Lithium cell balancing
« Reply #19 on: November 04, 2021, 05:27:33 AM »
Following . . .  :)

Fred8

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Re: Lithium cell balancing
« Reply #20 on: November 06, 2021, 12:43:14 AM »

couple that with a small bank of golf cart batteries (again relatively cheap due to economies of scale), to provide power for the furnace blower, the fridge and maybe a few led lights used after the cogen shuts down in the evening to provide lighting and i think one could make a system that does about everything one would need to do given the constraints of location and size at a low cost and give a good life span.

In that Atypical situation that would work.
How much and what size are the golf cart batteries where you are?  Definitely not cheap or all that readily available here. :0(

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add as much solar as one can afford, and the system gets much easier, even if the area is limited in that resource.

This is my philosophy.
I have all my inverters at least double overpaneled.  This has worked out VERY well.  At full output they would overload the HD wiring I put in but it's not about Max power, it's about getting decent power in bad conditions.  Winter fall off where I am is about 1/3rd the summer radiation so that is a big downrating for a start. Add in some Cloudy/ wet weather and I can be down to 10% of my generation I get on a clear summers day. THAT is what I am building for not the walk in 100Kwh a day I can get in summer.

The Kicker is being no natural or town gas, everything is electric so my demands can be huge compared to other people but not out of character for other homes in the area
By having plenty of solar you can run off what is being generated at the time ( on a decent day) without having to dip into your battery reserve.  If you can almost eliminate the day draw on the batteries by running " Direct" then the battery pack can be much smaller.
Thankfully I do not have to contend with Snow or daytime sub zero temps bugger that for a Joke!

Winter days can be mostly clear and beautiful and even the instant generation not too bad below what the summer is thanks to the over panelling  however, the real shortfall comes from having half the daytime hours.  It's the short days that hurt me the most not even the winter radiation fall off.  If I had the inverters running their rated capacity in panels, they would be useless pretty much.
IMHO, anything under 150% Panel to inverter ratio is a waste.  200% I consider to be the sweet spot.

For the most part you can get full rating out of the inverter which adds to more consistency of generation. If I had the inverters matching the panels I'd be getting stupid amperage on the good days and no more on the bad ones when I really need the power.

For batteries I have also found 3 and 4 aspect arrays to be best.  For me that's east, north, west and Flat.  For a battery you want a n even charging input not a peaked one. Getting the early charge after draining at night is also desirable.  Having  a flat panel(s) is beneficial for the overcast days although in that situation one is trying to gain fractions of a very diminished output to start with.

I usually set up a winter ground mount for a bit of extra boost which I tilt to the best winter angle. That was 3.5 Kw this year and a good help. Having perfect winter angle and alignment does give an edge on the roof mounted arrays which are simply NOT worth tilting not that I can do much about orientation. Then again, with one exception, they are all perfectly orientated at some part of the day. 

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throw in a spouse and a pack of teenage kids, and all bets are off.  :)

Again why I went Big.
Don't want to have to worry about the women's long showers, washing and drying one article of clothing in the early evening or late at night for the next day, leaving TV's on ( other than wearing out the TV for nothing) and all the other things that I got lectured about when I was a Kid for wasting power.   I have changed all the lights in the place to LED which use nothing but I still can't bear to see a light on in a room no one is in. Old habits die hard.


BruceM

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Re: Lithium cell balancing
« Reply #21 on: November 06, 2021, 06:29:37 AM »
"By having plenty of solar you can run off what is being generated at the time ( on a decent day) without having to dip into your battery reserve.  If you can almost eliminate the day draw on the batteries by running " Direct" then the battery pack can be much smaller."

I concur.  With present PV prices so good, while batteries still very expensive, the best economy is have lots of extra PV, modest battery bank and use a backup generator when necessary rather than oversize the batteries for more than a nights worth a power.  I"d like to add another 1500W array to face early morning sun.  I only use the inverter and it's big AC loads during sunny days; likewise cook electric on sunny days; only lights and electronics at night.  After destroying their first set of batteries in a year or two, most off grid newbies wise up and start doing simple power management.  Quite easy once you get into the swing of it.  Plenty of sun here in AZ, all year round.  Now that I have 2375 watts of PV, I haven't had to do any LIster/Generator battery charging even on cloudy days.




Fred8

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Re: Lithium cell balancing
« Reply #22 on: November 07, 2021, 12:24:26 PM »

Now that I have 2375 watts of PV, I haven't had to do any LIster/Generator battery charging even on cloudy days.

A very modest amount of panels.  Beyond my imagination how you can manage that.  Then again, I spose your generation factor is a lot higher than mine but still....

Here you can buy good used 250W panels for  $50 very easily, often less if you are prepared to bargain. They come and go in supply but sometimes there are plenty around and sales are slow so if you haggle, You can get them cheaper.  I bought a batch of brand new panels earlier in the year for $16 ea for 290s.
They were leftovers a distributor had buried in the back of his warehouse and only was prepared to sell in one lot. I knew he'd have lots of enquiries for ones and 2 and other piddling amounts  so I made him an offer for the lot which he took.  Forked the set of 28 onto my truck still in the Boxes and he was happy to sell them.

 Took some of the 250's I had on my roof down and replaced them with these and sold the 250's at $40 ea.  ;D
The guy I was selling them to wanted to upgrade his 190W panels and go up to 6Kw.

Batteries here are never cheap. Most people selling them used want delusional money and they are usually pretty suspect as to condition anyway. There were loads of 190 Ah UPS backup batteries being offered here by some different sellers Recently.  All 10 Yo and they all wanted over $1.50 to $2 /Ah for them.  Too much of a risk for me.

I regard 5Kw as a basic solar array these days so your power management must be excellent if you can live Frugally enough to survive on half  of that.  5Kw sure would give you a nice buffer and enable you to do a lot more and concern yourself less. You could run your AC and electric stove much more often with less dependence on sunny days as well as not having to worry about using other appliances. 

I think a couple of days battery reserve is good. Would give me more peace of mind.  Having enough panels to  meet your needs even on bad days would be possible for people like yourself whom use little power but for me it would be impractical although quite the dream. I spose it would be a lot more practical if I had wood heating.
 That's by far my biggest power concern and of course comes when there is the least power to be had.  Summer of Course there is plenty of power so I can run the AC much as I like and don't have to worry.

I find if I run it hard and run it early in the day so the house never gets heat soaked I don't need it at night when the sun has gone.

BruceM

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Re: Lithium cell balancing
« Reply #23 on: November 07, 2021, 04:42:19 PM »
Yes, I can see how 5KW of PV would be a good figure for many with a home designed for grid power.  Cheap enough to do these days.

I have solar hot water for space and domestic heating, with an 800 gallon insulated storage tank, propane refrigerator and freezer and a superinsulated home.  My major power concern is the desire to do something useful with the excess power I have every day.  My batteries are full before noon every day, even in winter; on  dark days they're full by early afternoon (this is Arizona at 5600ft).  I just switch to propane cooking when it's dark.

People can and have been comfortable on WAY less PV than I have now;  I was quite happy with just 875W of PV that I had for 7 years, but back then I ran the Listeroid for all my AC needs and on dark winter mornings to bulk charge the batteries.

I haven't added wind power as I had originally intended, because PV has gotten so cheap.











« Last Edit: November 07, 2021, 04:43:50 PM by BruceM »